JPS62196375A - Method and device for forming deposited film by microwave plasma chemical vapor deposition process - Google Patents

Abstract

PURPOSE:To stably and high speedily form a deposited film on the surface of a base material by arranging a microwave permeable base material extremely near to a window of a dielectric material and irradiating microwave from the outside and injecting a reacting gas for film formation to the base material from a reaction vessel side. CONSTITUTION:A window 3 of a dielectric material made of quartz glass wherein microwave is permeated therethrough and vacuum airtightness can be held is provided to a reaction vessel 1 constituted by providing an exhaust pipe 6 to a vacuum vessel 2. A base plate 9 consisting of a microwave permeable member is arranged extremely near to the above- mentioned window 3 of the dielectric material in the reaction vessel 1 side which is vacuumed and exhausted in the proper degree of vacuum. As the above-mentioned base plate 9, in such a case that microwave has >=500MHz frequency, a dielectric material such as quartz glass, Al2O3 and ceramic having >=0.0006 tandelta loss angle of the dielectric material is preferably used. The above-mentioned base plate 9 is made at the prescribed temp. by the radiation heat of a heater 10. Thereafter while discharging reaction gas for film formation to the neighborhood of the base plate 9 through the many discharge holes 7' of a feed pipe 7 for a gaseous raw material, film formation is performed on the base plate 9 by irradiating microwave 51 from an electric power source 5 for microwave, energizing and decomposing the above-mentioned gaseous raw material in a plasma generating region 11.

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 a semiconductor device, a photoreceptor device for electrophotography, a line sensor for image input, an imaging device, an optical The present invention relates to a method for forming an amorphous semiconductor film used in an electromotive force element, etc., and an apparatus most suitable for carrying out the method.

[Description of prior art]

Conventionally, amorphous silicon, such as hydrogen (H) or / and halogen (X) (e.g. fluorine, chlorine, etc.) compensated amorphous silicon (hereinafter, [a
−8i (H,X)]. ) and other amorphous semiconductor r1ζ deposited films have been proposed, and some of them have been put into practical use.

Such deposited films are produced using the plasma CVD method, in which raw material gas is decomposed by direct current, high frequency, or microwave glow discharge, and a thin film is deposited on a substrate such as glass, quartz, heat-resistant synthetic resin film, stainless steel, or aluminum. It is known to be formed by a method of forming a deposited film, and various apparatuses for this purpose have also been proposed.

In particular, in recent years, Prada 7 has been developed using microwave glow discharge decomposition.
CVD method (hereinafter referred to as *Mw-PCVD method)
is also attracting attention from an industrial perspective.

Such a conventional apparatus for forming a deposited film using the MW-PCVD method typically has an apparatus configuration shown in the schematic cross-sectional view of FIG. In Fig. 2, 1 indicates the entire reaction vessel, 2 a vacuum vessel, 3 a dielectric window made of alumina ceramics or quartz, 4 a waveguide, 5 a microwave power source, 5
1 is a microwave, 6 is an exhaust pipe, 7 is a ring-shaped source gas supply pipe, 71 is a valve, 8 is a substrate holding plate, 9 is a substrate, 1
0 indicates a heater, and 11 indicates a plasma generation region.

Deposited film formation using such conventional deposited film forming equipment is
This is done as follows.

That is, the inside of the vacuum container 2 is evacuated via the exhaust pipe 6, and the substrate 9 is heated and held at a predetermined temperature by the heater 10 built into the substrate holding plate 8. Next, in the case of forming, for example, an amorphous silicon deposited film, a raw material gas such as silane gas or hydrogen gas is fed into the raw material gas supply pipe 7, and a plurality of gas discharge holes 7 are opened to the raw material gas supply pipe 7. / , 7/, . . . into the reaction vessel 1. Simultaneously, a frequency of 500 Nff (Z or more, preferably 2.45
A GHz microwave 51 is generated, and the microwave is introduced into the reaction vessel 1 through the waveguide 4 and the dielectric window 3 . In this way, the raw material gas introduced into the reaction vessel 1 is excited by the microwave energy and dissociated, producing neutral radical particles to ion particles, electrons, etc., which react with each other and deposit on the surface of the substrate 9. A film is formed.

By the way, in such a MW-PCVD method, a high-frequency plasma CVD method (hereinafter referred to as 'RF-PCVD) using high-frequency power with a frequency of 13.56 MHz is generally used.
Plasma is generated by an electrodeless discharge, which is different from the method (referred to as "method"). That is, as shown in FIG.
will occur. Furthermore, since the ionized plasma acts as an electrical conductor, it acts as an absorber or a reflector for microwaves that have the property of spatially propagating inside a dielectric material. Furthermore, the electric field strength of the plasma decreases rapidly as it moves away from the dielectric window due to the skin effect.

In addition, since the electron temperature also decreases in proportion to the electric field strength distribution,
The density distribution of excited atoms generated by decomposition of the source gas also decreases as the distance from the dielectric window increases. like this,
The density distribution of excited electrons directly affects the deposition rate of the deposited film, which is fast near the dielectric window and rapidly slows down as it moves away from the dielectric window.

That is, the conventional MW-PCVD apparatus in which the substrate is disposed at a considerable distance from the dielectric window has the disadvantage that the film deposition rate is slow.

Another disadvantage is that microwave energy cannot be fully utilized when an apparatus with the same structure is used for plasma processing other than a-8i:)(:x films, such as deposition of electrical insulating films or dry etching processing). There was also.

On the other hand, when depositing a film with a low dielectric constant such as the 3-8i:H:X film used as the element material, the deposited film acts as an absorber or reflector for microwaves. Therefore, when a-8i: H: The microwave power used to enter the room and generate plasma decreases, and eventually it becomes impossible to input enough microwave power to generate plasma, and the plasma disappears.

That is, in a structure in which the substrate is disposed at a location where the deposition rate is slow as in the conventional apparatus, a desired film thickness of a-8i:
When attempting to deposit an H:X film, the X film is deposited on the dielectric window at a thickness of a-8i:I, which is even thicker than that of the a-8i:I film on the substrate.
The disadvantage was that the plasma disappeared before the 8i:H:X film reached the desired thickness.

[Purpose of the invention]

An object of the present invention is to overcome the problems in the conventional devices as described above, and to improve semiconductor devices, photosensitive devices for electrophotography, line sensors for image input, imaging devices, photovoltaic devices, and other various electronic devices, as well as optical devices. The deposited film as an element member used in an element etc. is processed by MW-PCV.
The object of the present invention is to provide a method that can be formed stably and at high speed by method D, and an apparatus that is optimal for carrying out the method.

Another object of the present invention is to obtain a-8i by MW-PCVD method.
: H: It is in.

Still another object of the present invention is to provide a method for forming a deposited film that can stably deposit an a-8i:H:X film without interruption of microwaves during deposition, and an apparatus most suitable for carrying out the method. It is about providing.

[Structure of the invention]

The present inventors have conducted intensive research to overcome the above-mentioned problems in conventional methods and devices and to achieve the above-mentioned object of the present invention, and have found that a-8i:H
:For efficiently forming the X film, the substrate (support)
It has been found that it is most preferable to arrange the microwave as close as possible to the plasma side of the dielectric member serving as the microwave introduction window.

However, in that case, it has been found that there is the above-mentioned problem that must be solved.

That is, in the case described above, since the a-8i:H:X film is deposited on the surface of the substrate opposite to the surface in contact with the dielectric window, plasma is generated inside the reaction vessel. In order to achieve this, it is essential that the microwaves propagated through the dielectric window also propagate inside the base.

As a result of further intensive research on this point, the present inventor found that a substrate material that efficiently propagates microwaves with a frequency of 500 MHz or higher has a dielectric loss angle (tan δ) of 0.005 or less and a relative permittivity (Eγ). ) is preferably 10 or less.

Such dielectric materials include, for example, quartz glass,
Alumina ceramics, Teflon, polystyrene, beryllia, steatite, etc. have a frequency of 2.45.
It has been found that the half-life depth of GHz microwave power is 1 m or more, and microwaves can be transmitted extremely efficiently.

On the other hand, dielectric materials with tan δ of 0.006 or higher, such as soda glass, have a large absorption of microwaves.
The microwave power at frequency 2.45 GHz is only 30
It turns out that half of that amount is absorbed at a depth of 1.5 cm and is used as heat energy.

Farewell, when a conductive material such as metal is used as the base,
It has also been found that the object of the invention cannot be achieved by using such materials, since the microwaves are completely reflected.

However, the present invention has been completed based on the above-mentioned knowledge, and includes a method for forming a deposited film by the MW-P ('VD method) and an optimal apparatus for carrying out the method. It is.

That is, the method of forming a deposited film by the MW-PCVD method of the present invention uses a microwave-transparent member as a substrate, and places the substrate very close to the side of the reaction vessel of the microwave transmission window from the microwave generation source. and eject a film-forming raw material gas from near the surface of the substrate on the reaction vessel side, and at the same time radiate microwave energy thereto to deposit a film on the surface of the substrate on the reaction vessel side. This is a characteristic feature.

The apparatus of the present invention includes the MW-PCVD of the present invention.
A microwave transmitting window which forms part of the wall of the reaction vessel and which introduces the microwave energy propagated from the microwave generation source into the injector, which is most suitable for carrying out the method of forming a deposited film by the method. A substrate made of a microwave-transparent member is installed very close to the side wall surface of the reaction vessel, and the plasma is prevented from entering the interface, and the raw material gas for film formation is introduced from the vicinity of the substrate into the substrate. It is characterized by having a means for supplying the liquid to the entire surface on the reaction vessel side.

In the method and apparatus of the present invention having the above configuration, the frequency of the microwave used is 500M.
Hz or higher, the microwave transparent material used for the substrate is a material such as quartz glass, alumina ceramics, Teflon, polystyrene, beryllia, steatite, etc., as examples of dielectric loss internal materials for microwaves at such frequencies. Such a member as a substrate can be made as thin as possible within a range that fully exhibits its permeability function and support function, but there are certain issues regarding manufacturing and handling. In terms of mechanical strength, etc., the thickness is usually 10μ or more.

The surface for forming a deposited film of such a member as a base body may be formed into an uneven shape, such as a dimple shape, depending on the intended use.

Furthermore, in the method and apparatus of the present invention having the above-mentioned configuration, when the raw material gas for forming a deposited film is excited and dissociated by microwave energy to form a deposited film on the surface of the substrate, the substrate is heated by radiant heat through means,
Of course, it is also possible to increase the efficiency of deposited film formation.

Hereinafter, the method and apparatus for forming a deposited film using the MW-P (VD method) of the present invention will be explained in more detail with reference to the embodiments shown in the drawings, but the present invention is not limited thereto.

FIG. 1 is a schematic cross-sectional view of an optimal example of an apparatus for carrying out the method of forming a deposited film by the MW-PCVD method of the present invention.

In the figure, the components of the device having the same functions as those before the conventional device (shown in FIG. 2) are indicated by the same symbols as in FIG. 1.

In the figure, 1 indicates the entire reaction vessel of the apparatus of the present invention. 2 is
A vacuum container for making the reaction container vacuum-tight, and 3
is a dielectric window made of a material (for example, quartz glass) that can efficiently transmit microwaves into the reaction vessel and maintain vacuum tightness. Reference numeral 4 denotes a microwave waveguide section, which is mainly made of a metal rectangular waveguide, and is connected to a microwave power source 5 via a three-pillar matching box and an isolator (not shown). Reference numeral 6 denotes an exhaust pipe whose one end opens into the vacuum container 2 and whose other end communicates with an exhaust device (not shown).

Reference numeral 8 denotes a holding portion for the base body 9, which has a structure to hold the base body 9 in close contact with the dielectric window 3. The base body 9 is made of the above-mentioned dielectric material that efficiently transmits microwaves.

The base 9 is held in close contact with the dielectric window 3 by the substrate holder 8, and no plasma is generated at the interface between the base 9 and the dielectric window 3. : This is a heater that heats and maintains the temperature at a temperature suitable for depositing the X film. In this embodiment, it is placed on the vacuum side of the base 9 and is heated indirectly by radiant heat, but if it is in a position where microwave transmission cannot be blocked, it can be installed on the wall of the vacuum container 2 and the base 9 is heated directly. It is also possible to have a structure in which

Reference numeral 7 denotes a raw material gas supply pipe whose one end opens near the substrate 9 of the reaction vessel and whose other end communicates with a raw material gas supply source (not shown) via a pulp means 71.

Reference numeral 11 denotes plasma generated in the reaction vessel by the microwave 51 transmitted through the dielectric window 3 and the substrate 9, and is generated on the side of the substrate 9 opposite to the dielectric window 3.

By the way, when the substrate is heated by a heating means in a reaction vessel, if the heating temperature reaches about 500°C or higher, the raw material gas decomposes even with the thermal energy alone and some reaction products are generated. is generated, which is a-8
This may have an undesirable effect on the formation of a film such as i:H:X, and the present invention includes a solution to this problem.

That is, in such a case, the substrate is heated and maintained at a temperature suitable for film formation using part of the microwave energy.

Specifically, by utilizing the fact that a material with a large dielectric loss angle (tan δ) has the property of containing microwave energy and generating heat, the base 9 is made of a material with a tan δ of 0.00.
When a dielectric material member of 6 or more is used, part of the microwave energy transmitted through the dielectric window 3 is absorbed by the base, and the base is heated from inside to a temperature suitable for film formation. It will be retained.

On the other hand, the remaining part of the microwave energy passes through the substrate, generates plasma in the film formation space of the reaction vessel, and contributes to depositing a film such as a-8i:H:X on the surface of the substrate. do.

However, if a material with a tan δ that is too large is used, the microwave power used for plasma generation will be attenuated, making it impossible to achieve a sufficient deposition rate. Selection of substrate material requires careful consideration of substrate temperature increase and deposition rate attenuation.

Further, when using a substrate material that does not absorb microwaves to a large extent, other heating means may be used as an auxiliary method.

〔Example〕

First, the valve 71 was closed and the inside of the vacuum container 2 was degassed through the exhaust pipe 6, and the pressure inside the reaction container was adjusted to below I.times.10-' Torr. Next, the heater lO is energized to heat the base 9.
The temperature was heated to and maintained at 250°C. There, Pulp 7
1 is opened and silane gas 50 is supplied via the raw material gas supply pipe 7.
The raw material gas consisting of a mixed gas of 0 secm and hydrogen gas of 200 secm was heated at an internal pressure of I
At the same time, the microwave power source 5 is energized to radiate microwaves with a frequency of 2.45 GHz into the reaction vessel through the dielectric window 3 and the dielectric base 9,
Plasma was generated to perform open film formation at predetermined times. after that,
After stopping heating the substrate, supplying gas, and irradiating microwaves, and allowing the substrate to cool, the substrate was carried out of the system. The same operation was carried out to form a deposited film 10 times in total, leaving the dielectric window 3 as it was and replacing only the substrate 9 with another one.

FIG. 3 shows the distribution of deposition rate changes at the surface of the substrate 9 and at positions farther away from the surface of the substrate 9 when deposition was performed by radiating microwave power of 900 W in this manner.

As is clear from FIG. 3, the base 9 near the dielectric window
The deposition rate was 75X/sec on the surface of the substrate, while the deposition rate at a position only 10 cIrL away from the substrate was 15A/sec. That is, compared to the location where the substrate was placed in the conventional example, when the substrate was placed very close to the dielectric window, the rate of deposited film formation was increased five times.

Moreover, when we tested the deposited films on the surfaces of 10 substrates, we found that all of them had extremely dense compositions, were homogeneous throughout, and had excellent electrical, optical, and photoconductive properties. It was invaded.

Furthermore, even after depositing an a-8i:H:X film of about 1 μm on the substrate and performing the deposition film formation 10 times, the a-8i:H:x film remains on the surface of the dielectric window in contact with the substrate. No evidence of accumulation was seen. This indicates that the substrate is effective as a film adhesion barrier for the dielectric window during film deposition. In general, when a-8i:H:X films with low electrical resistivity, such as those used in photoelectric conversion devices, are formed by conventional methods, if a film is deposited with a thickness of 1 μm, which is the film thickness required for the device, the dielectric A 5 μm thick a-8i:H:X film is deposited on the window.

When an a-8t:H:X film is present in a microwave transmission path, if the film thickness exceeds 4 to 5 μm, absorption and reflection of microwaves by the film cannot be ignored.

On the other hand, according to the present invention, even if there is a large amount, it is only about 1 μm at most, and at that point it is replaced with a new substrate. Power attenuation can be ignored. In fact, in this example, no increase in the reflected power of microwaves was observed during the first and tenth film depositions, and no change in the deposition rate was observed, so extremely stable film formation was achieved.

〔Effect of the invention〕

According to the present invention, by arranging the dielectric substrate that transmits microwaves in close proximity to the dielectric window for introducing microwaves,
A-8i:H with high lotus on the surface of the substrate opposite to the surface in contact with the window.
:X film can be deposited and the substrate is a-8i on the window.
By having the function of an anti-adhesion plate that prevents the adhesion of the :H:X film, plasma can be generated stably for a long period of time in the reaction vessel, and the a-8i:H:X film can be stabilized. can be deposited.

[Brief explanation of drawings]

FIG. 1 is a schematic cross-sectional view of an apparatus according to an embodiment of the present invention. Second
The figure is a schematic cross-sectional view of a deposition film forming apparatus using the conventional MW-PCVD method. FIG. 3 is a graph showing the rate of deposited film formation with respect to the distance from the microwave introduction window when the deposited film is formed according to the present invention. In the figure, 1... Reaction container 2... Vacuum container 3...
Dielectric window (microwave introduction window) 4... waveguide section
5...Microwave power supply 51...Microwave
6... Exhaust pipe 7... Raw material gas supply pipe 71...
・Valve 8...Base holding plate 9...Substrate 10
...Heater 11...Plasma generation area

Claims (6)

[Claims] (1) A microwave transparent member is used as a base, and the base is positioned very close to the side of the reaction vessel of the microwave transmission window from the microwave generation source, and the surface of the base on the reaction vessel side is Deposited film formation by a microwave plasma CVD method, characterized in that a deposited film is formed on the surface of the substrate on the reaction vessel side by ejecting a film-forming raw material gas from nearby and simultaneously radiating microwave energy thereto. Method. (2) The deposited film forming method according to claim 1, wherein the substrate is heated to a temperature suitable for film formation using radiant heat. (3) According to claim 1, the substrate is a dielectric member having a dielectric loss angle (tan δ) of 0.006 or more when the microwave frequency is 500 megahertz or more. The deposited film forming method described above. (4) A microwave transparent member is placed in close proximity to the side wall surface of the reaction vessel of the microwave transmission window that forms part of the wall of the reaction vessel and introduces microwave energy propagated from the microwave generation source into the reaction vessel. A base body is installed, the plasma is prevented from entering the interface thereof, and means is provided for supplying the raw material gas for film formation from the vicinity of the base body to the entire surface of the base body on the side of the reaction vessel. Deposited film forming apparatus using the microwave plasma CVD method. (5) A means for heating the substrate by radiant heat to a temperature suitable for thin film deposition is provided at a position near the atmosphere side of the microwave transmission window where transmission of microwave energy cannot be obstructed. The deposited film forming apparatus according to scope 4. (6) The base body is a dielectric member having a dielectric loss angle (tan δ) of 0.006 or more when the microwave frequency is 500 MHz or more. Deposited film forming device.