JP2620782B2 - Deposition film forming apparatus by plasma CVD method - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a deposited film on a substrate, especially a functional film, particularly a semiconductor device, a photosensitive device for electrophotography, a line sensor for image input, and an imaging device. Plasma CV suitable for forming amorphous, polycrystalline, etc. non-single-crystal deposited films used for photovoltaic devices, etc.
D device.

[Description of Prior Art]

Conventionally, as an element member used for a semiconductor device, an electrophotographic photosensitive device, an image input line sensor, an imaging device, a photovoltaic element, etc., for example, an amorphous material containing silicon (hereinafter simply referred to as “a-Si”) write.)
Films or amorphous films containing silicon hydride (hereinafter simply referred to as “a-SiH”) have been proposed, and some of them have been put to practical use. In addition to such a-Si films and a-SiH films, several methods for forming such a-Si films and a-SiH films and apparatuses for performing the same have been proposed, such as vacuum deposition, ion plating, and the like. There are methods such as a so-called thermal CVD method, a plasma CVD method, and an optical CVD method. Among them, the plasma CVD method is put to practical use as an optimal one, and is generally widely used.

Meanwhile, the plasma CVD method uses direct current, high frequency or microwave energy to excite (radicalize) a gas for forming a deposited film near the surface of a substrate to generate a chemical interaction, thereby causing a chemical interaction. A film is deposited on the surface, and various apparatuses have been proposed for that purpose.

FIG. 3 is a schematic cross-sectional view schematically showing a typical example of a conventional deposited film forming apparatus by a plasma CVD method. In the figure, reference numeral 1 denotes an entire cylindrical reaction vessel, and 2 denotes a side wall of the reactor. A cathode electrode also serves as a reactor, 3 is an upper wall of the reactor, and 4 is a bottom wall of the reaction vessel. The cathode electrode 2 and the upper wall 3
And the bottom wall 4 are insulated by an insulator 5 respectively.

Reference numeral 6 denotes a cylindrical substrate provided in the reaction vessel, and the cylindrical substrate 6 is grounded and serves as an anode electrode. A heater 7 for heating the substrate is provided in the cylindrical substrate 6 to heat the substrate to a set temperature before film formation,
It is used to maintain the substrate at a set temperature during film formation, or to perform an annealing process on the substrate after film formation. The cylindrical substrate 6 is connected to a rotation driving means 8 via a shaft, and rotates the cylindrical substrate 6 during film formation.

Reference numeral 9 denotes a source gas introduction pipe for forming a deposited film, in which a number of gas discharge holes 9a for discharging the source gas are provided in the reaction space, and the other end of the source gas introduction pipe 9 is provided with a valve 10;
Is connected to a source gas supply system 20 for forming a deposited film through the gate.

The source gas supply system 20 for forming a deposited film includes gas cylinders 201 to 2.
05, valves 211 to 215 provided on the gas cylinder, mass flow controllers 221-225, inflow valves 231-235 to the mass flow controller, outflow valves 241-245 from the mass flow controller, and pressure regulators 251-255. ing.

Reference numeral 11 denotes an exhaust pipe for evacuating the inside of the reaction vessel, and is connected to a vacuum exhaust device (not shown) via an exhaust valve 12.

 Reference numeral 13 denotes a means for applying a voltage to the cathode electrode 2.

The operation of such a conventional deposited film forming apparatus by the plasma CVD method is performed as follows. That is, while the gas in the reaction vessel is evacuated through the exhaust pipe 10, the cylindrical base 6 is heated and maintained at a predetermined temperature by the heating heater 7, and is further rotated by the rotary driving means 8. Next, in the case of forming an a-SiH deposition film, for example, through the source gas introduction pipe 9, a source gas such as silane is introduced into the reaction vessel, and the source gas is discharged from the gas introduction pipe. Hole 9a
From the substrate surface. Simultaneously with this, a high frequency, for example, is applied between the cathode electrode 2 and the base (assword electrode) 6 from the voltage applying means 13 to generate a plasma discharge. Thus, the raw material gas in the reaction vessel is excited and becomes an excited species, thereby generating radical particles such as Si ^* , SiH ^*, etc. (* indicates an excited state), electrons, ionic particles and the like.

That is, in the formation of such a deposited film, it is known that the gas pressure of the source gas introduced into the reaction space, the gas flow rate, the discharge power, and the like affect the film quality and thickness of the formed film,
In order to form a deposited film having a uniform thickness and film quality, the distribution of the source gas ejected into the reaction space from the source gas discharge hole 9a of the gas introduction pipe 9 and the plasma discharge formed in the reaction space is important. In the conventional apparatus as shown in FIG. 3, since the source gas is introduced from one end of the source gas introduction pipe 9, the flow rate of the gas is different between the upper part and the lower part of the reaction space. Increases the gas flow rate. Therefore, the radicals generated by the plasma discharge are more likely to flow to the outside of the system as it approaches the lower portion, and the efficiency of the plasma discharge decreases. Further, the source gas for forming a deposited film is excited by discharge energy to form a desired deposited film by chemical interaction (hereinafter, referred to as a “depositable gas”), for example, an a-SiH film. In the case of forming a silane gas such as SiH ₄ or Si ₂ H ₆ is used,
These source gases for forming a deposited film are used after being diluted with a diluting gas such as H ₂ , He, or Ar. In this case, in the conventional apparatus shown in FIG. In addition to the non-uniform intensity distribution of the plasma discharge, the mixing ratio of the deposition gas and the diluting gas also fluctuates, especially in the lower part on the exhaust side, where the ratio of the diluting gas becomes abnormally high. Problem. And this problem when using H ₂ gas as a diluent gas,
This is particularly noticeable.

As described above, in the conventional apparatus, the plasma intensity distribution in the reaction space becomes non-uniform, and the distribution of the source gas for forming a deposited film in the system becomes non-uniform. However, there is a problem that the thickness and quality of the deposited film are not uniform, and such a problem becomes more prominent as the length of the cylindrical substrate becomes longer.

For these reasons, although the plasma CVD method is considered to be the most suitable method, when forming a deposited film having a uniform film thickness and quality even on the upper and lower portions of the cylindrical substrate, the above-mentioned various methods are used. As a result, the film conditions are naturally limited, and as a result, various deposited films having a wide range of characteristics can be continuously formed in the same apparatus, or a multilayer structure having a plurality of deposited films having different characteristics on the same substrate can be deposited. It is very difficult to form films continuously in the same apparatus.

On the other hand, the various devices mentioned above are diversifying,
As a device element for this purpose, it is a social requirement to form a deposited film having a wide variety of characteristics and, in some cases, to form a deposited layer having a large area. There is a strong demand for the development of devices that can be mass-produced.

[Object of the invention]

SUMMARY OF THE INVENTION The present invention solves the above-mentioned problems with respect to a conventional apparatus for forming a deposited film used for a photovoltaic element, a semiconductor device, a line sensor for image input, an imaging device, a photosensitive device for electrophotography, and the like. It is intended to satisfy the following.

That is, the main object of the present invention is to maintain a uniform distribution and a dilution ratio of a deposition film forming gas in a reaction space, thereby enabling a plasma CVD method capable of constantly forming a deposition film having a uniform thickness and film quality. An object of the present invention is to provide a deposited film forming apparatus.

Another object of the present invention is to improve the productivity of a film while enabling uniformity and homogeneity of various characteristics, film formation speed, reproducibility, and film quality of a film to be formed, and particularly enable mass production. Another object of the present invention is to provide an apparatus for mass-producing a deposited film by a plasma CVD method, which can simultaneously increase the area of the film.

[Structure and effect of the invention]

The present inventors have overcome the above-mentioned problems of the conventional deposited film forming apparatus by the plasma CVD method, and as a result of intensive research to achieve the above-described object, as a result, a plurality of gas introduction systems were provided. Type of gas to be introduced into the gas introduction system and / or
Alternatively, the finding that the above-mentioned problems were solved and the above-mentioned objects were achieved by obtaining different gas release conditions in each gas introduction system led to the completion of the present invention.

That is, the deposition apparatus by the plasma CVD method of the present invention forms a reaction vessel having a reaction space in which plasma is generated therein, means for installing a substrate in the reaction space, and a deposition film in the reaction space. Forming a deposited film by a plasma CVD method, comprising: means for introducing a gas used for discharge, means for applying a discharge energy for exciting and exciting the gas, and means for exhausting the reaction space from below. In the apparatus, the means for introducing the gas has a plurality of gas introduction systems each having a plurality of gas introduction holes, and is diluted with a diluting gas or a diluting gas into the reaction space on the exhausting means side. At least one of the gas introduction systems is configured so that the gas discharge conditions are different in the vertical direction so that the deposited film forming source gas can be introduced.

Hereinafter, an apparatus for forming a deposited film by a plasma CVD method of the present invention will be described in detail with reference to the drawings, but the present invention is not limited thereto.

FIG. 1 (A) is a schematic longitudinal sectional view schematically showing a typical example of the apparatus of the present invention, and FIG. 1 (B) is a schematic transverse sectional view thereof.

In the figure, the same reference numerals as those in FIG. 3 described above denote the same parts as those described in FIG. That is, 1 is a reaction vessel, 2
Is a cathode electrode, 3 is an upper wall, 4 is a bottom wall, 5 is an insulator, 6 is a cylindrical base, 7 is a heater for heating, 8 is a rotation driving means,
Reference numeral 11 denotes an exhaust pipe, 12 denotes an exhaust valve, and 13 denotes a voltage applying unit.

Reference numerals 9 and 9 'denote gas introduction pipes for introducing a source gas for forming a deposited film into the reaction vessel.
a '. The gas introduction pipes 9, 9 'are connected to the valve 1 respectively.
The gas supply systems 20 and 20 'communicate with each other via 0 and 10', respectively.
5, 201 'to 205', valves 211 to provided on gas cylinders
215, 211'-215 ', mass flow controller 221-225,22
1′-225 ′, inflow valves 231-235,231′-235 ′, outflow valves 241-245,241′-245 ′ and pressure regulators 251-255,
251 'to 255'.

The source gas used to form the deposited film with the apparatus of the present invention may be of the type that excites by microwave energy and chemically interacts to form the desired deposited film on the substrate surface. Any material can be adopted as long as it forms an a-Si (H, X) film, specifically, hydrogen, halogen, or hydrocarbon is bonded to silicon. It is possible to use silanes and halogenated silanes in a gas state, or gaseous ones that can be easily gasified. One of these source gases may be used, or two or more thereof may be used in combination. These source gases are He, Ar
Diluted with an inert gas such as Further, the a-Si film can be doped with a p-type impurity element or an n-type impurity element, and a source gas containing such an impurity element as a constituent component can be used alone or with the aforementioned source gas and / or It can be mixed with a dilution gas and introduced into the reaction space.

When two or more source gases are used, one or more of them may be excited beforehand and then introduced into the reaction chamber. .

The substrate may be conductive, semiconductive, or electrically insulating, and specifically includes, for example, metals, ceramics, and glass. . The temperature of the substrate during the film forming operation is
Although not particularly limited, the temperature is generally in the range of 30 to 450 ° C, preferably 50 to 350 ° C.

In addition, in forming the deposited film, the pressure in the reaction chamber is set to 5 × 10 ⁻⁶ Torr or less, preferably 1 × 10 ⁻⁶ Torr or less before the source gas is introduced. Preferably, the pressure in the reaction chamber is on the order of 1 × 10 ^-2 Torr.

When forming a deposited film using the apparatus of the present invention shown in FIG. 1, the types or composition ratios of the gases supplied from the gas supply systems 20, 20 'are varied, and the gas introduction pipes 9,
By making the shape or distribution of the gas discharge holes 9a, 9a 'provided in the 9' different, the dilution rate of the source gas in the reaction space can be kept uniform and the flow rate of the source gas in the reaction space can be kept uniform. It becomes possible. Hereinafter, a specific example thereof will be described with reference to FIGS. 4 (A) to 4 (D).

In the figure, reference numeral 6 denotes a cylindrical substrate, 9, 9 'denote gas introduction tubes, and arrows denote gas release.

The examples shown in FIGS. 4A and 4B are examples in which a source gas for forming a deposited film is introduced from a gas introduction pipe 9 and only a dilution gas is introduced from a gas introduction pipe 9 '. Here, the length of the gas introduction pipe 9 ′ is shorter than the length of the gas introduction pipe 9. In this case, the dilution gas introduced from the gas introduction pipe 9 'is released only to the lower part of the reaction space.
The gas for forming a deposited film is released over the entire reaction space (FIG. 4A) or is discharged only to the upper portion of the reaction space (FIG. 4B), thereby forming a gas in the lower portion of the reaction space. It functions to adjust the gas pressure and make the gas distribution uniform throughout the reaction space.

The examples shown in FIGS. 4 (C) and 4 (D) are examples in which the dilution ratios of the respective deposition film forming source gases introduced from the gas introduction pipe 9 and the gas introduction pipe 9 'with the dilution gas are different. .
In this case, the gas with a low dilution rate (that is, a gas having a high ratio of the deposition gas) introduced from the gas introduction pipe 9 ′ is discharged only from the lower part of the reaction space, and is introduced from the gas introduction pipe 9. Either the high dilution gas is released over the entire reaction space (FIG. 4 (C)) or the high dilution gas is released only to the upper part of the reaction space (FIG. 4 (D)). The gas distribution can be made uniform over the entire space.

FIG. 2 (A) is a schematic longitudinal sectional view schematically showing another example of the device of the present invention, and FIG. 2 (B) is a schematic transverse sectional view thereof.

In the drawings, the same reference numerals as those in FIGS. 1 and 3 denote the same components in FIGS. 1 and 3, and 1 denotes a reaction vessel,
2 is a cathode electrode, 3 is a top wall, 4 is a bottom wall, 5 is an insulator, 6
Is a cylindrical substrate, 7 is a heater, 8 is a rotation driving means,
Reference numeral 11 denotes an exhaust pipe, 12 denotes an exhaust valve, and 13 denotes a voltage applying unit.

In this example, gas introduction pipes 9-1 and 9-2 are provided in the reaction space.
And a source gas supply system 20 for depositing a deposited film through the switching valve 14 through the two gas introduction pipes 9-1 and 9-2.
To communicate with An internal pressure sensor 15 is provided immediately before the switching valve 14. Also in this example, the gas introduction pipe 9-
By changing the shape and distribution of the gas discharge ports 9-1a and 9-2a provided in the gas introduction pipe 9-1 and the gas introduction pipe 9-2, the discharge state of the source gas released from the gas introduction pipe 9-1 and the gas introduction pipe The release state of the source gas released from 9-2 is made different.

In order to form a deposited film using the apparatus shown in FIG. 2, while monitoring the gas pressure with the internal pressure sensor 15, gas introduction suitable for the deposited film forming conditions such as the gas pressure and the gas flow rate of the deposited film to be formed. By appropriately selecting and using a tube, a plurality of kinds of deposited films having different film thicknesses, film qualities or various characteristics can be continuously formed in the same apparatus.
In particular, when obtaining a multi-layered light receiving member having a plurality of deposited films on the same substrate, it is possible to cope with variations in deposited film formation conditions due to internal pressure, flow rate, and the like, and variations in doping efficiency by selectively using a gas introduction pipe. Therefore, they can be efficiently formed in the same device.

〔Example〕

Hereinafter, the formation of a deposited film using the apparatus of the present invention shown in FIG. 1 will be described in more detail with reference to Examples, but the present invention is not limited thereto.

Example 1 In this example, four quartz glass tubes each having an outer diameter of 8 mmφ and a length of 1 m were used as the gas introduction tubes 9 and 9 ′, and the gas introduction tube 9 was perpendicular to the longitudinal direction of the gas tube. A gas discharge hole 9a having a diameter of 1 mm is provided with 20 pitches of 40 mm from the upper end (gas introduction system) so that the gas is released to the outside. The gas introduction pipe 9 'is perpendicular to the length direction of the gas pipe. The gas discharge hole 9a 'with a diameter of 1 mm is 80 cm from the upper end so that the gas is released
5 gaskets (10 mm pitch) were provided downward from the location (gas introduction system).

As substrates, two Al cylinders having a length of 358 mm and an outer diameter of 80 mmφ were prepared, and the two substrates were arranged in series in a reaction vessel.

Further, the gas cylinders 201 and 201 'are SiH ₄ gas, the gas cylinders 202 and 202' are B ₂ H ₆ gas, and the gas cylinders 203 and 203 'are NO gas.
Gas, the gas cylinder 204, 204 ', CH ₄ gas, the gas cylinder
The 205, 205 'to seal the H ₂ gas.

Prior to flowing these gases into the reaction vessel, valves 211 to 215, 21 of gas cylinders 201 to 205, 201 'to 205' are used.
Confirm that the valves 1 'to 215' are closed, open the valves of the other gas supply systems 20, 20 'and the exhaust valve 12 and degas until the pressure in the system becomes 1 × 10 ^-6 Torr or less. Thereafter, all valves of the gas supply systems 20, 20 'were closed, and then the heater 7 was energized to heat the Al cylinder until the surface temperature reached 300 ° C, and was maintained at 300 ° C.

Under these conditions, gas was introduced from the gas cylinder using only the gas introduction system under the conditions shown in Table 1 below, the high frequency power supply (13.56 MHz) was turned on, plasma was generated, and the deposited film was deposited on the Al cylinder. Was formed to obtain a three-layer light receiving member.

When the film thickness distribution of the two light-receiving members thus obtained was examined, the results shown in FIG. 5 (A) were obtained. In the figure, the vertical axis represents the measurement position on the light receiving member, and the horizontal axis represents the film thickness.

Next, film formation was performed under the same conditions as described above except that 100 SCCM of H ₂ gas was simultaneously released from the gas introduction system, and two light receiving members were obtained.

When the film thickness distribution of the obtained two light receiving members was examined, the result shown in FIG. 5 (B) was obtained.

Further, a total of four of the obtained light receiving members were installed in copying machines (trade name: NP-9030, manufactured by Canon Inc.), and a black image was formed on the entire surface. In the case where the film was formed by using both the gas introduction system and the gas introduction system, an image having large partial density unevenness was obtained. There was no difference between the members.

Furthermore, a current of 600 μA was charged to each of the four light receiving members by positive DC corona charging, the surface potential at that time was measured, and a semiconductor laser was used immediately after charging, and a spot diameter of 780 nm was used. Light of 80 μm was irradiated at an intensity of ² μJ / cm ² , and the potential immediately after the irradiation was measured. The results in Tables 2 (A) and 2 (B) below were obtained. Measurement position (1)
(12) are the same as those shown in FIGS. 5 (A) and (B).

From these facts, the case of using the gas introduction system and the case of using the gas introduction system only,
It was found that a film having a uniform film thickness and film quality was obtained.

Example 2 Four gas inlet pipes 9, 9 'each having an outer diameter of 80 mm and a length of 1 m
The gas introduction tube 9 has a diameter of 1 mm so that gas is released perpendicularly to the length direction of the gas tube.
(Gas introduction system) having 15 gas discharge holes 9a at a pitch of 40 mm from the upper end. The gas introduction pipe 9 'has a diameter such that gas is released perpendicularly to the length direction of the gas pipe. 1m
A gas introduction system (gas introduction system) was provided with four 40 m pitches of gas discharge holes 9a 'having a length of 60 cm from the upper end to a position 60 cm below the upper end.

Using this gas introduction system and this, a light receiving layer having a three-layer structure was formed on two Al cylinders installed in series in the same manner as in the example, under the film forming conditions shown in Table 3 below.

The film thickness and surface potential of the obtained light receiving member were measured in the same manner as in Example 1, and the results shown in Table 4 below were obtained. Note that the measurement positions (13) to (18) were determined in Example 1.
Are positions corresponding to the measurement positions (7) to (12).

From the results in Table 4, it was found that the film thickness and film quality unevenness were improved as compared with the case where only the gas introduction system in Example 1 was used.

〔The invention's effect〕

The deposited film forming apparatus by the plasma CVD method of the present invention is provided with a plurality of gas introduction systems, and different types or dilution rates of gas introduced from each gas introduction system, or different gas emission states. By simultaneously using such a plurality of gas introduction systems, the dilution gas is discharged to the lower part of the reaction space to make the gas flow rate uniform, or the gas having the changed dilution rate is separately supplied to the reaction space. Gas distribution can be made uniform. Such uniformization of the gas flow velocity and the gas distribution is particularly effective in the case of a long cylinder, that is, in the case of obtaining a light receiving member having a large area. Furthermore, by selectively using a plurality of different gas introduction systems for each layer to be formed, it is possible to cope with fluctuations in film forming conditions such as internal pressure and flow rate and / or fluctuations in doping efficiency with the same apparatus. In particular, it is suitable for obtaining a light receiving member having a multilayer structure.

[Brief description of the drawings]

FIG. 1 is a schematic cross-sectional view schematically showing a typical example of the apparatus of the present invention. FIG. 1 (A) is a longitudinal sectional view, and FIG. 1 (B) is a transverse sectional view. FIG. 2 is a schematic cross-sectional view schematically showing another example of the device of the present invention. FIG. 2 (A) is a longitudinal sectional view, and FIG. 2 (B) is a transverse sectional view. FIG. 3 is a schematic sectional view schematically showing a typical example of a conventional deposited film forming apparatus by a plasma CVD method. FIG. 4 is a diagram schematically showing an example in which gas is introduced from two gas introduction systems using the apparatus of the present invention. FIG. 5 is a diagram showing the measurement results of the film thickness in Example 1. Regarding FIGS. 1 to 4, 1... A reaction vessel, 2... A surrounding wall also serving as a cathode electrode,
3 ... top wall, 4 ... bottom wall, 5 ... insulator, 6 ... cylindrical base, 7 ... heater for heating, 8 ... rotation drive means, 9,
9 ', 9-1,9-2 ... Gas inlet pipe, 9a, 9'a, 9-1a, 9-2a
…… Gas release hole, 10,10 ′ …… Valve, 11 …… Exhaust pipe, 1
2 ... exhaust valve, 13 ... voltage application means, 14 ... switching valve, 15 ... internal pressure sensor, 20, 20 '... gas supply system, 2
01-205,201'-205 '... Gas cylinder, 211-215,211'
... 215 '... valve, 221-225,221'-225 '... mass flow controller, 231-235,231'-235 '... inflow valve, 241-245,241'-245 '... outflow valve, 251-255,
251 '~ 255' ... Pressure regulator.

 ────────────────────────────────────────────────── ─── Continuation of the front page (56) References JP-A-60-131970 (JP, A) JP-A-59-38375 (JP, A) JP-A-59-38377 (JP, A)

Claims (7)

(57) [Claims] 1. A reaction vessel having a reaction space in which plasma is generated therein, means for setting a substrate in the reaction space, and a gas used to form a deposited film in the reaction space. Means for discharging, a discharge energy applying means for exciting and exciting the gas to excite the gas, and a means for exhausting the reaction space from below. The means for introducing has a plurality of gas introduction systems each having a plurality of gas introduction holes, and a gas for dilution or a deposition film forming source gas diluted by the gas for dilution is introduced into the reaction space on the exhaust means side. An apparatus for forming a deposited film by a plasma CVD method, wherein at least one of the gas introduction systems is configured so as to be capable of introducing gas by changing a gas discharge condition in a vertical direction. 2. The plasma according to claim 1, wherein said plurality of gas introduction systems include a system for introducing a source gas for forming a deposited film and a system for introducing only a diluting gas. Deposition film forming equipment by CVD method. 3. A deposited film formation by a plasma CVD method according to claim 1, wherein each of said plurality of gas introduction systems introduces a gas having a different dilution ratio with a dilution gas. apparatus. 4. A system according to claim 1, further comprising means for monitoring a gas pressure in each of said plurality of gas introduction systems and having a different composition from said plurality of gas introduction systems and selecting an appropriate system. An apparatus for forming a deposited film by a plasma CVD method according to item (1). 5. A gas introduction system different for each layer to be formed,
2. A plasma CVD apparatus according to claim 1, further comprising means for selectively using said plurality of gas introduction systems.
Deposition film forming device by the method. 6. The gas introduction system according to claim 1, wherein each of said plurality of gas introduction systems has a gas introduction tube having a plurality of gas introduction holes, and said at least one gas introduction system has a gas introduction hole only on said exhaust means side. The plasma described in the above item (1)
Deposition film forming equipment by CVD method. 7. The gas introduction system according to claim 1, wherein each of the plurality of gas introduction systems has a gas introduction tube having a plurality of gas introduction holes, and a length of the gas introduction tube of the at least one gas introduction system is equal to that of another gas introduction system. 2. A deposition film forming apparatus according to claim 1, wherein said deposition film forming apparatus is provided on said exhaust means side with a length shorter than a length of a gas introduction pipe.