JPH01309973A - Thin film-forming equipment - Google Patents

Abstract

PURPOSE:To prevent a change with the lapse of time in microwave introduction efficiency and also prevent the adhesion of a film to a window for introducing microwaves by keeping the above window at a distance from a plasma chamber and also providing a means of purging a microwave-introducing part in magnetic field microwave thin film-forming equipment using a coaxial-type cavity resonator. CONSTITUTION:A gaseous raw material introduced into a plasma chamber 41 in a coaxial-type cavity resonator formed of a vacuum vessel 31 and a cylindrical base material 100 set in the vessel 31 is formed into plasmic state by means of microwaves introduced through a window 40 in a microwave introducing part 1 provided to the vessel 31, by which a thin film is deposited on the base material 100. In this equipment, the window is constituted so that it is kept at a distance from the plasma chamber 41, and a means 2 of purging the microwave-introducing part 1 with a purge gas is provided. By this constitution, the window 40 is kept at a distance from the plasma chamber 41 and further purged by means of a purge gas supplied by the purging means 2, so that the window 40 is not exposed to the plasma produced in the plasma chamber 41 and the adhesion of film to the window 40 can be practically removed.

Description

[Detailed Description of the Invention] [Summary] Regarding the improvement of a magnetic field μ-wave thin film forming apparatus using a coaxial cavity resonator, there is less adhesion of the film to the window of the μ-wave introduction part provided in the vacuum container. For the purpose of this, a raw material gas introduced into a plasma chamber in a vacuum container is turned into plasma by microwaves introduced through a window of a microwave introduction section provided in the vacuum container, and the material gas is set in the vacuum container. In the thin film forming apparatus for depositing a thin film on a cylindrical substrate, the window of the microwave introducing section is moved away from the plasma chamber, and a purge means is provided for purging the inside of the microwave introducing section using a purge gas. do.

Alternatively, a superconductor for magnetically shielding the microwave introducing section may be added to the above structure.

[Industrial application field]

The present invention utilizes magnetic field microwaves (
(μ wave) relating to improvements in thin film forming equipment.

The surface of the photoreceptor, which has a photosensitive layer formed on a cylindrical substrate, is uniformly charged, and a laser beam or the like is selectively irradiated on the photoreceptor based on the printed information to selectively attenuate the charged potential of the photoreceptor layer. Electrophotographic devices that form an image, develop it, transfer the resulting 1-toner image onto recording paper, and record it by running it are well known. , those equipped with a photosensitive layer of an amorphous silicon film, which has stronger mechanical strength than selenium-based ones, have come to be used.

[Conventional technology]

FIG. 3 shows the structure of a magnetic field μ-wave CVD apparatus (thin film forming apparatus) using a conventional coaxial cavity resonator used for forming this amorphous silicon film. This device is disclosed in Japanese Patent Application No. 187710/1989 filed by the present applicant, and FIG. 3(a) is a plan view of the main part, and FIG. 3(b) is a front view showing the overall outline. It is. In the figure, 31 is a vacuum container, 1
00 is a cylindrical base of an electrophotographic photoreceptor. Formation of an amorphous silicon film on the surface of the cylindrical substrate 100 using this apparatus is performed as follows.

First, as shown in the figure, the cylindrical base 100 is supported and set on the support stand 32 in the vacuum container 31, and the valve 33 is pressed until the inside of the vacuum container 31 reaches a predetermined degree of vacuum using a vacuum pump or the like.
Exhaust through. Next, the cylindrical base 10 is
0 together with the support base 32, and the heater 35 disposed inside the cylindrical base 100 rotates the cylindrical base 1.
00 to 150°C to 350”C. In this case,
Heater #36 monitors the substrate temperature and adjusts it to a constant temperature. Here, the valve 37 is opened and the silicon atom-containing gas (
Disilane, etc.) is introduced into the vacuum container 31, and the
The μ waves generated in step 8 are guided by a waveguide 39 and introduced into a plasma chamber 41 inside the vacuum container 31 through a window 40 of a μ wave input section 43 provided in the vacuum container 31. Vacuum container 31 and cylindrical base 1
Since 00 constitutes a coaxial cavity resonator, the μ-waves that enter the plasma chamber 41 between them resonate, and the raw material gas in the plasma chamber is thereby excited and turned into plasma. At the same time as this μ wave is introduced, a current I mag of a predetermined waveform,
r' mag is applied to the magnets 42 and 42' to generate a magnetic field and confine the plasma near the base. There, the introduced gas is efficiently decomposed and an amorphous silicon film is formed on the cylindrical substrate 100. In this case, μ-waves are used as the power source, and the gas pressure is 10-' to 10-'torr.
Since the film can be formed at a relatively low pressure, there is no possibility of powdery substances building up inside the device, which is a problem when using an RF power source.

[Problem to be solved by the invention]

However, in this conventional method, during film formation, a thin film is also deposited on the window 40 formed of quartz glass or the like, and as a result, absorption and reflection of μ waves occur here, reducing the efficiency of introducing μ waves. go. Eventually, the introduced μ power decreases significantly, and it becomes impossible to maintain the discharge.This limits the time for each film formation, and the amorphous silicon photoreceptor For relatively thick films such as
Conditions change between the early and late stages of film formation, resulting in a distribution in film quality. Additionally, when the film on the window gets thicker, it will need to be cleaned or replaced.

SUMMARY OF THE INVENTION An object of the present invention is to provide a thin film forming apparatus that can reduce the amount of film adhering to the window of a microwave introducing section provided in a vacuum container.

[Means to solve the problem]

In order to achieve the above-mentioned object, in the present invention, a raw material gas introduced into a plasma chamber in a vacuum container is turned into plasma by a μ wave introduced from a window of a μ wave introduction section provided in the vacuum container, and In a thin film forming apparatus for depositing a thin film on a cylindrical substrate having a cylindrical shape, a purge means moves a window of the μ-wave introducing section away from the plasma chamber and purges the inside of the μ-wave introducing section using a purge gas. The configuration includes the following.

Alternatively, a superconductor for magnetically shielding the μ-wave introducing section may be added to the above structure.

[Effect]

When forming a film on the surface of the cylindrical substrate, the film is formed by introducing the source gas from the source gas supply port and the 71 wave power from the window into the plasma chamber. In this case, in practice, the cylindrical substrate is heated to a predetermined temperature by a heater or the like, and the cylindrical substrate is rotated by a motor or the like to form a film.

During this film formation, the window of the μ-wave introduction part is away from the plasma chamber, and the inside of the μ-wave introduction part is purged by a purge means using a purge gas, so the window is not exposed to the plasma generated in the plasma chamber. . Therefore, there is almost no film adhesion to the window.

What is important here is to create conditions in which the purge gas does not cause discharge at the μ-wave introduction section where the μ-wave type force is strongest, in order to transmit all the μ-wave energy to the plasma chamber. Therefore, the purge gas must be difficult to cause discharge (high ionization energy and dissociation energy) and must not become an impurity to the film. Specifically, for example, a
-Si: When forming H (hydrogenated amorphous silicon), 5iHt, 5i2 such as +12 dilution, Ar dilution, etc.
Since 1To, etc. are used, llz gas, Ar gas, etc. can be considered as the purge gas, but 1 (2 gas) is most suitable.

Comparing ++ and Ar, the ionization energy is 15.7 eV for a total atom, which is almost equal to 13.6 eν for a H atom, but
The ionization cross section of the total atom is approximately three times larger. Furthermore, since cumulative ionization occurs in Ar via a metastable level, it is easy to discharge with low power. On the other hand, 11□ is the molecular dissociation energy 4.
It is a gas that is difficult to discharge because it requires 47 eV.

It is also important to maintain a pressure that makes it difficult for gas to discharge, and it is possible to discharge only in a plasma chamber where a magnetic field is applied by a magnet or the like.

At this time, by magnetically shielding with a superconductor so that the magnetic field does not enter the μ-wave introducing section, it is possible to prevent the purge gas from discharging in the μ-wave quadrant.

Furthermore, by providing a superconductor that magnetically shields the μ-wave introduction section, it is possible to prevent the purge gas from causing discharge in the μ-wave discharge section, and the decomposition efficiency of the raw material gas is improved.

〔Example〕

The present invention will now be described in detail with reference to FIGS. 1 and 2.

A first embodiment is shown in FIG.

FIG. 1(a) is a plan view showing the main structure of the thin film forming apparatus;
FIG. 1(b) is a front view showing the general outline of the same. In the figure, 1 is a μ-wave introduction part, and 2 is a purge means. Note that the same reference numerals are given to the same members as in the conventional one.

The window 40 provided in the μ-wave introduction section 1 is located farther away from the plasma chamber 41 than in the past, and the purge means 2 includes a purge gas supply pipe 3 connected to the μ-wave introduction section 1 near the window 40;
It is comprised of a purge gas supply source (not shown) connected to the purge gas supply pipe 3 via a valve 4 or the like.

During film formation, the inside of the vacuum container 31 is evacuated via the valve 33, and the cylindrical substrate 100 is heated to 150 to 350°C by the heater 35', and the cylindrical substrate 100 is heated by the motor 34, as in the conventional case. Rotate valve 3
A silane gas, for example, 5iH, is introduced into the vacuum container 31 through the
At this time, a purge gas such as H2 gas is supplied to the μ-wave introducing section 1 via the valve 4. and,
μ from the microwave type a38 through the waveguide 39 and window 40
Waves are introduced into the plasma chamber 41 to decompose the source gas and deposit an a-St:H film on the cylindrical substrate 100.

During this film formation, the window 40 is away from the plasma chamber 41, and the inside of the μ-wave introducing section 1 is purged with the purge gas supplied by the purge means 2. is not exposed and the window 40
There is almost no film adhesion to the surface.

When the above-described procedure was carried out using the conventional apparatus shown in FIG. 3, alignment could no longer be achieved when the film thickness on the cylindrical substrate lOO reached approximately 5 μm, and discharge could no longer be maintained at 30 μm. On the other hand, in film formation using the apparatus of this example, 30
．． It was confirmed that the crm deposition electrode formation was stable and that the film adhesion to the window 40 was less than 1/10 that of the conventional method.

FIG. 2 shows a second embodiment.

FIG. 2 is a plan view showing the main structure of the thin film forming apparatus. In the figure, 11 is a cylindrical superconductor for magnetic shielding provided in the μ-wave introducing section 1, and 12 is a cooling member for the superconductor 11. It is a means. Further, as in the previous example, the window 40 is separated from the plasma chamber 41 and is designed to be purged by the purging means 2.

What is important during film formation is that, as mentioned above, in order to transmit all the μ wave energy to the plasma chamber, the μ
The purpose is to create a condition in which the purge gas does not cause discharge in the wave introduction section 1. In addition, in film formation by magnetic field μ-wave CVD as in this example, generally 10-'torr or less (preferably 10-'torr or less)
A low pressure (below 0-'torr) is used, and no discharge occurs without a magnetic field.

Therefore, in this example, the problem is solved by magnetically shielding with the superconductor 11 so that the magnetic field of the magnets 42 and 42' provided to create a magnetic field in the plasma chamber 41 does not enter the μ-wave introducing section 1. ing.

Ferromagnetic materials (iron, nickel,
Cobalt, etc.), but when this is used, a strong magnetic field is generated around it, which causes a strong bias in the plasma in the plasma chamber, which is undesirable. On the other hand, when the superconductor 11 is used, the magnetic flux avoids the superconductor 11 due to the Meissner effect, so the magnetic flux cannot enter the μ-wave introducing section 1 surrounded by the superconductor 11. , magnetic shielding is possible. In this case, although some disturbance of the magnetic field occurs near the μ-wave introducing section 1, the magnetic field is not concentrated as strong as in ferromagnetic materials, so the influence on the plasma is small. The superconductor 11 is cooled to a temperature at which it becomes superconducting by supplying liquid nitrogen to the cooling means 12. 13 and 14 are an inlet and an outlet for liquid nitrogen.

In this example, the film is formed using the same procedure as in the previous example, but the superconductor 11 magnetically shields the μ-wave introduction section 1, so that the purge gas does not cause discharge in the μ-wave discharge section 1. , and all of the μ-wave energy can be transmitted to the plasma chamber 41. Therefore, in addition to the same effect as in the previous example, the effect of improving the decomposition efficiency of the raw material gas can be obtained.

〔Effect of the invention〕

As described above, according to the present invention, since there is less film adhesion to the window of the μ-wave introduction part, the μ-wave introduction efficiency does not change depending on the film formation time, and stable plasma can be obtained for a long time. . In addition, the number of times window materials need to be replaced and cleaned can be reduced.

Furthermore, by providing a superconductor that magnetically shields the μ-wave introducing section, it is possible to prevent the magnetic field acting on the plasma chamber from entering the μ-wave introducing section, thereby preventing discharge of the purge gas in the μ-wave introducing section. The decomposition efficiency of raw material gas can be improved.

[Brief explanation of the drawing]

FIGS. 1(a) and (b) are structural explanatory diagrams of a thin film forming apparatus according to a first embodiment of the present invention, and FIG. 2 shows the main structure of a thin film forming apparatus according to a second embodiment of the present invention. The plan view and FIGS. 3(a) and 3(b) are structural explanatory diagrams of a conventional amorphous silicon film forming apparatus, in which 1 is a μ-wave introducing section, 2 is a purge means, 11 is a superconductor, and 31 is a superconductor. A vacuum container, 38 a μ-wave power source, 39 a waveguide, 40 a window, 41 a plasma chamber, and 100 a cylindrical base.

Claims (1)

[Claims] 1. The raw material gas introduced into the plasma chamber (41) of the coaxial cavity resonator formed by the vacuum container (31) and the cylindrical base (100) set therein, Vacuum container (3
Window (40) of the microwave introduction part (1) provided in 1)
In a thin film forming apparatus that generates plasma by microwaves introduced from the cylindrical substrate (100) and deposits a thin film on the cylindrical substrate (100), the window (40) is moved away from the plasma chamber (41), and the microwave introduction section (1) ) using a purge gas. 2. The thin film forming apparatus according to claim 1, wherein the microwave introduction section (1) is provided with a superconductor (11) for magnetically shielding the section.