The present invention relates to a plasma processing apparatus for performing a process, such as a film-forming or the like, on a substrate by exciting plasma.
A plasma processing apparatus for performing a CVD process, an etching process, or the like on a substrate by exciting plasma in a processing container by using a microwave is used in a process of manufacturing, for example, a semiconductor device, an LCD device, or the like. As such a plasma processing apparatus, an apparatus, which supplies a microwave from a microwave source through a coaxial waveguide or a waveguide to a dielectric disposed on an inner surface of the processing container, and plasmatizes a predetermined gas supplied into the processing container by using energy of the microwave, is known.
Recently, a size of the plasma processing apparatus increases with an increasing size of a substrate, but when the dielectric disposed on the inner surface of the processing container is a single plate, it is difficult to prepare the dielectric having a large size, and thus manufacturing costs may be highly increased. Accordingly, in order to settle such inconvenience, the applicants previously suggested a technology of dividing a dielectric plate into a plurality of numbers by attaching a plurality of dielectrics on a lower surface of a lid of the processing container (Patent Document 1).
[Patent Document 1] Japanese Laid-Open Patent Publication No. 2006-310794
However, such a conventional plasma processing apparatus using a microwave has a configuration where a microwave of, for example, 2.45 GHz output from a microwave source penetrates through a dielectric disposed on a lower surface of a lid of a processing container and is supplied into the processing container. Here, the dielectric is disposed to cover almost all of a processing surface (upper surface) of a substrate received in the processing container, and an area of an exposed surface of the dielectric exposed inside the processing container was almost the same as an area of the processing surface of the substrate. Accordingly, a uniform process was performed on the entire processing surface of the substrate by using plasma generated on the entire lower surface of the dielectric.
However, as in the conventional plasma processing apparatus, when the area of the exposed part of the dielectric is almost the same as the area of the processing surface of the substrate, a used amount of the dielectric is increased, and it costs much. Specifically recently, the size of the substrate is being increased, and thus the used amount of the dielectric is increased more, thereby increasing expenses.
Also, when the dielectric is disposed on the entire lower surface of the lid of the processing container, it is difficult to uniformly supply a processing gas to the entire processing surface of the substrate. In other words, for example, Al2O3 or the like is used as the dielectric, but it is difficult to manufacture a gas supply hole in the dielectric compared to manufacturing a gas supply hole in the lid formed of a metal, and generally, the gas supply hole is formed only in an exposed place of the lid. Accordingly, it becomes difficult to uniformly supply a processing gas in a state like in a shower plate on the entire processing surface of the substrate.
In a plasma process, such as an etching, CVD (chemical vapor deposition), or the like, a self bias voltage (negative direct voltage) may be generated on the substrate by applying a high frequency bias on the substrate, so as to control energy of ions incident on a surface of the substrate from plasma. Here, it is preferable that the high frequency bias applied to the substrate is applied only to a sheath around the substrate, but, if a ground surface (the inner surface of the processing container) is difficult to be seen from the plasma since most of the inner surface of the processing container is covered by the dielectric, the high frequency bias may also be applied to a sheath around the ground surface. Accordingly, it is not only required to apply excessively large high frequency power to the substrate, but the ground surface is etched since the energy of ions incident on the ground surface is increased, and thus metal contamination may be generated.
Also, when a microwave of high power is transmitted so as to increase a processing rate, a temperature of the dielectric is increased due to incidence of ions or electrons from the plasma, thereby damaging the dielectric by a thermal stress, or generating impurity contamination as an etching reaction on the surface of the dielectric is accelerated.
As described above, in the plasma processing apparatus using the microwave, the microwave source outputting the microwave of 2.45 GHz is generally used based on reasons, such as easiness in obtainment, economic feasibility, etc. Meanwhile, recently, a plasma process using a microwave having a low frequency of 2 GHz or lower is being suggested, and a plasma process using a microwave having a relatively low frequency of, for example, 896 MHz, 915 MHz, or 922 MHz is being studied. The reason is as follows. Since a lowest limit of electron density for obtaining stable plasma having a low electron temperature is proportional to a square of a frequency, plasma suitable for a plasma process is obtained in wider conditions when the frequency is decreased.
The inventors variously studied about such a plasma process using the microwave having a low frequency of 2 GHz or lower. As a result, a new knowledge that when the microwave having a frequency of 2 GHz or lower is transmitted to the dielectric of the inner surface of the processing container, the microwave can be effectively propagated along a metal surface of the inner surface of the processing container, or the like, from the vicinity of the dielectric, and the plasma can be excited in the processing container by using the microwave that is propagated along the metal surface was obtained. Also, such a microwave that is propagated along the metal surface, between the metal surface and the plasma will be referred to as a “conductor surface wave” herein.
Meanwhile, when such a conductor surface wave is propagated along the metal surface and the plasma is excited in the processing container, if a shape or a size of a surface wave propagating portion that propagates the microwave in the vicinity of the dielectric is not uniform, the plasma excited in the processing container by the conductor surface wave also becomes non-uniform. As a result, a uniform process may not be performed on the entire processing surface of the substrate.
To solve the above and/or other problems, the present invention provides a plasma processing apparatus that excites plasma in a processing container by using a conductor surface wave, wherein uniformity of a process with respect to a substrate is improved.
According to an embodiment of the present invention, there is provided a plasma processing apparatus including a processing container which is formed of metal and receives a substrate to be plasma-processed, an electromagnetic wave source which supplies an electromagnetic wave required to excite plasma in the processing container, and a plurality of dielectrics, through which the electromagnetic wave supplied from the electromagnetic wave source transmits to the inside of the processing container and which have a part that is exposed to the inside of the processing container, provided on a lower surface of a lid of the processing container, wherein a metal electrode is provided on a lower surface of the dielectrics, and wherein a surface wave propagating portion, through which the electromagnetic wave is propagated, is formed on each of two different sides of such part of each dielectric that is exposed between the metal electrode and the lower surface of the lid, and the surface wave propagating portions on said two different sides have the substantially similar shapes as each other or the substantially symmetrical shapes to each other.
According to another embodiment of the present invention, there is provided a plasma processing apparatus including a processing container which is formed of metal and receives a substrate to be plasma-processed, an electromagnetic wave source which supplies an electromagnetic wave required to excite plasma in the processing container, and a plurality of dielectrics, through which the electromagnetic wave supplied from the electromagnetic wave source transmits to the inside of the processing container and which have a part that is exposed to the inside of the processing container, provided on a lower surface of a lid of the processing container, wherein a metal electrode is provided on a lower surface of the dielectrics, and wherein a surface wave propagating portion, through which the electromagnetic wave is propagated, is formed adjacent to at least a portion of such part of each dielectrics that is exposed between the metal electrode and the lower surface of the lid, and said adjacent surface wave propagating portion has a substantially similar shape as a shape of the dielectric, or substantially symmetrical shape to the shape of the dielectric.
According to another embodiment of the present invention, there is provided a plasma processing apparatus including a processing container which is formed of metal and receives a substrate to be plasma-processed, an electromagnetic wave source which supplies an electromagnetic wave required to excite plasma in the processing container, and a plurality of dielectrics, through which the electromagnetic wave supplied from the electromagnetic wave source transmits to the inside of the processing container and which have a part that is exposed to the inside of the processing container, provided on a lower surface of a lid of the processing container, wherein a metal electrode is provided on a lower surface of each of the dielectrics, and such part of each dielectric that is exposed between the metal electrode and the lower surface of the lid has a substantially polygonal outline when viewed from the inside of the processing container, and wherein the plurality of dielectrics are disposed with vertical angles of the polygonal outlines being adjacent to each other, and a surface wave propagating portion, through which the electromagnetic wave is propagated, is formed on the lower surface of the lid exposed in the processing container and a lower surface of the metal electrode.
In the plasma processing apparatus, the plasma may be excited in the processing container by a microwave (conductor surface wave) propagated along the surface wave propagating portion from the dielectrics. Also, according to the plasma processing apparatus, the shape or the size of the surface wave propagating portion formed around the dielectrics is almost uniform, and the plasma excited in the processing container by the conductor surface wave is uniform. As a result, a uniform process is performed on an entire processing surface of the substrate.
In the plasma processing apparatus, the dielectrics may have, for example, substantially tetragonal plate shapes. Here, the tetragon may be, for example, a square, a rhomb, a square having round corners, or a rhomb having round corners. Alternatively, the dielectrics may have, for example, substantially triangular plate shapes. Here, the triangle may be, for example, an equilateral triangle, or an equilateral triangle having round corners. A shape of the lower surface of the lid, which is surrounded by the plurality of dielectrics and exposed inside the processing container, and a shape of a lower surface of the metal electrode may be substantially identical, when viewed from the inside of the processing container.
An outer edge of each dielectric may be on an outer side than an outer edge of the metal electrode, when viewed from the inside of the processing container. Alternatively, an outer edge of each dielectric may be on a same line or on an inner side than an outer edge of the metal electrode, when viewed from the inside of the processing container.
A thickness of each dielectric may be, for example, equal to or less than 1/29 of a distance between centers of the neighboring dielectrics, and preferably, a thickness of each dielectric may be equal to or less than 1/40 of a distance between centers of the neighboring dielectrics.
The dielectrics may be, for example, inserted into a recess portion formed on the lower surface of the lid. Here, the lower surface of the lid exposed inside the processing container, and a lower surface of the metal electrode may be disposed on a same plane. Also, the lower surface of the lid exposed inside the processing container and a lower surface of the metal electrode may be covered by a passivation protective film. Also, an average roughness about the center line in the lower surface of the lid exposed inside the processing container and a lower surface of the metal electrode may be, for example, 2.4 μm or less, and preferably, an average roughness about the center line in the lower surface of the lid exposed inside the processing container and a lower surface of the metal electrode may be 0.6 μm or less.
A metal cover electrically connected to the lid may be adhered to a region adjacent to each dielectric, in the lower surface of the lid, and a surface wave propagating portion, through which an electromagnetic wave is propagated, may be formed on a lower surface of the metal cover exposed inside the processing container. Here, a side surface of the dielectric may be adjacent to a side of the metal cover. Also, the lower surface of the metal cover exposed inside the processing container and the lower surface of the metal electrode may be disposed on a same plane. Also, a shape of the lower surface of the metal cover and a shape of the lower surface of the metal electrode may be substantially same, when viewed from the inside of the processing container. Also, an average roughness about the center line in the lower surface of the metal cover exposed inside the processing container and the lower surface of the metal electrode may be, for example, 2.4 μm or less, and preferably, the lower surface of the metal cover exposed inside the processing container and the lower surface of the metal electrode may be, for example, 0.6 μm or less.
The plasma processing apparatus may include a plurality of connecting members, which penetrate through holes formed on the dielectrics, and fix the metal electrode to the lid. Here, an elastic member, which electrically connects the lid and the metal electrode, may be disposed on at least a part of the holes formed on the dielectrics. Also, the connecting members may be, for example, formed of a metal. Also, lower surfaces of the connecting members exposed inside the processing container may be disposed on a same plane as the lower surface of the metal electrode. Also, each dielectric may have, for example a substantially tetragonal plate shape, and the connecting members may be disposed on a diagonal of the tetragon. Also, 4 connecting members may be disposed per 1 dielectric.
The plasma processing apparatus may include an elastic member, which elastically supports the dielectric and the metal electrode toward the lid.
A continuous groove, for example, may be formed on the lower surface of the lid, and the surface wave propagating portion and the plurality of dielectrics may be disposed inside a region surrounded by the groove. Here, the surface wave propagating portion may be divided by the groove. Alternatively, a continuous convex portion may be formed, for example, on an inner side of the processing container, and the surface wave propagating portion and the plurality of dielectrics may be disposed in a region surrounded by the convex portion. Here, the surface wave propagating portion may be divided by the convex portion.
The plasma processing apparatus may include one or more metal rods which are on upper portions of the dielectrics, do not penetrate through the dielectrics, have lower ends adjacent to or close to upper surfaces of the dielectrics, and transmit an electromagnetic wave to the dielectrics. Here, the metal rods may be disposed on center portions of the dielectrics. Also, the plasma processing apparatus may include a sealing member, which divides an atmosphere inside the processing container from an atmosphere outside of the processing container, between the dielectrics and the lid.
An area of exposed parts of the dielectrics may be, for example, equal to or less than ½ of an area of the surface wave propagating portion. Preferably, an area of exposed parts of the dielectrics may be equal to or less than ⅕ of an area of the surface wave propagating portion. Also, the plasma processing apparatus may include a gas discharging unit which is on the surface wave propagating portion and discharges a predetermined gas to the processing container. Also, an area of exposed parts of the dielectrics may be, for example, equal to or less than ⅕ of an area of an upper surface of the substrate. Also, a frequency of an electromagnetic wave supplied from the electromagnetic wave source may be, for example, equal to or less than 2 GHz.
According to embodiments of the present invention, shapes or sizes of surface wave propagating portions formed around the dielectrics exposed inside the processing container become almost the same, and the plasma excited in the processing container by the conductor surface wave becomes uniform. As a result, a uniform process is performed on the entire processing surface of the substrate. Also, it is possible to drastically reduce the used amount of dielectrics since the plasma can be excited by using the electromagnetic wave (conductor surface wave) propagated along the surface wave propagating portion disposed around the dielectrics. Also, by reducing the area of the exposed part of the dielectrics exposed inside the processing container, damage, etching, or the like of the dielectric due to overheating of the dielectric is suppressed, while generation of metal contamination from the inner side of the processing container is removed. Specifically, when an electromagnetic wave having a frequency of 2 GHz or lower is used, the lowest electron density for obtaining stable plasma having a low electron temperature may be about 1/7 compared to when the microwave having a frequency of 2.45 GHz is used, and the plasma suitable for the plasma process can be obtained under wide conditions that has not been used before, and thus general-purpose of the processing apparatus can be remarkably increased. As a result, it is possible to perform a plurality of continuous processes having different processing conditions by using one processing apparatus, and thus it is possible to manufacture a product having high quality in a short time with a low expense.
G: substrate
1: plasma processing apparatus
2: container body
3: lid
4: processing container
10: susceptor
11: feeder
12: heater
20: exhaust port
25: dielectric
27: metal electrode
30, 46, 65: connecting member
32: space
37: O-ring
42, 52, 72: gas discharge hole
45: metal cover
55: side cover
56, 57: groove
58: side cover inner portion
59: side cover outer portion
85: microwave supplying device
86: coaxial waveguide
90: branch plate
92: metal rod
102: gas supply source
103: refrigerant supply source
Hereinafter, embodiments of the present invention will be described based on a plasma processing apparatus 1 using a microwave as an example of an electromagnetic wave.
(Basic Configuration of Plasma Processing Apparatus 1)
The plasma processing apparatus 1 includes a processing container 4 composed of a hollow container body 2 and a lid 3 attached to an upper part of the container body 2. A sealed space is formed inside the processing container 4. The entire processing container 4 (the container body 2 and the lid 3) is formed of a conductive material, such as an aluminum alloy, and is electrically grounded.
A susceptor 10 is provided as a holding stage for holding a semiconductor substrate or a glass substrate (hereinafter, referred to as a substrate) G, inside the processing container 4. The susceptor 10 is formed of, for example, an aluminum nitride, and a feeder 11, which electrostatically absorbs the substrate G while applying a predetermined bias voltage to the inside the processing container 4, and a heater 12, which heats the substrate G to a predetermined temperature, are provided inside the susceptor 10. In the feeder 11, a high frequency power supply source 13 for bias application provided outside the processing container 4 is connected through a matcher 14 including a condenser, or the like, while a high voltage direct current power supply source 15 for electrostatic absorption is connected through a coil 16. The heater 12 is connected to an alternating current power supply source 17 provided outside the processing container 4.
An exhaust port 20 for exhausting an atmosphere in the processing container 4 by using an exhaust device (not shown), such as a vacuum pump, provided outside the processing container 4 is provided on a bottom portion of the processing container 4. Also, a baffle plate 21 for controlling a flow of gas in a preferable state inside the processing container 4 is provided around the susceptor 10.
4 dielectrics 25 formed of, for example, Al2O3, are attached to a lower surface of the lid 3. A dielectric material, for example, fluororesin, quartz, or the like, may be used as the dielectric 25. As shown in
As shown in
A metal electrode 27 is adhered to the lower surface of each dielectric 25. The metal electrode 27 is formed of a conductive material, for example, an aluminum alloy. Like the dielectric 25, the metal electrode 27 is formed as a square plate shape. Also, in the present specification, a metal member having a plate shape attached to the lower surface of each dielectric 25 as above will be referred to as a “metal electrode”. Here, a width N of the metal electrode 27 is a little shorter than the width L of the dielectric 25. Thus, when viewed from the inside of a processing container, a surrounding portion of the dielectric 25 is exposed in a state showing a square outline, around the metal electrode 27. Also, when viewed from the inside of the processing container 4, vertical angles of the square outlines formed by the surrounding portions of the dielectrics 25 are adjacently disposed.
The dielectric 25 and the metal electrode 27 are attached to the lower surface of the lid 3 by a connecting member 30, such as a screw or the like. A lower surface 31 of the connecting member 30 exposed inside the processing container may be on the same plane as the lower surface of the metal electrode 27. Alternatively, the lower surface 31 of the connecting member 30 may not be on the same plane as the lower surface of the metal electrode 27. A spacer 29 having a ring shape is disposed in a penetrating place of the connecting member 30 with respect to the dielectric 25. An elastic member 29′, such as a wave washer, is disposed on the spacer 29, and thus upper and lower surfaces of the dielectric 25 does not have a gap. When there is an uncontrollable gap in the upper and lower surfaces of the dielectric 25, a wavelength of a microwave propagating the dielectric 25 becomes unstable, and thus uniformity of plasma may be deteriorated in general, or load impedance viewed from a microwave input side may become unstable. Also, when the gap is large, discharge may be generated. In order that the dielectric 25 and the metal electrode 27 are adhered to the lower surface of the lid 3 and is definitely electrically and thermally contacted at connecting portion, a member having elasticity may be used in the connecting portion. The elastic member 29′ may be, for example, a wave washer, a spring washer, a belleville spring, a shield spiral, or the like. A material may be a stainless steel, an aluminum alloy, or the like. The connecting member 30 is formed of a conductive metal, or the like, and the metal electrode 27 is electrically connected to the lower surface of the lid 3 through the connecting member 30 and is electrically grounded. The connecting member 30 is disposed, for example, in 4 places on a diagonal of the metal electrode 27 having a tetragonal shape.
An upper end of the connecting member 30 protrudes to a space 32 formed inside the lid 3. A nut 36 is attached to the upper end of the connecting member 30 protruding to the space 32, interposing an elastic member 35, such as a spring washer, a wave washer, or the like. The dielectric 25 and the metal electrode 27 are elastically supported to be adhered to the lower surface of the lid 3, by elasticity of the elastic member 35. Here, the adhesion of the dielectric 25 and the metal electrode 27 with respect to the lower surface of the lid 3 is easily adjusted by the nut 36.
An O-ring 37 as a sealing member is disposed between the lower surface of the lid 3 and the upper surface of the dielectric 25. The O-ring 37 is, for example, a metal O-ring. As will be described later, an atmosphere inside the processing container 4 is blocked from an atmosphere inside a coaxial waveguide 86 by the O-ring 37, and thus the atmosphere the inside the processing container 4 is separated from an atmosphere outside the processing container 4.
A longitudinal gas passage 40 is formed in the center of the connecting member 30, and a lateral gas passage 41 is formed between the dielectric 25 and the metal electrode 27. A plurality of gas discharge holes 42 are distributed and opened on the lower surface of the metal electrode 27. As will be described later, a predetermined gas supplied to the space 32 inside the lid 3 passes through the gas passages 40 and 41, and the gas discharge holes 42, and is distributed and supplied toward the inside of the processing container 4.
A metal cover 45 is attached to the region S in the center of the lower surface of the lid 3 surrounded by the 4 dielectrics 25. The metal cover 45 is formed of a conductive material, for example, an aluminum alloy, is electrically connected to the lower surface of the lid 3, and is electrically grounded. Like the metal electrode 27, the metal cover 45 has a square plate shape of the width N.
The metal cover 45 has a thickness of about a sum of thicknesses of the dielectric 25 and the metal electrode 27. Thus, the lower surface of the metal cover 45 and the lower surface of the metal electrode 27 are on the same plane.
The metal cover 45 is attached to the lower surface of the lid 3 by a connecting member 45, such as a screw or the like. A lower surface 47 of the connecting member 46 exposed inside the processing container is on the same plane as the lower surface of the metal cover 45. Alternatively, the lower surface 47 of the connecting member 46 may not be on the same plane as the lower surface of the metal cover 45. The connecting members 46 are disposed, for example, in 4 places on diagonals of the metal cover 45 having a tetragonal shape. In order to uniformly dispose gas discharge holes 52, a distance between the center of the dielectric substance 25 and the center of the connecting member 46 is ¼ of a distance L′ between the centers of the neighboring dielectrics 25.
The upper end of the connecting member 46 protrudes to the space 32 formed inside the lid 3. A nut 49 is attached to the upper end of the connecting member 46, which protrudes to the space 32 as above, interposing an elastic member 48, such as a spring washer, a wave washer, or the like. The metal cover 45 is elastically supported to be adhered to the lower surface of the lid 3 according to elasticity of the elastic member 48.
A longitudinal gas passage 50 is formed in the center of the connecting member 46, and a lateral gas passage 51 is formed between the lower surface of the lid 3 and the metal cover 45. The plurality of gas discharge holes 52 are distributed and opened on the lower surface of the metal cover 45. As will be described later, a predetermined gas supplied to the space 32 in the lid 3 is diffused and supplied toward the inside of the processing container 4 through the gas passages 50 and 51, and the gas discharge holes 52.
A side cover 55 is attached to the lower surface of the lid 3, in an outer region of the 4 dielectrics 25. The side cover 55 is formed of a conductive material, for example, an aluminum alloy, is electrically connected to the lower surface of the lid 3, and is electrically grounded. The side cover 55 also has a thickness of about the sum of thicknesses of the dielectric 25 and the metal electrode 27. Accordingly, a lower surface of the side cover 55 is on the same plane as the lower surface of the metal cover 45 and the lower surface of the metal electrode 27.
Double grooves 56 and 57 disposed to surround the 4 dielectrics 25 are formed on the lower surface of the side cover 55, and 4 side cover inner portions 58 are formed in the side cover 55 in an inner side area divided by the double grooves 56 and 57. The side cover inner portion 58 has almost the same shape as a right-angled isosceles triangle obtained by diagonally bisecting the metal cover 45 when viewed from the inside of the processing container 4. Here, a height of the isosceles triangle of the side cover inner portion 58 is a little (about ¼ of the wavelength of the conductor surface wave) longer than a height of an isosceles triangle obtained by diagonally bisecting the metal cover 45. This is because electric boundary conditions in base portions of the isosceles triangles viewed from the conductor surface wave are different in two cases.
Also, the grooves 56 and 57 have octagonal shapes when viewed from the inside of the processing container, in the present embodiment, but may also have tetragonal shapes. In this case, an area of the same right-angled isosceles triangle is formed between the corner of the tetragonal grooves 56 and 57 and the dielectric 25. Also, a side cover outer portion 59 covering a surrounding portion of the lower surface of the lid 3 is formed on the side cover 55, in an outer side area divided by the grooves 56 and 57.
As will be described later, during a plasma process, a microwave propagated to each dielectric 25 from a microwave supplying device 85 may be propagated along the lower surface of the metal cover 45, the lower surface of the metal electrode 27, and the lower surface of the side cover inner portion 58 from the vicinity of the dielectric 25 exposed to the lower surface of the lid 3. At this time, the grooves 56 and 57 operate as a propagation barrier unit so that the microwave (conductor surface wave) that was propagated along the lower surface of the side cover inner portion 58 is not propagated to an outer side (side cover outer portion 59) over the grooves 56 and 57. Accordingly in the present embodiment, the lower surface of the metal cover 45, the lower surface of the metal electrode 27, and the lower surface of the side cover inner portion 58, which are areas surrounded by the grooves 56 and 57 in the lower surface of the lid 3, become a surface wave propagating portion.
The side cover 55 is attached to the lower surface of the lid 3 by a connecting member 65, such as a screw or the like. A lower surface 66 of the connecting member 65 exposed inside the processing container is on the same plane as the lower surface of the side cover 55. Alternatively, the lower surface 66 of the connecting member 65 may not be on the same plane as the lower surface of the side cover 55.
An upper end of the connecting member 65 protrudes to the space 32 formed inside the lid 3. A nut 68 is attached to the top of the connecting member 65 protruding to the space 32 as above, interposing an elastic member 67, such as a spring washer, a wave washer, or the like. The side cover 55 is elastically supported to be adhered to the lower surface of the lid 3 by elasticity of the elastic member 67.
A longitudinal gas passage 70 is formed in a center of the connecting member 65, and a lateral gas passage 71 is formed between the lower surface of the lid 3 and the side cover 55. A plurality of gas discharge holes 72 are distributed and opened on the lower surface of the side cover 55. As will be described later, a predetermined gas supplied to the space 32 inside the lid 3 is diffused and supplied toward the inside of the processing container 4 through the gas passages 70 and 71, and the gas discharge holes 72.
A coaxial waveguide 86, which transmits the microwave supplied from the microwave supplying device 85 disposed outside the processing container 4, is connected to a surface center of the lid 3. The coaxial waveguide 86 includes an inner conductor 87 and an outer conductor 88. The inner conductor 87 is connected to a branch plate 90 disposed inside the lid 3.
As shown in
A press power of a spring 93 disposed on the upper portion of the lid 3 is applied to the upper end of the metal rod 92 through a supporter 94. A lower end of the metal rod 92 contacts a center of the upper surface of the dielectric 25 attached to the lower surface of the lid 3. A recess portion 95 for receiving the lower end of the metal rod 82 is formed in the center of the upper surface of the dielectric 25. The metal rod 92 is pressed down from upward without penetrating through the dielectric 25 while the lower end of the metal rod 92 is inserted into the recess portion 95 of the center of the upper surface of the dielectric 25, by the press power of the spring 93. The supporter 94 is formed of an insulator, such as Teflon (registered trademark), or the like. When the recess portion 95 is formed, reflection viewed from an input side of the microwave is suppressed, but the recess portion 95 may not be formed.
A microwave having a frequency of 2 GHz or lower, for example, 915 MHz, is introduced with respect to the coaxial waveguide 86, from the microwave supplying device 85. Accordingly, the microwave of 915 MHz is branched to the branch plate 90, and is transmitted to each dielectric 25 through the metal rod 92.
A gas pipe 100 for supplying a predetermined gas required for a plasma process is connected to the upper surface of the lid 3. Also, a refrigerant pipe 101 for supplying a refrigerant is formed inside the lid 3. A predetermined gas supplied from a gas supply source 102 disposed outside the processing container 4 through the gas pipe 100 is supplied to the space 32 inside the lid 3, and then is diffused and supplied toward the inside of the processing container 4 through the gas passages 40, 41, 50, 51, 70, and 71, and the gas discharge holes 42, 52, and 72.
A refrigerant supply source 103 disposed outside the processing container 4 is connected to the refrigerant pipe 101 through a pipe 104. A refrigerant is supplied from the refrigerant supply source 103 to the refrigerant pipe 101 through the pipe 104, thus the lid 3 is maintained as a predetermined temperature.
(Plasma Process in Plasma Processing Apparatus 1)
A case of forming a film of amorphous silicon, for example, on an upper surface of the substrate G in the plasma processing apparatus 1 according to an embodiment of the present invention comprised as above will be described. First, the substrate G is transferred into the processing container 4, and is held on the susceptor 10. Then, a predetermined plasma process is performed in the sealed processing container 4.
During the plasma process, a gas required for the plasma process, for example, a mixture gas of argon gas/silane gas/hydrogen is supplied into the processing container 4 from the gas supply source 102 through the gas pipe 100, the space 32, the gas passages 40, 41, 50, 51, 70, and 71, and the gas discharge holes 42, 52, and 72. Also, the inside of the processing container 4 is set to a predetermined pressure by being exhausted from the exhaust port 20. As described above, in the plasma processing apparatus 1 according to the present embodiment, the gas discharge holes 42, 52, and 72 are densely distributed and formed on the entire lower surface of the metal cover 45, the lower surface of the metal electrode 27, and the lower surface of the side cover 55, which are exposed in the processing container 4. Accordingly, during the plasma process, a predetermined gas is uniformly supplied from each of the gas discharge holes 42, 52, and 72 disposed on the entire lower surface of the lid 3 to the entire processing surface of the substrate G as in a shower plate, and thus it is possible to supply the predetermined gas on the entire surface of the substrate G held on the susceptor 10.
Also, while the predetermined gas is supplied into the processing container 4 as above, the substrate G is heated up to a predetermined temperature by the heater 12. Also, a microwave of, for example, 915 MHz, generated in the microwave supplying device 85 is transmitted to each dielectric 25 through the coaxial waveguide 86, the split plate 90, and the metal rod 92. Also, the microwave transmitted through each dielectric 25 is propagated along the lower surface of the metal cover 45, the lower surface of the metal electrode 27, and the lower surface of the side cover inner portion 58, which are the surface wave propagating portion, in a state of a conductor surface wave.
Here,
Meanwhile, while the four sides of the metal cover 45 and the metal electrode 27 are surrounded at the part (surrounding portion) of the dielectric 25 exposed in the processing container, only two sides of the side cover inner portion 58 are surrounded at the part (surrounding portion) of the dielectric 25 exposed in the processing container. Accordingly, about a half power of the conductor surface wave W is propagated to the lower surface of the side cover inner portion 58, compared to the metal cover 45 and the metal electrode 27. However, the side cover inner portion 58 has a shape that is almost similar to the right-angled isosceles triangle obtained by diagonally bisecting the side cover 55, and an area of the side cover inner portion 58 is almost a half of an area of the metal cover 45 or the metal electrode 27. Thus, the plasma is generated in the lower surface of the side cover inner portion 58 under the same conditions as in the lower surface of the metal cover 45 and the lower surface of the metal electrode 27.
Also, thinking based on the part (surrounding portion) of the dielectric 25 exposed in the processing container, as shown in
Moreover, in the plasma processing apparatus 1, the gas discharge holes 42, 52, and 72 are densely distributed and formed on the entire lower surface of the metal cover 45, the lower surface of the metal electrode 27, and the lower surface of the side cover 55, which are exposed in the processing container 4, as described above, and thus the predetermined gas may be supplied to the entire surface of the substrate G held on the susceptor 10. Thus, it is possible to perform the plasma process uniformly on the entire processing surface of the substrate G by generating the plasma by the power of the microwave under the uniform conditions with respect to the entire lower surface of the metal cover 45, the lower surface of the metal electrode 27, and the lower surface of the side cover inner portion 58, which are the surface wave propagating portion.
(Relationship Between Propagation and Frequency of Conductor Surface Wave)
Permittivity of plasma P generated in the processing container 4 is indicated as εr′−jεr″. The permittivity of the plasma P is expressed in a complex number due to a loss component. A real part εr′ of the permittivity of the plasma P is generally smaller than −1. The permittivity of the plasma P is represented by Equation 1 below.
Also, a propagation characteristic when a microwave is incident on the plasma P is represented by Equation 2 below.
Here, k denotes a wave number, ko denotes a wave number in vacuum, ω denotes a microwave angular frequency, vc denotes an electron collision frequency, and ωpe denotes an electron plasma frequency represented by Equation 3 below.
Here, e denotes an elementary electric charge, ne denotes electron density of the plasma P, ε0 denotes vacuum permittivity, and me denotes an electron mass.
A penetration length δ indicates how much microwave can be incident inside the plasma when the microwave is incident. In detail, the penetration length δ is an penetrating distance of the microwave until electric field strength E of the microwave is attenuated to 1/e of electric field strength E0 on the boundary surface of the plasma P. The penetration length δ is represented by Equation 4 below.
δ=−1/lm(k) (4)
Here, k denotes a wave number as described above.
When the electron density ne is larger than a cutoff density nc represented by Equation 5 below, the microwave is unable to be propagated in plasma, and thus the microwave incident on the plasma P is rapidly attenuated.
nc=ε0me
ω2/e2 (5)
According to Equation 4, the penetration length δ is several mm to tens of mm, and is decreased as electron density is increased. Also, when the electron density ne is sufficiently larger than the cutoff density nc, the penetration length δ does not depend much on a frequency.
Meanwhile, a sheath thickness t of the plasma P is represented by Equation 6 below.
Here, Vp denotes plasma electrical potential, kB denotes a Boltzmann constant, Te denotes an electron temperature, and λD is a Debye length represented by Equation 7 below. The Debye length λD indicates how quickly disorder of electrical potential in plasma is decreased.
According to Equation 6, the sheath thickness t is tens of μm to hundreds of μm. Also, it can be known that the sheath thickness t is proportional to the Debye length λD. Also in Equation 6, it is understood that the Debye length λD decreases as the electron density ne is increased.
┌Wavelength and Attenuation of Conductor Surface Wave┘
As shown in
Here, h is an eigen value, and is represented as follows in the inside and outside of a sheath.
Here, γ denotes a propagation constant, hi denotes an eigen value in the sheath g, and he denotes an eigen value in the plasma P. The eigen values hi and he are generally complex numbers.
A general solution of Equation 8 is as follows, from a boundary condition that the electric field strength in the z-direction is 0 with respect to the lower surface of the lid 3, which is a conductor.
H
y
A cos(hix)e−yz 0<x<t (11)
H
y
=Be
−jh
x
e
−yz
x>t (12)
Here, A and B denote arbitrary constants.
A following characteristic equation is induced as a predetermined constant is erased by using that tangential components of a magnetic field and an electric field become continuous, in a boundary between the sheath g and the plasma P.
(ε′r−j″εr)hi tan(hit)=jhe
h
i
2
−h
e
2=(1−εr′+jer″)k02 (13)
In Characteristic Equation 13, the sheath thickness t is obtained from Equation 6, and the permittivity εr′−jεr″ of the plasma P is obtained from Equation 1. Accordingly, by solving the Simultaneous Equation 13, the eigen values hi and he are respectively obtained. When a plurality of solutions exist, a solution where magnetic field distribution in a sheath is a hyperbolic function may be selected. Also, the propagation constant γ is obtained from Equation 9.
The propagation constant γ is represented as γ=α+jβ, by using an attenuation constant α and a phase constant β. The electric field strength E of the plasma is represented by Equation 14 below from a definition of a propagation constant.
E=E
0
×e
−jγz
=E
0
e
−αz
e
jβz (14)
Here, z denotes a propagation distance of a conductor surface wave TM, and E0 denotes electric field strength when the propagation distance z is 0. e−αz denotes an effect of the conductor surface wave TM being exponentially attenuated while being propagated, and ejβz denotes a rotation of a phase of the conductor surface wave TM. Also, since β=2π/λc, a wavelength λc of the conductor surface wave TM is obtained from the phase constant β. Accordingly, when the propagation constant γ is known, the attenuation of the conductor surface wave TM and the wavelength λc of the conductor surface wave TM may be calculated. Also, a unit of the attenuation constant α is Np(nepper)/m, and has a following relationship with a unit (dB/m) of each graph shown later.
1 Np/m=20/ln(10)dB/m=8.686 dB/m
By using the equations above, the penetration length δ, the sheath thickness t, and the wavelength λc of the conductor surface wave TM are respectively calculated when a microwave frequency is 915 MHz, an electron temperature Te is 2 eV, plasma electrical potential Vp is 24V, and the electron density ne is 1×1011 cm−3, 4×1011 cm−3, and 1×1012 cm−3. The results are shown in a following table.
A conductor surface wave cannot be propagated at certain electron density or below since it is cutoff at the level of above-mentioned electron density. Such electron density is referred to as conductor surface wave resonance density nr, and is twice a value of the cutoff density of Equation 5. The cutoff density is proportional to a square of a frequency, the conductor surface wave may be propagated in lower electron density as a frequency is lowered.
A value of the conductor surface wave resonance density nr is 1.5×1011 cm−3 at 2.45 GHz. Under an actual plasma processing condition, electron density near a surface may be 1×1011 cm−3 or lower, but under such a condition, the conductor surface wave is not propagated. Meanwhile, it is 2.1×1010 cm−3 at 915 MHz, and thus is about 1/7 of a case of 2.45 GHz. In 915 MHz, the conductor surface wave is propagated even when electron density near a surface is 1×1011 cm−3 or lower. As such, a frequency of 2 GHz or lower needs to be selected so as to propagate a surface wave even in low density plasma where electron density is about 1×1011 cm−3 near a surface.
Also, attenuation of the conductor surface wave is decreased when a frequency is decreased. This is described as follows. It is known that according to Equation 1, when a frequency is decreased, the real part εr′ of the permittivity of the plasma P is negatively increased, and thus plasma impedance is decreased. Accordingly, since a loss of a microwave in plasma is reduced as a microwave electric field applied to plasma is weakened compared to a microwave electric field applied to a sheath, the attenuation of the conductor surface wave TM is decreased.
When a conductor surface wave is used to generate plasma and a too high frequency is selected as a microwave frequency, uniform plasma is unable to be generated since the conductor surface wave is not propagated to a desired place. A frequency of about 2 GHz or lower needs to be selected so as to excite uniform plasma by using the conductor surface wave.
Meanwhile, in the plasma processing apparatus 1 shown in
As shown in
Alternatively, a convex portion may be formed in a continuous shape instead of a groove, thereby forming the conductor surface wave in a region surrounded by the convex portion. In this case, a height of the convex portion is higher than the sheath thickness t, and is smaller than ½ of the wavelength λ of the conductor surface wave. Also, the convex portion may be single, or double or more.
(Relationship (⅕) between Area of Exposed Parts of Dielectrics 25 and Surface Area of Substrate G)
In the plasma process performed inside the processing container 4, ion incidence on the surface of the substrate G held on the susceptor 10 plays an important role. For example, in a plasma film forming process, a thin film of high quality may be quickly formed even when a temperature of the substrate G is low, by performing film forming while ions in plasma being incident on the surface of the substrate G. Also, in a plasma etching process, it is possible to accurately form a minute pattern by anisotropic etching according to perpendicular incidence of ions on the surface of the substrate G. As such, in any plasma process, it is essential to control ion incidence energy on the surface of the substrate G to an optimal value for each process so as to perform a good process. The ion incidence energy on the surface of the substrate G may be controlled by a high frequency bias voltage applied from the high frequency power supply source 13 to the substrate G through the susceptor 10.
Meanwhile, by applying a high frequency bias voltage to the substrate G from the high frequency power supply source 13, plasma sheaths g and s are formed between the plasma P and the upper surface (processing surface) of the substrate G, and between the plasma P and a part of the ground electrode 3′ of the lower surface of the lid 3 (the lower surface of the metal cover 45, the lower surface of the metal electrode 27, and the lower surface of the side cover inner portion 58), in the processing container 4 under the plasma process. The high frequency bias voltage applied from the high frequency power supply source 13 is divided and applied to each of plasma sheaths g and s.
Here, As denotes a surface area of the processing surface (upper surface) of the substrate G, Ag denotes area of a portion of the ground electrode 3′ of the lower surface of the lid 3 facing the plasma P, Vs denotes a high frequency voltage applied to the plasma sheath s between the processing surface of the substrate G and the plasma P, and Vg denotes a high frequency voltage applied to the plasma sheath g between the lower surface of the lid 3 (the lower surface of the metal cover 45, the lower surface of the metal electrode 27, and the lower surface of the side cover inner portion 58) and the plasma P. The high frequency voltages Vs and Vg, and the areas As and Ag have a relationship of Equation 15 below.
(Vs/Vg)=(Ag/As)4 (15)
Brian Chapman, “Glow Discharge Processes,” A Wiley Interscience Publication, 1980.
When the high frequency voltages Vs and Vg applied to the plasma sheaths s and g are increased due to an effect of an electron current flowing through the plasma sheaths s and g, a direct voltage applied to the plasma sheaths s and g is increased. An increment of the direct voltage applied to the plasma sheaths s and g is almost the same as an amplitude (0 to peak value) of the high frequency voltages Vs and Vg. Ions in the plasma P are accelerated by the direct voltage applied to the plasma sheaths s and g, and incident on the processing surface of the substrate G, which is an electrode surface, and the lower surface of the lid 3 (the lower surface of the metal cover 45, the lower surface of the metal electrode 27, and the lower surface of the side cover inner portion 58), but such an ion incidence energy may be controlled by the high frequency voltages Vs and Vg.
In the plasma processing apparatus 1 according to the present embodiment, a high frequency voltage (Vs+Vg) applied between the processing surface of the substrate G and the lower surface of the lid 3 is divided and applied to each of the plasma sheaths s and g formed near the surface of the substrate G and the lower surface of the lid 3 (the lower surface of the metal cover 45, the lower surface of the metal electrode 27, and the lower surface of the side cover inner portion 58), by the high frequency power supply source 13. Here, it is preferable to decrease the high frequency voltage Vg applied to the plasma sheath g near the lower surface of the lid 3 as much as possible so that most high frequency voltage applied from the high frequency power supply source 13 is applied to the plasma sheath s near the surface of the substrate G. This is because, when the high frequency voltage Vg applied to the plasma sheath g near the lower surface of the lid 3 is increased, not only a power efficiency is deteriorated, but also energy of ions incident on the lid 3 (the lower surface of the metal cover 45, the lower surface of the metal electrode 27, and the lower surface of the side cover inner portion 58=ground electrode 3′) is increased, and thus, the lower surface of the lid 3 (the lower surface of the metal cover 45, the lower surface of the metal electrode 27, and the lower surface of the side cover inner portion 58) is sputtered, thereby generating metal contamination. In an actual plasma processing apparatus, the high frequency voltage Vg applied to the plasma sheath g near the lower surface of the lid 3 is not practical if it is not equal to or less than ⅕ of the high frequency voltage Vs applied to the plasma sheath s near the surface of the substrate G. In other words, it can be known that the area of the part of the ground electrode 3′ of the lower surface of the lid 3 facing the plasma P (the total area of the lower surface of the metal cover 45, the lower surface of the metal electrode 27, and the lower surface of the side cover inner portion 58, i.e., the area of the surface wave propagating portion) has to be 1.5 times or above the size of the surface of the substrate G, even at the lowest, based on Equation 15.
In a conventional microwave plasma processing apparatus, since most of the lower surface of the lid 3 facing the substrate G is covered with the dielectric 25 for transmitting a microwave, an area of a ground electrode contacting high density plasma is small, specifically in a plasma processing apparatus for a large substrate. As described above, in the plasma processing apparatus 1 processing a glass substrate of, for example, 2.4 m×2.1 m, the high density plasma P is generated in the region that is about 15% larger than the substrate size with respect to one side of the substrate, namely, about 30% larger than the substrate size with respect to both sides of the substrate, and the part of the lower surface of the lid 3 facing the plasma P (the lower surface of the metal cover 45, the lower surface of the metal electrode 27, and the lower surface of the side cover inner portion 58) becomes the ground electrode 3′. For example, in the part of the ground electrode 3′, when the dielectrics 25 are all grounding portions without being exposed inside the processing container 4, the area of the ground electrode 3′ facing the plasma P is 1.7((1+0.3)2) times larger than the substrate area. However, in the conventional microwave plasma processing apparatus, since most of the ground electrode 3′ is covered by the dielectric 25, a sufficient area was not obtained. Accordingly in the conventional microwave plasma processing apparatus for a large substrate, metal contamination may be generated when a high frequency bias is applied.
Accordingly, in the plasma processing apparatus 1 according to the present embodiment, an area of the exposed surface of the dielectrics 25 exposed inside the processing container 4 is decreased as much as possible, so that the area of the exposed surface of the dielectrics 25 is suppressed to ⅕ or lower than ⅕ of the area of the upper surface of the substrate G. Also, as described above, since the plasma P is generated in the processing container 4 by using the conductor surface wave propagated along the surface wave propagating portion of the lower surface of the lid 3 (the lower surface of the metal cover 45, the lower surface of the metal electrode 27, and the lower surface of the side cover inner portion 58) in the present invention, even if the exposed area of the dielectrics 25 is small, the plasma P may be effectively generated in the entire lower surface of the ground electrode 3′. As such, when the area of the exposed surface of the dielectrics 25 contacting the plasma P is equal to or lower than ⅕ of the area of the upper surface of the substrate G, the area of the ground electrode 3′ facing the plasma P is inevitably 1.5(1.7−⅕) times larger than the area of the surface of the substrate G, even at the lowest. Accordingly, it is possible to efficiently apply the high frequency voltage applied from the high frequency power supply source 13 to the plasma sheath s near the surface of the substrate G, without generating metal contamination, which is caused because the lower surface of the lid 3 is sputtered.
(Area of Exposed Parts of Dielectrics 25 in Inside of Processing Container 4)
A microwave, which is propagated in the dielectric 25 to the end of the dielectric 25, is propagated on a metal surface adjacent to the dielectric 25 (i.e., the lower surface of the metal cover 45, the lower surface of the metal electrode 27, and the lower surface of the side cover inner portion 58) as a conductor surface wave. Here, as shown in
Meanwhile, plasma is excited by a dielectric surface wave even in parts where the dielectrics 25 are exposed in the processing container 4. In the dielectric surface wave, a microwave electric field is applied in both of the dielectrics 25 and the plasma, whereas in the conductor surface wave, a microwave electric field is applied only to the plasma, and thus generally, the microwave electric field of the conductor surface wave applied to the plasma is strong. Accordingly, plasma having higher density than in the surfaces of the dielectrics 25 is excited in the surface wave propagating portion (i.e., the lower surface of the metal cover 45, the lower surface of the metal electrode 27, and the lower surface of the side cover inner portion 58), which is the metal surface.
When the area of the exposed part of the dielectric 25 is sufficiently smaller than the area of the part ‘a’ of the surface wave propagating portion, uniform plasma is obtained around the substrate G due to diffusion of the plasma. However, when the area of the exposed part of the dielectric 25 is larger than the area of one portion ‘a’ of the surface wave propagating portion, i.e., when the total area of the exposed parts of the dielectrics 25 is larger than ½ of the area of the surface wave propagating portion when viewed from the entire surface wave propagating portion, not only the plasma becomes non-uniform, but also power is concentrated to the surface wave propagating portion having the small area, and thus it is highly likely that abnormal discharge or sputtering is generated. Accordingly, the area of the total sum of the exposed parts of the dielectrics 25 may be equal to or less than ½, more preferably, equal to or less than ⅕ of the area of the surface wave propagating portion.
(Thickness of Dielectric 25)
In the present embodiment, the dielectric 25 and the metal electrode 27 are attached to the lower surface of the lid 3 by the connecting member 30, and the microwave cannot be propagated in the dielectric 25 around the connecting member 30 that electrically connects the metal electrode 27 to the lid 3. The microwave that escaped the vicinity of the connecting member 30 somewhat circulates each portion of the dielectric 25 according to an effect of diffraction, but microwave electric field strength of a corner portion of the dielectric 25 tends to be weakened compared to those of other portions. Uniformity of the plasma is deteriorated if microwave electric field strength becomes too weak.
The standardized electric field strength of a corner portion of the metal cover obtained as above is shown in
Strength of the microwave reaching the dielectric 25 by diffraction of the microwave propagating the dielectric 25 is dependent not only on the thickness of the dielectric 25, but also on a distance between the connecting member 30, which is a propagation obstacle, and the dielectric 25. As the distance increases, the strength of the microwave reaching the corner portion of the dielectric 25 increases. A distance between the connecting member 30 and the corner portion of the dielectric 25 is generally proportional to a distance (pitch of cell) between the centers of the dielectrics 25. Accordingly, it is good to set the thickness of the dielectric 25 to be lower with respect to the distance between the centers of the dielectrics 25. Since the pitch of the cell is 164 mm in
(Evenness of Surface Wave Propagating Portion)
When electron density increases, microwave electric field strength applied to a sheath is increased. When there is a minute corner portion in the lower surface of the metal cover 45, the lower surface of the metal electrode 27, and the lower surface of the side cover inner portion 58, which are the surface propagation part, an electric field is concentrated in the corner portion and the corner portion is overheated, and thus an abnormal discharge (arc discharge) may be generated. When at least one abnormal discharge is generated, a discharge unit moves around while melting a metal surface, thereby significantly damaging the metal surface. When the average roughness with respect to the center line in the lower surface of the metal cover 45, the lower surface of the metal electrode 27, and the lower surface of the side cover inner portion 58, which are the surface wave propagating portion, is sufficiently smaller than a thickness of the sheath, an electric field is applied to the metal surface on average despite of the minute corner portion. Accordingly, the electric field is not concentrated, and thus an abnormal discharge is not generated.
The sheath thickness t has been described above, and the sheath thickness t is inversely proportional to a square root of the electron density. It is sufficient to assume 1×1013 cm−3 as the maximum electron density. Here, a Debye length is 3.3 μm, and in case of Ar plasma, a thickness of a sheath is 3.5 times larger, i.e., 12 μm. Electric field concentration may be ignored in each corner portion if the average roughness of the metal surface with respect to the center line is equal to or lower than ⅕ of the thickness of the sheath, more preferably, equal to or lower than 1/20. Accordingly, it may be 2.4 μm, or more preferably, 0.6 μm or lower.
Hereinafter, the plasma processing apparatus 1 according to other embodiments will be described. Also, like reference numerals denote like elements as those of the plasma processing apparatus 1 described above with reference to
The metal electrode 27 is attached to the lower surface of each dielectric 25. The metal electrode 27 is formed of a conductive material, for example, an aluminum alloy. Like the dielectric 25, the metal electrode 27 has a square plate shape. However, the width N of the metal electrode 27 is a little shorter than the width L of the dielectric 25. Accordingly, when viewed from the inside of the processing container, the surrounding portion of the dielectric 25 is exposed in a state of showing a square outline, around the metal electrode 27. Also, when viewed from the inside of the processing container 4, vertical angles of the square outline formed by the surrounding portion of the dielectric 25 are disposed to be adjacent to each other.
The dielectric 25 and the metal electrode 27 are attached to the lower surface of the lid 3 by the connecting member 30, such as a screw or the like. The metal electrode 27 is electrically connected to the lower surface of the lid 3 through the connecting member 30, and is electrically grounded. A plurality of gas discharge holes 42 are distributed and opened on the lower surface of the metal electrode 27.
The metal cover 45 is attached to each region S of the lower surface of the lid 3. Each metal cover 45 is formed of a conductive material, for example, an aluminum alloy, electrically connected to the lower surface of the lid 3, and is electrically grounded. Like the metal electrode 27, the metal cover 45 has a square plate shape having the width N.
The metal cover 45 has a thickness of about a sum of thicknesses of the dielectric 25 and the metal cover 27. Accordingly, the lower surface of the metal cover 45 and the lower surface of the metal electrode 27 are on the same plane.
The metal cover 45 is attached to the lower surface of the lid 3 by the connecting member 46, such as a screw or the like. The plurality of gas discharge holes 52 are distributed and opened on the lower surface of the metal cover 45.
The side cover 55 is attached to the outer region of the 8 dielectrics 25, in the lower surface of the lid 3. The side cover 55 is formed of a conductive material, for example, an aluminum alloy, electrically connected to the lower surface of the lid 3, and electrically grounded. The side cover 55 also has a thickness of about the sum of the thicknesses of the dielectric 25 and the metal electrode 27. Accordingly, the lower surface of the side cover 55 is on the same plane as the lower surface of the metal cover 45 and the lower surface of the metal electrode 27.
A groove 56 disposed to surround the 8 dielectrics 25 is continuously formed on the lower surface of the side cover 55, and 8 side cover inner portions 58 are formed on the side cover 55 in the inner region divided by the groove 56. When viewed from the inside of the processing container 4, the side cover inner portion 58 has a shape that is almost the same as the right-angled isosceles triangle obtained by diagonally bisecting the metal cover 45. Here, a height of an isosceles triangle of the side cover inner portion 58 is a little longer (about ¼ of the wavelength of the conductor surface wave) than a height of the isosceles triangle obtained by diagonally bisecting the metal cover 45. This is because electric boundary conditions in base portions of the isosceles triangles viewed from the conductor surface wave are different in two cases.
Also, in the present embodiment, the groove 56 has an octagonal shape when viewed from inside the processing container, but may have a tetragonal shape. As such, a region of the same right-angled isosceles triangle is formed between a corner of the tetragonal groove 45, and the dielectric 25. Also, the side cover outer portion 59 covering the surrounding portion of the lower surface of the lid 3 is formed on the side cover 55, in the outer region divided by the groove 56.
During the plasma process, the microwave propagated from the microwave supplying device 85 to each dielectric 25 is propagated from the vicinity of the dielectric 25 exposed on the lower surface of the lid 3 along the lower surface of the metal cover 45, the lower surface of the metal electrode 27, and the lower surface of the side cover inner portion 58, and thus the lower surface of the metal cover 45, the lower surface of the metal electrode 27, and the lower surface of the side cover inner portion 58, which are regions surrounded by the groove 56 in the lower surface of the lid 3, become the surface wave propagating portion.
The side cover 55 is attached to the lower surface of the lid 3, by the connecting member 65, such as a screw or the like. The plurality of gas discharge holes 72 are distributed and opened on the lower surface of the side cover 55.
In the plasma processing apparatus 1 according to Modified Example 1 shown in
The metal electrode 27 is attached to the lower surface of each dielectric 25. The metal electrode 27 is formed of a conductive material, for example, an aluminum alloy. Like the dielectric 25, the metal electrode 27 also has a square plate shape. However, the width N of the metal electrode 27 is a little shorter than the width L of the dielectric 25. Accordingly, when viewed from the inside of the processing container, the surrounding portion of the dielectric 25 is exposed in a state of showing a square outline, around the metal electrode 27. Also, when viewed from the inside of the processing container 4, vertical angles of the square outline formed by the surrounding portion of the dielectric 25 are disposed to be adjacent to each other.
The dielectric 25 and the metal electrode 27 are attached to the lower surface of the lid 3, by the connecting member 30, such as a screw or the like. In the present embodiment, the lower end of the metal rod 92 penetrates through the dielectric 25, and the lower end of the metal rod 92 contacts the upper surface of the metal electrode 27. Also, an O-ring 37′ as a sealing member is disposed between the lower surface of the dielectric 25 and the upper surface of the metal electrode 27 so as to surround a connecting portion between the lower end of the metal rod 92 and the upper surface of the metal electrode 27. The metal electrode 27 is connected to the lower surface of the lid 3 through the connecting member 30, and is electrically grounded.
In the present embodiment, the lower surface of the lid 3 is exposed in the processing container 4 in each region S of the lower surface of the lid 3, and the outer region of the 8 dielectrics 25. Also, recess portions 3a, into which the dielectric 25 and the metal electrode 27 are inserted, are formed on the lower surface of the lid 3. As the dielectric 25 and the metal electrode 27 are inserted into each recess portion 3a, the lower surface of the lid 3 and the lower surface of the metal electrode 27, which are exposed in the processing container 4, are on the same plane.
The groove 56 disposed to surround the 8 dielectrics 25 is continuously formed on the lower surface of the lid 3, and 8 lid lower surface inner portions 3b are formed on the lower surface of the lid 3, in the inner region divided by the groove 56. The lid lower surface inner portion 3b has a shape almost the same as a right-angled isosceles triangle obtained by diagonally bisecting the metal electrode 27, when viewed from the inside of the processing container 4.
In the plasma processing apparatus 1 according to Modified Example 2, during the plasma process, the microwave propagated from the microwave supplying device 85 to each dielectric 25 is propagated from the vicinity of the dielectric 25 exposed on the lower surface of the lid 3, along the lower surface of the metal electrode 27, each region S of the lid 3, and a lower surface of each lid lower surface inner portion 3b. Even in the plasma processing apparatus 1 according to Modified Example 2, the plasma is generated by the power of the microwave under the uniform conditions in the entire lower surface of the metal electrode 27 and each region S of the lid 3 and the lower surface of each lid lower surface inner portion 3b, which are the surface wave propagating portion, and thus it is possible to perform the uniform plasma process on the entire processing surface of the substrate G.
In the plasma processing apparatus 1 according to Modified Example 3, the metal electrode 27 attached to the lower surface of each dielectric 25, the metal cover 45 attached to the region S, and the side cover 55 attached to the outer region of the dielectrics 25 are formed as one body. Also, the groove 56 is continuously formed on a periphery portion of the lower surface of the side cover 55, and the entire inner region divided by the groove 56 (i.e., the lower surface of the metal electrode 27, the lower surface of the metal cover 45, and the lower surface of the side cover 55) is the surface wave propagating portion.
Also by using the plasma processing apparatus 1 according to Modified Example 3, it is possible to perform a uniform plasma process on the entire processing surface of the substrate G by generating the plasma by using the power of the microwave under the uniform condition in the entire lower surface of the metal electrode 27, the lower surface of the metal cover 45, and the lower surface of the side cover 55, which are the surface wave propagating portion.
The metal electrode 27 is attached to the lower surface of each dielectric 25. The metal electrode 27 is formed of a conductive material, for example, an aluminum alloy. Like the dielectric 25, the metal electrode 27 also has a square plate shape. However, the width N of the metal electrode 27 is a little shorter than the width L of the dielectric 25. Accordingly, when viewed from the inside of the processing container 4, the surrounding portion of the dielectric 25 is exposed in a sate showing a square outline, around the metal electrode 27. Also, when viewed from the inside of the processing container 4, vertical angles of the square outlines formed by the surrounding portion of the dielectric 25 are disposed to be adjacent to each other.
The dielectric 25 and the metal electrode 27 are attached to the lower surface of the lid 3 by the connecting member 30, such as a screw or the like. The metal electrode 27 is electrically connected to the lower surface of the lid 3 through the connecting member 30, and is electrically grounded.
In the present embodiment, the lower surface of the lid 3 is in a state exposed inside the processing container 4 in each region S of the lower surface of the lid 3 and the outer region of the 8 dielectrics 25. Also, the lower surface of the lid 3 has a plane shape as a whole. Accordingly, the lower surface of the metal electrode 27 is disposed lower than the lower surface of the lid 3.
The groove 56 disposed to surround the 8 dielectrics 25 is continuously formed on the lower surface of the lid 3, and the 8 lid lower surface inner portions 3b are formed on the lower surface of the lid 3 in the inner region divided by the groove 56. The lid lower surface inner portion 3b has a shape that is almost the same as a right-angled isosceles triangle obtained by diagonally bisecting the metal electrode 27, when viewed from the inside of the processing container 4. Also, the plurality of gas discharge holes 52 are distributed and opened on each region S of the lower surface of the lid 3, and the plurality of gas discharge holes 72 are distributed and opened on each lid lower surface inner portion 3b.
In the plasma processing apparatus 1 according to Modified Example 4, during the plasma process, the microwave propagated from the microwave supplying device 85 to each dielectric 25 may be propagated from the vicinity of the dielectric 25 exposed to the lower surface of the lid 3, along the lower surface of the metal electrode 27, each region S of the lid 3, and the lower surface of the lid lower surface inner portion 3b. Also by using the plasma processing apparatus 1 according to Modified Example 4, it is possible to perform a uniform plasma process on the entire processing surface of the substrate G by generating the plasma by using the power of the microwave under the uniform condition, in the lower surface of the metal electrode 27 and each region S of the lid 3 and the entire lower surface of each lid lower surface inner portion 3b, which are the surface wave propagating portion.
(Location of Outer Edge of Dielectric)
Also, as shown in
(Shape of Lower Surface of Lid)
Also, as shown in
Alternatively, the metal cover 45 and the side cover 55 may be omitted, and as shown in
Alternatively, as shown in
(Shape of Dielectric and Metal Electrode)
Alternatively, as shown in
(Structure of Connecting Member)
Also, as described above, the dielectric 25 and the metal electrode 27 are attached by the connecting member 30 in the lower surface of the lid 3. Here, as shown in
The connecting member 30 for fixing the dielectric 25 and the metal electrode 27 has been described, but the same may be applied to the connecting member 46 for fixing the metal cover 45 and the connecting member 65 for fixing the side cover 55. Also, although a rotation preventing function of the screw (connecting member 30) is not shown in the types of
(Plasma Doping Process)
Also, a plasma doping process (ion injecting process) may be performed by using a plasma processing apparatus of the present invention. Here, in an RLSA plasma processing apparatus, since a lower surface of a lid is covered by an upper dielectric, an opposite electrode with respect to a susceptor does not exist above a substrate, and thus a chamber wall serves as a ground. Thus, it is required to straightly draw ions to the substrate by providing a ground plate operating as an opposite electrode, above the substrate, in the RLSA plasma processing apparatus. However, when the ground plate is provided in plasma, ions going to the substrate collide with the ground plate, thereby damaging the ground plate to generate heat. In other words, due to efficiency of ions lowered by plasma doping, sputtering and heat converted by collision, contamination is generated.
In this behalf, according to the plasma processing apparatus of the present invention, the exposed area of the dielectric 25 exposed inside the processing container 4 is small, and the most of the lower surface of the lid 3 exposed in the upper part in the processing container 4 is a metal surface. Accordingly, almost all of the lower surface of the lid 3 functions as a ground electrode, and thus even when a ground electrode is omitted, it may be considered that plasma doping (ion injection) is easily performed in perpendicular with respect to the upper surface of the substrate G.
Also, electric potential can be controlled since a negative DC may be applied when a ground plate is provided, and thus a depth of plasma doping may be controlled. Accordingly, in the plasma processing apparatus of the present invention, a case of controlling the depth of the plasma doping may be considered when performing the plasma doping process by providing a ground plate.
For example, in the plasma processing apparatus 1 described with reference to
Also, since it is required to give energy to ions reaching the substrate G, a magnetic bias voltage is generated on the substrate G by applying RF power from the high frequency power supply source 13 to the feeder 11 installed in the susceptor 10. Here, it is possible to generate a negative self-bias on the surface of the substrate G substantially without increasing plasma electric potential of a time average, since the lower surface of the lid 3 (the lower surface of the side cover 55, the lower surface of the metal cover 45, and the lower surface of the metal electrode 27) exposed on the upper part in the processing container 4 functions as the ground surface when the RF power is applied to the substrate G.
Here, as shown in
The total dose amount becomes 1×1015 cm−2. When this is divided by hundred thousand times, one dose amount is 1×1010 cm−2. Here, as shown in
When the plasma doping is performed, damage is not generated at all if an electric field is about 17 kV/cm. The high dose amount is injected after being divided by about hundred thousand times, and damage-free ion injection may be generated via new ion injection of removing static charge every time the high dose amount is injected.
When a dose amount of 1×1015 cm−2 is continuously injected, accumulated static charge becomes 1.1×1016 unit/cm2 and a generated electric field becomes E=1.7×109 V/cm=1.7×106 kV/cm, which exceeds 300 kV/cm of dielectric breakdown electric field strength of Si by far, and thus strong damage is generated. Accordingly, ions should be injected after minutely dividing the amount of ions into a minute amount so as to remove generated static charge.
In the plasma processing apparatus 1 according to Modified Example 5, the gas supply source 102 includes a first gas supply source 102a, which supplies a predetermined gas (for example, BF3) for processing used in film forming, etching, or the like, and a second gas supply source 102b, which supplies a predetermined gas (for example Ar) for plasma excitation, such as a rare gas, or the like. The predetermined gas for film forming or etching supplied from the first gas supply source 102a through a first passage 125 is diffused and supplied from each gas discharge hole 121 of the lower surface of the lower gas nozzle 120 toward the inside of the processing container 4 in the lower portion of the inside of the processing container 4. Meanwhile, the predetermined gas for plasma excitation supplied from the second gas supply source 102b through a second passage 126 is dispersed and supplied from each of the gas discharge holes 42, 52, and 72 of the lower surface of the metal cover 45, the lower surface of the metal electrode 27, and the lower surface of the side cover 55 toward the inside of the processing container 4 in the upper portion of the inside of the processing container 4.
As such, according to the plasma processing apparatus 1 of Modified Example 5, excessive dissociation is suppressed by supplying the gas for processing from the lower portion, where an electron temperature is lowered, and the gas for plasma excitation from the upper portion, thereby performing good plasma process on the substrate G.
While this invention has been particularly shown and described with reference to exemplary embodiments thereof, the present invention is not limited thereto, and it will be understood by those skilled in the art that various changes in form and details may be made therein without departing from the spirit and scope of the invention as defined by the appended claims.
The plasma processing apparatus according to the present invention may form an Al2O3 protective film or the like via anodic oxidation of a non-aqueous solution, after performing surface-planarization of electric field complex polishing or electric field polishing on an inner surface of the processing container 4. However, with respect to the plasma processing apparatus performing plasma doping, an MgF2 protective film is more preferable than the Al2O3 protective film since injection is performed by using 100% fluorine gas, such as AsF3, PF3, or BF3. The MgF2 protective film may be formed under processing conditions of, for example, AlMg (4.5% to 5%) Zr (0.1%)/ F2 process (200° C.)/350° C. anneal.
For example, an Ni film or Al film having a thickness of, for example, about 10 μm may be formed as a conductor film on the surface of the dielectric 25, except on a portion exposed inside the processing container 4 and an outer circumferential portion of the recess portion of the dielectric 25. As such, by forming the conductor film on the surface of the dielectric 25, an adverse affect on the O-ring 37 or the like is avoided since the microwave is not propagated with respect to locations aside from portion exposed inside the processing container 4. Forming locations of the conductor film may include at least a part among the recess portion 95 formed in the center of the upper surface of the dielectric 25, a portion adjacent to the connecting member 30, and a contacting surface with the metal electrode 27, in addition to a contacting location with the O-ring 37.
An alumina film, an yttria film, a Teflon (registered trademark) film, or the like may be formed as a protective film on the lower surface of the lid 3 or the inner side of the container body 2. Also, the plasma processing apparatus according to the present invention may process a large glass substrate, a circular silicon wafer, or an polygonal SOI (Silicon On Insulator). Also, in the plasma processing apparatus according to the present invention, all plasma processes, such as a film forming process, a diffusing process, an etching process, an ashing process, etc. can be performed. Also in the above, the microwave of 915 MHz is described as an example of the microwave having a frequency of 2 GHz or lower, but the frequency is not limited thereto. For example, a microwave of 896 MHz or 992 MHz may also be applied. Also, not only the microwave but also an electromagnetic wave may be applied. Also, an alumina film may be formed on surfaces of the lid 3, the container body 2, the metal electrode 27, the metal cover 45, the side cover 55, the connecting members 30, 46, and 65, etc. In the above, an example of discharging the gas from the gas discharge holes 42, 52, and 72 opened on the upper surface of the processing container 4 has been described, but alternatively, the gas may be discharged toward a lower space of the lid 3 from a container side wall. Also, the present application defines a metal body disposed on the lower surface of the dielectric as a “metal electrode”, and the metal electrode 27 of an embodiment is formed to have a metal plate shape and electrically connected to the lid. However, the metal electrode 27 may be a metal film adhered to the lower surface of the dielectric 25, instead of the metal plate, and may float without being electrically connected to the lid.
The present invention may be used in, for example, a CVD process or an etching process.
Number | Date | Country | Kind |
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2008-153324 | Jun 2008 | JP | national |
Filing Document | Filing Date | Country | Kind | 371c Date |
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PCT/JP2009/060345 | 6/5/2009 | WO | 00 | 3/14/2011 |