JPS63103088A - Plasma treating device - Google Patents

Abstract

PURPOSE:To uniformize energy of ions incident on a base plate by providing a slit to one part of a cavity resonator and opposing this slit to a plasma generation chamber and providing a magnetic field generating means to the plasma generation chamber. CONSTITUTION:A plasma generation chamber 6 is regulated to fixed pressure by feeding etching gas through a gas feed pipe 9 and exhausting it through a gas exhaust pipe 10. Microwave is oscillated by the action of a magnetron 3 and fed to a cavity resonator 1 via a waveguide 2 and energy of microwave wherein magnitude is made large is projected to the plasma generation chamber 6 via the slit of a slit plate 5. Therefore plasma caused by microwave is generated between the slit plate and an electrode 7 and when high-frequency voltage is impressed on the electrode 7 from a high-frequency electric source 11, high-frequency current is allowed to uniformly flow between the electrode 7 and the slit plate 5 because the electrode 7 and the slit plate 5 are parallel provided. Thereby the electric field generated between the electrode 7 and plasma is made uniform and energy of ions of etching gas is uniformly made incident on all surfaces of a wafer 12.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Application Field] The present invention relates to the production of semiconductor devices using low temperature plasma, particularly CVD and etching sputtering.

The present invention relates to a plasma processing apparatus suitable for high-speed processing of various techniques such as ashing.

[Conventional technology]

Devices that use low-temperature plasma can be roughly divided into those that use technology to generate plasma by applying a high-frequency voltage of about 10 KHz to 30 cm2 to one side of parallel plate electrodes in a vacuum (Semiconductor Research 18; P121 ~P170, Semiconductor Research 19; P225~P267) and 2.45
Some use a technique that generates plasma by introducing GHz microwaves into a vacuum chamber. Conventionally, among these techniques, techniques using parallel plate electrodes have been mainly used.

On the other hand, with the miniaturization of semiconductor devices, it has become a problem that device characteristics are affected by ion bombardment generated during plasma processing. Furthermore, there is a demand for increasing processing speed in order to improve processing capacity.

When increasing the processing speed, it is not sufficient to simply increase the plasma density or radical (active particles immediately before ionization) concentration. Ion energy plays an important role in dry etching by plasma processing and plasma CVD.

In the case of dry etching, if the ion energy is too high, the underlying film may be scraped or the crystal structure may be affected.
Element characteristics deteriorate. On the other hand, if it is too small, the polymer formed on the etched surface will not be removed sufficiently and the etching rate will decrease. Or conversely, a polymer protective film is not formed and the side surfaces of the pattern are etched, resulting in problems such as poor pattern dimensional accuracy.

Even in plasma CVD, ion energy influences film formation, such that when the ion energy is low, the film composition becomes coarse, and when the ion energy is high, the film composition becomes dense.

Therefore, increasing the density of plasma and appropriately controlling ion energy will be essential for future plasma processing. As well-known examples, methods using microwaves have been proposed as shown in Japanese Patent Laid-Open No. 56-13480 and Japanese Patent Laid-Open No. 56-96841.

When generating plasma using microwaves, even if the microwaves generated by a magnetron are radiated into a low-pressure plasma generation chamber, 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 do so. Therefore, in order to generate plasma using microwaves, there is a method to match the cyclotron frequency at which electrons rotate in a plane perpendicular to the magnetic field and the microwave frequency to create a resonance state and supply energy to the electrons, and a method to supply energy to the electrons. There are two methods: increasing the amplitude of microwaves by radiating them into a resonator, and increasing the electric field strength to supply energy to electrons. The former is Japanese Patent Application Publication No. 1983.
-13480, which uses magnetic field microwaves or ECR (Elect-ron Cyclotro
It is called the Re5onance) method. The latter is shown in Japanese Patent Application Laid-Open No. 56-96841.

Since the microwave-generated plasma is directly supplied with energy to the electrons by the microwave, 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 controlling the voltage between the sheaths,
It is possible to control the high plasma density and appropriate ion energy necessary for high speed.

[Problem that the invention seeks to solve]

I mentioned earlier that ion energy plays an important role in plasma processing.

Among the conventional technologies, the ECR method has a
As shown in Figure 0, when a high frequency voltage is applied to the electrode on which the substrate is placed, since there is no ground electrode on the opposite side of this electrode, the high frequency current flows between it and the surrounding odor chamber, causing an electric shock on the substrate. There was a problem that the effect of ion energy was strong around the substrate and weak at the center, making it impossible to process the entire substrate under uniform conditions.

In addition, in the method using a cavity resonator, the structure generates plasma inside the resonator, so when plasma is generated, the wavelength of the microwave changes depending on the density of the plasma.
There was a problem in that the resonance conditions were not met and the plasma became unstable. That is, since the resonance condition is satisfied until plasma is generated, the electric field strength of the microwave increases and plasma is generated. However, when plasma is generated and the plasma density becomes sieved, the wavelength of the microwave changes, the resonance condition is no longer satisfied, and the electric field strength decreases. Then, the supply of energy to electrons decreases, and the plasma density decreases. When the plasma density decreases, the resonance condition is satisfied,
Plasma density increases again. Because of this phenomenon, it has been difficult to generate plasma stably.

In addition, if a high-frequency voltage applying electrode is provided inside the cavity resonator in order to control the energy of ions incident on the substrate from these plasmas, there is a problem that reflection of microwaves occurs and the plasma becomes even more unstable. there were.

An object of the present invention is to generate stable and high-density plasma and to make the energy of ions incident on the substrate uniform over the entire substrate.

[Means for solving problems]

Generally, when microwaves propagate in a waveguide or a cavity resonator, which is considered to be a type of waveguide, a current corresponding to the electric field and magnetic field flows on the surface of the waveguide.

Therefore, if a slit is provided in a part of the waveguide to cross this current, charges will accumulate at both ends of the slit, and this will change as the microwave travels, causing the electric field between both ends of the slit to change, causing the waveguide to pass through the waveguide. Microwaves are radiated to the outside.

The purpose is to provide a structure in which microwaves are supplied to the plasma generation chamber from a slit provided in a waveguide based on this principle, or to connect a waveguide to a cavity resonator and supply microwaves to this cavity resonator. This is achieved by providing a radiation slit and supplying microwaves to the plasma generation chamber.

[Effect]

In the conventional ECR system, microwaves are directly radiated into the plasma generation chamber from the opening of the waveguide. For this reason, if a ground electrode is installed between the plasma generation chamber and the opening of the waveguide, the microwaves will be reflected by the ground electrode and cannot be supplied to the plasma generation chamber.

In the present invention, the end face of the waveguide has a closed structure, and a slit for radiating microwaves is provided in this end face.

Then, if necessary, the end face of this waveguide was brought to earth potential.

The opening area of the slit can be set to 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 generated evenly over the entire surface of the substrate. Furthermore, a sufficient amount of microwaves can be supplied through the slit, and high-density plasma can be generated.

On the other hand, when a cavity resonator is connected to the waveguide, microwaves with increased amplitude due to resonance within the cavity resonator are radiated into the plasma generation chamber through the slit. Therefore, high-density plasma can be generated without requiring the plasma generation chamber to have a cavity resonator structure as in the conventional case.

Therefore, the electrode structure according to the present invention is not limited by the relationship with a cavity resonator, as in the prior art. In addition, since no plasma is generated within the cavity resonator, there is no change in the resonance state.
Plasma can be stably generated. Furthermore, by connecting the cavity resonator to ground potential, it can be used as a counter electrode parallel to the electrode, as in the case of the F and CR methods, and the ion effect can be generated uniformly over the entire substrate. .

[Example] Embodiments of the present invention will be described below with reference to FIG.

The cavity resonator 1 is an EOI mode circular cavity resonator,
Microwaves are supplied from a magnetron 3 through a waveguide 2. The waveguide 2 is mounted eccentrically with respect to the circular cavity resonator 1 in order to improve coupling with the EOI mode. A ceramic plate 4 and a slit plate 5 are fixed to the other side of the circular cavity resonator 1. A plasma generation chamber 6 is connected below it. Note that the structure is sealed in vacuum by a ceramic plate 4.

The planar structure of the slit plate 5 has a ring-shaped slit opening in a direction perpendicular to the electric field of the E old mode, as shown in FIG. 2B. When using a 2.45 GHz microwave, the length of each slit 5c is 6, which corresponds to 1/2 wavelength of the microwave, in order to improve the radiation of the microwave from the slit.
The dimensions are 0 or more.

The plasma generation chamber 6 (FIG. 1) has an electrode 7. Gas supply pipe 9
．． A gas exhaust pipe 10 is provided. The electrode 7 is fixed to the plasma generation chamber 6 via an insulating material 8, and is further connected to a high frequency power source 11.

A plasma processing gas can be supplied to the gas supply pipe 9 from a gas source (not shown) at a set flow rate.

A vacuum pump (not shown) is connected to the gas exhaust pipe 10, so that the pressure inside the plasma generation chamber can be controlled at 1 to 10'' Torr.

The magnetron 3 is operated to oscillate microwaves, which are supplied to the cavity resonator 1 through the waveguide 2. The energy of the microwave with increased amplitude inside the cavity resonator is transferred to the slit plate 5.
is emitted into the plasma generation chamber through the slit. Since the amplitude of the microwave radiated into the plasma generation chamber is large in the cavity resonator 1, the plasma is lit and maintained even if the plasma generation chamber 6 does not have a cavity resonator structure.

First, let us explain the case of etching. Etching gas is supplied from the gas supply pipe 9, exhausted from the gas exhaust pipe 10 to maintain a constant pressure, and microwaves are supplied to generate plasma between the slit plate 5 and the electrode 7 by the microwaves. Since the microwave acts directly on the electrons in the plasma, the potential difference between this plasma and the electrode 70 is 20 to 30 V.
level.

A processing wafer 12 is placed on the electrode 7 , and a high frequency voltage is applied to the electrode 7 from the high frequency power supply 11 . Electrode 7 and slit plate 5
are installed in parallel, and the high frequency current flows evenly between the electrode 7 and the slit 5. Therefore, the electric field generated between the electrode and the plasma becomes uniform, and etching gas ions having uniform energy over the entire surface are incident on the wafer 12 while being controlled by the application of a high frequency voltage.

The ions of the etching gas and the active species (radicals) of the etching gas excited in the plasma react with the film to be processed on the wafer 12, and etching progresses.

Since the energies of the incident ions are uniform at this time,
Uniform etching is possible over the entire wafer.

Next, the application of this apparatus to plasma CVD will be explained.

A mixed gas of SiH4 and N2, N20 is supplied from the gas supply pipe 9, and N20, SiH4 is generated by plasma.
is decomposed to produce Si04, which is deposited on the wafer 12. Furthermore, the film quality is controlled by the incidence of ions from the plasma. At this time, since the incident energy of ions can be equalized, a uniform film can be formed over the entire surface of the wafer.

In this example, the microwave mode in the circular waveguide is EOI
[However, this occurrence is not limited to this case. However, microwave radiation is more efficient if the slit is perpendicular to the current flowing on the surface of the cavity resonator, so in the case of HOI mode, the structure is shown in Figure 3, and in the case of H1l mode, it is shown in Figure 4. The structure shown is shown below.

As described above, according to the present invention, the effects of ions essential for plasma processing can be equalized, and stable plasma can be generated.

In the actual example shown in Figure 1, since microwaves are only radiated into the plasma generation chamber, the density of the generated plasma is 10
When it exceeds 11 cWL-3, microwaves are reflected and the plasma density cannot be increased any further. Plasma density is 10! If the above is necessary, coil 13. The coil 14 provides a magnetic field 15 parallel to the microwave radiation direction.

In the case of this embodiment, since the amplitude of the microwave is increased by the cavity resonator 1, there is no need to create an electron cyclotron resonance state, and the magnetic field strength can be selected depending on the required plasma density. Furthermore, since the amplitude of the microwave is larger than that of the conventional resonance method, it has the effect of creating a stable discharge in areas with a higher degree of vacuum.

FIG. 6 shows an embodiment in which the present invention is applied to ashing processing.

In this embodiment, the parts having the same numbers as those shown in FIG. 1 are the same, so only the different parts will be explained.

A mesh plate 20 is provided inside the plasma processing chamber 6, and the wafer 12 is placed on a table 21.

Oxygen gas is supplied from the gas supply pipe 9, the magnetron 3 is operated, microwaves are supplied, and plasma is generated between the slit plate 5 and the mesh plate 20.

Since the mesh plate 20 has dimensions that do not allow microwaves to pass through, the plasma is confined between the mesh plate 5 and the slits. Oxygen gas is turned into a radical state by the plasma and is supplied onto the wafer 12 through the mesh plate 2o. The resist film on the wafer is subjected to an ashing process by these oxygen radicals.

In the above embodiments, a combination of a circular cavity resonator and a slit plate has been described, but the present invention is not limited to this.

An example applied to a sputtering apparatus will be explained in FIG.

The processing chamber 33 is made of ceramics, and has a gas supply port and a gas exhaust port (not shown) that allow the processing chamber to have a pressure of 10" Torr to 1
It is a trap so that the pressure can be controlled to 0-2 Torr.

A target 34 and a wafer table 36 are located inside the processing chamber 33.
There is. A high frequency power source 35 is connected to the target, and a wafer table 36 is connected to ground. A shield chamber 40 and a rectangular ring-shaped resonator 31a are provided outside the processing chamber 33.

A ring-shaped resonator is a rectangular waveguide formed into a ring, and the circumferential length of the ring is an integral multiple of 1/2 of the wavelength inside the tube. A portion of the ring-shaped waveguide is provided with an end wall to prevent the phase of the resonating microwave from shifting.

FIG. 8 shows the planar structure of the ring-shaped resonator 31a.

The resonator 31 includes a magnetron 32. Microwaves are supplied from the waveguide 30. A coil 37. is installed outside the shield chamber 40 (FIG. 7). There is a coil 38 which generates a Cubs magnetic field 42. The shield chamber is made of aluminum or stainless steel, and uses a material that does not allow microwaves to escape, but allows magnetic fields to pass through.

A circumferential slit 43 is provided inside the ring-shaped resonator. When microwaves are supplied to the ring-shaped resonator, the amplitude of the microwaves is amplified within the resonator, and the microwaves with large amplitude are radiated into the processing chamber 33 through the slit 43.

Argon gas was introduced into the processing chamber 33 at 10 Torr.
When maintained at the same level, plasma confined in the cup magnet f#J42 is generated between the target 34 and the wafer table 36. Next, a high frequency voltage is applied from the high frequency power supply 35.

Additional argon gas ions are introduced into the target, and the target material is sputtered to form a film on Ueno S39.

As described in the embodiment shown in FIG. 5, this system can stably generate plasma even under conditions of a higher degree of vacuum by using microwaves with a large amplitude, and has the effect of improving film quality.

This system combining a ring-shaped resonator and a slit can be used not only for sputtering but also for etching and plasma CVD.

FIG. 9 shows an example applied to etching.

Since the basic configuration is the same as the sputtering apparatus explained in FIG. 7, only the different points will be explained.

Inside the processing chamber 33 is a lower electrode 46. There is an upper electrode 45, and a lower electrode is fixed to the processing chamber via an insulator 41, so that a high frequency voltage can be applied from a high frequency power source 47. Upper electrode 45 is connected to ground.

Etching gas is introduced and the inside of the processing chamber 33 is heated to 10-2To.
The pressure is maintained at the rr level, and microwaves are supplied to the ring-shaped resonator 31. The amplitude of the microwave is amplified and radiated into the processing chamber through the slit 43, and plasma generated by the microwave is generated between the upper electrode 45 and the lower electrode 46.

When a high-frequency voltage is applied to the lower electrode 46, a high-frequency current flows evenly between the parallel electrodes, and ions incident on the wafer 39 are accelerated by a uniform potential difference between the sheaths, making it possible to obtain uniform etching processing characteristics over the entire surface of the wafer. .

As described above, according to the invention, when generating plasma using microwaves, an electrode can also be installed on the surface of the wafer that faces the electrode to be processed. Therefore, uniform plasma processing becomes possible. Furthermore, since the plasma generation chamber does not need to have a cavity resonator structure, the electrode structure,
This has the effect of eliminating restrictions on the structure of the plasma generation chamber.

〔Effect of the invention〕

The present invention has the effect of stabilizing the generation of plasma using microwaves.

According to the present invention, there is an effect that there is no restriction on the device configuration due to the relationship with the cavity resonator. Therefore, by connecting the cavity resonator to ground potential, it is possible to configure a counter electrode parallel to the electrode on which the object to be processed is placed. As a result, the energy of the Ca wave can be propagated through the slit provided in the counter electrode, so that the effects of ions and radicals generated by this energy can be uniformly applied to the object to be treated.

Furthermore, the influence of ions and radicals can be uniformly generated. As a result, plasma processing can be performed at high speed and with optimal ion energy. Furthermore, fine patterns can be formed on semiconductor urchins with high precision, high speed, and low damage. Furthermore, there is an effect that uniform film formation can be performed at high speed.

[Brief explanation of the drawing]

FIG. 1 is a perspective view of an embodiment of the present invention. Figure 42 is a plan view of the slit used in the embodiment shown in Figure 1, and Figure 3 is a plan view of the slit used in the embodiment shown in Figure 1.
FIG. 4 is a plan view of a third embodiment of the slit shown in FIG. 2, FIG. 5 is a sectional view of another embodiment of the present invention, and FIG. FIG. 7 is a cross-sectional view of an embodiment when the present invention is applied to an ashing device, FIG. 7 is a cross-sectional view of an embodiment when the present invention is applied to a sputtering device, and FIG.
FIG. 9 is a plan view of a resonator used in the sputtering apparatus shown in the figure, and FIG. 9 is a sectional view showing an embodiment of the present invention applied to an etching or CVD apparatus. 1... Cavity resonator, 5... Slit plate, 6...
...Plasma generation chamber, 7... Electrode, 11... High frequency power supply, 31... Ring-shaped resonator, 33...
Processing chamber, 34...Target, 36...
Wafer table, 35...high frequency power supply.

Claims (1)

[Claims] 1. A plasma processing apparatus characterized in that a slit is provided in a part of a cavity resonator, and the slit is installed facing a plasma generation chamber. 2. The plasma processing apparatus according to claim 1, wherein the cavity resonator is cylindrical, and the slit is provided at the bottom of the cylinder, and serves as one of the partition walls of the plasma generation chamber. . 3. The plasma processing apparatus according to claim 1, wherein the plasma generation chamber includes a magnetic field generation means for generating a magnetic field for generating plasma. 4. The plasma processing apparatus according to claim 1, wherein the plasma generation chamber includes a grid lattice for suppressing ions in the plasma. 5. The plasma processing apparatus according to claim 1, wherein the cavity resonator is ring-shaped, and the slit is provided on a side wall of the ring facing the plasma generation chamber.