JPH055897B2 - - Google Patents

Description

[Detailed description of the invention]

[Technical field to which the invention pertains] The present invention relates to a film deposited on a substrate, particularly a functional film, particularly an amorphous amorphous material used for semiconductor devices, photoreceptor devices for electrophotography, line sensors for image input, imaging devices, photovoltaic devices, etc. The present invention relates to microwave plasma CVD devices such as devices and etching devices for forming semiconductor films. [Description of Prior Art] Amorphous silicon has conventionally been used as an element member for semiconductor devices, photoreceptor devices for electrophotography, line sensors for image input, imaging devices, photovoltaic devices, and various other electronic devices, optical devices, etc. , for example hydrogen or/
and amorphous silicon (hereinafter referred to as [A-Si (H,
It is written as [Xna]. ) have been proposed, and some of them have been put into practical use. These deposited films can be deposited using the plasma CVD method.
That is, it is formed by a method in which a raw material gas is decomposed by direct current, high frequency, or microwave glow discharge, and a thin film-like deposited film is formed on a substrate such as glass, quartz, heat-resistant synthetic resin film, stainless steel, or aluminum. This is known, and various devices for this purpose have been proposed. In particular, in recent years, a plasma CVD method (hereinafter referred to as MW-PCVD method) using microwave glow discharge decomposition has attracted industrial attention. Such a conventional deposited film forming apparatus using the MW-PCVD method typically has an apparatus configuration as shown in the perspective schematic diagram of FIG. In FIG. 3, 301 is a reactor vessel, which has a vacuum-tight structure. 302 is a microwave introduction window made of a material (for example, quartz glass, alumina ceramics, etc.) that can efficiently transmit microwave power into the reaction vessel and maintain vacuum tightness; The transmission section is mainly a metal waveguide, and is connected to a microwave power source (not shown) via a matching box isolator (not shown). 304 is an exhaust pipe that opens into the reactor vessel 301 at one end and communicates with an exhaust system (not shown) at the other end. 305 is a substrate on which a deposited film is to be formed, and 306 is a discharge space surrounded by the substrate. Formation of a deposited film using such a conventional deposited film forming apparatus is performed in the following manner. In FIG. 3, an exhaust valve (not shown) is opened, and the inside of the vacuum container 301 is degassed using a vacuum pump (not shown) to adjust the pressure inside the reaction container to 1×10 ^-7 Torr or less. Next, the heater 307 is energized to maintain the temperature of the substrate 305 at a temperature suitable for film deposition. Therefore, in the case of forming, for example, an amorphous silicon deposited film, a raw material gas such as silane gas or hydrogen gas is introduced into the reaction vessel via a raw material gas supply means (not shown). At the same time, a microwave power supply is energized to generate microwaves with a frequency of 500 MHz or more, preferably 2.45 GHz, which are passed through the waveguide and through the microwave introduction window 302 to the reactor vessel 3.
01. Thus reactor vessel 301
The gas inside is excited by microwave energy and dissociates, forming a deposited film on the substrate surface. In such a deposited film forming apparatus, a drawback of the conventional technology is the durability and transmission efficiency of the introduction window when introducing microwave power into the reaction vessel. Conventionally, materials with small dielectric constant (E) and small dielectric loss angle (tan δ) have been used for microwave power introduction windows in order to prevent transmission loss as much as possible. Examples of materials selected based on the dielectric constant and dielectric loss angle include beryllia (BeO), Teflon, and alumina ceramics. In addition, the characteristics that an introduction window material should have include heat resistance due to discharge heat radiation, thermal shock resistance, and vacuum holding ability, and the reason why there is no existing material that is excellent as an introduction window material with these characteristics. This is the current situation. In the conventional microwave power introduction window, microwave power is 10W/cm ² ~
If plasma discharge is excited and sustained by continuous introduction in the range of 50 W/cm ² , the window material will be destroyed within a short period of time. There is no highly durable window material available for this continuous use, and the current situation is that it cannot withstand practical use at all when productivity is considered. [Object of the Invention] The present invention overcomes various problems in conventional devices as described above, and is applicable to semiconductor devices, photosensitive devices for electrophotography, line sensors for image input, imaging devices, photovoltaic devices, and other various electronics. The object of the present invention is to provide an apparatus and an etching apparatus that can stably and rapidly form a deposited film as an element member used for an element, an optical element, etc. by microwave plasma CVD method. Specifically, the first objective is to provide a highly durable microwave introduction window material with excellent heat resistance. The second objective is to provide a highly durable microwave introduction window material with excellent thermal shock resistance. The third object is to provide a microwave introduction window material that has excellent vacuum retention properties. Fourth, it is an object of the present invention to provide a microwave introducing window and an introducing window material that have excellent microwave power transmission characteristics. [Structure of the Invention] The present invention provides a deposited film forming apparatus using a microwave plasma method, which can achieve the above-mentioned objects. The present inventor conducted extensive research to overcome the above-mentioned problems in conventional devices, and found that A-Si
It was concluded that in order to efficiently and stably deposit (H, Reached. The inventors of the present invention have found that, in order to achieve the above-mentioned objects of the present invention, the problems can be solved by using alumina ceramics, which is suitable as a highly durable introduction window material. In general, alumina ceramics are ceramics that contain approximately 80% or more of α-alumina components, but other components or impurities are
Glassy substances such as SiO ₂ , MgO, and CaO are present. The characteristics of alumina ceramics, such as heat resistance, mechanical strength, and high insulation properties, are largely controlled by the content of glass as an impurity. In other words, the higher the α-alumina content and the lower the glass-based components, the higher the thermal, mechanical, and electrical properties of alumina ceramics, and the α-alumina content is 99.5%. % or more alumina ceramics have shown excellent properties. On the other hand, as a result of research conducted by the present inventors, it has become clear that high purity alumina ceramics are not necessarily superior as alumina ceramics used as the microwave introducing window material in the present invention. The microwave introduction window material that can achieve the object of the present invention is alumina ceramics, and has a glassy component ratio of 1% to 1% as an impurity selected from SiO ₂ , CaO, and MgOB, and other components. is α-alumina, preferably SiO ₂ ,
The glassy component as an impurity selected from CaO and MgO is 1% to 8%, and other components are α-
We came to the conclusion that it is alumina ceramics, which is characterized by being alumina. The microwave introduction window must have excellent properties such as vacuum retention, heat resistance, thermal shock resistance, and microwave transmission. In particular, with conventional window materials, the microwave introduction window was destroyed in a short period of time due to thermal shock due to heat absorption of microwave power and radiant heat from the plasma discharge space. By using it as a window material, it is possible to form a deposited film continuously and stably. The characteristics of the alumina ceramics according to the present invention are:
This shows that the glassy component as an impurity component selected from SiO ₂ , CaO, and MgO needs to be present in an optimal range for the microwave introduction window material. That is, on the other hand, if the glassy component selected from SiO ₂ , CaO, and MgO is present in a composition ratio exceeding 10%, the glassy component itself has poor thermal conductivity compared to α-alumina. This is not preferable because it becomes alumina ceramics with low thermal conductivity, cannot withstand thermal shock due to microwave absorption heat generation and plasma radiant heat, and is likely to be destroyed. On the other hand, in the case of alumina ceramics in which the glassy component is less than 1% in composition ratio, that is, the α-alumina component exceeds 99.5% in composition ratio, it can be used for general purposes by firing at a high temperature, but microwave introduction is not possible. As a window material, it is not preferable because the bond between alumina particles is weak and it cannot withstand thermal shock due to microwave absorption heat generation and plasma radiant heat, resulting in destruction. As mentioned above, the characteristics of the present invention are SiO ₂ , CaO, MgO
An alumina ceramic material containing a glassy component as an impurity selected from 1% or more and 10% or less, preferably 1% or more and 8% or less, and other components being α-alumina, is suitable for microwave introduction windows. As a material, alumina ceramics is extremely stable against extremely severe thermal shock from both its internal heat generation due to microwave absorption and external heat due to radiation from plasma generated on the reaction vessel side. Enables continuous reaction over a long period of time. Hereinafter, the microwave introduction window of the present invention will be explained in detail with reference to Examples, but the structure of the microwave introduction window of the present invention and the apparatus for forming a deposited film by microwave plasma CVD are not limited thereto. Fig. 1 is a diagram of a deposited film forming apparatus using the microwave introduction window of the present invention, in which Fig. 1a is a side sectional view, and Fig. 1b is a cross-sectional view in the plane of Each represents a side view. In FIG. 1, a reactor vessel 101 has an exhaust pipe 104,
Exhaust valve (not shown), vacuum pump (not shown)
It is composed of Inside the reactor vessel 101, cylindrical substrates 105 are arranged concentrically with respect to the discharge space 106, and between the adjacent cylindrical substrates,
A gas introduction pipe 108 having a plurality of gas introduction holes on the side surface is also arranged concentrically. By installing such a gas introduction pipe, the flow of gas within the plasma space can be made uniform, and the effect of confining the plasma within the plasma space is increased, which, together with the effects of the present invention, further stabilizes the plasma. , uniformity can be measured. For plasma discharge, gas is introduced from the gas introduction pipe 108, microwave power generated by a microwave generator (not shown) is passed through the waveguide 103, and the microwave is introduced into the reactor via the microwave introduction wave 102. Container 101
to be introduced within. The shape of the microwave introduction window may be rectangular or circular, but in this example, a circular, disc-shaped window material was used. In Figure 2, the microwave power 201 shows the shape of the microwave introduction window alone and the introduction window material.
is introduced through a rectangular waveguide 202, a circular waveguide 203, and an introduction window 204. Rectangular waveguide 20
2 and the circular waveguide 203 are converted into a horn type in FIG. 2, but they may be directly converted from a rectangular waveguide to a circular waveguide without using a horn type conversion section. Alternatively, the light may be guided directly to the introduction window 204 using a rectangular waveguide without circular conversion. When the microwave mode used is TE ₁₁ mode, the microwave introduction window 204
It is designed using the well-known formula below. In the formula, λ is the resonant wavelength (12.245 cm for 2.45 GHz microwave), a is the radius (cm) of the circular introduction window, d is the thickness (cm), and is the relative dielectric constant. Therefore, the dielectric constant of alumina ceramics ≒
10. When the radius a = 101.6 cm, the resonance condition can be satisfied with the thickness d = 1.91 cm. Here, the length d=1.91 cm corresponds to 1/2 the wavelength of the microwave propagating within the alumina ceramics. Alumina ceramics shape radius a = 101.6 cm,
For the thickness d=1.91 cm, it is preferable to use one layer in the thickness direction, but there is no problem even if the layer is divided into multiple layers in the thickness direction. In this example, the thickness is 1.27cm in the thickness direction.
d = 1.91 cm by stacking two 0.64 cm disc-shaped ceramics. In the embodiment of the present invention, under the conditions of manufacturing an electrophotographic photoreceptor drum using the deposition film apparatus shown in FIGS. , conducted an evaluation of the introduced window materials. The electrophotographic photosensitive drum in Examples was produced as follows. That is, in FIG. 1, the interior of the reactor vessel 101 is evacuated by a vacuum pump (not shown) through an exhaust pipe 104 by opening an exhaust valve (not shown). A booster pump and oil rotary pump were used in combination. Next, the substrate 105 is heated and maintained at a predetermined temperature by a heater 107 built into the substrate. Next, a raw material gas such as silane gas or hydrogen gas is supplied into the reactor vessel 101 through the gas introduction pipe 108 while maintaining a vacuum level of 1×10 ^-2 Torr or less. Next, a 2.45 GHz microwave generated by a microwave generator (not shown) is introduced into the discharge space 106 via the waveguide 103 and the microwave introduction window 102. In this way, the source gas in the discharge space 106 is excited and dissociated by the microwave energy, generating neutral radical particles, ion particles, electrons, etc., which react with each other to form a deposited film on the conductive substrate. be done. Example 1 Continuous discharge was carried out using alumina ceramics with different vitreous component composition ratios as the microwave introduction window material under the discharge conditions shown in Table 1, and the stability of discharge and the failure of alumina ceramics to continue discharge due to destruction were evaluated. The discharge maintenance time until it became possible was measured. The results are shown in Table 2. As is clear from Table 2, the alumina ceramics according to the present invention were found to have extremely excellent discharge stability and heat resistance.

【table】

【table】

[Table] Example 2 Using alumina ceramics with different vitreous component composition ratios as a microwave introduction window material, continuous discharge was performed under the discharge conditions shown in Table 3, and the deposition rate of the deposited film on a cylindrical substrate shape was measured. And the discharge maintenance time until the alumina ceramics became unable to continue discharge due to destruction was measured. The results are shown in Table 4.

【table】

[Table] As is clear from the above results, the alumina ceramics according to the present invention has a high deposition rate, that is, it has excellent microwave transparency in the microwave introduction window, and has extremely excellent discharge stability and heat resistance. I understand. The reason that the deposition rate decreases in alumina ceramics with a glass content of over 10% is because glass has poor thermal conductivity, and the film deposited on the surface of the alumina ceramic used as a microwave introduction window crystallizes due to high temperature. , inhibits microwave transmission, resulting in a decrease in deposition rate, and also causes destruction of the microwave introduction window. Example 3 Using the deposited film forming apparatus shown in FIG. 1 and under the deposited film forming conditions shown in Table 5, an electrophotographic image forming member having the layer structure shown in FIG. 4 was formed using the alumina ceramics shown in Example 2. The material was formed using a microwave introduction window. As shown in FIG. 4, an electrophotographic image forming member suitable for the microwave introduction window of the present invention has a first layer formed on an aluminum cylindrical substrate 401 and having a function of blocking charge injection from the substrate. 402, a second layer 403 that generates and transports charges through light irradiation and exhibits the main function of image formation, and a free surface 40.
5, and a third layer having the function of retaining ionic charges due to corona charging, etc., and preventing injection of charges into the second layer to improve charging ability. Alumina ceramic windows 2-1 to 2 of Example 2
Regarding -7, electrophotographic image forming member D3-1~
D3-8 was created. Table 6 shows the presence or absence of cracks in the alumina ceramic window during formation of an electrophotographic image forming member and the results of the electrophotographic properties. Alumina ceramic window samples 2-1, 2-7,
Similarly to Example 2, Sample No. 2-8 was destroyed during the formation of the deposited film. Also, alumina ceramic window sample 2-2~
Similar to Example 2, Sample No. 2-6 did not break. Furthermore, the produced electrophotographic image forming member was mounted on a copying machine (NP7550 manufactured by Canon Inc.), and the electrophotographic characteristics were measured. Samples D3-1, D3-7, D3
-8 was because the alumina ceramic window was broken.
The sample was thin and the electrophotographic properties could not be evaluated.
Unbroken sample D3 of alumina ceramic window
-2 to D3-6 exhibited electrophotographic properties sufficient for practical use.

【table】

[Table] * ×... Destruction ○... No destruction [Summary of the effects of the invention] As explained above based on the examples, in the deposited film forming apparatus by the microwave plasma CVD method according to the present invention, ,
Use alumina ceramics in which the composition ratio of a glassy component selected from SiO ₂ , CaO, and MgO is 1% to 10%, preferably 1% to 8%, and the other component is α-alumina. By using the microwave introduction window material of the present invention, which exhibits extremely efficient microwave transmission and has extremely stable characteristics over long periods of use, it is possible to create device production equipment with excellent mass productivity. It is.

[Brief explanation of the drawing]

FIG. 1a shows the microwave plasma of the present invention.
FIG. 1b is a side cross-sectional view of a deposited film forming apparatus using the CVD method, and FIG. 1b is a cross-sectional view taken along the plane X in FIG. 1a. Figure 2 is a diagram of the microwave introduction window, and Figure 3 is a diagram of the microwave introduction window.
1 is a schematic perspective view of a deposited film forming apparatus using a CVD method.
Further, FIG. 4 is a diagram showing the layer structure of the electrophotographic image forming member used in the examples. In the figure, 101...reactor vessel, 102,
204... Microwave introduction window, 103... Waveguide, 104... Exhaust pipe, 105... Cylindrical base,
106...Discharge space, 107...Heater, 10
8... Gas introduction pipe, 109... Moving flange, 110... Base rotation motor, 201...
Microwave, 202... Rectangular waveguide, 203...
Circular waveguide, 301... Reactor vessel, 302...
Microwave introduction window, 303... Waveguide, 304...
... Exhaust pipe, 305 ... Cylindrical base, 306 ... Discharge space, 307 ... Heater, 400 ... Cross-sectional view of image forming member, 401 ... Aluminum substrate, 4
02... Lower charge injection blocking layer, 403... Photoconductive layer, 404... Surface layer, 405... Free surface.

Claims (1)

[Claims] 1 consisting of a substantially closed reaction vessel accommodating a substrate, means for introducing at least one reaction gas into the reaction vessel, and means for introducing microwave energy into the reaction vessel; A microwave plasma CVD device that deposits a thin film on a substrate by exciting a glow discharge inside the device,
The means for introducing microwave energy is made of a microwave-transparent material that maintains the gas atmosphere of the reaction vessel and introduces microwave energy, and the material is SiO ₂ ,
Microwave plasma CVD characterized by being alumina ceramics containing a glassy component selected from CaO and MgO in a composition ratio of 1% to 10%, and other components being substantially α-alumina. Device.