JPH0585633B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Application of the Invention] The present invention relates to a method for forming a thin film by sputtering and an apparatus for forming the same.

[Background of the invention]

Sputtering is one of the methods for manufacturing thin films for thin film integrated circuits and semiconductor devices in vacuum. This sputtering method, for example ^,
A glow discharge is generated in the atmospheric gas at a low pressure of about 10 ^-2 Torr to ionize the gas into a plasma, and the plasma ions are accelerated by the voltage applied between the cathode and the anode, causing them to collide with the target material placed on the cathode. Then, by the collision of these ions, constituent atoms or particles of the target material are ejected and deposited on a substrate disposed near the anode, thereby forming a thin film of the target material on the substrate. Until now, various methods have been used to realize this sputtering method, but these have had problems in terms of thin film formation speed and film quality. That is,
In the method of exciting a discharge by directly applying a DC voltage or RF voltage to the cathode and anode, the plasma density during discharge is low and the amount of ions that collide with the target is small, so the thin film formation rate is extremely slow. In addition, a magnetron type that generates a magnetic field perpendicular to the direction of the electric field on the target material, causes the electric field and magnetic field to cause the electrons to move in a spiral trajectory, and to lengthen the mean free path in the discharge space. In the sputtering method, conductive metals such as Al, Ta, and Ti are sputtered at high speed, and the thin film formation speed is also high, on the order of several μm/minute. However, since the degree of vacuum is approximately 10 ^-3 to ^{10 -2} Torr, discharge gas may be mixed into the formed thin film, resulting in problems with the quality of the film due to the small crystal grain size of the thin film and increased resistance. . moreover,
Since the degree of vacuum is as described above, the sputtered target particles collide with gas particles in the space on the way to the substrate and are scattered. For this reason,
When the target particles are incident on the substrate, the perpendicularity to the substrate surface is poor, and the coating properties of the stepped portions on the substrate and the filling of holes such as through holes are insufficient.
There were problems such as disconnections in wiring sections and increased interlayer resistance in multilayer wiring. In addition, when a dielectric material such as SiO ₂ , Al ₂ O ₃ , Si ₃ N ₄ is used as the target material, RF power is applied to the electrode to cause a discharge.
Sputtering is being done. However, such dielectric materials have physical properties inherent to the material, such as the degree to which ions are ejected into space due to collision energy (this is called sputter yield).
It is characterized by low For this reason, even with the magnetron sputtering method, the thin film formation rate is slow, so a large amount of RF power is applied to increase the ion energy during discharge.
However, if the energy of the ions collided with the target is increased, the amount of target particles sputtered increases, but if too much power is applied, the ions will be driven into the target and the target will no longer be sputtered. Additionally, as a result of the large temperature difference between the front and back surfaces of the target, large temperature stress is applied within the target, causing problems such as destruction of the target, making it difficult to achieve high productivity in the formation of dielectric films. Nakatsuta.

Therefore, in recent years, as a sputtering method to solve these problems, a method has been proposed in which plasma is generated using a microwave oscillator in the processing chamber of a high-frequency sputtering device (for example, Japanese Patent Application Laid-Open No. 75839/1983). A sputtering device to which this method is applied will be explained based on FIG. 1. This is done by introducing microwaves generated by a microwave oscillator 3 into a vacuum chamber 13 through an introduction path 12, converting gas introduced from a gas introduction port 15 into plasma, and connecting it to a target 1 placed on a target electrode 16. Between the wafers 2 placed on the wafer stage 17,
The material of the target 1 is formed into a film on the wafer 2 by generating high-density plasma. According to this method, when forming a SiO ₂ thin film on wafer 2, 1KW of high frequency power is used to form a SiO 2 thin film of 1500Å/
Thin films can be formed at a speed of about minutes. However, this method reduces the gas pressure during sputtering.
10 ^-1 Torr, and the degree of vacuum is low compared to the sputtering method that does not generate microwaves, so the incorporation of sputter gas into the film is unavoidable, and the insulation of the SiO ₂ thin film formed is low. There were problems such as a decrease in breakdown voltage and the presence of a large number of pinholes, and it was not possible to obtain a film quality that could be used in practical applications such as semiconductor thin film devices. Furthermore, since the microwave is introduced near the gas inlet 15 and the generated plasma reaches between the wafer 2 and the target 1 through thermal diffusion, the plasma density in this space is not uniform. However, it has been difficult to make the thickness of the thin film uniform, making it difficult to apply it to semiconductor thin film devices.

[Purpose of the invention]

An object of the present invention is to provide a thin film forming method and an apparatus for forming the same, which can increase the thin film forming speed and uniformly form a thin film that can be applied to semiconductor thin film devices, etc., at a high degree of vacuum, without depending on the target material. It's about doing.

[Summary of the invention]

In order to achieve the above object, in the present invention,
In a thin film forming method in which a thin film is formed on a substrate facing the target by sputtering a target in a vacuum container, the introduction window is By supplying microwaves into a magnetic field formed nearby to generate an ECR discharge near the introduction window, and simultaneously applying high frequency power to the target,
The present invention provides a thin film forming method and a forming apparatus thereof, characterized in that a high-density and uniform plasma is formed between the target and the substrate.

[Embodiments of the invention]

An embodiment of the present invention will be described below with reference to FIG. In the figure, the same parts are given the same reference numerals.

A substrate electrode 11 and an anode 10 each having a flat surface are placed in a vacuum chamber 13, which has a substantially rectangular shape and is set to a degree of vacuum of about 10 ^-4 Torr and into which an inert gas such as argon is introduced, through a predetermined space 8. They are placed almost facing each other. A target material 1 is placed on the surface of the anode 10 on the space 8 side. As the target material 1, for example, SiO ₂ , Si ₃ N ₄ or Al ₂ O ₃ can be used depending on the desired thin film. A part of the anode 10 on the opposite side to the space 8 protrudes into the atmosphere and is connected to the RF power source 6 for sputtering. Note that a matching circuit 5 for controlling sputtering is provided between the anode 10 and the RF power source 6 for sputtering. On the other hand, the substrate electrode 11 functions as a cathode, and on the surface on the space 8 side,
A substrate, for example a wafer 2, on which a thin film is to be formed is placed. Furthermore, a part of the substrate electrode 11 is protruded into the atmosphere and is grounded.

Next, the space 8 between the anode 10 and the substrate electrode 11
Microwave introduction paths 4 are respectively arranged from the atmospheric side toward the inside of the vacuum chamber 13 so as to surround it from both sides. This microwave introduction path 4 is for introducing microwaves into the space 8. That is, the microwave introduction path 4 is open to the vacuum chamber 13, and one end thereof is a microwave introduction window 9. The atmosphere side of the microwave introduction path 4 is connected to a waveguide 12 that generates microwaves, and further connected to the waveguide 1
2 is connected to a microwave power source 3. Vacuum chamber 1
3, a plurality of magnetic field coils 7 are arranged substantially facing each other at positions sandwiching each microwave introduction path 4.

Next, the thin film forming operation in the sputtering apparatus configured as described above will be explained.

The microwave power source 3 is operated to generate microwaves from the waveguide 12. The generated microwaves pass through the microwave introduction path 4 and are introduced into the space 8 within the vacuum chamber 13 through the microwave introduction window 9. Furthermore, the magnetic field coil 7 is activated, and the microwave introduction window 9
Generates a magnetic field nearby. At this time, the circular motion frequency of electrons in this magnetic field (electron cyclotron frequency) is made to match the frequency of the microwave to achieve resonance absorption, that is, electron cyclotron resonance (electron cyclotron resonance).
Set to cause Cyclotron Resonance (hereinafter abbreviated as "ECR discharge"). Due to this ECR discharge, the space 8 can obtain a higher ion density, for example, about 10 ¹² ions/cm ³ than in the case of glow discharge. Further, since the microwaves are introduced from the periphery of the space 8, the micro density generated in the space 8 becomes uniform.

In this state, RF is applied from the high frequency power source (RF power source) 6 to the cathode 10 through the matching circuit 5.
Turn on the power. RF power is consumed through the target material 1, the space 8, and the anode (substrate electrode) 11. At this time, a DC bias is generated at the cathode as a negative potential. Due to this negative potential, in space 8
The ECR discharge is excited, and the incoming gas, such as argon gas, becomes plasma, and high-density ions are accelerated and collide with the target material 1 to release target particles. The particles then pass through the space 8 and form a thin film of target material on the surface of the wafer 2.

The method for exciting ECR discharge in the space between the cathode and anode is not limited to this. Another embodiment of the present invention will be described with reference to FIG.

Here, a large number of microwave introduction paths 4 are arranged around a vacuum chamber 13 having a substantially spherical shape so as to be open toward the vacuum chamber 13. A waveguide 12 is connected to each end of the microwave introduction path 4 on the atmosphere side, and each waveguide 12 is connected to a microwave power source 3, respectively. A microwave introduction window 9 is provided near the end of the microwave introduction path 4 on the vacuum chamber 13 side. A magnetic field coil 7 is arranged around each microwave introduction path 4 so as to surround the microwave introduction path 4. Although the target electrode, substrate electrode, etc. are omitted in FIG. 3 for clarity, they can be arranged in the same manner as shown in FIG. 2.

Even in the sputtering device configured in this way,
Microwaves are introduced into the space within the vacuum chamber 13, and ECR discharge can be generated in the space 8 by the action of the magnetic field coil 7, so that high-density and uniform plasma can be generated.

When a thin film was formed by the forming method according to the present invention, the following results were obtained. That is, 6×
At a vacuum level of 10 ^-6 Torr, the high frequency power is 1KW,
The microwave power was 120W, and the target material was
When SiO ₂ is used, the thin film formation rate is 2000Å/
It was hot for more than a minute. Furthermore, the thickness distribution of the thin film formed on the wafer could be extremely uniform within ±5%.

〔Effect of the invention〕

According to the present invention, plasma density can be made uniform and increased in a high vacuum of about 10 ^-4 Torr or less.
Since sputtering is performed using ECR discharge, thin films can be formed at high speed even when using a target material with a low sputter yield.
It can be applied to semiconductor thin film devices, etc.
Furthermore, since it can be set to a high vacuum, there is no risk of gas molecules in the space colliding and scattering before the target particles adhere to the substrate on which the thin film is to be formed, reducing gas intrusion into the thin film. A dense film without pinholes can be formed.

[Brief explanation of the drawing]

FIG. 1 is a schematic configuration diagram showing the configuration of a sputtering device using a conventional sputtering method, FIG. 2 is a schematic configuration diagram showing the configuration of a sputtering device using a sputtering method according to an embodiment of the present invention, and FIG. It is a schematic block diagram which shows the structure of the sputtering apparatus based on another Example of this invention. 1...Target material, 2...Wafer, 3...Microwave power source, 4...Microwave introduction path, 5...
Matching circuit, 6... RF power source for sputtering, 7... Magnetic field coil, 8... Plasma generation space, 9... Microwave introduction window, 10... Cathode (target electrode),
11... Substrate electrode, 12... Waveguide, 13... Vacuum chamber.

Claims (1)

[Scope of Claims] 1. A thin film forming method in which a thin film is formed on a substrate facing the target by sputtering a target in a vacuum vessel, the method comprising sputtering a target in a vacuum container, the sputtering method comprising sputtering a target and forming a thin film on a substrate facing the target. By supplying microwaves into a magnetic field formed near the introduction window through an introduction window to generate an ECR discharge near the introduction window, and at the same time applying high frequency power to the target, the target and the substrate are A thin film forming method characterized by forming high-density and uniform plasma between 2. A thin film forming apparatus for forming a thin film on a substrate placed on a substrate electrode facing the target by sputtering a target on a target electrode in a vacuum chamber, the thin film forming apparatus forming a thin film on a substrate placed on a substrate electrode facing the target. a plurality of microwave supply means arranged symmetrically around the periphery and supplying microwaves from outside the vacuum vessel through an introduction window between the target electrode and the substrate electrode; a plurality of magnetic field generating means arranged in pairs on the outer periphery of each of the plurality of microwave supply means, and a power applying means for applying high frequency power to the target electrode; By supplying microwaves from the microwave supply means into a magnetic field generated near the window, an ECR discharge is generated near the introduction window, and at the same time, high frequency power is applied to the target electrode by the power application means. . A thin film forming apparatus, characterized in that a high-density and uniform plasma is generated between the target electrode and the substrate electrode.