JPH11185993A - Plasma processing method and device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To generate uniform and stable plasma and to suppress the occurrence of a hollow cathode discharge causing the deterioration of homogeneity of processing speed in a wafer plane or the mixing of impurities into the wafer by the spattering of a solid material. SOLUTION: A vacuum container 1 is exhausted by a pump 3 while the prescribed gas is introduced into it from a gas feed unit 2 to keep the vacuum container 1 at the prescribed pressure, high-frequency power of 100 MHz is fed to an antenna 6 mounted on a dielectric window 5 by an antenna high-frequency power supply 4, and a positive DC potential is applied to a circular conductor 10 constituting part of the inner wall of the vacuum container 1, thereby stable plasma is generated, and a wafer 8 mounted on an electrode 7 is processed.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a plasma processing method and apparatus for dry etching, sputtering, plasma CVD, etc., used for manufacturing electronic devices such as semiconductors and micromachines, and more particularly, to plasma processing using plasma using electromagnetic waves. The present invention relates to a method and an apparatus.

[0002]

2. Description of the Related Art Japanese Patent Application Laid-Open No. 8-83696 describes the importance of using high-density plasma in order to cope with miniaturization of electronic devices such as semiconductors. Low electron temperature plasma, which has high electron temperature and low electron temperature, has attracted attention.

[0003] Strongly negative gases such as Cl ₂ and SF ₆
In other words, when a gas that easily generates negative ions is turned into plasma, when the electron temperature is about 3 eV or less, a larger amount of negative ions is generated than when the electron temperature is high. Utilizing this phenomenon, it is possible to prevent an abnormal etching shape called a notch, which is caused by the accumulation of positive charges at the bottom of the fine pattern due to excessive incidence of positive ions. It can be carried out.

Further, CxFy and CxHy generally used when etching an insulating film such as a silicon oxide film are used.
When a gas containing carbon and fluorine such as Fz (x, y, and z are natural numbers) is plasmatized, when the electron temperature is about 3 eV or less, the decomposition of the gas is suppressed as compared with the case where the electron temperature is high. Generation of atoms, F radicals, and the like is suppressed. Since F atoms, F radicals, and the like have a high silicon etching rate, the lower the electron temperature, the higher the etching selectivity with respect to silicon.

[0005] When the electron temperature becomes 3 eV or less, the ion temperature also drops, so that ion damage to the substrate in plasma CVD can be reduced.

A technique that can generate plasma having a low electron temperature has been attracting attention at present from a plasma source using electromagnetic waves. This generates plasma by radiating electromagnetic waves into a vacuum vessel, and various forms of antennas and dielectric windows for radiating electromagnetic waves are used.

FIG. 5 is a perspective view of an etching apparatus provided with a spiral antenna type plasma source proposed by us. In FIG. 5, the pump 3 evacuates while introducing a predetermined gas from the gas supply unit 2 into the vacuum vessel 1, and maintains the inside of the vacuum vessel 1 at a predetermined pressure while the antenna high-frequency power supply 4 supplies 50 to 150 MHz. When high frequency power is supplied to the spiral antenna 6 on the dielectric window 5, plasma is generated in the vacuum vessel 1, and plasma processing such as etching, deposition, and surface modification is performed on the substrate 8 mounted on the electrode 7. It can be performed. At this time, as shown in FIG. 5, by supplying high-frequency power to the electrode 7 from the electrode high-frequency power supply 9, the ion energy reaching the substrate 8 can be controlled.

FIG. 6 is a perspective view of an etching apparatus equipped with a spoke antenna type plasma source. In FIG. 6, the pump 3 is evacuated while introducing a predetermined gas from the gas supply unit 2 into the vacuum vessel 1, and the high frequency power of 500 MHz is supplied by the high frequency power supply for antenna 4 while maintaining the inside of the vacuum vessel 1 at a predetermined pressure. Is supplied to the spoke antenna 6 made of a radial conductor on the dielectric plate window 5, plasma is generated in the vacuum chamber 1, and etching, deposition, surface modification, etc. are performed on the substrate 8 placed on the electrode 7. Can be performed. At this time, as shown in FIG. 6, by supplying high-frequency power to the electrode 7 from the electrode high-frequency power supply 9, the ion energy reaching the substrate 28 can be controlled. In addition, about this method,
S. Samukawa et al., "New Ultra-High-Frequency Plasm
a Source for Large-Scale Etching Processes ", Jpn.
J. Appl. Phys., Vol. 34, Pt. 1, No. 12B (1995).

FIG. 7 is a perspective view of an etching apparatus equipped with a slot antenna type plasma source. In FIG. 7, the pump 3 is evacuated while introducing a predetermined gas from the gas supply unit 2 into the vacuum vessel 1, and while maintaining the inside of the vacuum vessel 1 at a predetermined pressure, a high-frequency power supply for antenna 4 uses a waveguide to guide the gas. The derived 2.45 GHz high frequency power,
When supplied to the slot antenna 6 provided in the electromagnetic wave guide 16 on the dielectric window 5, plasma is generated in the vacuum vessel 1, and the substrate 8 mounted on the electrode 7 is etched.
Plasma treatment such as deposition and surface modification can be performed.
At this time, as shown in FIG. 7, by supplying high-frequency power to the electrode 7 from the electrode high-frequency power supply 9, the ion energy reaching the substrate 8 can be controlled.

As described above, there are various modes for generating plasma by radiating an electromagnetic wave into a vacuum vessel. However, it is considered that the mechanism of energy absorption of the electromagnetic wave is performed by the same mechanism. I have.
As shown in FIG. 8, the inner wall surface of the vacuum vessel 1 is made of an insulator such as aluminum oxide (alumite).
The potential is lower than the plasma space potential, and the vicinity of the surface is an ion sheath 14 having a very low electron density. Even when the inner wall surface of the vacuum vessel is made of a conductor such as stainless steel, it is kept at the ground potential so as not to radiate high-frequency noise. The ion sheath 14 has a very small electron density. If the DC magnetic field is not present, although less electromagnetic frequency than the electron plasma frequency f _p (~ number GHz) can not penetrate into the plasma, the electron plasma frequency f _p is proportional to the square root of the plasma density N _e Therefore, in the ion sheath, the electron plasma frequency becomes extremely low, and electromagnetic waves can enter. Also, in the plasma,
Since the electromagnetic wave penetrates to the plasma skin depth (to c / 2πfp to several cm), the energy of the electromagnetic wave is absorbed as the kinetic energy of the electrons in the skin portion. Therefore, the electromagnetic wave radiated from the dielectric window propagates while attenuating the ion sheath + skin.

[0011]

SUMMARY OF THE INVENTION However, FIGS.
The conventional method shown in FIG. 7 has a problem that the plasma is unstable. When the plasma generation conditions (gas type, gas pressure, magnitude of high frequency power, etc.) change, the place where a higher density portion of the plasma is formed may change, or the plasma may flicker. In addition, a portion having a higher density of plasma may be formed directly above the substrate, and there is a problem that the uniformity of the processing speed in the substrate surface is poor. In addition, when a solid material constituting a vacuum container has a hole-like shape, a hollow cathode discharge occurs inside the hole, thereby deteriorating the uniformity of the processing speed within the substrate surface and the impurity on the substrate due to the sputtering of the solid material. There is a problem that it causes mixing.

The present invention has been made in view of the above-mentioned conventional problems, and is capable of generating uniform and stable plasma, deteriorating in-plane uniformity of a processing speed, and impinging impurities on a substrate due to sputtering of a solid material. It is an object of the present invention to provide a plasma processing method and apparatus capable of suppressing the occurrence of hollow cathode discharge that causes mixing.

[0013]

According to a first aspect of the present invention, there is provided a plasma processing method, wherein the inside of a vacuum vessel is evacuated while supplying gas into the vacuum vessel, and the inside of the vacuum vessel is controlled to a predetermined pressure.
A plasma processing method for processing a substrate mounted on an electrode in a vacuum vessel by generating plasma in the vacuum vessel by radiating an electromagnetic wave into the vacuum vessel, and forming a part of an inner wall of the vacuum vessel. It is characterized in that a positive DC voltage is applied to the annular conductor.

The plasma processing method according to the first aspect of the present invention is a particularly effective plasma processing method when the frequency of the electromagnetic wave is 50 MHz to 3 GHz.

This is a particularly effective plasma processing method when no DC magnetic field exists in the vacuum vessel.

In the plasma processing method according to the first aspect of the present invention, it is preferable that the annular conductor is disposed substantially in parallel with the substrate.

Preferably, the annular conductor is made of a substance containing silicon or carbon as a main component.

Preferably, the width of the annular conductor is larger than the plasma skin depth or 1 to 10 cm.

Preferably, the positive DC voltage is higher than the plasma space potential or the positive DC voltage is 10 V
Desirably, the voltage is from 120 V to 120 V.

The plasma processing apparatus according to the second aspect of the present invention includes a means for supplying gas into the vacuum vessel, a means for evacuating the vacuum vessel, a dielectric window, and an electromagnetic wave through the dielectric window into the vacuum vessel. Antenna, a high-frequency power supply capable of supplying high-frequency power to the antenna, an electrode for mounting the substrate, an annular conductor forming a part of the inner wall of the vacuum vessel, and an annular conductor And means for applying a positive DC voltage to the power supply.

The plasma processing apparatus of the second invention of the present application is a plasma processing apparatus particularly effective when the frequency of the electromagnetic wave is 50 MHz to 3 GHz.

Further, the plasma processing apparatus is particularly effective when there is no means for applying a DC magnetic field in the vacuum vessel.

In the plasma processing apparatus according to the second aspect of the present invention, it is preferable that the annular conductor is disposed substantially parallel to the substrate.

Preferably, the annular conductor is made of a substance containing silicon or carbon as a main component.

Preferably, the width of the annular conductor is larger than the plasma skin depth or 1 to 10 cm.

Preferably, the positive DC voltage is higher than the plasma space potential or the positive DC voltage is 10 V
Desirably, the voltage is from 120 V to 120 V.

[0027]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below with reference to FIGS.

FIG. 1 is a perspective view of a plasma processing apparatus used in the embodiment of the present invention. In FIG. 1, while a predetermined gas is introduced from a gas supply unit 2 into a vacuum vessel 1, exhaust is performed by a pump 3, and while maintaining the inside of the vacuum vessel 1 at a predetermined pressure, a frequency of 100 MHz is supplied by an antenna high-frequency power supply 4. By supplying high frequency power to the spiral antenna 6 arranged on the dielectric window 5, the vacuum vessel 1
A plasma is generated in the inside, and plasma processing such as etching, deposition, and surface modification can be performed on the substrate 8 placed on the electrode 7. An electrode high frequency power supply 9 for supplying high frequency power to the electrode 7 is provided.
Can be controlled. A DC power supply 11 is connected to the annular conductor 10 having a thickness W = 2 cm and arranged substantially in parallel with the substrate 7 so that the potential of the annular conductor 10 can be adjusted. Note that, when the substrate 8 is a silicon-based material, the annular conductor 10 is made of a material containing silicon as a main component in order to avoid contamination of the substrate 8 with impurities. Also,
The annular conductor 10 forms a part of the inner wall of the vacuum vessel 1.

The potential of the annular conductor 10 is changed to the ground potential (= 0).
V), when the plasma generation conditions (gas type, gas pressure, magnitude of high frequency power, etc.) change, the place where the higher density part of the plasma is formed may change or the plasma may flicker. there were. In addition, a portion having a higher density of plasma may be formed directly above the substrate 8, and the uniformity of the processing speed in the substrate surface was poor. Further, hollow cathode discharge occurred inside the viewing window 12 provided in the vacuum vessel 1.

Then, when the plasma space potential was measured using the Langmuir probe method, the value was about 30 V
Therefore, the potential of the annular conductor 10 was set to 40 V, which was higher than that, and the stability of the plasma was examined. As a result, the plasma generation conditions (gas type, gas pressure, high-frequency power, etc.) changed. However, the place where the higher density portion of the plasma was formed did not change or the plasma flickered. Further, a portion having a higher density of plasma was not formed immediately above the substrate 8, and the uniformity of the processing speed in the substrate surface was improved. Further, no hollow cathode discharge occurred inside the viewing window 12 provided in the vacuum vessel 1.

The reason why an excellent plasma can be obtained when the potential of the annular conductor 10 is set higher than the plasma space potential is as follows. That is, as shown in FIG. 2, the vacuum vessel 1 is grounded, and is electrically insulated from the annular conductor 10 by the insulating material 13. When the potential of the annular conductor 10 is higher than the plasma space potential, an electronic sheath 15 is formed near the surface of the annular conductor 10. Therefore, when the potential of the annular conductor 10 is low, the ion sheath 14 which has been a propagation path of the electromagnetic wave disappears,
Also, since the width of the annular conductor 10 is larger than the plasma skin depth, the electromagnetic wave propagated from the upstream antenna 6 side cannot propagate to the substrate 8 downstream from the vicinity of the annular conductor 10 in the end, The light is reflected toward the dielectric window 5 near the annular conductor 10. At this time, a standing wave rises along the inner wall surface of the vacuum vessel 1 from the dielectric window 5 to the annular conductor 10, and a stable plasma state can be obtained.

In the above-described embodiment of the present invention, the case where the high frequency power of 100 MHz is supplied to the spiral antenna has been described. However, the form and frequency of the antenna are not limited to this, and are 50 MHz to 3 GHz.
The present invention is effective in a plasma processing method and apparatus using a frequency of z. For example, by applying the present invention to the spoke antenna system shown in FIG. 3 and the slot antenna system shown in FIG. 4, uniform and stable plasma can be generated, and the uniformity of the processing speed in the substrate surface can be improved. It is possible to provide a plasma processing method and apparatus capable of suppressing generation of a hollow cathode discharge which causes deterioration and contamination of a substrate due to sputtering of a solid material.

In the above-described embodiment of the present invention, the case where no DC magnetic field exists in the vacuum vessel has been described. However, when there is no DC magnetic field large enough to allow electromagnetic waves to enter the plasma, for example, The present invention is effective even when a small DC magnetic field of about several tens of gauss is used to improve the ignitability. However, the present invention is particularly effective when no DC magnetic field exists in the vacuum vessel.

In the above-described embodiment of the present invention, the case where the ring-shaped conductor is arranged substantially in parallel with the substrate has been described. It is possible to obtain a suitable plasma. However, if emphasis is placed on the uniformity of the processing speed in the plane of the substrate, it is preferable that the annular conductor is disposed substantially parallel to the substrate.

Further, in the above-described embodiment of the present invention, the case where the annular conductor is made of a substance containing silicon as a main component has been described. Other materials can be used as the ring conductor. For example, the ring conductor may be made of a substance containing carbon as a main component.

Further, in the above-described embodiment of the present invention, the case where the width of the annular conductor is 2 cm has been described. However, if the width of the annular conductor is larger than the plasma skin depth, the reflection of electromagnetic waves is effective. Can be done. But,
Even if the width of the annular conductor is smaller than the plasma skin depth,
Since the electromagnetic wave can be greatly attenuated, the width of the annular conductor may be approximately 1 cm or more. If the width of the ring-shaped conductor is too large, the ring-shaped conductor may be etched by negative ions to deteriorate the atmosphere in the vacuum vessel, and the flowing DC current may increase. It is desirable that it is about 10 cm or less.

Further, in the above-described embodiment of the present invention, the case where the positive DC voltage applied to the annular conductor is 40 V has been described, but the positive DC voltage applied to the annular conductor is smaller than the plasma space potential. If it is higher, the reflection of electromagnetic waves can be performed effectively. However, even if the positive DC voltage applied to the annular conductor is lower than the plasma space potential,
Compared to the case where the potential of the inner wall of the vacuum vessel is the ground potential or the case where the inner wall of the vacuum vessel is made of an insulator such as aluminum oxide, the reflectivity of the electromagnetic wave is higher, so the voltage is applied to the annular conductor. The positive DC voltage may be about 10 V or more. However, the lower the positive DC voltage applied to the ring-shaped conductor, the smaller the DC current flowing. Therefore, the positive DC voltage applied to the ring-shaped conductor should not be too high. Also, if the positive DC voltage applied to the annular conductor is too high, a discharge occurs between the annular conductor and the plasma, and the annular conductor may be rapidly etched. Is preferably about 120 V or less.

[0038]

As is clear from the above description, according to the plasma processing method of the first invention of the present application, the inside of the vacuum vessel is evacuated while supplying the gas into the vacuum vessel, and the inside of the vacuum vessel is maintained at a predetermined pressure. A plasma processing method for generating plasma in a vacuum container by radiating electromagnetic waves into the vacuum container while controlling the substrate, and processing a substrate mounted on an electrode in the vacuum container, wherein the inner wall of the vacuum container is Since a positive DC voltage is applied to the annular conductor that forms a part of the substrate, uniform and stable plasma can be generated. It is possible to suppress the occurrence of hollow cathode discharge that may cause impurities to enter the semiconductor device.

Further, according to the plasma processing apparatus of the second invention of the present application, means for supplying gas into the vacuum vessel, means for evacuating the vacuum vessel, a dielectric window, and a vacuum through the dielectric window. An antenna for radiating electromagnetic waves into the container, a high-frequency power supply capable of supplying high-frequency power to the antenna, an electrode for mounting a substrate, and an annular conductor forming a part of an inner wall of the vacuum container; And means for applying a positive DC voltage to the annular conductor, so that uniform and stable plasma can be generated. , The occurrence of hollow cathode discharge which may cause impurities to be mixed into the substrate.

[Brief description of the drawings]

FIG. 1 is a perspective view showing a configuration of a plasma processing apparatus used in an embodiment of the present invention.

FIG. 2 is a schematic view showing a state near an annular conductor in an embodiment of the present invention.

FIG. 3 is a perspective view showing a configuration of a plasma processing apparatus used in another embodiment of the present invention.

FIG. 4 is a perspective view showing a configuration of a plasma processing apparatus used in another embodiment of the present invention.

FIG. 5 is a perspective view showing a configuration of a plasma processing apparatus used in a conventional example.

FIG. 6 is a perspective view showing a configuration of a plasma processing apparatus used in a conventional example.

FIG. 7 is a perspective view showing a configuration of a plasma processing apparatus used in a conventional example.

FIG. 8 is a schematic diagram showing a state near the inner wall of a vacuum vessel in a conventional example.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 ... Vacuum container 2 ... Gas supply unit 3 ... Pump 4 ... High frequency power supply for antennas 5 ... Dielectric window 6 ... Antenna 7 ... Electrode 8 ... Substrate 9. ..High-frequency power supply for electrodes 10 ... Circular conductor 11 ... DC power supply 12 ... View window

──────────────────────────────────────────────────の Continued on the front page (51) Int.Cl. ⁶ Identification code FI H01L 21/3065 H01L 21/31 C 21/31 21/302 B

Claims (18)

[Claims] 1. While evacuating the inside of a vacuum vessel while supplying gas into the vacuum vessel and controlling the inside of the vacuum vessel to a predetermined pressure,
A plasma processing method for processing a substrate mounted on an electrode in a vacuum vessel by generating plasma in the vacuum vessel by radiating an electromagnetic wave into the vacuum vessel, and forming a part of an inner wall of the vacuum vessel. A plasma processing method comprising applying a positive DC voltage to an annular conductor. 2. The electromagnetic wave has a frequency of 50 MHz to 3 GHz.
2. The plasma processing method according to claim 1, wherein z is z. 3. The plasma processing method according to claim 1, wherein no DC magnetic field exists in the vacuum vessel. 4. The plasma processing method according to claim 1, wherein the annular conductor is disposed substantially parallel to the substrate. 5. The plasma processing method according to claim 1, wherein the annular conductor is made of a substance containing silicon or carbon as a main component. 6. The plasma processing method according to claim 1, wherein the width of the annular conductor is larger than the plasma skin depth. 7. The plasma processing method according to claim 1, wherein the thickness of the annular conductor is 1 to 10 cm. 8. The plasma processing method according to claim 1, wherein the positive DC voltage is higher than the plasma space potential. 9. The plasma processing method according to claim 1, wherein the positive DC voltage is 10 V to 120 V. 10. A means for supplying gas into a vacuum vessel;
A means for evacuating the vacuum vessel, a dielectric window, an antenna for radiating electromagnetic waves into the vacuum vessel through the dielectric window, a high-frequency power supply capable of supplying high-frequency power to the antenna, and a substrate are mounted. A plasma processing apparatus comprising: an electrode for mounting; an annular conductor forming a part of an inner wall of a vacuum vessel; and means for applying a positive DC voltage to the annular conductor. 11. An electromagnetic wave having a frequency of 50 MHz to 3 G
11. The plasma processing apparatus according to claim 10, wherein the frequency is Hz. 12. The plasma processing apparatus according to claim 10, wherein there is no means for applying a DC magnetic field in the vacuum vessel. 13. The plasma processing apparatus according to claim 10, wherein the annular conductor is disposed substantially parallel to the substrate. 14. The plasma processing apparatus according to claim 10, wherein the annular conductor is made of a substance containing silicon or carbon as a main component. 15. The plasma processing apparatus according to claim 10, wherein the width of the annular conductor is larger than the plasma skin depth. 16. The plasma processing apparatus according to claim 10, wherein the width of the annular conductor is 1 to 10 cm. 17. The plasma processing apparatus according to claim 10, wherein the positive DC voltage is higher than the plasma space potential. 18. The plasma processing apparatus according to claim 10, wherein the positive direct current voltage is 10 V to 120 V.