WO2000059018A1

WO2000059018A1 - Plasma processing system

Info

Publication number: WO2000059018A1
Application number: PCT/JP2000/002003
Authority: WO
Inventors: Kazuhiro Kubota; Atsushi Kawabata; Shigeki Tozawa; Hiraku Ishikawa; Haruhito Nishibe
Original assignee: Tokyo Electron Limited; Semiconductor Leading Edge Technologies, Inc.
Priority date: 1999-03-30
Filing date: 2000-03-30
Publication date: 2000-10-05
Also published as: JP2000286235A; KR20010052447A; JP4450883B2; KR100408084B1

Abstract

A plasma processing system comprises a chamber capable of maintaining a vacuum inside, a discharge unit for evacuating the chamber, a gas supply unit for supplying process gas to the chamber, a lower electrode arranged in the chamber and adapted to support an object to be processed, and an upper electrode arranged opposite to the lower electrode. Outside the chamber is provided a high-frequency power supply, from which a power feeder extends to the lower electrode. Impedance adjustment means adjusts the impedance of a return current path that extends from the plasma of the process gas produced between the upper electrode and the lower electrode energized through the feeder by the high-frequency power supply back to the high-frequency power supply through the inner wall of the chamber.

Description

Description Plasma processing equipment Technical field

The present invention relates to a plasma processing apparatus for performing a plasma process such as an etching process or a film forming process on a processing target such as a semiconductor wafer. Background technology

In the manufacture of semiconductor devices, plasma processing such as dry etching and plasma CVD (Chemical Vapor Deposition) is frequently used.

As an apparatus for performing such plasma processing, for example, an apparatus shown in FIG. 7 is used. In FIG. 7, reference numeral 1 denotes a grounded chamber. A lower electrode 2 for horizontally supporting a semiconductor wafer W to be processed is provided in the chamber 1. The lower electrode 2 is placed on a metal support 4 via an insulating member 3. The lower electrode 2 and the support 4 can be moved up and down by an elevating mechanism (not shown). Outside the support 4, a baffle plate 5 for gas diffusion is provided. The lower central part of the support 4 is covered with bellows 6. This bellows 6 separates the vacuum part from the atmospheric part. A bellows cover 7 composed of a lower member 7a and an upper member 7b is provided outside the bellows 6. A high-frequency power supply 11 provided below the chamber 11 is connected to the lower electrode 2 via a matching box 10 and a power supply rod 8. Around the power supply rod 8, a metal grounding pipe 9 extending downward from the support 4 is provided. A slide contact 26 is provided between the ground pipe 9 and the chamber 11 so as to establish conduction between them. In this case, the slide contact 26 has a large number of resilient contacts on its inner periphery, and even if the ground pipe 9 slides in the slide contact 26, the ground pipe 9 and the slide contact 26, that is, a stable electrical connection with the chamber 11 can be obtained. Further, a coolant passage 13 is formed in the lower electrode 2, and the coolant flows through the coolant supply pipe 14. It's swelling.

A shower head 16 is provided on the top wall of the chamber 11 so as to face the lower electrode 2. The processing gas introduced from the gas introduction unit 18 is discharged toward the semiconductor wafer W from a number of gas discharge holes 17 provided on the lower surface.

Reference numeral 22 denotes a transfer port for loading and unloading the semiconductor wafer W that can be opened and closed by the gate valve 23. Reference numeral 24 denotes an exhaust port for evacuating the inside of the chamber 11.

In such an apparatus, first, the semiconductor wafer W is transferred from the transfer port 22 to the lower electrode 2 located at the transfer position. Next, the lower electrode 2 is raised by the lifting mechanism, and the semiconductor wafer W is arranged at the processing position. The semiconductor wafer W is suction-held on the lower electrode 2 by an electrostatic chuck (not shown).

After that, the inside of the chamber 11 is maintained at a predetermined degree of vacuum through the exhaust port 24, and a predetermined processing gas is introduced into the chamber 11 from the shower head 16. Further, a high frequency is applied from the high frequency power supply 11 to the lower electrode 2 via the matching box 10 and the power supply rod 8 to generate plasma, and the semiconductor wafer W is subjected to predetermined plasma processing.

By the way, due to the skin effect that the high-frequency current is localized only near the surface of the conductor, the return current of the high-frequency current applied to the lower electrode 2 from the high-frequency power supply 11 changes the inner wall of the chamber 11 according to the arrow in the figure. Through to the bottom wall. Here, the bottom wall of the chamber 11 and the bellows cover 7 and the bellows 6 are screwed and electrically connected to each other. Therefore, the return current flows from the bottom wall of the chamber 1 to the surface of the lower member 7 a of the bellows force bar 7, the outer surface of the bellows 6, the surface of the upper member 7 b of the bellows cover 7, the surface of the support 4, and the ground pipe. Return to the high frequency power supply 11 through the inside of 9. Since the contact impedance between the slide contact 26 and the ground pipe 9 is higher than the impedance of the current path near the bellows 6, the current flowing through the slide contact 26 is small.

Therefore, most of the return current flows through the bellows 6. As a result, a large potential difference is generated at both ends of the bellows 6, for example, abnormal discharge occurs between the upper member 7 b and the lower member 7 a of the bellows cover 7, or around the support 4, and plasma leakage occurs. Occurs. For this reason, the plasma density on the semiconductor wafer W may decrease. In addition, the occurrence of such abnormal discharge adversely affects the processing. However, such abnormal discharge cannot be detected during plasma processing.

The present invention has been made in view of such circumstances, and has as its object to provide a plasma processing apparatus in which abnormal discharge due to a high-frequency current return current is unlikely to occur. It is another object of the present invention to provide a plasma processing apparatus capable of detecting an abnormal state of plasma such as abnormal discharge during plasma processing. Summary of the invention

In order to solve the above problems, a plasma processing apparatus of the present invention

A chamber whose inside can be maintained in a vacuum state,

An exhaust mechanism that evacuates the chamber.

A gas introduction mechanism for introducing a processing gas into the chamber;

A lower electrode disposed in the chamber and supporting the object to be processed;

An upper electrode provided to face the lower electrode,

A high-frequency power supply provided outside the chamber,

A power supply member extending from the high-frequency power supply to the lower electrode,

A recurrent current circuit which returns from the plasma of the processing gas formed between the upper electrode and the lower electrode by the high frequency power applied to the lower electrode via the power supply member to the high frequency power through at least the inner wall of the chamber. Impedance adjustment means for adjusting the impedance;

It is characterized by having.

In this way, by providing the impedance adjusting means for adjusting the impedance of the return current circuit returning from the plasma to the high frequency power supply through at least the inner wall of the chamber and setting the impedance of the return current circuit to the optimum value, Abnormal discharge and plasma leakage can be reduced.

In this case, a capacitor having a variable capacity can be provided as the impedance adjusting means. In this case, the impedance can be easily adjusted to the optimum value by adjusting the capacitance of the capacitor. In this way, the capacitor By controlling the impedance by adjusting the capacitance, it is possible to adjust the error between the return current circuits (eg, manufacturing error). Even if the impedance changes over time due to long-term use of the device, it can be adjusted to an appropriate value by adjusting the capacitor capacity.

The plasma apparatus further includes a detector for detecting plasma emission in an area inside the chamber where plasma emission is not substantially observed when the plasma processing apparatus is in a normal state; and a detector for the capacitor according to an output of the detector. It is preferable to add control means for adjusting the capacity. In this case, when the detector detects the plasma emission due to the abnormal discharge, the capacitor can be adjusted to adjust the capacitance and eliminate the abnormal discharge, and the impedance of the return current circuit can be adjusted in real time so that abnormal discharge does not occur. Value can be controlled.

Preferably, the apparatus further comprises a lifting mechanism for raising and lowering the lower electrode in the chamber.

In this case, preferably, the elevating mechanism has a driving unit extending below the lower electrode, and is provided between the lower surface of the lower electrode and a bottom surface in the chamber so as to be extendable and contractible. A conductive bellows for isolating the driving unit from the inside of the chamber.

In this case, preferably, the power supply member is a bar member that forms a part of the drive unit. Further, preferably, a grounding pipe forming a part of the driving unit is provided around the power supply member.

In this case, it is preferable that a slide contact is provided between the bottom wall of the chamber and the grounding pipe to realize sliding between the two and stable electrical conduction.

In this case, the impedance adjusting means shunts the return current returning to the high-frequency power supply at least through the inner wall of the chamber to the bellows side and the ground pipe side, and adjusts the impedance of the return current circuits. It is preferable that

In this way, the impedance adjusting means divides the return current returning from the plasma to the high-frequency power source from the inner wall of the chamber to the bellows and the ground pipe, By lowering the impedance of the return current circuit, the potential difference between both ends of the bellows and the potential difference between the inner wall of the chamber and the high-frequency ground can be reduced, and as a result, around the lower electrode Abnormal discharge and plasma leakage can be reduced.

As the impedance adjusting means, a means having a capacitor of a predetermined capacity provided between the bottom wall of the chamber and the bellows is preferable. By using the condenser in this manner, the current flowing to the bellows side can be adjusted, and the return current returning from the plasma to the high frequency power supply can be effectively transmitted from the inner wall of the chamber to the bellows and the ground pipe. It becomes possible to diverge.

It is preferable that an insulating member is interposed between the bottom wall of the chamber and the bellows. As the insulating member, polyetheretherketone or polyimide is preferable. Since these materials have high load-bearing capacity and low dielectric constant, they can have a thickness of, for example, about 5 mm, which is sufficiently lower than the capacity of a single capacitor. As a result, the capacitance can be adjusted with only one capacitor.

Further, by making the capacity of the capacitor one variable, the capacity of the capacitor one can be easily adjusted to an optimum value. Then, as in the case described above, by adjusting the capacitance of the capacitor and controlling the impedance, it becomes possible to adjust an error between devices (such as a manufacturing error) of the return current circuit. Even if the impedance changes over time due to long-term use of the device, it can be adjusted to an appropriate value by adjusting the capacitance of one capacitor.

Further, the plasma processing apparatus of the present invention,

A chamber that can maintain a vacuum inside,

An exhaust mechanism for evacuating the chamber,

A gas introduction mechanism for introducing a processing gas into the chamber;

Plasma generating means for converting a processing gas into plasma in order to perform plasma processing on the object to be processed;

And a detector for detecting plasma emission in an area inside the chamber such that plasma emission is not substantially observed when the plasma processing apparatus is in a normal state. As described above, by providing the detector for detecting the plasma light emission in the region inside the chamber where the plasma light emission is not substantially observed when the plasma processing apparatus is in the normal state, the detector can prevent the abnormal discharge in the chamber one. At the time when the accompanying plasma emission is detected, it is possible to take appropriate measures to eliminate the abnormal discharge, thereby reducing the adverse effect on the processing of the object. BRIEF DESCRIPTION OF THE FIGURES

FIG. 1 is a sectional view showing a plasma processing apparatus according to one embodiment of the present invention. FIG. 2 is a cross-sectional view showing an impedance adjustment mechanism in the device of FIG. FIG. 3 is a diagram showing a condenser-mounting portion on the bottom wall of the chamber in the apparatus of FIG.

FIG. 4 is a diagram showing the relationship between the thickness of the insulating member used in the impedance adjusting mechanism of FIG. 1 and the capacitance.

FIG. 5 is a circuit diagram showing an equivalent circuit of the plasma processing apparatus of the present invention.

FIG. 6 is a cross-sectional view showing a main part of a plasma processing apparatus according to another embodiment of the present invention.

FIG. 7 is a cross-sectional view showing a conventional plasma processing apparatus. BEST MODE FOR CARRYING OUT THE INVENTION

Hereinafter, embodiments of the present invention will be described with reference to the accompanying drawings.

FIG. 1 is a sectional view showing a plasma processing apparatus according to one embodiment of the present invention. In the figure, reference numeral 1 denotes a conductive chamber made of, for example, aluminum whose surface is anodized. This chamber 11 is grounded. A lower electrode 2 for horizontally supporting a semiconductor wafer W as an object to be processed is provided in the chamber 11. The lower electrode 2 is made of a conductor such as aluminum, and is placed on a support 4 made of a conductor such as aluminum via an insulating member 3. A disk-shaped gas diffusion baffle plate 5 having a large number of gas passage holes is provided on the outer peripheral side of the support base 4. The baffle plate 5 is made of a conductor such as aluminum, and is screwed to the support 4 to be electrically connected thereto. The lower electrode 2 has a semiconductor An electrostatic chuck (not shown) for holding the wafer W by suction is provided.

The lower central portion of the support 4 is covered with a bellows 6 made of, for example, stainless steel. This bellows 6 separates the vacuum part from the atmospheric part. The upper end and the lower end of the bellows 6 are screwed to the lower surface of the support 4 and the upper surface of the bottom wall of the chamber 11, respectively. A bellows cover 7 is provided outside the bellows 6. The bellows cover 7 is separated into a lower member 7a and an upper member 7b so as to be able to cope with expansion and contraction of the bellows 6.

A high-frequency power supply 11 provided below the chamber 11 is connected to the lower electrode 2 via a matching box 10 and a power supply rod 8. Around the power supply rod 8, a metal ground pipe 9 extending downward from the support 4 is provided.

The lower electrode 2 is formed with a refrigerant flow path 13, through which the refrigerant flows through a refrigerant supply pipe 14. Although not shown, the lower electrode 2 is provided with lift pins that can be protruded and retracted in order to transfer the semiconductor wafer W.

On the top wall 1 a of the chamber 11, a shower head 16 functioning as an upper electrode facing the lower electrode 2 is provided. On the lower surface of the shower head 16, a large number of discharge holes 17 are formed. A gas inlet 18 is provided above the shower head 16. A processing gas supply source 20 for supplying a predetermined processing gas into the chamber 11 through the shower head 16 is connected to the gas inlet 18. Then, a processing gas is supplied into the chamber 11, and a high-frequency power is applied to the lower electrode 2, whereby plasma is formed between the lower electrode 2 and the shower bed 16, and a predetermined amount is formed on the semiconductor wafer W. The plasma processing is performed. A transfer port 22 for loading and unloading the semiconductor wafer W is provided on the side wall 1 b of the chamber 1 so as to be opened and closed by a gate valve 23. When loading and unloading the semiconductor wafer W, the lower electrode 2 is moved to a position corresponding to the transfer boat 22. At this time, the lower electrode 2 is moved integrally with the insulating member 3 and the support base 4 by a lifting mechanism (not shown). -An exhaust port 24 is provided near the bottom of the side wall 1b of the chamber 11. An exhaust device 25 is connected to the exhaust port 24 via a pipe. Soshi By operating the exhaust device 25, the inside of the chamber 11 can be evacuated to a predetermined degree of vacuum.

A slide contact 26 is provided between the ground pipe 9 and the bottom wall 1c of the chamber 11 so as to establish electrical continuity therebetween. In this case, the slide connector 26 has a large number of resilient contacts on its inner periphery, and even if the ground pipe 9 slides in the slide contact 26 (the lower part). Even if the electrode 2 moves up and down), stable electrical continuity between the grounding pipe 9 and the slide contact 26, that is, the chamber 11 can be obtained.

At the connection between the bellows 6 and the bottom wall 1 c of the chamber 11, the plasma passes through the chamber 1, passes through the support 4 and the inside of the grounding pipe 9, and returns to the high-frequency power supply 1 1. An impedance adjustment mechanism 30 for adjusting the impedance of the circuit is provided.

As shown in FIG. 2, the impedance adjusting mechanism 30 includes an insulating member 31 interposed between the bottom wall 1 c of the chamber 11 and the support 6 a of the bellows 6, and a bottom of the chamber 11. A condenser 32 of a predetermined capacity connected to the wall 1 c and the support 6 a of the bellows 6. The support base 6a made of stainless steel is screwed by screws 33 with an insulating member 31 interposed between the support base 6a and the bottom wall 1c of the chamber 11.

The insulating member 31 is used to insulate the bottom wall 1c of the chamber 11 from the support 6a of the bellows 6, and has a large withstand load and a small dielectric constant. As such a material, polyetheretherketone (PEEK) or polyimide is preferable.

The capacitor 132 adjusts the voltage applied to the bellows 6 to reduce the impedance of the return current circuit. For example, the capacitor 32 can adjust the voltage applied to the bellows 6 to a voltage value at which abnormal discharge does not occur around the support 4.

As a result of such adjustment, the return current also flows to the ground tube 9 via the slide contact 26. That is, the condenser 32 distributes the return current of the bottom wall 1 c of the chamber 1 to the bellows 6 side and the slide contact 26 side. It has the function of lowering the impedance of the entire return current circuit ₍ the required capacity of the capacitor 32 is different depending on the setting of the device, for example, about 120 OO pF. To obtain the required capacity For this purpose, a plurality of capacitors 1 may be used, and for this purpose, a plurality of capacitor mounting portions 35 may be provided on the bottom wall 1c of the chamber 11 as shown in FIG. In order to obtain a capacity of 0 PF, two capacitors of 5000 pF and two capacitors of l OOO pF may be attached to the four attachment portions 35.

The bottom wall 1c of the chamber 11 and the support 6a of the bellows 6 are both conductors. Therefore, a kind of capacitor is formed by interposing the insulating member 31 between them. However, as described above, by forming the insulating member 31 relatively thick using a resin having a low dielectric constant, the capacitance of the insulating member 31 as a capacitor can be ignored. That is, the capacity can be adjusted only by the attached capacitor 132.

For example, when PEEEK is used for the insulating member 31, the relationship between the thickness and the capacitance is as shown in FIG. As shown in FIG. 4, for example, when the thickness is set to 5 mm, the capacitance is about 400 pF. This value is negligible compared to the capacitance of the capacitor 132 of 1200 pF.

Next, the operation of the plasma processing apparatus configured as described above will be described.

First, the lower electrode 2 is arranged at the transfer position by a lifting mechanism (not shown). Next, the gate valve 23 is opened, and the semiconductor wafer W is carried into the chamber 11 via the transfer port 22 by a transfer arm or the like (not shown) and placed on the lower electrode 2. The semiconductor wafer W is sucked and held on the lower electrode 2 by an electrostatic chuck (not shown). Thereafter, the lower electrode 2 is raised by the elevating mechanism, and is positioned so that the gap between the lower electrode 2 and the shower head 16 becomes a predetermined distance. In this state, the coolant flows through the coolant channel 13 and the lower electrode 2 is controlled to a predetermined temperature. On the other hand, the interior of the chamber 11 is evacuated by the exhaust device 25 through the exhaust port 24 to be in a high vacuum state.

Next, a predetermined processing gas is supplied from the processing gas supply source 20 through the processing gas inlet 18 and the gas discharge hole 17 of the shower head 16 forming the top wall of the conductive container 15, The liquid is discharged toward the semiconductor wafer W, and the inside of the chamber 11 is set to several tens of mTorr. At the same time, high-frequency power of a predetermined frequency and voltage is applied to the lower electrode 2 from the high-frequency power supply 11 via the matching box 10 and the power supply rod 8. As a result, plasma of the processing gas is generated in the space between the lower electrode 2 and the shower head 16. Thus, a predetermined plasma process is performed on the semiconductor wafer W.

During this plasma processing, the return current returning from the plasma to the high-frequency power supply 11 is diverted to the bellows 6 side and the slide contact 26 side.

This will be described with reference to an equivalent circuit shown in FIG. The high-frequency power from the high-frequency power supply (RF power supply) 11 is supplied to the lower electrode 2 via the matching box 10 and the power supply rod 8, and forms plasma. The return current from the plasma reaches the bellows 6 via the top wall la, the side wall 1 b and the bottom wall 1 c of the chamber 1. At this time, by adjusting the capacitance C _h between the capacitor one 3 2 forces the bottom wall 1 c preparative bellows 6 of Inpi one dance adjusting mechanism 3 0, the current I p of the bottom wall lc, the bellows side of the current lb And the current on the slide contact side. The return current _Ib on the bellows side returns to the high-frequency power supply 11 through the outside of the bellows 6, the surface of the support 4, and the inside of the grounding pipe 9. The return current I c on the slide contact side returns to the high-frequency power supply 11 through the outside of the grounding pipe 9, the surface of the support 4, and the inside of the grounding pipe 9.

When the bellows is connected to the bottom wall of the chamber as in the past, only a small amount of current flows through the slide contact because the impedance of the slide contact is large, and most of the current flows to the bellows side. Flows. Therefore, abnormal discharge occurs when both the voltage of the bellows and the voltage Vw of the chamber wall increase.

On the other hand, when the bellows and the bottom wall of the chamber are insulated, no current flows through the bellows, and I,> = Ic. In this case, since the contact impedance between the slide contact 26 and the ground pipe 9 is high, the abnormal discharge also occurs when the voltage Vw on the wall of the chamber increases. Furthermore, by resonating the L b and C _t) and, although may be a voltage V _w is 0 the chamber one wall, the voltage V _b of the base in this case rose becomes high.

On the other hand, by appropriately adjusting the value of as described above, the current IP Is divided into a current I on the bellows side and a current _Ie on the slide contact side, thereby reducing the impedance of the entire return current circuit.

Both V,, and v _w can be made lower than before. Therefore, abnormal discharge does not occur in the portion between the lower member 7a and the upper member 7b of the bellows cover 7 and in the peripheral portion of the support 4, so that plasma leakage can be prevented, and the semiconductor can be prevented from leaking. The plasma density on the wafer W is unlikely to decrease. In addition, the reaction product does not accumulate on the periphery of the support base 4 and the lower portion of the side wall 1b of the chamber, and the generation of particles due to the separation can be prevented.

Actually, in a plasma processing apparatus for a wafer of 300 mm, the gap between the lower electrode 2 and the shear head 16 (gap between the upper and lower electrodes) was set to 40 mm, and the inside of the chamber 11 was set. The processing gas is introduced into the chamber, the internal pressure of the chamber is set to 5 OmTorr, and a high-frequency power supply of 11 W to 43.5 W is supplied from the high-frequency power supply of 11 to 3.6 W. Plasma was generated by variously changing the capacitance of a plurality of 30 capacitors 13 and the plasma state was visually observed. As a result, it was confirmed that no abnormal discharge or plasma leakage occurred when the total capacity of the capacitor 132 was set to 1200 pF.

This is theoretically presumed to be the result of the reduced impedance of the high-frequency power return current circuit, as described above. However, it is difficult to actually measure the voltage value of each part of the bellows-chamber, and when the value of the capacitor 32 is 1200 pF, the impedance of the restart current circuit becomes minimum. It is not always possible to determine that it is.

Also, not only the impedance of the return current circuit, but also the ratio of the amount of current flowing through the bellows to the amount of current flowing through the slide contact, and the relationship between the phase of the current flowing through the bellows and the phase of the current flowing through the slide contact, It may have a subtle effect on the plasma state.

The value of the present invention is not to minimize the impedance of the return current circuit, but to visually check the light emission state of the plasma, and to set the capacitor 32 so that there is no abnormal discharge or plasma leakage. The value can be set to the optimum value, that is, the impedance of the return current circuit of high frequency power can be adjusted. The point is that.

In the above embodiment, the example in which the capacity of the capacitor is fixed has been described, but it is also possible to use a capacitor having a variable capacity (a variable capacitor). In this case, the impedance of the return current circuit can be more easily controlled to the optimum value. By adjusting the capacitance of one capacitor and controlling the impedance in this way, an error between devices (such as a manufacturing error) of the return current circuit can be adjusted. Even if the impedance changes over time due to long-term use of the device, the impedance can be adjusted to an appropriate value by adjusting the capacitor and capacitance. A plasma processing apparatus using such a variable capacitor will be described with reference to FIG. FIG. 6 is a cross-sectional view showing a main part of a plasma processing apparatus capable of controlling the impedance of a return current circuit using a variable capacitor. 6, the same components as those in FIGS. 1 and 2 are denoted by the same reference numerals, and description thereof is omitted. A variable capacitor is provided in place of the capacitor 32 in FIG. One terminal of the variable capacitor 40 is connected to the support 6 a of the bellows 6, and the other terminal is connected to the bottom wall 1 c of the chamber 11. The shaft 40a of the variable capacitor 140 is connected to a drive mechanism 44 composed of, for example, a stepping motor. Then, for example, the capacity of the variable capacitor 40 can be changed by rotating the stepping motor.

A plasma detection window 41 made of, for example, quartz is provided below the side wall 1 b of the chamber 11. A photodetector 42 for detecting light from plasma passing through the detection window 41 is provided near the outside of the plasma detection window 41. Since the detection window 41 is provided below the side wall 1 b of the chamber 11, the photodetector 42 does not generate plasma emission if the plasma processing apparatus is in a normal state or does not generate plasma emission. The system detects plasma emission in an area inside the chamber where only weak emission occurs. In such a region, strong plasma emission is generated only when an abnormal discharge occurs substantially. Therefore, the detector 42 detects the plasma emission only when an abnormal discharge occurs substantially. The detector 42 is connected to a control device 43, which controls the drive mechanism 44 of the variable condenser 40. In the device configured as described above, when the plasma device is operating normally, the detector 42 does not substantially detect the emission of plasma, but when an abnormal discharge occurs, the plasma associated therewith is not detected. Is detected. Then, a signal from the photodetector 42 is sent to the control device 43, and a control signal is output from the control device 43 to the drive mechanism 44 in accordance with the degree of abnormal discharge, that is, the intensity of plasma emission. The capacity of the variable capacitor 140 is adjusted. The control device 43 may monitor the output of the photodetector 42 and output a signal to an alarm device (not shown) to generate an alarm when abnormal discharge is detected.

As described above, when the photodetector 42 detects the plasma emission accompanying the abnormal discharge, the control signal from the controller 43 to the drive mechanism 44 adjusts the capacity of the capacitor 140, so that Abnormal discharge can be eliminated. That is, the impedance of the return current circuit can be controlled in real time to an appropriate value that does not cause abnormal discharge.

In the above embodiment, the case where a capacitor is used as the impedance adjustment means has been described.However, if a state without abnormal discharge or plasma leakage can be realized, a coil is used instead of the capacitor. Is also good. Further, the device configuration to which the present invention is applied is not limited to the above-described embodiment, but may be applied to any device of a type in which high frequency is applied to the lower electrode and the lower electrode is movable.

Furthermore, the present invention is applicable to various processes such as etching and CVD film formation, regardless of the processing form, as long as a plasma is generated by applying a high frequency and the object to be processed is processed by the plasma. be able to. Furthermore, the object to be processed is not limited to a semiconductor wafer, but may be another object such as a glass substrate of a liquid crystal display device. As described above, according to the present invention, the impedance adjusting means for adjusting the impedance of the return current circuit returning from the plasma to the high-frequency power supply through at least the inner wall of the chamber and the bellows is provided, and the impedance of the return current circuit is optimized. The potential difference between the bellows ends and the potential difference between the chamber and the inner wall and the high-frequency ground can be reduced by setting the value of the bellows. As a result, abnormal discharge around the lower electrode and plasma Leakage can be reduced. More specifically, the impedance adjusting means diverts the return current returning from the plasma to the high-frequency power source from the inner wall of the chamber to the bellows and the grounding pipe, thereby lowering the impedance of the return current circuit. Therefore, the potential difference between both ends of the bellows and the potential difference between the inner wall of the chamber and the high-frequency ground portion can be reduced.As a result, abnormal discharge around the lower electrode and plasma leakage can be reduced. it can. Such impedance adjustment can be easily realized by providing a capacitor between the bottom wall of the chamber and the bellows and adjusting the capacitance.

As described above, abnormal discharge around the lower electrode and plasma leakage are reduced, so that the plasma density on the object to be processed can be increased.

Further, by providing a capacitor having a variable capacitance and adjusting the capacitance of the capacitor, the impedance can be easily adjusted to an optimum value. By adjusting the capacitance of the capacitor and controlling the impedance in this manner, it is possible to adjust the error between the return current circuits (such as a manufacturing error). Even if the impedance changes over time due to long-term use of the device, it can be adjusted to an appropriate value by adjusting the capacitance of the capacitor.

A detector for detecting plasma emission in a region of the chamber where plasma emission is not substantially observed when the plasma processing apparatus is in a normal state; and a capacitance of the capacitor according to an output of the detector. By adding control means to adjust the capacitance, it is possible to eliminate the abnormal discharge by adjusting the capacitance of the capacitor when the detector detects the plasma emission accompanying the abnormal discharge, and to reduce the impedance of the return current circuit. Can be controlled in real time to an appropriate value that does not cause abnormal discharge.

Further, by providing a detector for detecting plasma emission in an area inside the chamber where plasma emission is not substantially observed when the plasma processing apparatus is in a normal state, plasma generated by an abnormal discharge in the chamber by the detector is provided. When light emission is detected, it is possible to take appropriate measures to eliminate abnormal discharge, and to reduce the adverse effect on the processing of the object.

Claims

The scope of the claims

1. A chamber whose interior can be maintained in a vacuum state,

An exhaust mechanism for evacuating the inside of the chamber,

A gas introduction mechanism for introducing a processing gas into the chamber;

An upper electrode provided to face the lower electrode,

A high-frequency power supply provided outside the chamber,

The impedance of the return current circuit that returns from the plasma of the processing gas formed between the upper electrode and the lower electrode to the high-frequency power supply through at least one inner wall of the chamber by the high-frequency power supply applied to the lower electrode via the power supply member Means for adjusting impedance

A plasma processing apparatus comprising:

2. Elevating mechanism for raising and lowering the lower electrode in the chamber

The plasma processing apparatus according to claim 1, further comprising:

3. The elevating mechanism has a driving unit extending below the lower electrode, and is provided so as to be expandable and contractible between a lower surface of the lower electrode and a bottom surface in the chamber. 3. The plasma processing apparatus according to claim 2, further comprising: a conductive bellows isolated from the inside of the chamber.

4. The power supply member is a rod member forming a part of the drive unit.

4. The plasma processing apparatus according to claim 3, wherein:

5. A ground pipe forming a part of the drive unit is provided around the power supply member.

5. The plasma processing apparatus according to claim 4, wherein:

6. Between the bottom wall of the chamber and the ground pipe, there is provided a slide contact that realizes sliding between the two and stable electrical conduction.

6. The plasma processing apparatus according to claim 5, wherein:

7. Impedance adjustment means should be at least high frequency 7. The method according to claim 5, wherein the return current returning to the power supply is divided into the bellows side and the ground pipe side, and the impedance of the return current circuit is adjusted. The plasma processing apparatus as described in the above.

8. The impedance adjusting means includes a capacitor provided between a bottom wall of the chamber and the bellows.

The plasma processing apparatus according to any one of claims 3 to 7, wherein:

9. The capacitor has a variable capacity

9. The plasma processing apparatus according to claim 8, wherein:

10. A detector for detecting plasma emission in an area in the chamber where plasma emission is not substantially observed when the plasma processing apparatus is in a normal state;

10. The plasma processing apparatus according to claim 9, further comprising: control means for adjusting a capacity of the capacitor according to an output of the detector.

11. The impedance adjusting means has an insulating member interposed between the bottom wall of the chamber and the vent.

The plasma processing apparatus according to any one of claims 3 to 10, wherein:

12. The insulating member is made of polyetheretherketone or polyimide

The plasma processing apparatus according to claim 11, wherein:

1 3. The impedance adjustment means is a capacitor whose capacity is variable.

The plasma processing apparatus according to any one of claims 1 to 7, wherein:

14. A detector for detecting plasma emission in an area in the chamber where plasma emission is not substantially observed when the plasma processing apparatus is in a normal state;

14. The plasma processing apparatus according to claim 13, further comprising: control means for adjusting a capacity of the capacitor according to an output of the detector.

1 5. A chamber whose inside can be maintained in a vacuum state,

An exhaust mechanism for evacuating the inside of the chamber, A gas introduction mechanism for introducing a processing gas into the chamber;

A plasma processing apparatus, comprising: a detector for detecting plasma emission in an inner region of the chamber such that plasma emission is not substantially observed when the plasma processing apparatus is in a normal state.