JPH0831444B2 - Plasma processing device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial application] The present invention relates to a plasma processing apparatus using low-temperature plasma, and in particular, high speed of each technology such as CVD, etching, sputtering, and ashing used in the manufacture of semiconductor elements. The present invention relates to a plasma processing apparatus suitable for processing.

[Conventional technology]

The equipment using low-temperature plasma is roughly divided into those that use a technology of generating plasma by applying a high-frequency voltage of about 10 kHz to 30 kHz to one of parallel plate electrodes in a vacuum (Semiconductor Research 18; P121 to P170, Semiconductor Research 19; P225-P267),
In some cases, a technique of introducing a 2.45 GHz microwave into a vacuum chamber to generate plasma is used. Conventionally, of these, the technique using parallel plate electrodes has been mainly used.

On the other hand, with the miniaturization of semiconductor devices, it has become a problem that the device characteristics are affected by the impact of ions generated during plasma processing. Further, in order to improve the processing capacity, it is required to increase the processing speed.

When increasing the processing speed, it is not enough to simply increase the density of plasma or the concentration of radicals (active particles immediately before ionization). Ion energy plays an important role in dry etching by plasma treatment and plasma CVD. For example, in the case of dry etching, if the ion energy is too large, the underlying film is scraped or the crystal structure is affected, resulting in deterioration of the device characteristics.
On the other hand, if it is too small, the polymer formed on the etched surface is not sufficiently removed, and the etching rate decreases. Alternatively, on the contrary, a protective film made of a polymer is not formed, the side surface of the pattern is etched, and the dimensional accuracy of the pattern deteriorates. Also, in plasma CVD,
Ion energy influences film formation, such that when ion energy is weak, the film composition becomes coarse, and when energy is strong, the film becomes dense.

Therefore, densification of plasma and proper control of ion energy are indispensable for future plasma processing. Known examples include JP-A 56-13480 and JP-A 5-13480.
A method using microwaves as disclosed in Japanese Patent Publication No. 6-96841 has been proposed.

When plasma is generated by microwaves, even if the microwaves generated by the magnetron are radiated to the plasma generation chamber where the pressure is low, the electric field strength of the microwaves is not sufficient, so sufficient energy is not supplied to the electrons and plasma is generated. It is difficult to get it done. Therefore, in order to generate plasma by microwaves, a method of matching the cyclotron frequency at which electrons rotate in a plane perpendicular to the magnetic field with the frequency of microwaves to bring them into a resonance state to supply energy to the electrons, Are radiated to the cavity resonator to increase the amplitude of the microwave and increase the electric field strength to supply energy to the electrons. The former is JP Sho
56-13480, the magnetic field microwave or ECR (Electron Cyclotron Resonance)
It is called the law. The latter is disclosed in JP-A-56-96841.

In the plasma generated by microwaves, energy is directly supplied from the microwaves to the electrons, so that the inter-sheath voltage formed between the plasma and the substrate hardly changes. Therefore, by applying a high frequency voltage to the electrode on which the substrate is placed and arbitrarily controlling the inter-sheath voltage, it is possible to control the high plasma density and appropriate ion energy required for high speed operation.

[Problems to be solved by the invention]

Although it has been described above that the energy of ions plays an important role in plasma processing, the conventional technique has the following problems in this respect.

Among the conventional techniques, in the ECR method, as shown in JP-A-56-13480, when a high frequency voltage is applied to an electrode on which a substrate is placed, there is no ground electrode on the side facing this electrode, and therefore the high frequency current is applied. Flows into the surrounding processing chamber, so that the effect of ion energy on the substrate is strong around the substrate and weak at the center, and there is a problem that the entire substrate cannot be processed under uniform conditions.

Further, in the method using the cavity resonator, since the plasma is generated in the resonator, when the plasma is generated, the microwave wavelength changes depending on the density of the plasma. There was a problem that became unstable. That is, since the resonance condition is satisfied until the plasma is generated, the electric field strength of the microwave is increased, and the plasma is generated. However, when plasma is generated and the plasma density is increased, the wavelength of the microwave is changed, the resonance condition is not satisfied, and the electric field strength is reduced. Then, the supply of energy to the electrons is reduced and the plasma density is reduced. When the plasma density decreases, the resonance condition is satisfied and the plasma density increases again. Due to such a phenomenon, it is difficult to stably generate plasma.

Further, if a high frequency voltage applying electrode is provided in the cavity resonator in order to control the energy of the ions that enter the substrate from these plasmas, the microwaves will be reflected and the plasma will become more unstable. was there.

An object of the present invention is to provide a plasma processing apparatus capable of generating stable and high-density plasma and making the energy of ions incident on a substrate uniform over the entire substrate.

[Means for solving problems]

In general, when a microwave propagates in a waveguide or a cavity resonator which is considered as a kind of waveguide, a current corresponding to an electric field or a magnetic field flows on the surface of the waveguide. Therefore,
If a slit is provided in a part of the waveguide so that it crosses this current, charges accumulate at both ends of the slit, and this changes with the progress of microwaves. Microwaves are radiated to the outside of.

According to this principle, a microwave is supplied to the plasma generation chamber from a slit provided in the waveguide according to this principle, or the waveguide is connected to a cavity resonator and the microwave is applied to the cavity resonator. This is achieved by providing a slit for radiating the microwave and supplying the microwave to the plasma generation chamber from the slit.

[Action]

The conventional ECR method radiates microwaves directly into the plasma generation chamber from the opening of the waveguide. Therefore, if the ground electrode is installed between the plasma generation chamber and the opening of the waveguide, the microwave is reflected by the ground electrode and cannot be supplied to the plasma generation chamber.

On the other hand, in the present invention, the end face of the waveguide is closed, and the end face is provided with a slit for radiating microwaves. Then, if necessary, the end face of this waveguide was set to the ground potential.

The opening area of the slit can be about 1/3 of the entire end face of the waveguide. Therefore, when a high-frequency voltage is applied to the electrode on which the substrate is placed, the high-frequency current flows evenly between the end face of the waveguide and the electrode, and the effect of ions can be evenly generated on the entire surface of the substrate. Further, a sufficient amount of microwaves can be supplied through the slit, and high density plasma can be generated.

On the other hand, when the cavity resonator is connected to the waveguide, the microwave whose amplitude is increased due to resonance in the cavity resonator is radiated to the plasma generation chamber through the slit. Therefore, high-density plasma can be generated without forming the plasma generation chamber in the conventional cavity resonator structure.

Therefore, the electrode structure according to the present invention is not restricted by the relationship with the cavity resonator as in the conventional case. Further, since plasma is not generated in the cavity resonator, there is no change in the resonance state and it is possible to stably generate plasma. Furthermore, by setting the cavity resonator to the ground potential, EC
As in the case of the R method, the counter electrode can be parallel to the electrode, and the effect of ions can be uniformly generated on the entire substrate.

〔Example〕

An embodiment of the present invention will be described below with reference to FIGS.

FIG. 1 is a vertical cross-sectional view of the apparatus of this embodiment. In the figure, the cavity resonator 1 is an E ₀₁ mode circular cavity resonator, and a microwave is supplied from a magnetron 3 through a waveguide 2. The waveguide 2 is mounted eccentrically to the circular cavity resonator 1 in order to improve the coupling with the E ₀₁ mode. A ceramics plate 4 is fixed to the cavity resonator 1 on the side opposite to the waveguide mounting side. The ceramic plate 4 is brazed to the metal flange 4b through a thin-walled cylindrical portion. In addition, on the lower surface side of the ceramic plate 4, a plating pattern 4a having a pattern shape shown by the hatched portion in FIG. 2 is provided corresponding to the E ₀₁ mode cavity oscillator.
Is formed with a thickness of about 0.1 mm. The slit portion 4c that radiates microwaves of the ceramic plate 4 has a ring-shaped slit opening portion in the direct field direction with respect to the electric field of E ₀₁ mode, and each slit portion 4c has a length of 2.45 GHz microwave. In this case, in order to improve the radiation from the slit, the dimension is 60 mm or more, which corresponds to 1/2 wavelength of the microwave. The plating pattern 4a and the metal flange 4b are electrically connected. Further, the metal flange 4b and the plasma generating chamber 8 are connected via the O-ring 5, so that the plasma generating chamber 8 can be exhausted to a negative pressure. Below the ceramic plate 4, there is a gas dispersion plate 7 made of quartz. As shown in FIG. 3, the gas distribution plate 7 has a gas supply path 7a.
Is provided, and the gas for plasma processing is uniformly blown out from the gas blowing hole 7b to the plasma generation chamber 8. This gas supply path 7a is entirely provided below the plating pattern 4a as shown by the broken line in FIG.
The gas for plasma processing is guided by the gas supply pipe 9,
The gas is supplied uniformly to the gas supply path 7a through the gas sump 6.

The plasma generation chamber 8 is exhausted from an exhaust port 10 by a vacuum pump (not shown). A substrate electrode 12 is provided below the gas dispersion plate 7. The substrate electrode 12 is insulated from the plasma generation chamber 8 by a ceramic cover 13 and is connected to a 13.56 MHz high frequency power supply 15. A quartz cylinder 11 thicker than the gas dispersion plate 7 is fitted on the inner surface of the plasma generation chamber 8. The cavity resonator 1 and the plasma generation chamber 8 are grounded.

In the above apparatus, power is supplied to the magnetron 3 from a power source (not shown) to generate microwaves, which are supplied to the cavity resonator 1 by the waveguide 2. The microwave whose amplitude is increased in the cavity resonator 1 is radiated to the plasma generation chamber 8 from the slit portion 4c.

The plasma generation chamber 8 is supplied with a gas for plasma processing from a gas source (not shown) through the gas supply pipe 9, the gas reservoir 6, and the gas dispersion plate 7, and is exhausted from the exhaust port 10, thereby
^-3 Torr pressure controllable.
Since the microwave radiated to the plasma generation chamber 8 has a large amplitude, the plasma is turned on and maintained even if the plasma generation chamber 8 does not have the cavity resonance structure.

Next, as a specific plasma treatment, the case of etching will be described first.

First, the etching gas is supplied from the gas supply pipe 9,
After setting the plasma generation chamber 8 to a preset pressure of 1 to 10 ^-3 Torr, the magnetron 3 is operated to generate plasma.

The etching gas supplied from the gas supply pipe 9 passes through the gas reservoir 6 and the gas supply passage 7a of the gas dispersion plate 7, and is evenly supplied to the plasma generator 8 from the gas blowing holes 7b of the gas dispersion plate 7. The etching gas supplied in this manner is excited in plasma to become ions and radicals.

In the plasma generated by the microwave, the microwave directly acts on the electrons in the plasma, so that the potential difference between the plasma and the substrate 14 is at a level of 20 to 30V. Therefore, the energy of the ions incident on the substrate 14 is weak and anisotropic etching cannot be performed only by plasma generated by microwaves. In this embodiment, the high frequency power source 15 is applied to the substrate electrode 12.
A high-frequency voltage is applied to the substrate 14 to accelerate ions in the plasma and cause the ions to enter the substrate 14. Further, the ion energy can be arbitrarily controlled by the applied voltage and can be set to an appropriate value. Therefore, it is possible to perform anisotropic etching with high precision.

When a high frequency voltage is applied to the substrate electrode 12, a high frequency current passes through the plasma and flows to the ground side. In this case, if the high frequency current is not uniform, the energy of the ions incident on the substrate 14 will not be uniform on the substrate 14, and the etching rate will vary on the substrate 14. However, in this embodiment, the ground potential plating pattern 4a is provided at a position facing the substrate electrode 12, so that the high-frequency current flows evenly on the substrate electrode 12.

The etching characteristics of the SiO ₂ film by the conventional equipment are as follows: etching rate 360 nm / min, etching rate ratio to the underlying Si film is 10
And the uniformity was ± 5%. When the etching rate is increased to 500 nm / min or more with this conventional device, the etching rate ratio with the underlying film is reduced by 5 times, and the uniformity is ± 12%.
Fell to. On the other hand, in the device according to the present invention, the etching rate is 520 nm / min, and the etching rate ratio with the underlying Si film is
10 times, uniformity ± 5% can be obtained.

Although the above is the case of etching, also in the case of plasma CVD, it is possible to form a film on the surface of the substrate 14 by supplying a gas for film formation from the gas supply pipe 9 similarly to etching. At this time, the film quality can be controlled by controlling the energy of the ions incident on the substrate 14. As described above, the apparatus of the present invention enables uniform and high-quality film formation.

As described above, the apparatus of the present invention can be applied to the processing performed using the energy of the plasma and the ions incident from the plasma.

Although one embodiment has been described in the above description, the structure of the resonator and the frequency of the high frequency power source are not limited to the above embodiment. The structure of the resonator can be arbitrarily selected as the resonance mode and structure as long as the resonance condition is satisfied, such as a rectangular structure resonator and a coaxial structure resonator. Also, the frequency of the high frequency power supply can be arbitrarily selected from DC to several tens of MHz. However, when the target of plasma treatment is an insulating film, a high frequency of 100 kHz to several tens of MHz is suitable.

According to the embodiment of the present invention described above, when the plasma is generated by using the microwave, the electrode of the ground potential is also installed on the surface facing the electrode for processing the substrate, and Since the gas for plasma processing can be blown out uniformly from the electrode surface, there is an effect that uniform plasma processing can be performed. Further, since it is not necessary to make the plasma generation chamber have a cavity resonator structure, there is an effect that the structure of the electrode and the plasma generation chamber is not restricted.

〔The invention's effect〕

According to the present invention, in a plasma processing apparatus, there is an effect that plasma generation using microwaves is stabilized.

Further, according to the present invention, there is an effect that the device structure is not restricted by the relationship with the cavity resonator. Therefore, by setting the cavity resonator to the ground potential, a counter electrode parallel to the electrode on which the processing target is placed can be formed. As a result, the energy of the microwave can be propagated through the slit provided in the counter electrode, and the effect of ions and radicals generated by this energy can be uniformly applied to the object to be processed.

Moreover, the influence of ions and radicals can be generated uniformly. As a result, plasma processing with high-speed and optimum ion energy can be performed. Further, in the case of patterning a semiconductor wafer, a fine pattern can be formed with high accuracy, high speed and low damage. Furthermore, there is an effect that uniform film formation can be performed at high speed.

[Brief description of drawings]

FIG. 1 is a vertical cross-sectional view of an embodiment of the plasma processing apparatus according to the present invention, FIG. 2 is a plan view showing the details of the ceramic plate in FIG. 1, and FIG. 3 is a gas dispersion plate in FIG. It is a longitudinal cross-sectional view showing details. Explanation of symbols 1 ... Cavity resonator, 4 ... Ceramic plate 4a ... Plating pattern, 7 ... Gas dispersion plate 8 ... Plasma generation chamber, 12 ... Substrate electrode, 14 ... Substrate, 15 ... High frequency power supply

Claims (2)

[Claims] 1. A plasma generation chamber having a cavity resonator adapted to introduce microwaves from a microwave generation source, a gas supply means, an exhaust means, and a means for placing a substrate to be processed. A plasma processing apparatus, wherein the cavity resonator is attached to the plasma generation chamber via a means for sealing a vacuum and a slit plate capable of electromagnetically coupling microwaves. apparatus. 2. A structure in which a thin metal cylinder is joined to a ceramic plate by means of a vacuum sealing means and a slit plate capable of electromagnetically coupling microwaves, and a flange portion attached to the ceramic plate allows vacuum sealing. At the same time, the plasma processing apparatus according to claim 1, wherein a slit is formed on the surface of the ceramic plate by plating and the slit is electrically connected to the metal cylinder.