The present invention relates to a plasma processing apparatus.
As the semiconductor industry develops, various proposals are being made for plasma processing apparatuses, such as dry etching apparatuses and sputtering apparatuses. Patent Publication 1, for example, discloses that a CCD camera is embedded in a lower electrode of a plasma processing apparatus, and an image of plasma generated in a chamber is taken in a status where a processing target has not yet been mounted on the lower electrode.
When holes, such as trenches and via holes, are formed in a processing target by a dry etching apparatus, if an image of etched surfaces constituting bottoms of the trenches and holes can be taken, and then whether etching residues are generated or not can be observed in real-time, and thus the process conditions can be controlled based on the observation. For example, in the case of the dry etching of a processing target made of a silicon material, a phenomena where an SiO2 (silicon dioxide) deposit, which is a reaction product during etching, is deposited on the etching surface and remains as etching residue may occur (black silicon phenomena). If the generation of this black silicon phenomena can be monitored in real-time during etching, the process conditions can be changed according to the monitoring. However, the CCD camera embedded in the lower electrode as disclosed in Patent Publication 1 can not observe the processing target during etching.
[Patent Publication 1] Japanese Patent Application Laid-Open Publication No. 2002-93788
An object of the present invention is to provide a plasma processing apparatus that can observe a status of a processing target in real-time.
The present invention provides a plasma processing apparatus, comprising, a vacuum chamber in an internal space of which a processing target is disposed at a bottom wall side, a coil for generating plasma disposed outside and above the vacuum chamber and provided with conductors arranged so that a gap is formed in a plane view, a top wall of the vacuum chamber closing a top of the internal space and provided with a transparent section at a position corresponding to the gap between the conductors of the coil in the plane view, and an imaging device disposed above the coil and being capable of putting at least a part of the processing target in the internal space of the vacuum chamber into a field of view thereof through the gap between the conductors of the coil and the transparent section of the top wall.
The imaging device can put the processing target in the vacuum chamber into the view field through the gap of the coil and the transparent section of the top wall. Thus, the processing target can be captured even after the processing target is placed in the internal space and the internal space is closed by the top wall. In other words, the imaging device can capture the processing target during plasma processing. Therefore, the status of the processing target during plasma processing in the vacuum chamber can be observed in real-time by the image captured by the imaging device.
If the wall comprises a plate made of quartz, it is preferable that the transparent section is formed by polishing at least an outer surface of the plate opposing to the inner space at the portion corresponding to the gap between the conductors of the coil in the plane view. The transparency further improves by polishing an inner surface of the plate located at the internal space side at the portion corresponding to the gap between the conductors of the coil in the plane view.
If continuously exposed to plasma, the inner surface of the plate made of quartz is gradually etched. Therefore even if the inner face of the plate made of quartz is polished, a drop in transparency or fogging is generated if the status of being exposed to plasma continues. In order to prevent the drop in transparency or fogging, it is preferable that the transparent section further comprises a window plate made of sapphire installed in an inner surface of the plate located at the internal side at the portion corresponding to the gap between the conductors of the coil in the plane view. Sapphire is a material having high transparency, and has strong resistance to a gas generally used for plasma processing, such as F gas, Cl gas, and Br gas. Therefore, in the window plate made of sapphire, the drop in transparency or fogging is not generated even if the status of being exposed to plasma continues.
An alternative is that the top wall has a ceramic substrate having a window section penetrating in the plate thickness direction at which a window plate made of sapphire is disposed.
For alignment of the imaging device with respect to the gap of the coil and the transparent section of the top wall, it is preferable to provide a moving mechanism for horizontally moving the imaging device above the coil. The moving mechanism may move the imaging device automatically, such as an XY table, or move the imaging device manually.
The top wall of the vacuum chamber of the plasma processing apparatus of the present invention has a transparent section at a position corresponding to the gap between the conductors of the coil in the plane view. The imaging device can put the processing target in the vacuum chamber into filed of view thereof through the gap and transparent section. Therefore the status of the processing target during plasma processing in the vacuum chamber can be observed in real-time using the image captured by the imaging device.
1: substrate.
2: resist mask
7: trench
8: deposit
11: dry etching apparatus
12: vacuum container
13: bottom wall
14: side wall
15: internal space
16: top wall
21: mounting stage
22: lower electrode
23: electric power supply for bias
23
a: high frequency AC power supply
23
b: matching circuit
24: gas inlet
25: gas supplying section
27: exhaust outlet
28: depressurizing section
29: dielectric plate
30: transparent section
31: upper polished section
32: lower polished section
34: window plate
35: casing
35
a: top wall
36: coil
37: conductor
38: electric power supply for coil
38
a: high frequency AC power supply
38
b: matching circuit
39A, 39B, 39C, 39D: gap
40: casing
41, 42: window hole
45: camera
46: XY table
46
a: Y axis slider
46
b: Y axis drive motor
46
c: X axis slider
46
d: X axis drive motor
47: laser light source
49: display section
50: warning light
51: operating/inputting section
54: apparatus control section
55: control section
56: operation condition storage section
57: monitoring section
61: brightness detection section
62: reference brightness storage section
63A: comparison section
64A: judgment section
Embodiments of the present invention will be described with reference to the accompanying drawings.
In the internal space 15, a mounting stage 21 for removeably supporting the substrate 1 is disposed at the bottom wall 13 side. The mounting stage 21 has a lower electrode 22, and the substrate 1 is mounted on the top face of the lower electrode 22. The lower electrode 22 is electrically connected to a power supply for bias 23. The power supply for bias 23 has a high frequency AC power supply 23a and a matching circuit 23b for adjusting the impedance.
A gas inlet 24 provided in the vacuum container 12 is connected to a gas supplying section 25 including an MFC (mass flow controller) for supplying etching gas to the internal space 15 of the vacuum container 12 at a desired flow rate. A depressurizing section 28 having a valve, TMP (turbo-molecular pump), and a vacuum pump (e.g. rotary pump, dry pump) is connected to an exhaust outlet 27 provided in the vacuum container 12.
In the present embodiment, the top wall 16 has a dielectric plate (plate) 29 made of quartz. The dielectric plate 29 partially has a portion having transparency in a plate thickness direction, i.e. a transparent section 30. As most clearly shown in
An antenna or coil 36 for generating plasma is accommodated inside a casing 35 having a function of an electromagnetic shield and installed above the vacuum container 12. As shown in
As most clearly show in
A casing 40 is installed on the casing 35 accommodating the coil 36. The above mentioned high frequency power supply for coil 38 is accommodated inside the casing 40.
As shown in
As shown in
A camera 45 is installed on the X axis slider 46c of the XY stage 46, and can move in a horizontal direction (X and Y axis directions) above the coil 36 by the XY stage 46. The camera 45 has an imaging device such as a CCD, and a filed of view thereof is directed downward in a vertical direction. The camera 45 also has a laser light source 47 for measuring distance. The camera 45 also has various functions, including adjustment functions for magnification, focal point, and sensitivity. The image captured by the camera 45 is output to a monitoring section 57 of later mentioned control section 55. The camera 45 can either be a video camera, which can shoot moving images, or a camera which can shoot still images.
A positional relationship of the transparent section 30 of the dielectric plate 29, coil 36, window hole 41 of the casing 35, window hole 42 of the casing 40, and camera 45 will be described with reference to
As shown in
The dry etching apparatus 11 also has a control section 55 for controlling the operation of the entire device, including the gas supplying section 25, depressurizing section 28, high frequency power supply for coil 38, power supply for bias 23, XY stage 46, camera 45, warning light 50, and display section 49. As shown in
The monitoring section 57 monitors the indication of the generation of black silicon based on the image captured by the camera 45. The monitoring section 57 has a brightness detection section 61, reference brightness storage section 62, comparison section 63A, and judgment section 64A.
The brightness detection section 61 detects etched surface on the surface of the substrate 1 (a bottom of a concave section such as a trench and hole processed by dry etching) based on the image captured by the camera 45. Referring to
The reference brightness storage section 62 stores the reference brightness Bs(t) for judging the indication of the generation of black silicon in the target area 68A.
The comparison section 63A compares the measured average brightness Bdet calculated by the brightness detection section 61 and the reference brightness Bs(t) stored in the reference brightness storage section 62. Specifically, the comparison section 63A compares the measured average brightness Bdet of the target area 68A at a certain time “t” with the reference brightness Bs(t) at this time “t”. More specifically, the comparison section 63A calculates a ratio of the measured average brightness Bdet with respect to the reference brightness Bs(t) at a same predetermined time.
The judgment section 64A judges whether there is the indication of the generation of black silicon based on the comparison result by the comparison section 63A. Specifically, the judgment section 64A judges that there is the indication of the generation of black silicon if the ratio of the measured average brightness Bdet with respect to the reference brightness Bs(t) becomes equal to or less than a predetermined ratio (brightness ratio threshold) BRthsy. In the present embodiment, the brightness ratio threshold BRthsy is set to about 0.8 (80%). The condition for that the judgment section 64A judges that there is the indication of the generation of black silicon are shown in the following expression (1).
The judgment section 64A may judge that there is the indication of the generation of black silicon if the measured average brightness Bdet becomes less than the reference brightness Bs(t) by a predetermined brightness in difference (brightness difference threshold) ΔBthsy or more. The condition when the judgment section 64A judges that there is the indication of the generation of black silicon, in this case, are shown in the following expression (2).
Bs(t)−Bdet≦ΔBthsy (2)
In the following description, it is assumed that the brightness ratio threshold BRthsy in the expression (1) is used.
Now a dry etching method using the dry etching apparatus 11 of the present embodiment will be described. As mentioned above, the substrate 1 is made of silicon material. For process conditions, the etching gas supplied from the gas supplying section 25 is SF6/O2/He gas, and the flow rates of the SF6 gas, O2 gas, and He gas are respectively 60 sccm, 40 sccm, and 1000 sccm (SF6/O2/He=60/40/1000 sccm). The power applied from the high frequency power supply for coil 38 to the coil 36 is 1500 W, and the power applied from the power supply for bias 23 to the lower electrode 22 is 80 W. The pressure in the internal space 15 of the vacuum container 12 is maintained to be 30 Pa.
Referring to
Then, at step S5-4, the camera 45 captures an image of the surface of the substrate 1 (initial image) in a status where plasma 70 is being generated but etching has not yet started. Further, at step S5-5, the brightness detection section 61 calculates the in-plane average brightness of the target area 68A in the initial image, i.e. the initial measured average brightness Bdet. Then, at step S5-6, the reference brightness storage section 62 corrects the reference brightness Bs(t) based on the initial measured average brightness Bdet. For example, if the initial measured average brightness Bdet is darker than a stored value of the reference brightness Bs(t) at the etching time t=0, then the reference brightness storage section 62 shifts the reference brightness Bs(t) to the lower brightness side, as shown by an arrow “A1” in
After the above processes at steps S5-1 to 5-6 has been completed, at step S5-7, the bias voltage starts to be applied from the power supply for bias 23 to the lower electrode 22 to start dry etching of the substrate 1. During the dry etching, portions of the substrate 1 not coated with the resist mask 2 but exposed to the plasma 70 are etched by F radicals as etching species, positive ions (S ions, O ions or the like), and the He component. The O component reacts with the Si atoms of the substrate 1, and forms a side wall protective film of SiO2.
The inner face 29b of the dielectric plate 29 made of quartz is gradually etched if the status of being exposed to the plasma 70 continues. However in the present embodiment, the window plate 34 made of sapphire is fixed to the lower polished section 32 of the inner face 29b of the dielectric plate 29, so as to prevent a drop in transparency or cloudiness of the transparent section 30 of the dielectric plate 29. Sapphire is a material having high transparency, and a strong resistance to the plasma of gas normally used for plasma processing, such as F gas, Cl gas and Br gas. Therefore a window plate 34 made of sapphire does not generate a drop in transparency or cloudiness even if a status of being exposed to the plasma 70 continues, and the transparent section 30 maintains an appropriate transparency. Since the transparent section 30 maintains an appropriate transparency, the camera 45 can capture an image of the substrate 1 in the vacuum 12 at good quality through the transparent section 30.
During etching, the processes at steps S5-8-S5-12 are repeated with a sufficiently short time space. First, at step S5-8, the camera 45 captures an image of the surface (area 67A) of the substrate 1. Then, at step S5-9, the brightness detection section 61 calculates the measured average brightness Bdet of the target area 68A based on the image captured by the camera 45. Then in step S5-10, the comparison section 63A compares the measured average brightness Bdet and the reference brightness Bs(t). Specifically, the comparison section 63A determines a quotient resulting when the measured average brightness Bdet is divided by the reference brightness Bs(t) (Bdet/BS(t)). Further, at step S5-11, the judgment section 64A judges whether there is the indication of the generation of black silicon based on the quotient calculated by the comparison section 63A in step S5-10 and the brightness ratio threshold BRthsy.
If the above Expression (1) is not established in step S5-11, that is, if the judgment section 64A judged that there is no indication of the generation of black silicon, then it is judged whether the etching process reaches an end point at step S5-12. The end point of etching can be judged by receiving the laser irradiated from the laser light source 47 to the substrate 1 by the camera 45 to measure the etching depth. The end point of etching can also be judged by the etching time. If the end point of etching is detected at step S5-12, then the etching process ends at step S5-13. On the other hand, if the end point of etching is not detected at step S5-12, the processes at steps S5-8 to S5-11 are repeated.
If expression (1) is established in the above step S5-11, that is, if the judgment section 64A judges that there is the indication of the generation of black silicon, then the apparatus control section 54 changes the process conditions into conditions whereby priority is given to the prevention of the generation of black silicon rather than to the selection ratio at step S5-4. Also if it is judged that there is the indication of the generation of black silicon, then the warning light 50 is turned ON or a predetermined message is displayed on the display section 49 at step S5-15, so as to notify the operator that there is an indication of the generation of black silicon.
When the measured average brightness Bdet changes, as shown in
The change of the process conditions when it is judged that there is an indication of the generation of black silicon (step S5-14) will be described.
Firstly, the generation of black silicon can be suppressed by increasing the bias voltage to be applied from the power supply for bias 23 to the lower electrode 22. In the present embodiment, the initial value of the power of the bias voltage is 50 W, and the generation of black silicon can be suppressed by increasing this to 80 W, for example. If the bias voltage is increased, then the speed of ions which collide with the base of the trenches 7 increases. In other words, the energy of ion collision increases by increasing the bias voltage. As a result, the SiO2 deposit 4 can be sputtered from the base of the trenches 7 by a sputtering method. If the bias voltage is too high, on the other hand, the resist mask 2 tends to be damaged by ions, and the selective ratio drops. Therefore if no indication of the generation of black silicon is detected, the bias voltage is set low, assigning priority to the selection ratio (50 W in the case of the present embodiment), and the bias voltage is increased only when an indication of the generation of black silicon is detected (80 W in the case of the present embodiment), thereby both the appropriate selection ratio and the prevention of the generation of black silicon can be implemented.
Secondly, the generation of black silicon can be suppressed by decreasing the pressure in the internal space 15 of the vacuum container 12. The initial value of the pressure is 30 Pa in the case of the present embodiment, and the generation of black silicon can be suppressed by decreasing the pressure down to 25 Pa, for example. If the pressure inside the vacuum container 12 is decreased, the time of the etching gas remaining in the vacuum container 12 is decreased, so the etching gas is exhausted out of the vacuum container 12 before excessive SiO2 deposits 4 are formed on the base of the trenches 7. If the pressure inside the vacuum container 12 is low, on the other hand, the speed of ions increases, so the resist mask 2 tends to be damaged, and the selection ratio drops. Therefore if no indication of the generation of black silicon is detected, the pressure is set high, assigning priority to the selection ratio (30 Pa in the case of the present embodiment), and the pressure is set low only when an indication of the generation of black silicon is detected (25 Pa in the case of the present embodiment), thereby both the appropriate selective ratio and the prevention of the generation of black silicon can be implemented.
Thirdly, the generation of black silicon can be suppressed by decreasing the ratio of the O2 gas in the etching gas. In the present embodiment, the initial value of the supply flow rate of O2 gas is 40 sccm, and the generation of black silicon can be suppressed by decreasing the supply flow rate to 20 sccm, for example. Black silicon is caused by SiO2 deposits 4, so if the supply flow rate of the O2 gas to the vacuum container 12 is decreased so as to decrease the O component in the vacuum container 12, the generation of SiO2 deposits 4 is suppressed. On the other hand, if the supply flow rate of O2 gas to the vacuum container 12 is decreased, the formation of the side wall protective layer made of SiO2 is also suppressed, so maintaining the side walls of the trenches in a vertical shape becomes difficult. Therefore if no indication of the generation of black silicon is detected, the supply flow rate of O2 gas is set high (40 sccm in the case of the present embodiment), assigning priority to the formation of the side wall protective layer, and the supply flow rate of O2 gas is decreased only when an indication of the generation of black silicon is detected (20 sccm in the case of the present embodiment), thereby both the profiles of the trenches 7 and the prevention of the generation of black silicon can be implemented.
By changing the process conditions as above, the generation of deposits 4 in the base of the trenches 7 is suppressed, and the generation of black silicon is prevented. One of increasing the bias voltage, decreasing the pressure of the vacuum container 12 and decreasing the supply flow rate of the O2 gas can be executed, or two or more can be executed in combination.
If the change of the process conditions in step S5-14 is not executed, the amount of deposits 4 in the base of the trenches 7 increases, so the measured average brightness Bdet drops continuously even after the etching time t1, as shown by the solid line in
The top wall 16 in the first alternative shown in
The top wall 16 in the second alternative shown in
The top wall 16 of the third alternative shown in
The top wall 16 of the fourth alternative shown in
The present invention was described using an inductive coupled dry etching processing device, but the present invention can also be applied to other plasma processing apparatuses, such as dry etching apparatuses, sputtering apparatuses and plasma CVDs.
The present invention was completely described with reference to the accompanying drawings, but various changes and modifications are possible by experts skilled in the art. Such changes and modifications shall be included in the present invention as long as they do not depart from the spirit and scope of the present invention.
Number | Date | Country | Kind |
---|---|---|---|
2004-380279 | Dec 2004 | JP | national |
Filing Document | Filing Date | Country | Kind | 371c Date |
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PCT/JP05/22353 | 12/6/2005 | WO | 00 | 8/29/2007 |