JPS642192B2 - - 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 a semiconductor device, a photosensitive device for electrophotography, a line sensor for image input, and an imaging device. Microwave plasma is ideal for forming non-monocrystalline deposited films such as amorphous or polycrystalline for use in photovoltaic devices, etc.
This article relates to a deposited film forming apparatus using the CVD method.

[Description of prior art]

Conventionally, amorphous silicon, such as amorphous silicon containing hydrogen atoms and/or halogen atoms, has been used as element members for semiconductor devices, photosensitive devices for electrophotography, line sensors for image input, imaging devices, photovoltaic devices, etc. Assilicon (hereinafter referred to as "a-Si(H,X)")
Membranes, etc. have been proposed, and some of them have been put into practical use. In addition to such a-Si (H, Ion plating method, thermal CVD method using thermal energy,
There are plasma CVD methods that use discharge energy, optical CVD methods that use light energy, etc. Among them, microwave plasma that uses microwave energy
The CVD method is attracting attention as the optimal method.

By the way, what is the microwave plasma CVD method?
This method utilizes microwave energy to excitedly species (radicalize) the raw material gas for forming a deposited film near the substrate surface to cause chemical interaction, thereby depositing a film on the substrate surface. For example, the device shown in FIG. 2 has been proposed as a device for this purpose.

The example shown in FIG. 2 is a deposited film forming apparatus using a plasma CVD method using microwave energy. In FIG. 2, 201 indicates the entire reaction vessel, 202 indicates the side wall, and 203 indicates the bottom wall. ing. 204 is a multi-perforated inner wall, 205 is an exhaust pipe,
206 is an exhaust valve, 207 is a gas introduction pipe, 20
8 is a valve provided on the gas introduction pipe, 209 is a cylindrical substrate, 210 is a substrate holder, 211 is a heater, 212 is a support leg, 213 is a microwave source, 214 is a microwave, 215 is a waveguide, 21
6 indicates a dielectric window, A indicates a reaction chamber, and B indicates a source gas chamber.

Deposited film formation using such a conventional microwave plasma CVD deposited film forming apparatus is performed as follows. That is, the gas in the reaction chamber A of the reaction container 201 is evacuated through the exhaust pipe 205, and the cylindrical base 209 is heated to the heater 2.
11 to heat and maintain the temperature at a predetermined temperature. Next, for example, a-Si (H,
X) In the case of forming a deposited film, a raw material gas such as silane is introduced into the gas chamber B, and the raw material gas is released into the reaction chamber A from a large number of holes in the multi-perforated inner wall 204 of the gas chamber B. Ru. At the same time, microwave generation source 213 generates microwave 214, which passes through waveguide 215 and is introduced into reaction chamber A through dielectric window 216. In this way, the raw material gas in the reaction chamber A is excited and activated (excited speciation) by the microwave energy, and forms Si ^* , SiH ^*, etc. (* represents an excited state).
Radical particles, electrons, ion particles, etc. are generated, and these react with each other to form a deposited film on the surface of the substrate 209.

Although these conventional apparatuses for forming deposited films using the microwave plasma CVD method are generally widely adopted as optimal, there are several problems.

That is, in the conventional deposited film forming apparatus using microwave plasma CVD method, the cylindrical substrate is placed in the center of the reaction vessel, the raw material gas is introduced from the side wall, and the exhaust means is provided on the bottom wall of the reaction vessel. , the raw material gas used to form the deposited film moves with two velocity vectors, one in the horizontal direction and one in the vertically downward direction, and the distribution of the raw material gas is different above and below the cylindrical substrate. The thickness of the film deposited on the surface of the shaped substrate naturally differs between the upper and lower parts.

In order to adjust the non-uniformity of the film thickness, the positions of the gas release holes provided in the multi-perforated inner wall are made non-uniform.
As a result, it has been proposed to make the film thickness uniform above and below the cylindrical substrate, but even under various conditions such as gas flow rate, gas pressure, length of the cylindrical substrate, etc. Determining the position of the gas release holes so that the thickness of the film formed on the substrate surface is uniform requires considerable effort.

In addition, when the cylindrical substrate is placed in the center of the reaction vessel and the raw material gas is introduced from the side wall of the reaction vessel, most of the raw material gas is exhausted without being used effectively, and a deposited film is also formed on the wall of the reaction vessel. There is also the problem that the raw material gas utilization efficiency is less than 20% due to overconsumption.

Separately, at the same time as the various devices mentioned above are diversifying, mass production of deposited film products with stable characteristics has become a social demand. In order to achieve mass production,
An apparatus in which a plurality of cylindrical substrates can be installed in a reaction vessel has been proposed, for example, in Japanese Patent Laid-Open No. 60-29470.

The deposited film forming apparatus using the mass-produced glow discharge decomposition method described in this publication has an external electrode plate having a gas ejection part and an internal electrode plate having a gas suction part arranged concentrically, and both electrodes The plates are arranged to face each other via a plurality of cylindrical substrates, and the raw material gas is ejected from the outer electrode plate toward the central axis of the reaction chamber and sucked through the gas suction hole provided in the inner electrode plate. This is what happens.

However, when providing a mass-produced deposited film forming apparatus using the microwave plasma CVD method, the method of introducing and suctioning the raw material gas disclosed in the above publication may be applied as is, or by reversing the direction of gas inflow and outflow. I can't. That is, the device disclosed in the above publication uses a glow discharge decomposition method using a high-frequency electric field using electrodes, and the outer electrode plate and the inner electrode plate are electrically connected and have the same potential. Glow discharge occurs between the substrates and between the internal electrode plate and the cylindrical substrate. On the other hand, in a deposited film forming apparatus using the microwave plasma CVD method, as mentioned above, the raw material gas is decomposed by the micro energy introduced into the reaction vessel, and due to the interaction of the various excited species generated, Since a deposited film is formed on a substrate, it is important to consider how to efficiently form a plasma atmosphere formed by microwave energy and how to stably maintain the desired plasma atmosphere formed. How to efficiently and uniformly supply raw material gas into the plasma atmosphere, how to efficiently generate various desired excited species, and how to uniformly distribute the generated various excited species over the entire area near the substrate surface. It is necessary to take each of these conditions into consideration, and if the raw material gas introduction method and suction method disclosed in the above-mentioned publication were used as they were, or if the gas inflow and outflow directions were reversed, these conditions would not be satisfied. No equipment is available.

In this way, the deposited film forming apparatus using the microwave plasma CVD method generally satisfies the requirements such as the characteristics of various devices, and is suitable for the target and purpose of application, and in some cases, has a large area and is stable. The reality is that there is a strong need for equipment that can regularly mass-produce deposited film products at low cost.

[Purpose of the invention]

The present invention provides a photovoltaic element, a semiconductor device,
The purpose is to solve the above-mentioned problems and meet the above-mentioned requirements regarding conventional devices for forming deposited films used in image input line sensors, imaging devices, electrophotographic photoreceptor devices, etc. It is.

That is, the main object of the present invention is to develop a microwave plasma CVD method for regularly mass-producing deposited films with uniform thickness and quality and excellent electrical, optical, and photoconductive properties. An object of the present invention is to provide a deposited film forming apparatus using a method.

Another object of the present invention is to provide a deposited film forming apparatus using the microwave plasma CVD method, which improves the utilization efficiency of raw material gas and enables improved productivity and mass production of deposited films.

[Structure of the invention]

The present inventors have conducted extensive research to overcome the aforementioned problems with conventional CVD-based deposited film forming apparatuses and to achieve the above-mentioned objectives. Arranged at predetermined intervals, microwaves are introduced into the space surrounded by the plurality of cylindrical bases along the longitudinal direction of the cylindrical bases, and in the direction of introducing the microwaves into the space. With respect to the central axis along the line, a raw material gas introduction pipe, a cylindrical substrate, and an exhaust means are arranged concentrically in this order from the central axis toward the side wall of the reaction vessel,
Furthermore, by making it possible to emit the raw material gas toward the central axis, the above-mentioned problems were solved, and the present invention was completed based on the knowledge that could achieve the above-mentioned objects.

That is, the present invention provides a reaction vessel whose interior can be reduced in pressure, a plurality of substrate support means for supporting a plurality of cylindrical substrates for forming a deposited film disposed inside the reaction vessel,
means for introducing microwaves into a space surrounded by the plurality of cylindrical substrates along the longitudinal direction of the cylindrical substrates; a plurality of tubular source gas introduction means installed along the longitudinal direction of the cylindrical substrates; It consists of an exhaust wall member that surrounds the plurality of cylindrical substrates and has a large number of exhaust holes on almost the entire surface, and a means for evacuating the inside of the reaction vessel, and a means for evacuating the inside of the reaction vessel, which With respect to the central axis, the plurality of tubular raw material gas introducing means, the plurality of substrate supporting means, and the exhaust wall member are arranged concentrically in this order from the central axis toward the wall of the reaction vessel, and According to the microwave plasma CVD method, the tubular raw material gas introducing means is provided with a large number of gas discharge holes extending at least along the longitudinal length of the cylindrical base for releasing the raw material gas toward the central axis. The present invention relates to a deposited film forming apparatus.

In the device of the present invention, the raw material gas is first emitted toward the central axis of the microwave introduction space, so the raw material gas is efficiently excited by the microwave energy and surrounded by a plurality of cylindrical substrates. A plasma atmosphere is formed. Furthermore, since uniform exhaust is performed from the exhaust wall member having a large number of exhaust holes provided so as to surround the plurality of cylindrical substrates, the generated radical particles,
Excited species such as ionic particles and electrons move toward the wall of the reaction vessel and are uniformly distributed near the cylindrical substrate, which affects the quality, thickness, and electrical, optical, and photoconductive properties of the film. This makes it possible to efficiently mass-produce deposited films with stable physical properties and improve the efficiency of raw material gas utilization.

The raw material gas used in forming the deposited film by the apparatus of the present invention may be of the kind that can be excited by microwave energy and chemically interact with it to form the desired deposited film on the substrate surface. For example, in the case of forming an a-Si (H, Gaseous silanes and halogenated silanes, or easily gasified silanes can be used. These source gases may be used alone or in combination of two or more. Also,
These raw material gases may be used after being diluted with an inert gas such as He or Ar. Furthermore, a-Si
The (H, It can be mixed with a diluent gas and introduced into the reaction chamber.

Furthermore, even if the substrate is conductive,
It may be semiconductive or electrically insulating, and specific examples include metal, ceramics, glass, etc. The substrate temperature during the film forming operation is not particularly limited, but is between 30 and 450.
It is generally in the range of 50°C, preferably 50°C.
~350℃.

In addition, when forming a deposited film, the pressure inside the reaction chamber is increased by 5x before introducing the raw material gas.
10 ^-6 Torr or less, preferably 1 x 10 ^-6 Torr or less, and when introducing the raw material gas, the pressure inside the reaction chamber is 1 x 10 ^-2 to 1 Torr, preferably 5 x 10 ^-2 to 1 Torr.
It is desirable to do so.

Note that in forming a deposited film using the apparatus of the present invention, the raw material gas is normally introduced into the reaction chamber without prior treatment (excitation speciation) as described above, where it is excited speciation by microwave energy and chemically generated. This is carried out by causing interaction, but if two or more types of raw material gases are used, it is also possible to make one of them into an excited species in advance and then introduce it into the reaction chamber.

Hereinafter, the apparatus for forming a deposited film using the microwave plasma CVD method of the present invention will be explained in more detail with reference to the embodiment shown in FIG. 1, but the apparatus of the present invention is not limited thereto.

The embodiment apparatus shown in FIG. 1 is a typical example of a deposited film forming apparatus by the plasma CVD method using microwave energy of the present invention, and FIG. 1A is a perspective view schematically showing the entire apparatus, and FIG. 1B is a schematic longitudinal cross-sectional view thereof, and FIG. 1C is a schematic cross-sectional view thereof. In the figure, reference numeral 101 indicates the entire reactor whose interior can be reduced in pressure, and reference numeral 102 indicates a substrate support means for supporting a cylindrical substrate for forming a deposited film placed within the reaction vessel. The cylindrical base 10 is attached to the base support means 102.
2' is attached. A heating heater 103 is provided inside the cylindrical substrate support means 102 to heat the substrate to a predetermined temperature before film formation, to maintain the substrate at a predetermined temperature during film formation, or to perform an annealing treatment after film formation. used for. The cylindrical substrate support means 1
02 is mechanically connected to a driving means (not shown) that provides rotation (rotation), and the cylindrical substrate support means 102 is rotated (rotated) by the driving means during film formation.
let 104 is an exhaust pipe provided on the side wall of the reaction container for evacuating the inside of the reaction container, one end of which opens into the reaction container, and the other end of which is connected to the exhaust valve 10.
5 to an exhaust system (not shown). An exhaust wall member 106 is provided to surround the plurality of cylindrical bases, and the exhaust valve 10
5 is opened and evacuated using an exhaust device (not shown), the gas in the reaction vessel is discharged from the exhaust wall member 1.
The air is evacuated through a large number of exhaust holes 107 provided in 06, and adjusted to a predetermined degree of vacuum. The exhaust hole 107 provided in the exhaust wall member 106 has a size of 0.02 to 1 cm to prevent the internal pressure of the film forming chamber from increasing due to being blocked by powder generated by decomposition of gases that do not contribute to deposition. 0.1 to 8 holes/cm ²
It is desirable to provide a ratio of . Microwave waveguides 108 are provided above and below the reaction vessel so that microwaves can be introduced into the space surrounded by the cylindrical substrate along the longitudinal direction of the cylindrical substrate. In the example of the apparatus shown in FIG. 1, microwaves can be introduced from above and from below, but microwaves may be introduced only from above or below. The other end of the waveguide 108 is
Connected to a microwave source (not shown). Reference numeral 109 denotes a raw material gas introduction pipe for forming a deposited film inserted into the center of the reaction vessel from the bottom wall of the reaction vessel 101 along the longitudinal direction of the cylindrical substrate. It communicates with a raw material gas supply device (not shown) via the fuel cell.
The raw material gas introduction pipe 109 is provided with a pipe such that the raw material gas is mainly emitted toward the central axis of the reaction vessel.
A large number of gas release holes 111, 111 on the inside, and a small number of gas release holes 11 on the outside if necessary.
1', 111', . . . are provided.

In the apparatus of the present invention configured as described above, the raw material gas released from the gas discharge holes 111, 111, . . . is decomposed by microwaves in the space surrounded by the cylindrical base. It reaches the surface of the cylindrical substrate 102' and forms a deposited film on the surface of the substrate. The remaining source gas that does not contribute to the formation of the deposited film is exhausted through the exhaust hole 107 of the exhaust wall member 106. Note that the arrows in the figure indicate the flow of such gas.

The device of the present invention can be used not only for films made of a-Si(H,X) but also for films made of a-Si(H,X) containing oxygen atoms, carbon atoms, or nitrogen atoms, ) or a-Si(H,X) containing group atoms (e.g. B), Si ₃ N ₄ ,
It can also be applied to the production of insulating films such as SiC, SiO ₂ and SiO.

〔Example〕

Next, the operation of the apparatus for forming a deposited film using the microwave plasma CVD method of the present invention will be explained with reference to examples, but the following examples are not intended to limit the operation of the apparatus.

Example 1 A film composed of a-Si:H was formed on a cylindrical Al substrate using the apparatus shown in FIG. Further, the exhaust holes 107 of the exhaust wall 106 in the apparatus used in this example were circular with a radius of 0.1 cm, and the density was 3 holes per 1 cm ² .

That is, first, a cylindrical substrate support means equipped with four cylindrical Al substrates is installed in the reaction vessel 101,
The exhaust valve 105 was opened and the inside of the reaction vessel was evacuated through the exhaust pipe 104 to bring the inside of the reaction vessel to a degree of vacuum of 10 ^-5 Torr. At the same time, while the six cylindrical Al substrates are rotated (rotated) by a driving means (not shown), the substrate temperature is increased to 300°C by the heating heater 103.
It was kept at ℃.

Add 5 to 40 volume% of SiH ₄ gas to these areas.
Mixed gas of _H2 gas 95-60% by volume, gas flow rate 0.1
After introducing gas into the reaction vessel through the gas introduction pipe 109 at ~2/hr and adjusting the exhaust valve 105 to set the internal pressure of the reaction vessel to 0.01Torr, 2.45GHz microwaves are radiated to a- A deposited film composed of Si:H was formed.

After a predetermined period of time has passed, the heating heater 103 and its rotation are stopped, and the substrates are left to cool. Then, the exhaust valve is opened to return the inside of the reaction vessel to atmospheric pressure, and the six cylindrical Al substrates on which the deposited films have been formed are placed in the system. I took it outside.
The thickness of the deposited film was measured to determine the deposited film, and the gas utilization efficiency was determined to be 80%.

[Summary of effects of the invention]

In the apparatus of the present invention, the raw material gas is first discharged toward the central axis of the microwave introduction space, so that a plasma space is efficiently formed by microwave energy. Furthermore, by providing an exhaust wall member having a large number of exhaust holes around the cylindrical substrate and disposing the cylindrical substrate between the exhaust wall member and the raw material gas introduction pipe, the distribution of excited species during the formation of a deposited film is improved. can be made uniform in the vicinity of the substrate, it is possible to form a deposited film with uniform thickness and quality, and it is possible to improve the utilization efficiency of the raw material gas.

[Brief explanation of the drawing]

FIG. 1A shows the microwave plasma of the present invention.
FIG. 1B is a schematic perspective view showing a typical example of a deposited film forming apparatus using a CVD method, and FIG. 1B is a schematic vertical cross-sectional view thereof, and FIG. 1C is a schematic cross-sectional view thereof. FIG. 2 is a vertical cross-sectional view schematically showing an example of a deposited film forming apparatus using a conventional plasma CVD method. 1A to 1C, 101...reaction vessel, 102...substrate support means for supporting a cylindrical substrate, 102'...cylindrical substrate, 103...heater, 104...exhaust pipe, 105... Exhaust valve, 106... Exhaust wall, 107... Exhaust hole, 1
08...Microwave waveguide, 109...Source gas introduction pipe, 110...Valve, 111, 111'...
...Gas release hole. Regarding FIG. 2, 201...reaction vessel, 202
... Side wall, 203 ... Bottom wall, 204 ... Multi-perforated inner wall, 205 ... Exhaust pipe, 206 ... Exhaust valve,
207...Gas introduction pipe, 208...Valve, 20
9... Cylindrical base, 210... Base holding cylinder,
211...Heater, 212...Support leg, 213
...Microwave source, 214...Microwave,
215...Microwave waveguide, 216...Dielectric window.

Claims (1)

[Claims] 1. A reaction vessel whose interior can be depressurized, a plurality of substrate support means for supporting a plurality of cylindrical substrates for forming deposited films disposed within the reaction vessel, and a space surrounded by the plurality of cylindrical substrates. a means for introducing microwaves along the longitudinal direction of the cylindrical substrate; a plurality of tubular raw material gas introduction means installed along the longitudinal direction of the cylindrical substrate; an exhaust wall member having a large number of exhaust holes, and a means for evacuating the interior of the reaction vessel; , the plurality of substrate support means, and the exhaust wall member are arranged concentrically in this order from the central axis toward the wall of the reaction vessel, and further, the plurality of substrate support means and the exhaust wall member are arranged in this order from the central axis toward the wall of the reaction vessel, and the tubular raw material gas introducing means has a plurality of substrate support means and the exhaust wall member facing toward the central axis. A microwave plasma characterized in that a large number of gas discharge holes are provided at least along the longitudinal length of a cylindrical substrate to discharge raw material gas.
Deposited film forming equipment using CVD method.