Patent Application
20170186591
The various embodiments described herein pertain generally to a cleaning method of a plasma processing apparatus and the plasma processing apparatus.
Conventionally, in a manufacturing process of a semiconductor device, there is employed a plasma processing apparatus configured to generate plasma from a gas and perform an etching process or the like on a processing target substrate (e.g., a semiconductor wafer) with the generated plasma. As such a plasma processing apparatus, there is known a so-called capacitively coupled plasma processing apparatus in which an upper electrode and a lower electrode are disposed to face each other within a processing chamber, and the plasma is generated by applying a high frequency power between the upper electrode and the lower electrode. Further, there is also known a technique of controlling a plasma density by using a magnetic field in the plasma processing apparatus having such a configuration (see, for example, Patent Document 1).
In this plasma processing apparatus, if a plasma process such as plasma etching is performed repeatedly, a deposit such as polymer may be deposited within the processing chamber, so that an adverse effect may be caused on the plasma process. For this reason, a cleaning process of removing the deposit within the processing chamber is performed periodically. As such a cleaning method, there is known a method of removing the deposit by generating plasma of a cleaning gas within the processing chamber (see, for example, Patent Document 2).
Patent Document 1: Japanese Patent Laid-open Publication No. 2013-149722
Patent Document 2: Japanese Patent Laid-open Publication No. 2009-099858
In the conventional plasma processing apparatus as described above, the inside of the processing chamber is cleaned to remove the deposit such as the polymer. Recently, since miniaturization and high integration of semiconductor devices such as memory is approaching the limit, a 3D NAND memory in which a capacity thereof is increased by being stacked is becoming a mainstream. As for such a 3D NAND memory, though the capacity of the memory can be enhanced by increasing the stacking number, a processing time of the plasma etching also increases with the increase of the stacking number. As a result, a large amount of deposit may be deposited within the processing chamber. Therefore, the aforementioned cleaning process needs to be performed frequently. In this regard, it has been required to develop a method of conducting the cleaning process efficiently in a short period of time.
For example, in the capacitively coupled plasma processing apparatus in which the upper electrode and the lower electrode are disposed within the processing chamber to face each other, the thickness (amount) of the deposit deposited on the upper electrode may become non-uniform depending on, e.g., a distribution of a plasma density in the plasma process. In such a case, if it is attempted to remove a thick deposit portion on which a thickness of the deposit is large, a thin deposit portion on which a thickness of the deposit is small is continuously cleaned even after the deposit on the thin deposit portion is removed. As a result, the upper electrode is etched to be consumed.
In view of the foregoing, exemplary embodiments provide a cleaning method of a plasma processing apparatus and the plasma processing apparatus capable of suppressing consumption of an upper electrode when performing a cleaning process and capable of improving production efficiency by performing the cleaning process efficiently in a short period of time as compared to the conventional cases.
In one exemplary embodiment, there is provided a cleaning method of a plasma processing apparatus. Here, the plasma processing apparatus includes a processing chamber configured to accommodate a processing target substrate therein; a lower electrode provided within the processing chamber and configured to mount the processing target substrate thereon; an upper electrode, provided within the processing chamber, facing the lower electrode; a high frequency power supply configured to apply a high frequency power between the upper electrode and the lower electrode; and an electromagnet, provided on an upper portion of the processing chamber, including concentrically arranged annular coils. Further, the cleaning method, in which a deposit deposited on the upper electrode of the plasma processing apparatus is removed, includes introducing a preset cleaning gas into the processing chamber and generating plasma of the preset cleaning gas by applying the high frequency power between the upper electrode and the lower electrode from the high frequency power supply; and generating a magnetic field by supplying electric currents to the coils, and adjusting an amount of the electric current supplied to each of the coils individually depending on a distribution of a thickness of the deposit deposited on the upper electrode in a radial direction thereof.
In another exemplary embodiment, there is provided a plasma processing apparatus configured to process a processing target substrate with plasma. Here, the plasma processing apparatus includes a processing chamber configured to accommodate the processing target substrate therein; a lower electrode provided within the processing chamber and configured to mount the processing target object thereon; an upper electrode, provided within the processing chamber, facing the upper electrode; a high frequency power supply configured to apply a high frequency power between the upper electrode and the lower electrode; an electromagnet, provided on an upper portion of the processing chamber, including concentrically arranged annular coils; and a controller configured to, when performing a cleaning process of removing a deposit deposited on the upper electrode, introduce a preset cleaning gas into the processing chamber; generate plasma of the preset cleaning gas by applying the high frequency power between the upper electrode and the lower electrode from the high frequency power supply; generate a magnetic field by supplying electric currents to the coils; and adjust an amount of the electric current supplied to each of the coils individually depending on a distribution of a thickness of a deposit deposited on the upper electrode in a radial direction thereof.
According to the exemplary embodiments, consumption of the upper electrode when performing the cleaning process can be suppressed, and the cleaning process can be performed efficiently in a short period of time, as compare to the conventional cases. Therefore, the production efficiency can be improved.
In the following, exemplary embodiments will be described in detail, and reference is made to the accompanying drawings, which form a part of the description.
A circular plate-shaped mounting table 14 configured to mount the semiconductor wafer W thereon is provided in a lower portion of the processing chamber 12. The mounting table 14 includes a base 14a and an electrostatic chuck 14b. The base 14a is formed of a conductive member such as aluminum.
An annular focus ring 26 is provided on a peripheral region of a top surface of the base 14a to surround the semiconductor wafer W. Further, the electrostatic chuck 14b is provided on a central region of the top surface of the base 14a. The electrostatic chuck 14b has a circular plate shape, and includes an electrode film embedded in an insulating film. The electrostatic chuck 14b is configured to attract and hold the semiconductor wafer W as a processing target substrate with an electrostatic force generated by a DC voltage applied to the electrode film of the electrostatic chuck 14b from a DC power supply (not shown).
In the state that the semiconductor wafer W is mounted on the electrostatic chuck 14b, a central axis line Z that passes through a center of the semiconductor wafer W in a vertical direction substantially coincides with central axis lines of the base 14a and the electrostatic chuck 14b.
The base 14a constitutes a lower electrode. A first high frequency power supply 18 configured to generate a high frequency power for plasma generation is connected to the base 14a via a first matching device 22. The first high frequency power supply 18 generates a high frequency power having a frequency of, e.g., 100 MHz. The first matching device 22 is equipped with a circuit configured to match an output impedance of the first matching device 22 and an input impedance at a load side (lower electrode). Further, the first high frequency power supply 18 may be connected to the upper electrode 16.
In the present exemplary embodiment, the first high frequency power supply 18 is configured to apply the high frequency power for plasma generation in a pulse shape having a preset frequency (e.g., 90 kHz) and a preset duty ratio (e.g., 50%). Accordingly, there are provided a plasma generation period and a plasma non-generation period, and electric charges can be suppressed from being accumulated at a certain portion on the semiconductor wafer W. That is, during the plasma generation period, the electric charges may be accumulated at a portion where electron density is high since the electron density in the plasma is non-uniform. By providing the plasma non-generation period, however, the accumulated electric charges can be dispersed to the surrounding, so that the problem that the electric charges are accumulated can be resolved. Therefore, the insulating film or the like can be suppressed from being damaged.
Further, a second high frequency power supply 20 configured to generate a high frequency bias power for ion attraction is also connected to the base 14a via a second matching device 24. The second high frequency power supply 20 generates a high frequency power having a frequency (e.g., 3.2 MHz) lower than the frequency of the high frequency power from the first high frequency power supply 18. Further, the second matching device 24 includes a circuit configured to match an output impedance of the second matching device 24 and an input impedance at a load side (the lower electrode). Further, under the focus ring 26, a side surface of the mounting table 14 is surrounded by a shield ring 28.
An upper electrode 16 is provided above the mounting table (lower electrode) 14, facing the mounting table 14 with a processing space S therebetween. The upper electrode 16 has a circular plate shape and forms the processing space S while partitioning the processing space S from thereabove. The upper electrode 16 is disposed such that a central axis line thereof substantially coincides with the central axis line of the mounting table 14. In the present exemplary embodiment, a member which forms a surface of the upper electrode 16 facing the mounting table 14 is made of quartz. A non-illustrated cover ring is provided around the upper electrode 16 which is made of the quartz. Further, the material of the upper electrode 16 may not be limited to the quartz, and the upper electrode 16 may be made of silicon. Furthermore, a thermally sprayed film of a fluorine compound containing, by way of non-limiting example, yttrium oxide (Y2O3), or YF3 may be formed on the surface of the upper electrode 16 facing the processing space S. In case that the upper electrode 16 is made of silicon, a DC voltage may be applied to the upper electrode 16.
The upper electrode 16 also has a function as a shower head configured to introduce a preset processing gas into the processing space S in a shower shape. In the present exemplary embodiment, the upper electrode 16 is provided with a buffer room 16a, a gas line 16b and a multiple number of gas holes 16c. The buffer room 16a is connected with one end of the gas line 16b. Further, the multiple number of gas holes 16c are connected to the buffer room 16a. The gas holes 16c are extended downwards and opened toward the processing space S. Meanwhile, a non-illustrated gas exhaust device such as a TMP (Turbo Molecular Pump) and a DP (Dry Pump) is connected to a bottom portion of the processing chamber 12 and is configured to maintain a pressure within the processing chamber 12 in a preset decompressed atmosphere.
An electromagnet 30 is provided on the upper electrode 16. The electromagnet 30 includes a core member 50 and coils 61 to 64. The core member 50 has a structure in which a columnar portion 51, a plurality of cylindrical portions 52 to 55 and a base portion 56 are formed as a single body. The core member 50 is made of a magnetic material. The base portion 56 has a substantially circular plate shape, and a central axis line of the base portion 56 accords to the central axis line Z. The columnar portion 51 and the plurality of cylindrical portions 52 to 55 are protruded downwards from a bottom surface of the base portion 56. The columnar portion 51 has a substantially circular column shape, and a central axis line thereof accords to the central axis line Z. A radius L1 (see
Each of the cylindrical portions 52 to 55 has a cylindrical shape extended in the direction of the central axis line Z. As depicted in
As an example, the radii L2, L3, L4 and L5 are 76 mm, 127 mm, 178 mm and 229 mm, respectively. In this case, L4 and L5 are larger than the radius (150 mm) of the semiconductor wafer W. Accordingly, the coil 64 is positioned above the focus ring 26 which is located at an outside of the semiconductor wafer W. Further, center positions of the coils 61, 62, 63 and 64 are spaced apart from the central axis line Z by 50 mm, 100 mm, 150 mm and 200 mm, respectively.
A groove is formed between the columnar portion 51 and the cylindrical portion 52. As depicted in
In the electromagnet 30 having the above-described configuration, by supplying an electric current to one or more of the coils 61 to 64, a magnetic field B having a horizontal magnetic field component BH according to a radial direction with respect to the central axis line Z can be formed in the processing space S.
Further,
If an electric current is supplied to the coil 62 of the electromagnet 30, the magnetic field B as shown in
Further, if an electric current is supplied to the coil 64 of the electromagnet 30, the magnetic field B as shown in
In the plasma processing apparatus 10, the processing gas from the gas supply system is supplied into the processing space S from the upper electrode 16 serving as the shower head, and the high frequency power from the first high frequency power supply 18 is supplied to the mounting table 14 serving as the lower electrode, so that the high frequency electric field is generated between the upper electrode 16 and the mounting table 14. Accordingly, plasma of the processing gas is generated in the processing space S. The semiconductor wafer W can be processed with active species of molecules or atoms constituting the processing gas dissociated in the plasma. Further, by adjusting the high frequency bias power applied from the second high frequency power supply 20 to the mounting table 14 serving as the lower electrode, it is possible to adjust the degree of ion attraction.
Further, the plasma processing apparatus 10 includes the controller Cnt. The controller Cnt is implemented by a programmable computer or the like. The controller Cnt controls the high frequency power supplied from the first high frequency power supply 18, the high frequency power supplied from the second high frequency power supply 20, a gas exhaust rate of the gas exhaust device, the kind of the gas supplied from the gas supply system and a flow rate thereof, and a value and a direction of the electric current supplied to the coils 61 to 64 of the electromagnet 30. To this end, the controller Cnt outputs control signals to the first high frequency power supply 18, the second high frequency power supply 20, the gas exhaust device, the individual constituent components of the gas supply system, the electric current source connected to the electromagnet 30 according to a recipe which is stored in a memory of the controller Cnt or inputted by an input device.
According to the exemplary embodiment, when performing a cleaning process of removing a deposit deposited on the upper electrode 16, by the controller Cnt, a cleaning gas is introduced into the processing chamber 12, and plasma of the cleaning gas is generated by applying the high frequency powers to the mounting table 14 as the lower electrode from the first high frequency power supply 18 and, when necessary, from the second high frequency power supply 20 as well. Further, by the controller Cnt, the magnetic field is generated by supplying the electric current to the coils 61 to 64 of the electromagnet 30, and the amount of the electric current supplied to each of the coils 61 to 64 is adjusted depending on a thickness distribution of the deposit on the upper electrode 16 in the radial direction.
In the plasma processing apparatus 10 having the above-described configuration, by disposing the focus ring 26 around the semiconductor wafer W, a plasma state around the outside of the semiconductor wafer W is made to be the same as a plasma state above the semiconductor wafer W, and a variation in an etching state at a peripheral portion of the semiconductor wafer W is suppressed. Therefore, processing uniformity over the surface of the semiconductor wafer W can be improved.
If a plasma etching process is performed on the semiconductor wafer W in the plasma processing apparatus 10, a deposit is deposited on an inner wall of the processing chamber 12, the quartz-made upper electrode 16, and so forth. Thus, the cleaning process is performed at a preset timing, for example, at a timing upon the lapse of a preset period during which the semiconductor wafer W is processed.
In this cleaning process, a preset cleaning gas (e.g., CF4+O2) is introduced into the processing chamber 12 through the upper electrode 16. Further, by applying the high frequency powers to the mounting table 14 as the lower electrode from the first high frequency power supply 18 and, when necessary, from the second high frequency power supply 20 as well, the cleaning gas is excited into plasma, and the deposit is removed with action of the plasma. Here, the thickness (amount) of the deposit deposited on the surface of the quartz-made upper electrode 16 facing the mounting table 14 may be differed depending on the positions on the upper electrode 16 in the radial direction.
In the example of
As shown in
Further,
As stated above, when the thicknesses of the deposit are different depending on the positions on the upper electrode 16 in the radial direction, if the cleaning process is performed at a uniform cleaning rate at each position, the upper electrode 16 would be first exposed at a portion where the thickness of the deposit is small. By continuously performing the cleaning process in this state, the deposit at a portion where the thickness of the deposit is large is removed. As a result, at the portion where the upper electrode 16 is first exposed, the upper electrode 16 is etched to be consumed.
According to the present exemplary embodiment, however, the cleaning process is performed in the state that the magnetic field is formed by flowing the electric current to each of the coils 61 to 64 of the electromagnet 30. Further, by adjusting a cleaning rate depending on the thickness of the deposit at each position on the upper electrode 16 in the radial direction, the state of the magnetic field is controlled such that the cleaning rate is relatively higher at the portion where the thickness of the deposit is large, whereas the cleaning rate is relatively lower at the portion where the thickness of the deposit is small.
Further,
As can be seen from
In addition, in case of forming the stronger magnetic field by the coils 61 to 64 of the electromagnet 30, the etching rate (cleaning rate) at the central portion of the upper electrode tends to be increased, as compared to a case of forming the weaker magnetic field. Meanwhile, the etching rate (cleaning rate) at the peripheral portion of the upper electrode tends to be equal to or lower than that in case of forming the weaker magnetic field. As such, the etching rate (cleaning rate) at each position on the upper electrode 16 in the radial direction can be controlled by adjusting the intensity of the magnetic field formed by the coils 61 to 64 of the electromagnet 30.
Accordingly, the state of the magnetic field formed by the electromagnet 30 can be changed by adjusting the amount of the electric currents supplied to the respective coils 61 to 64 of the electromagnet 30. As a result, the etching rate (cleaning rate) can be controlled such that the etching rate (cleaning rate) is increased at the portion of the upper electrode 16 where the amount (thickness) of the deposit is large, whereas the etching rate (cleaning rate) is decreased at the portion of the upper electrode 16 where the amount (thickness) of the deposit is small. Therefore, at the portion where the amount (thickness) of the deposit is small, it is possible to suppress the surface of the upper electrode 16 from being exposed early before the cleaning process is completed, and, thus, it is also possible to suppress the upper electrode 16 from being etched to be worn out.
Here, it should be noted that the present exemplary embodiment is not limiting, and various changes and modifications may be made. By way of example, the cleaning gas is not limited to the aforementioned example of CF4/O2 or O2/He, and various other gas systems such as NF3/O2 may be used.
The cleaning method of the plasma processing apparatus and the plasma processing apparatus according to the present exemplary embodiments are applicable to the field of manufacture of semiconductor devices and thus have industrial applicability.
| Number | Date | Country | Kind |
|---|---|---|---|
| 2014-041911 | Mar 2014 | JP | national |
| Filing Document | Filing Date | Country | Kind |
|---|---|---|---|
| PCT/JP2015/000713 | 2/17/2015 | WO | 00 |
