JPH04110472A - Device and method for film formation by plasma - Google Patents

Abstract

PURPOSE:To stably form a high-quality conductive film with good reproducibility at high efficiency by opposing a nonadhesive cover to a microwave introducing window and providing it in a vacuum chamber and allowing the film nonforming gas to flow into the gap between the window and this cover and also introducing discharged gas into a sample and utilizing plasma discharge to perform film formation. CONSTITUTION:In the case of performing plasma chemical vapor deposition, when microwave generated in a magnetron 10 is introduced into a vacuum circular waveguide 3 through a rectangular waveguide 11 in the atmosphere, a cover 16 is nonadhesively provided to the face in a vacuum chamber 2 side of a microwave introducing window 4. Furthermore film nonforming gas such as hydrogen is introduced through a gap between the cover 16 and the window 4 from an introduction system 8. A vapordeposited film is prevented from being stuck on the window 4. Further film formation gas such as SiH4, and CH4, is introduced from a gas introduction system 7. Film formation is performed on the surface of a sample 6 to be film-formed by utilizing plasma discharge due to the magnetic field in a magnetic coil 14.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to an improvement in a plasma film forming apparatus that performs film forming processing using microwave discharge plasma and a plasma film forming method using the same.

[Prior Art] Microwave discharge plasma is a plasma with excellent generation efficiency of high-energy electrons, and as a high-density, highly reactive plasma, it is useful for forming thin films at high speed and forming high-quality thin films. In particular, microwave discharge plasma that utilizes cyclotron resonance conditions of electrons in a magnetic field has enhanced its characteristics, and as a film forming apparatus using the chemical vapor deposition method, for example, the method described in JP-A-56-155535 A device configuration as seen is disclosed. Microwave Blazer=3 In a Zuma film forming apparatus, microwaves are generally guided by a waveguide and introduced into a vacuum chamber through a window formed by an insulating film. A device with such a configuration has S:i
-0, or an insulating film such as a Six film, or conductivity of 0-9S/
When used for forming a semiconductor film of less than clIn, it can be used without any major problems. However, when attempting to form a conductive thin film with a conductivity of "-98/cm or higher" using an apparatus with such a configuration, although a film with good characteristics is initially obtained, the microwave discharge tends to stop, and Further, there was a problem in that the quality of the obtained film was easily variable. In particular, when forming a thin film with high conductivity, microwave discharge tends to stop even in the early stages of discharge, making it difficult to utilize microwave discharge plasma. In addition, such difficulties
In the case of a plasma film forming apparatus that uses microwave discharge plasma for sputter film forming 1. Both were common problems.

[Note] The value of 1-○-9S/σ1 used as a guideline for electrical conductivity is based on conventional experimental results, and depends on the microwave electric field. This is because the limit at which the induced current along the i-plane cannot be ignored is considered to be a film with a conductivity higher than the value of the film.

[Problems to be Solved by the Invention] Therefore, the F objective of the present invention is to achieve a conductivity of 10-98/an or more based on the technical background as stated in the following.
The second purpose is to develop a microwave discharge plasma deposition system that can be used to form conductive thin films, and the second purpose is to use this system to form conductive thin films with a conductivity of 10-"S/cm or more." The object of the present invention is to provide each possible plasma film forming method.

[Means for Solving the Problems] A plasma film forming apparatus of the present invention for solving the above problems has a configuration including a vacuum chamber, a waveguide for supplying microwave power to the vacuum chamber, and a , in a plasma deposition apparatus that is equipped with a means for introducing a discharge gas and a means for holding a sample to be deposited, and is capable of performing a deposition process using plasma generated by microwave discharge; A non-contact shield is provided on the vacant chamber side, which is shielded from the atmosphere and faces the microwave introduction window that introduces microwaves into the vacuum chamber.

Furthermore, the configuration of the plasma film forming method of the present invention for solving the two-part problem includes a vacuum chamber, a waveguide for supplying microwave power to the vacuum chamber, and a discharge gas introduced into the vacuum chamber. and means for holding the sample to be film-formed, and the sample 11. In this film-forming method, a non-film-forming gas is supplied to the gap between a non-adhesive shield provided opposite the microwave introduction window in the vacuum chamber, and a non-film-forming gas is supplied to the gap between the shield and the shield, which has been placed in the vacuum chamber in advance. 1. A discharge gas is introduced into the film-forming sample, and a thin film is formed on the surface of the sample using plasma discharge.
This is a serious matter.

[Function] In the present invention, the shields installed at the microwave introduction windows l and 7 of the vacuum chamber are provided to prevent a high conductivity film from being deposited on the microwave introduction window surface. This is installed non-adherently on the microwave introduction window surface. This is to ensure that microwaves can penetrate into the cavity even if a high conductivity film is attached to the two-part shield. The reason why a high-conductivity film placed on the microwave introduction window will inhibit microwaves from entering the vacuum chamber is that when viewed from the waveguide side, the extension of the conductor surface on the inside of the waveguide is a vacuum. This is to form the end of the waveguide with a conductor that reaches the indoor surface and continues with the high conductivity film. The shielding arrangement of the present invention prevents the formation of such a completely continuous conductor surface. If a non-conductive area is secured on the microwave introduction window surface, microwave 1. Therefore, the induced current induced on the waveguide-side surface of the conductive film flows into the vacuum chamber side of the conductive film, allowing microwaves to enter the vacuum chamber. In this case, it is important to secure a sufficient area for the induced current to flow into the vacuum chamber side of the conductive film, so that the conductive film on the shielding surface is connected to the conductive film on the microwave introduction window surface and the wall surface of the vacuum chamber. When the continuous area becomes large, it becomes a national policy to prevent microwaves from entering the vacuum chamber. Therefore, the shield is installed in a non-contact manner on the window and the wall surface of the vacuum chamber near the window.

More specifically, since it is desirable to secure a non-conductive part of the circumference of the microwave wavelength edge, microwave Securing a gap with a circumferential length of seven wavelengths or more is effective in reducing the amount of film deposited on these areas by supplying a film-forming gas to the shield and the window. It is also effective in reducing the amount of coating deposited on the shield and the window surface.

The above-mentioned shield has little effect in reducing the adhesion of the film to the window surface in the pressure range where the gas flow is laminar.
: ], This works effectively in the case of a plasma film forming apparatus that utilizes plasma discharge of less than Om Torr. In this pressure range, the probability of collision between gas molecules is low, so the gas molecules travel almost straight, and the adhesion of the film to the two-part window surface is greatly reduced. In particular, in plasma film deposition equipment that forms a magnetic field in at least a portion of the inside of the vacuum chamber and utilizes microwave conditions based on electron cyclotron resonance, the film deposition pressure is low and the gas flow is similar to that of the molecular flow. The shield of the present invention works effectively because it is close to the area. However, it is desirable to have less film adhesion to the two-part shield. In a plasma film deposition apparatus that utilizes electron cyclotron resonance, the main generation region of deposition species is the magnetic field strength region that satisfies the electron cyclotron resonance conditions, so the microwave introduction window provided with the above-mentioned shield is located 10 ann from this region. It is desirable to install them at a distance of at least 100 degrees. Furthermore, it is particularly effective to install the two-part window in a shaded part when viewed from the magnetic field strength part that satisfies the electron cyclotron resonance conditions.

When a highly conductive film is attached to the shield, the microwave introduction window acts as an impedance window for microwaves. For this reason, microwave reflection increases unless impedance matching is achieved.

Since the impedance of the window changes over time due to the adhesion of the conductive film to the two-part shield, it is desirable to provide an automatic tuning mechanism in the microwave waveguide.

By utilizing the above-described effects, plasma deposition of a film with high conductivity becomes possible using microwave discharge.

[Example] Hereinafter, an example of the present invention will be described using FIG. 10 and FIG. 2.

FIG. 1 is a schematic vertical cross-sectional view of essential parts of a plasma film forming apparatus according to a first embodiment of the present invention.

The configuration of this device is to form a magnetic field in a vacuum chamber, generate plasma by microwave discharge using the cyclo-1-ron resonance of electrons in the magnetic field, and decompose the film-forming raw material gas to form a film. Although it is a film device, it can also be used as a simple microwave chemical vapor deposition device without forming a magnetic field.

First, the overall configuration will be explained according to FIG. 1. A plasma generating section 1 is located inside a circular microwave waveguide 3 that constitutes a part of a vacuum chamber 2, and has a microwave introduction window 4 made of quartz or alumina. This makes it possible to separate the vacuum from the atmosphere and allow microwaves to pass through. A sample stage 5 is provided inside the vacuum chamber 2, and a sample 6 to be film-formed is placed on this stage. The gas supply system 7 is for introducing a film-forming raw material gas, and the raw material gas is supplied toward the film-forming sample 6. The gas supply system 8 is for introducing a non-film-forming discharge gas. Something,
It is located at the microwave introduction window 4.

The treated exhaust gas is exhausted from the exhaust port 9. Magne 1
～Microwaves generated by Ron 10 (2, 4, 5G I
(z) is guided to the vacuum circular waveguide 3 by a rectangular waveguide 11 in the atmosphere, but a microwave monitor 1-2 and a microwave tuner 13 are installed in the rectangular waveguide 11 in the atmosphere. ing. A ceramic coil] 4 is placed around the "plasma generation section", which generates a magnetic field (875G) that satisfies the electron cyclo I-ron resonance (itEcR) conditions.
This is to generate This results in 10 rn TO
It becomes possible to generate plasma discharge in the pressure range below r.r.

[Note: IECR refers to electron cyclo1-ron resonance, which is a phenomenon that occurs when the microwave frequency matches the frequency of the cyclo1-ron motion of electrons in a magnetic field.

Further, the frequency of the electron cytalotron motion changes depending on the magnetic field strength, and satisfies the ECR condition at a specific magnetic field. The magnetic field (magnetic flux density) at this time is called an ECR magnetic field.

The position of the microwave introduction window 4 is determined by the magnetic field position 15 or 12+ :I-Ocl]I which satisfies the ECR conditions.
Moreover, it is installed at a position that is in the shadow when viewed from the magnetic field position 15 that satisfies the ECR conditions. This is microwave introduction window 4
This is to reduce the amount of film adhering to the surface of the film, and this is also why the gas supply system 8 is placed at the position of the microwave introduction window 4. In the case of chemical vapor deposited gummies, it is difficult to completely avoid film adhesion to the microwave introduction window 41.In order to reduce this, in this device, the vacuum chamber side of the microwave introduction window 4 is A shield 1G was installed non-adherently on the surface. Cover 1
- C3 is installed so as to secure a gap of at least the microwave wavelength between the microwave introduction window and the wall surface of the vacuum chamber in the vicinity. This is to prevent the conductive film of the shield 16 from being completely continuous with the contact surface of the vacuum chamber.

When a conductive film is attached to the surface 1 of the shield 1, the impedance of microwave propagation increases, but this can be solved by matching with the microwave tuner 133. Specifically, matching should be made so that the amount of reflected waves observed by the microwave monitor 12 does not increase.1. By making the microwave tuner 13 an automatic device, the effects of impedance changes are reduced. Therefore, according to this apparatus, it becomes possible to use microwave plasma to form a film with relatively high conductivity.

FIG. 2 is a schematic vertical cross-sectional view of main parts of a plasma film forming apparatus according to a second embodiment of the present invention. The reference numerals in FIG. 2 are the same as those in FIG.

In the first embodiment shown in FIG. 1, the microwave introducing window 4 is in the form of a plate and is installed at the position of the rectangular waveguide 11, but the present invention has a second embodiment.
As shown in the figure, this is the case where the microwave introduction section 4 is a cylindrical tube.13 In this embodiment, the gas supply system 8 is installed to supply a non-film forming gas toward the tip of the cylindrical tube. There is. In this case, the rate at which conductive films are deposited on the surface of the shield (S) increases, but the inner circumference of the circular microwave waveguide 3 is longer than the inner circumference of the rectangular waveguide 11. Therefore, it is necessary to use a long sulin I as an entry route for the micro 1 skin that is worn in places where the skin is exposed to the skin.
The advantage of being able to secure - is Jroru. However, since the impedance changes significantly due to the conductive film being deposited on the surface of the shield 16, it is desirable that the microwave tuner 3 be an automatic device.

In the above examples, the film is formed by a chemical vapor deposition method that utilizes plasma decomposition of the film-forming MF material gas.
The present invention is also effective in the case of film formation by sputtering. Sputtering equipment that uses microwave plasma has a configuration in which argon gas is introduced, a target is placed near the plasma generated by microwave discharge, and a negative potential is applied to it. It is the same as in the case of chemical vapor deposition that the attachment of a conductive film obstructs the penetration of microwaves into the vacuum chamber, and the present invention can be used as a countermeasure against this problem.

Next, we will explain the results of experiments conducted using the plasma film deposition apparatus shown in Figs. 1 and 2. First, we will explain the case where the apparatus of the present invention shown in Fig. 1 is used for plasma chemical vapor deposition. do. S'l from gas supply system 7
H, and CH4 at a total flow rate of 3 to 10c a 7 minutes, 0.3%
B and H diluted with hydrogen were introduced at a rate of 3 to 10 cc/min, and hydrogen was introduced from the gas supply system 8 at a rate of 20 to 60 cc/min at a pressure of 0.3 to 10 mT.

P-type machine crystal hydrogenated silicon carbide (μ
The formation of c-8iC:H) was investigated. This film is difficult to form using conventional RF plasma chemical vapor deposition methods;
Although it is formed by microwave plasma chemical vapor deposition, it has a conductivity of about Is/an, making it difficult to form a stable film.

Substrate temperature is 150℃, microwave power is 100~50℃
0W What happened?

[Note] RF plasma refers to plasma generated by a high-frequency electric field in the radio wave range, which has a longer wavelength than microwaves.

If the mital wave introduction window 4 does not have a shield 16, the p-type μC with a wide optical gap and high conductivity except for the very beginning.
-S i C: I( was difficult to obtain, and furthermore, the formation of microwave plasma was difficult.

When shield 16 was installed, microwave reflection increased over time at the beginning, but when microwave tuner 1
By retuning in step 3, p-type μC-8JC with a stable optical gap and high conductivity: ■-
■ was obtained. When the microwave tuner 13 was made into an automatic device, it became possible to stably obtain a p-type μc-8], C: II with a wide optical cap and high conductivity from the beginning.

Next, the formation of hydrogenated amorphous germanium (a-Ge: 1-I) was investigated using the apparatus of the present invention shown in FIG. Although it is difficult to form a high-quality film at high speed using the conventional R-type plasma chemical vapor deposition method, this film has an electrical conductivity of about 1-0-'S/>.

Ge■-■, , is introduced from the gas supply system 7 at 5 to 15 cc/min, hydrogen is introduced from the gas supply system 8 at 5 to 30 cc/min, and the pressure is 0.3 to 1 m T' o r r. We investigated film formation. The substrate temperature was −70° C., and the microwave power was 50 to 300 W. In this study, an automatic microwave tuner 13 was used.

If there is no cover 6, a - G e: I 2
~r) At the time when the μrn film was formed, it became difficult to start plasma discharge, and it became necessary to remove the pancreas that had landed on the microwave introduction window 4. When a shielding roller was installed, it became possible to stably obtain a-e;II with high photoconductivity over a long period of time, and the reproducibility was significantly improved.

Although an example in which the present invention is applied to a chemical vapor deposition method that utilizes plasma decomposition of a film-forming raw material gas has been described above, the present invention is also effective in forming a conductive film by sputtering. Sputtering equipment that uses microwave plasma has a configuration in which argon gas is introduced, a target is placed near the plasma generated by microwave discharge, and a negative potential is applied to it. The fact that the adhesion of the conductive film inhibits microwaves from entering the vacuum chamber is the same as in the case of chemical vapor deposition, and the present invention can be used as a countermeasure for this.

[Effects of the Invention] As described above, according to the present invention, microwave discharge plasma, which is useful for forming thin films at high speed and forming high-quality thin films, can be used to form electrocardiographic thin films with a conductivity of ○−' S/cm or more. It becomes possible to utilize it for formation. - As a result, it becomes possible to stably form a conductive, high-quality film, which has been difficult to form using conventional RF discharge plasma film forming methods, with good reproducibility, at high speed, and over a long period of time.

[Brief explanation of drawings]

FIG. 1 is a schematic vertical cross-sectional view of a main part of a plasma film forming apparatus according to a first embodiment of the present invention, and FIG. 2 is a schematic vertical cross-sectional view of a main part of a plasma film forming apparatus according to a second embodiment of the present invention. It is a diagram. <Explanation of symbols> 1... Plasma generation part, 2... Vacuum chamber, 3... Circular waveguide, 4... Microwave introduction window, 5... Sample stage, 6 Sample, 7, 8...・Gas introduction system, 9... Exhaust port, Work Magne I-ron, 11... Rectangular waveguide, 12 ・Microwave monitor, 13... Tuner, 14... Magnetic coil, 15 ECR magnetic field, 16...Microwave introduction Koiji.

Claims (1)

[Claims] 1. A vacuum chamber, a waveguide for supplying microwave power to the vacuum chamber, means for introducing discharge gas into the vacuum chamber, and means for holding a sample to be deposited. In a plasma film forming apparatus capable of performing film forming processing using plasma generated by microwave discharge, the vacuum chamber is isolated from the atmosphere and faces a microwave introduction window that introduces microwaves into the vacuum chamber. A plasma film deposition apparatus characterized by having a non-adhesive shield provided on the vacuum chamber side. 2. The plasma film forming apparatus according to claim 1, wherein a gap having a circumferential length equal to or longer than a microwave wavelength exists between the shield, the window, and a wall surface of the vacuum chamber in the vicinity of the window. 3. The plasma film forming apparatus according to claim 1, further comprising a mechanism for supplying a non-film forming gas to the shield and the window. 4. The plasma film forming apparatus according to any one of claims 1 to 3, further comprising a mechanism capable of supplying a non-film forming gas to a gap between the shield and the window. 5. The plasma film forming apparatus according to any one of claims 1 to 4, wherein the plasma film forming apparatus utilizes plasma discharge of 10 mTorr or less. 6. Claims 1 to 5, wherein the plasma film forming apparatus forms a magnetic field in at least a portion of the interior of the vacuum chamber and generates plasma discharge by utilizing electron cyclotron resonance. plasma film deposition equipment. 7. According to claim 6, the microwave introduction window of the plasma film forming apparatus is located at a distance of 10 cm or more from a magnetic field strength section that satisfies electron cyclotron resonance conditions in the vacuum chamber. plasma film deposition equipment. 8. A claim characterized in that the microwave introduction window of the plasma film forming apparatus is located in a shaded area when viewed from a magnetic field strength area that satisfies electron cyclotron resonance conditions in the vacuum chamber. 8. The plasma film forming apparatus according to items 6 and 7. 9. The plasma film forming apparatus according to any one of claims 1 to 8, wherein the waveguide section of the plasma film forming apparatus is provided with a microwave automatic tuning mechanism. 10. A vacuum chamber, a waveguide for supplying microwave power to the vacuum chamber, a means for introducing discharge gas into the vacuum chamber, and a means for holding a sample to be deposited; In the method of forming a film on the sample using plasma generated by the above method, a non-film-forming gas is supplied to a gap between a non-contact shield provided opposite to the microwave introduction window in the vacuum chamber. In addition, a plasma film forming method characterized in that a discharge gas is introduced into a sample to be film-formed that has been placed in a vacuum chamber in advance, and a thin film is formed on the surface of the sample using plasma discharge. 11. The plasma film forming method according to claim 10, in which plasma discharge is used to form a film on the surface of the sample to be film-formed while the reflection of microwaves that generate plasma is controlled to be constant by an automatic tuning mechanism. A plasma deposition method characterized by forming a thin film.