JP2001007086A - Plasma treatment apparatus - Google Patents

Abstract

PROBLEM TO BE SOLVED: To generate a stable plasma. SOLUTION: An etching apparatus 100 has a lower and upper electrodes 106, 108 arranged opposed in a processing chamber 102. A high frequency power at 60 MHz is applied to the upper electrode 108 via a first matching unit 122 and a first band cut filter 124, and a high frequency power at 13.56 MHz is applied to the lower electrode 106 via a second matching unit 132 and a second band cut filter 134. Harmonics-removing filters 130, 128, 138 for removing harmonic components from a plasma are inserted respectively in a seconds matching unit 132 and the second band cut filter 134. The first and second band cut filters 124, 134 form virtual ground circuits for the high frequency powers at 13.56 MHz and 60 MHz.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

[0001] The present invention relates to a plasma processing apparatus.

[0002]

2. Description of the Related Art Conventionally, in a process of etching a polysilicon film, a high-frequency power having the same frequency is applied to an upper electrode and a lower electrode which are opposed to each other in a processing chamber, and the processing gas is turned into a plasma and placed on the lower electrode. An apparatus for performing an etching process on the processed object is used. However, in this apparatus, if an anti-etching anti-reflection film for preventing irregular reflection during exposure of the photoresist film is formed between the photoresist film as a mask and the polysilicon film, the anti-reflection film is formed. It becomes difficult to process the lower polysilicon film. Therefore, by applying high-frequency power to the upper electrode at a higher frequency than that of the lower electrode to independently control the plasma generation and the ion energy of the ions in the plasma, even if the anti-reflection film is formed, the polysilicon A technique capable of performing a predetermined process on a film has been proposed.

[0003]

However, in the above conventional apparatus, when a high frequency power of 30 MHz or more is applied to the upper electrode, a high frequency system formed between the upper electrode and the lower electrode via the plasma processing space is formed. Since it becomes an inductive load, the voltage phase and current phase of the high-frequency power in the processing space are shifted, and the plasma becomes unstable,
There is a problem that uniform processing cannot be performed.

Further, in the above-described conventional apparatus, the high frequency applied to each electrode enters the matching device on each counter electrode side via plasma. Therefore, when high-frequency power of different frequencies is applied to each electrode as described above, the matching state of each matching device is affected by the matching state of the matching device on the counter electrode side and the length of the high-frequency power supply cable. In addition, there is a problem that poor control occurs and the controllability of plasma and ion energy is reduced.

Further, in the above-described conventional apparatus, since harmonic components generated by plasma discharge enter the matching device or the high-frequency power supply, matching adjustment and power adjustment become difficult, and control of plasma and ion energy becomes more difficult. There is a problem.

The present invention has been made in view of the above-mentioned problems of the conventional plasma processing apparatus, and an object of the present invention is to solve the above problems and other problems. Another object of the present invention is to provide a new and improved plasma processing apparatus.

[0007]

According to the present invention, in order to solve the above-mentioned problems, as in the first aspect of the present invention,
A first electrode and a second electrode, which are opposed to each other in the processing chamber;
A first high-frequency power supply for applying a first high-frequency power of a predetermined frequency to the electrode via a first power supply system, and a second high-frequency power supply for applying a second high-frequency power to the second electrode on which the object to be processed is mounted via the second power supply system. In a plasma processing apparatus including a second high-frequency power supply for applying a second high-frequency power having a relatively low frequency, the first power supply system includes a filter for removing a higher-order harmonic of the first high-frequency power, and a first high-frequency power. , A first matching device, and a filter for removing the second high-frequency power. The filter for removing the high-order harmonics of the first high-frequency power is most suitable for the first high-frequency power supply. It is installed in a close position,
A plasma processing apparatus is provided in which a filter for removing the second high-frequency power is provided at a position closest to the first electrode.

According to the present invention, a filter for removing high-order harmonics of the first high-frequency power is provided at a position closest to the first high-frequency power supply in the first power supply system. Therefore, high-order harmonics generated during plasma generation do not enter the first high-frequency power supply, so that power supply control can be performed accurately and stable power supply can be performed.

In addition, since a filter for removing low-order harmonics of the first high-frequency power is provided, low-order harmonics generated during plasma generation can be used for adjusting the first high-frequency power supply and the first matching device. Does not enter the detection unit that detects As a result, the power supply control and the adjustment of the first matching device can be accurately performed, so that the plasma control can be reliably performed.

Further, since a filter for removing the second high-frequency power is provided at a position closest to the first electrode of the first power supply system, the high frequency applied to the second electrode is supplied to the first electrode via the plasma. Intrusion into the matching device and the first high-frequency power supply can be prevented. Further, a grounding path for the second high-frequency power is formed by the filter for removing the second high-frequency power.
The first electrode can be a virtually grounded electrode with respect to the second electrode. As a result, the matching state of the second matching unit is not affected by the matching state of the first matching unit and the length of the first power supply system, and the matching operation of the second matching unit can be performed accurately.

The second power supply system may be, for example,
As in the invention described in (1), the second high-frequency power source side
It is preferable to provide a filter for removing harmonics of the high-frequency power, a second matching device, and a filter for removing the first high-frequency power. By adopting such a configuration, it is possible to prevent the harmonics generated during plasma generation from entering the second high frequency power supply by the filter for removing the harmonics of the second high frequency power, and further, to remove the first high frequency power by the filter for removing the first high frequency power. Since the high frequency applied to the electrode can be prevented from entering the second matching device and the second high frequency power supply, the control of the second high frequency power supply and the second matching device can be performed accurately. In addition, since the ground path of the first high-frequency power is formed by the filter that removes the first high-frequency power, the second electrode can be a virtually grounded electrode with respect to the first electrode. As a result, the first
Since the matching state of the matching unit does not depend on the matching state of the second matching unit or the length of the second power supply system, the first matching unit can perform a predetermined matching operation.

In addition, if both a filter for removing the second high-frequency power of the first power supply system and a filter for removing the first high-frequency power of the second power supply system are provided, the first electrode and the second electrode are removed.
A capacitive load can be added to the high-frequency system sandwiching the plasma processing space between the electrodes. With this configuration, even when the frequency of the first high frequency power is set to 30 MHz or more, for example, the inductive load is canceled and the high frequency system can be made a capacitive load. As a result, since the voltage phase and the current phase of the high-frequency power in the processing space can be made the same, stable plasma can be generated and uniform processing can be performed on the object.

In order to selectively remove low-order harmonics of the first high-frequency power, for example, a filter for removing low-order harmonics of the first high-frequency power is provided. , It is preferable to configure a filter having a sharp frequency characteristic. Further, since such a filter has a steep frequency characteristic, the basic high frequency of the first high frequency power is not attenuated.

In order to selectively remove high-order harmonics, a filter for removing high-order harmonics of the first high-frequency power is provided with a filter having a slow frequency characteristic. It is preferable that the filter be composed of a simple filter. Further, since such a filter has a frequency characteristic for removing high-order harmonics, even if the frequency characteristic of the filter is slow, the basic high frequency of the first high-frequency power is not attenuated.

In order to selectively remove high-order harmonics that degrade the controllability of the second high-frequency power supply and to prevent attenuation of the basic high-frequency power of the second high-frequency power, for example, As in the present invention, it is preferable that the filter for removing higher harmonics of the second high-frequency power be a filter that removes higher-order harmonics of the second high-frequency power and has a slow frequency characteristic.

[0016]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, a preferred embodiment in which a plasma processing apparatus according to the present invention is applied to a plasma etching apparatus will be described in detail with reference to the accompanying drawings.

(1) Overall Configuration of Etching Apparatus First, an outline of an etching apparatus 100 to which the present invention can be applied will be described with reference to FIG. The processing chamber 102 of the etching apparatus 100 is formed in an airtight processing container 104. In the processing chamber 102, a lower electrode (second electrode) 106 on which an object to be processed, for example, a semiconductor wafer (hereinafter, referred to as “wafer”) W can be placed, and an upper electrode (first electrode) 108. They are arranged facing each other.

The upper electrode 108 has a first high frequency power supply 11
A predetermined frequency output from 0, for example, 30 MHz or more,
A first high-frequency power of preferably 60 MHz is applied through the first high-frequency cable 111, the first matching unit 122, and the first band-cut filter 124, which are features of the present embodiment. The lower electrode 106 has a frequency lower than the frequency of the high-frequency power from the first high-frequency power supply 110 output from the second high-frequency power supply 114, for example, 10
The second high-frequency power of a frequency equal to or higher than 30 MHz and lower than 30 MHz, preferably 13.56 MHz, passes through the second high-frequency cable 115, the second matching unit 132, and the second band-cut filter 134, which are features of the present embodiment. Applied. The detailed configuration of the first and second matching units 122 and 132 and the first and second band cut filters 124 and 134 will be described later.

By applying the electric power, the gas supply system 11
8, a processing gas, for example, H
The mixed gas of Br and Cl ₂ is turned into plasma, and a predetermined etching process is performed on the polysilicon film formed on the wafer W by the plasma. Further, the gas in the processing chamber 102 is exhausted from the exhaust system 120.

(2) Configuration of First and Second Matching Units (a) First Matching Unit The first matching unit 122 shown in FIG.
For adjusting the impedance so that the reflected wave is minimized with respect to the high-frequency output applied to the
Coil L1, first to fourth capacitors C1, C2, C
3, C4. The first coil L1 and the first capacitor C1 are sequentially interposed between the first high-frequency cable 111 and the upper electrode 108 from the first high-frequency power supply 110 side. A grounded second capacitor C is provided between the first high-frequency cable 111 and the first coil L1.
2 are connected.

The first coil L1 and the second capacitor C2 are
When a 60 MHz high frequency power is applied to the upper electrode 108, a fourth harmonic or higher harmonic (240 MHz or more) (hereinafter referred to as “upper high harmonic”) component of 60 MHz generated by plasma discharge is removed. An upper high-order harmonic elimination filter (a filter for removing high-order harmonics of the first high-frequency power) 128 according to the embodiment is formed, and is provided in the vicinity of a connection portion of the first matching unit 122 with the first high-frequency cable 111. Have been. Further, the upper high-order harmonic elimination filter 128 needs to selectively remove the upper high-order harmonic component and prevent attenuation of the fundamental high frequency (60 MHz) of the first high-frequency power. Therefore, the inductance value of the first coil L1 and the capacitance value of the second capacitor C2 are determined by whether the upper high-order harmonic elimination filter 128 has a slower frequency characteristic than the later-described upper low-order harmonic elimination filter 130,
For example, they are set to 0.13 μH and 66 pF, respectively.

With this configuration, since the upper high-order harmonic component does not enter the first high-frequency power supply 110, it is possible to prevent erroneous detection from occurring in the high-frequency detection unit (not shown) provided in the first high-frequency power supply 110. As a result, the first high-frequency power supply 110 can be reliably controlled based on the detection information obtained by the high-frequency detection unit, so that stable power supply can be performed. In addition, the upper high-order harmonic elimination filter 128 is provided in the first
Match the input impedance of the matching unit to the first
It also has a function of adjusting to 50Ω which is the same as that of the high-frequency cable 111.

The first coil L1 and the first capacitor C
1 is connected to the grounded third capacitor C3, and the first and third capacitors C1 and C3 and the first matching unit 1 to which the first capacitor C1 is connected.
The first matching device that performs the above-described matching operation is configured by the inductive component of the internal wiring 22. The capacitance values of the first and third capacitors C1 and C3 are appropriately adjusted according to the matching state of the first matching device.

A grounded fourth capacitor C4 is connected in parallel between the third capacitor C3 and the first capacitor C1. The fourth capacitor C4 is
Along with the inductive component of the wiring near the capacitor C4,
A series resonance circuit is formed for the second and third harmonic (120 MHz, 180 MHz) (hereinafter referred to as “upper lower harmonic”) components of the first high frequency power generated by the plasma discharge, and the upper lower harmonic is formed. An upper low-order harmonic elimination filter (a filter that eliminates low-order harmonics of the first high-frequency power) 130 according to the present embodiment that removes the second-order harmonic component is configured. Therefore, the capacitance value of the fourth capacitor C4 is, for example, 85% in order to selectively remove the upper low-order harmonic component.
It has been set to pF. Further, since the upper low-order harmonic elimination filter 130 is constituted by a series resonance circuit, the frequency characteristic becomes steeper than that of the upper high-order harmonic elimination filter 128.

With this configuration, since the upper low-order harmonic component does not enter the high-frequency detector, erroneous detection by the detector can be prevented. As a result, the matching state of the first matching device can be reliably adjusted based on the detection information.
8, a predetermined power can be applied, and stable plasma can be generated. Further, the upper low-order harmonic component can be prevented from entering the first high-frequency power supply 110, so that the control of the first high-frequency power supply 110 can be performed more reliably.

(B) Second Matching Unit The second matching unit 132 adjusts the impedance so that the reflected wave is minimized with respect to the high-frequency output applied to the lower electrode 106. It is configured substantially the same as the matching unit 122. That is, the second coil L2 and the fifth to seventh capacitors C
Reference numerals 5, C6, and C7 are provided at positions corresponding to the first coil L1 and the first to third capacitors C1, C2, and C3, respectively. A third coil L3 is interposed between the fifth capacitor C5 and the lower electrode 106, and the fifth and seventh capacitors C5 and C7 and the third coil L3
Form a second matching device. The reason why the capacitor corresponding to the fourth capacitor C4 is not provided in the second matching unit 132 is that the fundamental frequency of the second high-frequency power is 13.56.
MHz, and the frequency difference between the second and third harmonics (27.12 MHz and 40.68 MHz) of the second high-frequency power is small. This is because power can be stably supplied to the lower electrode 106 without removing the second and third harmonics. Further, the capacitance values of the fifth and seventh capacitors C5 and C7 are appropriately adjusted according to the matching state.

The second coil L2 and the sixth capacitor C
No. 6 is the fourth or higher harmonic of 13.56 MHz (54.24 MHz or higher) generated by the plasma discharge (hereinafter, referred to as 54.24 MHz).
It is called "lower high-order harmonic component". ) A lower high-order harmonic elimination filter according to the present embodiment for removing a component (a filter for eliminating a harmonic (high-order harmonic) of the second high-frequency power)
138, and is provided in the vicinity of the connection portion of the second matching unit 132 with the second high-frequency cable 115. Further, the lower high-order harmonic removal filter 138 needs to selectively remove the lower high-order harmonic components and prevent attenuation of the fundamental high frequency (13.56 MHz) of the second high-frequency power. Therefore, the inductance value of the second coil L2 and the capacitance value of the sixth capacitor C6 are set such that the frequency characteristics of the lower high-order harmonic filter 138 are slow or set to, for example, 0.5 μH and 18 pF, respectively.

With this configuration, since the lower high-order harmonic component does not enter the second high-frequency power supply 114, the occurrence of erroneous detection can be prevented by the high-frequency detection unit (not shown) provided in the second high-frequency power supply 114, and the stable operation can be achieved. Power can be supplied. Further, the lower high-order harmonic elimination filter 138 is provided in the second
Match the input impedance of the matching device to the second
It also has a function of adjusting the same to 50Ω as the high-frequency cable 115.

(3) Configuration of First and Second Band-Cut Filters (a) First Band-Cut Filter The first band-cut filter (filter for removing the second high-frequency power) 124 is an eighth capacitor connected in series. C8 and the fourth coil L4. One end of the first band cut filter 124 is grounded, and the other end is the upper electrode 1.
08, a series resonance circuit is formed for the frequency of the second high frequency power applied to the lower electrode 106. Further, the capacitance value of the eighth capacitor C8 and the inductance value of the fourth coil L4 are determined by the first band cut filter 124 applied to the lower electrode 106.
The impedance is set to be low for a high frequency of 3.56 MHz and to be high for a high frequency of 60 MHz applied to the upper electrode 108.

With this configuration, for the frequency of the second high-frequency power, the first band-cut filter 124 serves as a ground path, and the upper electrode 108 virtually serves as a ground electrode with respect to the lower electrode 106. As a result, since the matching state of the second matching unit is not affected by the state of the first matching unit on the upper electrode 108 side or the length of the first high-frequency cable 111, a predetermined high-frequency power can be applied to the lower electrode 106, The ion energy of the ions can be accurately controlled. Also,
The first high frequency power is the first high frequency power due to the impedance characteristic.
Since the power does not pass through the band cut filter 124, power can be reliably supplied to the upper electrode 108.

(B) Second Band Cut Filter The second band cut filter (filter for removing the first high-frequency power) 134 includes a grounded ninth capacitor C 9 connected between the lower electrode 106 and the second band cut filter 134. A series resonance circuit is formed with respect to the frequency of the first high-frequency power applied to the upper electrode 108 by the inductive component of the power supply system that supplies the second high-frequency power output from the matching device to the lower electrode 106. . The capacitance of the ninth capacitor C9 is determined by the second band cut filter 134
Is set to have a low impedance with respect to a high frequency of 60 MHz applied to the device and a high impedance with respect to a high frequency of 13.56 MHz.

With this configuration, for the frequency of the first high-frequency power, the second band cut filter 134 serves as a ground path, and the lower electrode 106 virtually serves as a ground electrode with respect to the upper electrode 108. The high frequency applied to the electrode 108 is applied to the second matching unit 132 through the plasma.
Can be prevented. As a result, the matching state of the first matching unit is changed to the state of the second matching unit on the lower electrode 106 side or the second matching unit.
Since it is not affected by the length of the high-frequency cable 115, a predetermined power can be applied to the upper electrode 108, and the plasma generation and the control of the plasma density can be performed accurately. The second high frequency power is supplied to the second band cut filter 12.
4, the power supply to the lower electrode 106 can be reliably performed. In order to further exert the above-described effects of the first and second band-cut filters 124 and 134, the upper electrode 108 and the lower electrode 1 are respectively required.
It is preferable to dispose it near 06.

The first and second band cut filters 124 and 134 also have a function of making the voltage phase and the current phase of the high-frequency power in the plasma processing space 102a shown in FIGS. 1 and 2 the same. Therefore, the eighth capacitor C8 constituting the first band cut filter 124
, The inductance value of the fourth coil L4, and the second
The capacitance value of the ninth capacitor C9 constituting the band cut filter 134 is set as follows.

(C) Eighth and ninth capacitors C8, C
9 and the inductance value of the fourth coil L4 First, the upper electrode 10 is connected via the plasma processing space 102a.
The high-frequency system between the lower electrode 8 and the lower electrode 106 can be considered as an equivalent circuit shown in FIG. When a high frequency power of 30 MHz or more is applied to the upper electrode 108, the high frequency system equivalently becomes an inductive load (delay characteristic). Therefore, the first and second band cut filters 12 according to the present embodiment as capacitive loads (leading elements) are added to the high-frequency system.
If 4,134 is added, the inductive load is canceled out and becomes a capacitive load. As a result, the voltage and current phases of the high-frequency power in the processing space 102a are in phase, so that stable plasma can be generated.

Therefore, the eighth and ninth capacitors C8,
The capacitance value of C9 and the inductance value of the fourth coil L4 are such that the high-frequency system becomes a capacitive load even when high-frequency power of 30 MHz or more is applied to the upper electrode 108, and that the first and second band cut filters 124 , 13
For example, 55p so that each function of 4 can be secured
F, 100 pF, and 2.25 μH.

The present embodiment is configured as described above, and since the ion energy of plasma and ions can be easily controlled, the polysilicon film formed under the antireflection film has a high selectivity. In addition, uniform processing can be performed at a high etching rate.

As described above, a preferred embodiment of the present invention has been described with reference to the accompanying drawings, but the present invention is not limited to such a configuration. In the scope of the technical idea described in the claims, those skilled in the art
Various changes and modifications can be conceived, and it is understood that these changes and modifications also belong to the technical scope of the present invention.

[0038]

According to the present invention, the voltage and current phases of the high-frequency power in the processing space can be made in phase, and the matching state of the matching unit can be changed according to the state of the matching unit on the counter electrode side and the length of the power supply system. Can be adjusted without being affected. As a result, uniform processing can be performed on the object without causing a difference between apparatuses.

[Brief description of the drawings]

FIG. 1 is a schematic sectional view showing an etching apparatus to which the present invention can be applied.

FIG. 2 is a schematic explanatory diagram for explaining an equivalent circuit between an upper electrode and a lower electrode when generating plasma in the etching apparatus shown in FIG. 1;

[Explanation of symbols]

 REFERENCE SIGNS LIST 100 Etching apparatus 102 Processing chamber 106 Lower electrode 108 Upper electrode 110 First high-frequency power supply 114 Second high-frequency power supply 122 First matching unit 124 First band cut filter 128 Upper high-order harmonic removal filter 130 Upper low-order harmonic removal filter 132 2nd matching unit 134 2nd band cut filter 138 Lower high order harmonic removal filter W wafer

Continued on the front page F term (reference) 4K057 DA20 DB06 DD08 DE01 DE11 DM05 DM33 DM40 DN01 5F004 AA01 BA04 BA09 BB11 BB13 BB18 BC08 DA00 DA04 DB02 EA22 5F045 AA08 AF03 BB02 DP03 DQ10 EH14 EH19

Claims (6)

[Claims] A first electrode and a second electrode opposed to each other in a processing chamber; a first high frequency power supply for applying a first high frequency power of a predetermined frequency to the first electrode via a first power supply system;
And a second high-frequency power supply for applying a second high-frequency power having a frequency relatively lower than the predetermined frequency to the second electrode on which the object is placed via a second power supply system. The first power supply system includes a filter that removes higher harmonics of the first high-frequency power;
A filter for removing low-order harmonics of high-frequency power, a first matching device, and a filter for removing the second high-frequency power; 1 Provided at the position closest to the high frequency power supply;
The plasma processing apparatus according to claim 1, wherein the filter for removing the second high-frequency power is provided at a position closest to the first electrode. 2. A filter for removing harmonics of the second high-frequency power sequentially from the second high-frequency power supply side, a second matching device, and the first high-frequency power, wherein the second power supply system removes the first high-frequency power. The plasma processing apparatus according to claim 1, further comprising a filter. 3. The plasma processing apparatus according to claim 1, wherein the filter for removing low-order harmonics of the first high-frequency power is a filter having sharp frequency characteristics. 4. A plasma processing apparatus according to claim 1, wherein said filter for removing higher harmonics of said first high-frequency power is a filter having a slow frequency characteristic. apparatus. 5. A filter for removing higher harmonics of the second high frequency power, wherein the filter removes higher harmonics of the second high frequency power and has a slow frequency characteristic. , 2, 3 or 4. 6. The frequency of the first high frequency power is 30M
Hz or higher.
6. The plasma processing apparatus according to any one of 4 and 5.