JP2005203491A - Equipment and method for plasma processing - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide plasma processing equipment and plasma processing method suitable for a high-speed and very precise etching process. <P>SOLUTION: The plasma processing equipment comprises a processing chamber 1 which is connected to an evacuation apparatus and hence can reduce the pressure, a gas supply apparatus for supplying a gas to the processing chamber 1, a plasma generating means for generating plasmas inside the processing chamber, and a means 12 for applying high-frequency voltage to a workpiece 10. The plasma processing equipment is equipped with a means 11 and 14 for converting voltage having a pulse waveform or rectangular waveform into one having a sinusoidal waveform. The high-frequency voltage application means 12 applies the converted high-frequency voltage having a sinusoidal waveform to the workpiece. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to a plasma processing apparatus and a plasma processing method, and more particularly to a plasma processing apparatus suitable for performing etching processing on a sample such as a semiconductor element substrate using plasma and applying a high frequency voltage to the sample. is there.

  A conventional etching plasma processing apparatus uses, for example, a high-frequency power source and a matching unit, as described in Patent Document 1, and a sinusoidal high-frequency voltage is applied to an electrode on which a wafer, which is a material to be processed, is placed. . A conventional plasma processing apparatus is shown in FIG. In this figure, 1 is a processing chamber, 1a is a container, 1b is a discharge tube, 2 is a quartz window, 2a is a shower plate, 3 is a coil, 4 is a yoke, 5 is a high-frequency power source, 6 is a matching unit, 7 Is a coaxial waveguide (cable), 8 is an antenna, 9 is a wafer mounting electrode, 10 is a wafer, 13 is a DC power supply, 14 is a capacitor, 61 is a high frequency power supply, and 62 is a matching unit. In order to control the etching shape of the wafer 10, a high frequency power supply 61 is connected to the wafer mounting electrode 9 via a matching unit 62, so that a high frequency voltage can be applied to the wafer 10. In the conventional plasma processing apparatus, a power source that outputs a sine wave voltage waveform has been used as the high-frequency power source 61. FIG. 7 shows a circuit configuration example of the matching unit 62 and the high-frequency power source 61 connected to the wafer mounting electrode 9. FIG. 8 shows a sine wave voltage waveform output from the high frequency power supply 61, and FIG. 9 shows a sine wave voltage waveform on the wafer 10. In this case, the frequency of the sine wave voltage waveform is 350 kHz.

  When the conventional high frequency power supply 61 is used, it is necessary to make the load impedance of the plasma coincide with the internal impedance of the high frequency power supply 61 by the variable L (or variable C) constituting the matching unit 62, and to further make the phase difference between the current and the voltage zero. was there. That is, it is necessary to eliminate the complex impedance of the load, and it is necessary to monitor the impedance and the phase difference and perform feedback control of variable L (or variable C). Such control has a complicated structure.

In addition, in the sinusoidal voltage waveform at the wafer, high energy ions are incident on the wafer from the plasma when the voltage is negative. High energy ions contribute to etching, whereas low energy peak ions contribute little to etching. Therefore, the longer the time of the negative voltage of the sine waveform, the higher the etching rate. However, in the case of a high frequency power source that outputs a high frequency voltage waveform of the sine wave, the duty ratio cannot be changed and the etching efficiency is not good. there were. In particular, the longer the maximum negative voltage, the higher the ratio of high-energy ions incident on the wafer. However, when a normal sine wave high-frequency voltage waveform is used, the high energy of the ion energy distribution incident on the wafer. The ratio of ions to low energy ions could not be varied by approximately 1: 1. Further, since the conventional high frequency power supply 61 outputs a sine wave, the ratio of the time of the positive voltage to the time of the negative voltage (hereinafter referred to as “duty ratio”) cannot be changed.
JP-A-5-174959

  An object of the present invention is to provide a plasma processing apparatus and a plasma processing method suitable for high-speed and high-precision etching processing.

  In order to achieve the above object, a high-frequency pulse power source (rectangular wave power source) and a filter circuit are used to have a high-frequency applying means for generating a high-frequency voltage waveform on the material to be processed. A high-frequency pulse power source capable of outputting a pulse voltage waveform (rectangular voltage waveform) was connected to an electrode on which the material to be processed was placed via a filter circuit. Thereby, a sinusoidal voltage waveform is applied to the material to be processed. Since the high-frequency pulse power supply can output with low impedance and can output regardless of the load impedance, the matching device is not required and the configuration can be simplified. In addition, the high-frequency pulse power supply can change the duty ratio, and by applying a pulse voltage waveform with a changed duty ratio to the filter circuit, a sine wave with a changed duty ratio can be applied to the wafer, which is the material to be processed. it can. Therefore, the amount of high energy ions incident on the wafer can be changed by changing the duty ratio of the high frequency pulse power supply. As a result, high-speed and high-precision etching can be performed.

  That is, the present invention relates to a processing chamber to which an evacuation apparatus is connected and the inside of which can be depressurized, a gas supply device to the processing chamber, a plasma generating means for generating plasma in the processing chamber, and a high-frequency voltage to the material to be processed. And a means for converting a pulse waveform or a rectangular waveform voltage into a sinusoidal waveform voltage, wherein the high frequency voltage applying means is subject to the converted high frequency voltage having a sinusoidal waveform. A plasma processing apparatus to be applied to a material.

  Further, the present invention is the plasma processing apparatus, wherein the means for applying the high frequency voltage of the sine wave waveform to the material to be processed includes a high frequency pulse power source that outputs a pulse waveform or a rectangular waveform voltage and a filter circuit.

  The present invention is the plasma processing apparatus, wherein the high-frequency pulse power source is a high-frequency pulse power source that outputs a voltage having a pulse waveform with a variable duty ratio.

  Furthermore, the present invention is a plasma processing apparatus in which the high-frequency pulse power source is a high-frequency pulse power source that outputs a voltage of a rough pulse wave (a rough rectangular waveform: a waveform including a trapezoidal wave, an overshoot, ringing, or sag).

  The present invention is also the plasma processing apparatus, wherein the filter circuit is a filter circuit including a transformer that converts an output voltage of a high-frequency pulse power supply.

  The present invention provides a plasma processing apparatus in which the filter circuit includes a low-pass filter, a band-pass filter, or a high-pass filter for converting a frequency component included in a high-frequency pulse power source into a desired sine wave frequency to be applied to a material to be processed. It is.

  Furthermore, the present invention provides a processing chamber to which an evacuation device is connected and whose inside can be depressurized, a gas supply device to the processing chamber, a plasma generating means for generating plasma in the processing chamber, and a high-frequency voltage to the material to be processed. The high-frequency voltage applying means applies a voltage having a sine wave waveform with a duty ratio smaller than 50% or a voltage with a sine wave waveform with a duty ratio larger than 50% to the material to be processed. A plasma processing apparatus.

  In the present invention, the means for applying a voltage having a sine wave waveform with a duty ratio smaller than 50% or a sine wave waveform with a duty ratio larger than 50% to the material to be processed is a pulse waveform or a rectangular waveform having a variable duty ratio. This is a plasma processing apparatus having a high frequency pulse power supply that outputs a voltage of 1 and a filter circuit.

  Then, the present invention relates to a pulse having a variable duty ratio in a method of reducing the pressure in the processing chamber, generating plasma in the processing chamber, applying a high frequency voltage to the material to be processed, and performing plasma processing on the material to be processed. In this plasma processing method, a waveform or rectangular waveform voltage is converted into a sinusoidal waveform high-frequency voltage, and the converted sinusoidal waveform high-frequency voltage is applied to a workpiece.

  Furthermore, the present invention is a plasma processing method in which the duty ratio is changed according to processing conditions of a material to be processed.

  According to the present invention, the pulse voltage waveform is changed to a sine wave voltage waveform at the filter circuit output unit, and the sine wave voltage waveform is generated on the wafer 10, thereby simplifying the apparatus and applying a duty variable sine wave. Efficient and highly accurate etching is possible, and the material selection ratio is improved.

The best mode for carrying out the present invention will be described.
Hereinafter, an embodiment of a plasma processing apparatus and a plasma processing method of the present invention will be described with reference to FIGS. FIG. 1 shows a magnetic field UHF etching apparatus which is an embodiment of the plasma processing apparatus of the present invention. After the pressure inside the processing chamber 1 defined by the container 1a, the discharge tube 1b and the quartz window 2 is reduced by a vacuum exhaust device (not shown), an etching gas is introduced into the processing chamber 1 by a gas supply device (not shown). Adjust to the desired pressure. The processing chamber 1 is in a magnetic field region generated by the coil 3 and the yoke 4. In this case, the 450 MHz UHF wave oscillated from the high-frequency power source 5 propagates through the matching device 6 through the coaxial waveguide (or coaxial cable) 7 and passes through the quartz window 2 from the antenna 8. Is incident on the processing chamber 1. The UHF wave generates plasma in the processing chamber 1 by interaction with the magnetic field. The wafer 10 placed on the wafer mounting electrode 9 is etched from the plasma generated by the UHF wave. Further, in order to control the etching shape of the wafer 10, a high frequency pulse power source (rectangular wave power source) 12 is connected to the wafer mounting electrode 9 via a filter circuit 11, and a sinusoidal voltage waveform can be applied. ing. A capacitor 14 for blocking a DC voltage is inserted between the filter circuit 11 and the wafer mounting electrode 9. The wafer mounting electrode 9 has an electrode surface covered with a sprayed film (not shown), and is connected to a DC power source 13. Thereby, the wafer 10 is fixed to the wafer mounting electrode through electrostatic spraying by electrostatic adsorption. Further, a quartz plate 2a made of quartz is provided immediately below the quartz window 2, and the etching gas flows between the quartz window 2 and the shower plate 2a, and the central portion of the shower plate 2a. Is introduced into the processing chamber 1 through a gas inlet provided in the chamber. Since etching gas is supplied from directly above the wafer 10, highly uniform etching processing is possible. The installation location of the gas inlet is not limited to the central portion, and may be provided on the entire upper surface of the wafer.

  FIG. 2 shows a circuit configuration example of the filter circuit 11 and the high-frequency pulse power source 12 connected to the wafer mounting electrode 9. The pulse voltage waveform output from the high-frequency pulse power supply 12 is boosted by the transformer 22 and then applied to the filter unit 23 including an inductance and a capacitor. Since the filter unit 23 constitutes a low-pass filter, a band-pass filter, or a high-pass filter, the output voltage waveform of the filter unit 23 can be a sine wave voltage waveform, and a sine wave voltage waveform is applied to the wafer mounting electrode 9. it can. The sine wave voltage waveform output from the filter unit 23 is applied to the wafer mounting electrode 9 via a capacitor 14 that blocks a DC voltage. The DC power supply 13 for electrostatic adsorption is connected to the wafer mounting electrode 9 through a high frequency filter. The high frequency filter prevents the high frequency voltage from flowing into the DC power supply 13. FIG. 4 shows a pulse voltage waveform output from the high-frequency pulse power supply 12, and FIG. 5 shows a sine wave voltage waveform on the wafer 10. Although a waveform in which the positive voltage and the negative voltage are asymmetric is used here, a symmetric waveform may be used. In this case, the frequency of the pulse voltage waveform is 350 kHz. As the high-frequency pulse power source 12, a pulse power source used for reactive sputtering or the like can be used. By using an inverter type or flyback type pulse power supply, a pulse voltage waveform can be output even if the plasma impedance changes, and the matching unit can be omitted. The capacitor 21 is used for cutting the DC component of the high-frequency pulse power supply 12 for the transformer 22. When the output voltage waveform of the high-frequency pulse power supply 12 does not include a DC component, the capacitor 21 can be omitted. The transformer 22 is for boosting the output voltage of the high-frequency pulse power supply 12. If the output voltage of the high-frequency pulse power supply 12 satisfies the voltage required for plasma processing, it can be omitted as shown in FIG. The filter unit 23 can use a variable inductance and a variable capacitance capacitor, and the filter unit 23 is not limited to the illustrated configuration, and may be any configuration that can extract a desired sine wave voltage waveform from the pulse voltage waveform. For example, as shown in FIG. 14, in order to cancel capacitive components such as an electrostatic adsorption film and an ion sheath, a variable inductance may be provided in the power supply line. In this case, there is an effect that the burden on the high-frequency pulse power supply 12 is reduced and the reliability is further improved.

  The voltage waveform in the wafer of FIG. 4 is the same as that in FIG. 9, and the same voltage waveform as that in the case of using the conventional high frequency power supply 61 can be obtained even when the high frequency pulse power supply 12 is used. Further, when the high-frequency pulse power source 12 is used, it is not necessary to connect a matching unit, so that the apparatus can be simplified. By using the high-frequency pulse power source 12, and particularly using the high-frequency pulse power source that can output regardless of the load impedance with a low impedance output, the matching device is not required and the configuration can be simplified. Furthermore, compared with the conventional high frequency power supply 61, the inverter type or flyback type high frequency pulse power supply 12 can simplify the circuit structure of the power supply and reduce the cost of the power supply in terms of the operation principle of the power supply. Therefore, in the case of the present embodiment, there is an effect that the plasma processing apparatus can be simplified by using the high-frequency pulse power source 12 and the filter circuit 11.

  Moreover, in the high frequency pulse power supply 12, the duty ratio can be changed. FIG. 10 shows a pulse voltage waveform output from the high-frequency pulse power supply 12 with a duty ratio of 30%, and FIG. 11 shows a sine wave voltage waveform on the wafer 10 at that time. The filter circuit 11 can apply a voltage waveform in which the duty ratio of the sine wave is changed to the wafer. When the constants of the filter circuit are optimized, a waveform with a substantially flat bottom of the negative voltage as shown in FIG. 15 can be obtained. As the time of negative voltage increases, the amount of high energy ions incident on the wafer from the plasma increases. As the ion energy increases, the etching reaction efficiency (chemical sputtering rate) increases. Therefore, as the amount of ions on the high energy side increases, the etch rate increases. In other words, since the ion energy distribution is monochromatic, the etching shape is vertical and high-precision processing can be performed. For example, vertical and high-precision processing in gate etching. Furthermore, since the relationship between the ion energy and the chemical sputtering rate differs depending on the material to be etched, the etching selectivity of a plurality of materials to be etched can be improved by selecting the optimum ion energy. For example, improvement of the hard mask selection ratio in low dielectric constant (Low-k) insulating film etching and improvement of the selection ratio with the ultrathin oxide film of the base in gate etching. As described above, a pulse voltage waveform with a changed duty ratio is applied to the filter circuit 11, and as a result, a sinusoidal voltage waveform with a changed duty ratio is generated on the wafer 10, thereby enabling highly efficient and highly accurate etching. Processing is possible and the material selection ratio is improved.

  FIG. 12 shows a pulse voltage waveform output from the high-frequency pulse power supply 12 with a duty ratio of 70%, and FIG. 13 shows a sine wave voltage waveform on the wafer 10 at that time. As the duty ratio increases, the absolute value Vdc of the DC voltage component of the high frequency voltage at the wafer 10 increases. That is, the positive voltage decreases. In general, the plasma potential is a positive voltage. The plasma potential when the wafer 10 is positive is about wafer voltage + about 20V, and the plasma potential when the wafer 10 is negative is about 20V. Since the processing chamber 1 is grounded, an ion sheath is formed in the vicinity of an effective ground portion on the inner surface of the processing chamber 1, and a high frequency voltage corresponding to a plasma potential is applied to the ion sheath. Since ions accelerated by the electric field of the ion sheath sputter the wall surface of the processing chamber, the wafer 10 is contaminated with metal, and finally the electrical characteristics of the device deteriorate. In addition, since an aluminum anodized earth on the inner wall of the processing chamber is similarly sputtered, when an etching gas containing a fluorine-based gas is used, an AlF deposit adheres to the quartz shower plate 2a or the like. This AlF deposit eventually peels off as the amount of deposition increases, and falls on the wafer 10 to become foreign matter, causing problems such as a decrease in device yield. In general, the smaller the ratio of the area of the wafer 10 to which the high frequency voltage is applied / the effective earth area, the smaller the Vdc / Vpp ratio (where Vpp is as shown in FIG. The high-frequency voltage peak-to-peak voltage is large. By increasing the diameter of the wafer 10 from φ200 mm to φ300 mm, the ratio of the wafer 10 area / effective earth area is increased and the plasma potential is increased, so that metal contamination countermeasures have become important. In the case of the present embodiment, the plasma potential can be reduced as the duty ratio increases, which is effective in suppressing metal contamination, reducing foreign matter, and improving yield.

  In each of the above embodiments, the case where a high frequency voltage is applied to the wafer 10 has been described. However, there is no particular limitation as long as the high frequency voltage is applied to the inside of the processing chamber. For example, in the case of an insulating film etching apparatus, a silicon plate is installed at a position facing the wafer 10 and a high frequency voltage is applied to remove excess fluorine radicals in the plasma generated by the chlorofluorocarbon gas. , Improve the mask selection ratio. In the case of such an apparatus, even if a high-frequency pulse power source and a filter circuit are connected to the silicon plate, the same effect can be obtained. Further, even if a high frequency pulse power source and a filter circuit are connected to both the wafer 10 and the silicon plate, the same effect can be obtained, and the frequency of both high frequency voltages is made the same, and the phase difference between the two voltages is controlled (particularly the phase difference). By setting the angle to around 180 degrees, a greater effect (especially a plasma potential suppressing effect) can be obtained. Particularly in the case of an insulating film etching apparatus, since a high-output high-frequency voltage is applied to the wafer 10, the plasma potential increases, the side wall of the processing chamber 1 is sputtered, and the plasma diffuses to the lower portion of the processing chamber 1. Occurrence is a problem. In the case of the present embodiment, since the plasma potential can be suppressed, there is an effect in reducing foreign matter, and there is an effect in that the apparatus operating rate can be improved and the device yield can be improved.

  In the above embodiment, the etching apparatus using the magnetic field UHF discharge has been described as an example, but other discharges (magnetic field microwave discharge, capacitively coupled discharge, inductively coupled discharge, magnetron discharge, surface wave excited discharge, transfer) A dry etching apparatus using coupled discharge has the same effect. In each of the above embodiments, the etching apparatus has been described. However, other plasma processing apparatuses that perform plasma processing, such as a plasma CVD apparatus, an ashing apparatus, and a surface modification apparatus, have similar operational effects. In each of the above embodiments, the high-frequency pulse power supply 12 is used, but there is no particular limitation on the power supply system such as a switching power supply system, an arbitrary voltage generator + a high-frequency power amplifier, or the like. In the above embodiment, the high-frequency pulse power source that can output a pulse voltage waveform is described as an ideal case, but a trapezoidal wave or a similar waveform in which some waveforms are disturbed due to frequency characteristics is used. The effect is obtained.

The longitudinal cross-sectional view of the magnetic field UHF etching apparatus which is one Example of the plasma processing apparatus of this invention. FIG. 3 is an explanatory diagram of a circuit configuration example of a high-frequency pulse power source 12 and a filter circuit 11 connected to the wafer mounting electrode 9 in the embodiment. Explanatory drawing of an example of the high frequency voltage waveform which is the output of the high frequency pulse power supply 12 in an Example. Explanatory drawing of an example of the high frequency voltage waveform in the wafer 10 in an Example. FIG. 3 is an explanatory diagram of a circuit configuration example of a high-frequency pulse power source 12 and a filter circuit 11 connected to the wafer mounting electrode 9 in the embodiment. The longitudinal cross-sectional view of the magnetic field UHF etching apparatus in the conventional plasma processing apparatus. Explanatory drawing of the circuit structural example of the high frequency power supply 61 and the matching device 62 connected to the electrode 9 for wafer mounting in the conventional plasma processing apparatus. Explanatory drawing of the high frequency voltage waveform which is the output of the high frequency power supply 61 in the conventional plasma processing apparatus. Explanatory drawing of the high frequency voltage waveform in the wafer 10 in the conventional plasma processing apparatus. Explanatory drawing of an example of the high frequency voltage waveform of the output of the high frequency pulse power supply which made the duty ratio 30% in an Example. FIG. 4 is an explanatory diagram illustrating an example of a voltage waveform on the wafer when the duty ratio of the high-frequency pulse power supply is 30% in the embodiment. Explanatory drawing of an example of the high frequency voltage waveform of the output of the high frequency pulse power supply which made the duty ratio 70% in an Example. FIG. 4 is an explanatory diagram illustrating an example of a voltage waveform on the wafer when the duty ratio of the high-frequency pulse power supply is 70% in the embodiment. FIG. 3 is an explanatory diagram of a circuit configuration example of a high-frequency pulse power source 12 and a filter circuit 11 connected to the wafer mounting electrode 9 in the embodiment. FIG. 4 is an explanatory diagram showing an example of a voltage waveform on the wafer 10 when the duty ratio of the high-frequency pulse power supply is 30% and the circuit constants of the filter are optimized in the embodiment.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 1 ... Processing chamber, 1a ... Container, 1b ... Discharge tube, 2 ... Quartz window, 2a ... Shower plate, 3 ... Coil, 4 ... Yoke, 5 ... High frequency power supply, 6 ... Matching device, 7 ... Coaxial wave guide Tube (cable), 8 ... antenna, 9 ... wafer mounting electrode, 10 ... wafer, 11 ... filter circuit, 12 ... high frequency pulse power supply, 13 ... DC power supply, 14 ... condenser, 21 ... condenser, 22 ... transformer , 23 ... Filter section, 31 ... Voltage waveform, 41 ... Voltage waveform at wafer, 61 ... High frequency power supply, 62 ... Matching device, 81 ... Voltage waveform, 91 ... Voltage waveform at wafer, 101 ... Voltage waveform, 111 ... Wafer Voltage waveform at 121, 121 ... voltage waveform, 131 ... voltage waveform at wafer.

Claims (10)

A processing chamber to which an evacuation device is connected and whose inside can be decompressed, a gas supply device to the processing chamber, plasma generating means for generating plasma in the processing chamber, and means for applying a high-frequency voltage to the material to be processed A plasma processing apparatus comprising:
A plasma processing apparatus comprising: means for converting a voltage having a pulse waveform or a rectangular waveform into a voltage having a sine wave waveform; and the high-frequency voltage applying means applies the converted high-frequency voltage having a sine wave waveform to a workpiece. . The plasma processing apparatus according to claim 1,
The plasma processing apparatus, wherein the means for applying the high frequency voltage of the sine wave waveform to the material to be processed includes a high frequency pulse power source that outputs a voltage of a pulse waveform or a rectangular waveform, and a filter circuit. The plasma processing apparatus according to claim 2, wherein
The plasma processing apparatus, wherein the high-frequency pulse power source is a high-frequency pulse power source that outputs a voltage having a pulse waveform with a variable duty ratio. The plasma processing apparatus according to claim 2 or 3,
The plasma processing apparatus, wherein the high-frequency pulse power source is a high-frequency pulse power source that outputs a voltage having a general pulse waveform or a general rectangular waveform. The plasma processing apparatus according to claim 2, wherein
The plasma processing apparatus, wherein the filter circuit is a filter circuit including a transformer for converting an output voltage of a high-frequency pulse power supply. The plasma processing apparatus according to claim 2, wherein
A plasma processing apparatus, wherein the filter circuit includes a low-pass filter, a band-pass filter, or a high-pass filter for converting a frequency component included in a high-frequency pulse power source into a desired sine wave frequency to be applied to a material to be processed. A processing chamber to which an evacuation device is connected and whose inside can be decompressed, a gas supply device to the processing chamber, plasma generating means for generating plasma in the processing chamber, and means for applying a high-frequency voltage to the material to be processed A plasma processing apparatus comprising:
The high frequency voltage applying means applies a voltage having a sine wave waveform with a duty ratio smaller than 50% or a sine wave waveform with a duty ratio larger than 50% to a material to be processed. The plasma processing apparatus according to claim 7, wherein
The means for applying a voltage having a sine wave waveform with a duty ratio smaller than 50% or a sine wave waveform having a duty ratio larger than 50% to the material to be processed outputs a pulse waveform or a rectangular waveform voltage having a variable duty ratio. A plasma processing apparatus having a pulse power supply and a filter circuit. In a method of reducing the pressure inside the processing chamber, generating plasma in the processing chamber, applying a high frequency voltage to the material to be processed, and performing plasma processing on the material to be processed,
A plasma processing method comprising: converting a pulse waveform or a rectangular waveform voltage having a variable duty ratio into a high frequency voltage having a sinusoidal waveform, and applying the converted high frequency voltage having a sinusoidal waveform to a workpiece. The plasma processing method according to claim 9, wherein
A plasma processing method, wherein the duty ratio is changed according to processing conditions of a material to be processed.

Images