JPS60245126A - Manufacture of photoelectric converter - Google Patents

Abstract

PURPOSE:To manufacture a photoelectric converter in a mass production by setting the gas pressure of a glow discharge atmosphere, gas components and composition ratio to the prescribed ranges, reducing the etching action of F in a plasma and improving the film forming velocity of an alpha-Si:H:F film. CONSTITUTION:Regulating valves 4-6 are opened to discharge H2 or He, SiF4 and SiH4 from tanks 1-3, to regulate the flow rates at 7-9, to control the SiF4 at 20-50vol% of SiF4+SiH4 and carrier at 50-90vol% of produced gas and to feed them to a reaction chamber 13. The generated gas pressure is held at 0.2- 3Torr by a rotary pump 18 and a diffusion pump 19. An inner cylindrical glass substrate 15 is rotatably driven at 16, power of 50-3,000W and 1 - several 10MHz is supplied by the coil 14, a substrate is separately held at 150-250 deg.C to form an alpha-Si:H:F film. According to this configuration, the etching action of the F in a plasma is suppressed to form a stable and durable alpha-Si:H:F film at a high speed of ten and several-several tens mum/hr, thereby obtaining photoelectric converters adapted for a mass production.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for manufacturing a photoelectric conversion element made of fluorinated amorphous silicon.

In 1975, 5pear and 1recomber et al. developed hydrogenated amorphous silicon (J21, A-8) produced by glow discharge decomposition of Schiff 7 gas (SiE(+)).
t: Abbreviated as H, simple amorphous silicon is a-S
Since the first successful control of valence electrons in a film (i and S), a
-8i: Research and development regarding H membranes is extremely active both academically and in terms of applied technology.

In this a-Sl:H film, dangling bonds (dangling bonds) are terminated with hydrogen, reducing the number of dangling bonds to 1.
As a result, the localized unit density in the forbidden band was drastically reduced, and valence electron control became possible by adding phosphorus or boron.

In other words, this a-S'h:H film has the characteristics of a crystalline semiconductor in which valence electrons can be controlled, and also has the advantage that it is easy to form a thin film, can be made into a large area, and is low in cost. Therefore, a-Si, :H film can be used as a solar cell,
Application research for use in photoelectric conversion devices such as optical sensors, electrophotographic photoreceptors, image sensors, and thin film transistor arrays is progressing rapidly.

In this way, the a-3i-:H film is a material suitable for photoelectric conversion devices, but it is not durable enough for applications in devices used under harsh conditions, such as solar cells for power generation and electrophotographic photoreceptors for ultra-high-speed copying. I have a sexual problem. This is because amorphous materials such as a-Si:H films are generally not in a thermal equilibrium state, and when heat or light energy is applied from the outside, the structure of the film changes to a stable state.

In fact, it has been reported that dark resistivity of a-Si:H film decreases due to long-term strong light irradiation, hydrogen in the film is released at high temperatures of 300°C or higher, and electrical properties deteriorate. .

In view of the above-mentioned circumstances, attention has been paid to fluorinated amorphous silicon (hereinafter a-Si:H:F) films. Since fluorine is a single valence electron, it terminates dangling bonds in the same way as hydrogen, and the bond energy (s, oaev) between silicon atoms and fluorine atoms is equal to the bond energy (s, oaev) between silicon atoms and hydrogen atoms (3,10).

ev) Since the a-3IH:F film is larger than the a-8L:H film, it can be expected to have better stability than the a-8L:H film, making it advantageous for photoelectric conversion devices that require durability under harsh conditions. it is conceivable that.

However, since the glow discharge decomposition method using a mixed gas of SiF4 and hydrogen is normally used to fabricate this a-8i:H:F film, the fluorine in the plasma is chemically extremely activated, and as a result, this fluorine ) element has an etching effect and is known to limit the film formation rate of the a-8IE(:F' film.
As photoelectric conversion elements made of :H:F films are applied to devices in various fields, it is desired to achieve high-speed film formation in order to improve mass productivity.

The purpose of the present invention is to provide a method for manufacturing a photoelectric conversion element suitable for mass production by reducing the yfing effect of fluorine in plasma as much as possible to improve the deposition rate of an a-Si:H:F film. There is a particular thing.

According to the present invention, a-Si and layer-forming gas are introduced into the reaction chamber, and glow discharge is generated within the reaction chamber to form an a-81 photoelectric conversion layer containing hydrogen and fluorine on the substrate. In the manufacturing method, the gas pressure for forming the a-Si layer during glow discharge is O12~3 TOrr.
K is set, and the a-8i layer forming gas is composed of a fluorine-containing silicon compound, a hydrogen-containing silicon compound, and a carrier gas, and the gas of the fluorine-containing silicon compound is A method for manufacturing a photoelectric conversion element is provided, characterized in that the volume is set to 20% to 50%.

The present invention will be explained in detail below.

Unlike the fabrication of the a-Si:H film, the fabrication of the a-Si:H:F film uses a fluorine-containing silicon compound such as SiF4. Since this gas has a strong etching effect in plasma, it is impossible to fabricate a fluorinated a-Si film using only a fluorine-containing silicon compound by a glow discharge decomposition method. Therefore, the present inventors used SiF4 gas and used other mixed gases such as [I SiF4+H1t system, (i
il 5iF4-1- S>H+thread, (iii) Si
Experiments using the F4+SiH4+H9 system as a-Si and layer formation gas revealed that method (1) had very narrow conditions for film formation, and the film formation rate was extremely slow at about 0.46 μm/hour. In the method (II), the rate is about 2 μm/hour at most. In the method of 2007, a film formation rate of 10-odd μm/hour to several tens of μm/hour has been achieved, and in this regard, it is important to set the gas pressure and gas composition ratio during glow discharge.

That is, the pressure of the A-8L layer forming gas to which a carrier gas consisting of a fluorine-containing silicon compound, a hydrogen-containing silicon compound, hydrogen gas, and a rare gas is added is set to 0.2 to 3 Torr during glow discharge. It is better to do so.

Outside the scope of the present invention, which is related to the gas composition ratio of fluorine-containing silicon compounds in the total gas, it is difficult to form a film, the speed of film formation is slow, and the film quality is remarkable. inferior to

Therefore, it cannot be made of the A-81 material required by various photoelectric conversion devices.

In addition, it is important to specify the gas composition ratio in relation to the pressure of this A-8L layer forming gas. 20-50% volume
It is recommended to set it to .

If this gas composition ratio exceeds 50%, peeling of the film may occur or the film may not be formed. On the other hand, if it is less than 20%, a film with extremely low fluorine content will be produced, making it impossible to obtain an a-Si film with excellent durability.

Furthermore, according to the present invention, as a result of repeated various experiments by the present inventors, regarding the above-mentioned gas pressure and gas composition ratio,
When gas is introduced into the reaction chamber 1 for generating glow discharge, the amount of gas per unit time introduced into the glow discharge decomposition region for forming the a-81 layer is 20% relative to the volume of the glow discharge decomposition region. It has been found that it is important to set the time within a range of 1,507 minutes.

In other words, the reason why the gas flow rate was specified by such an indication is that as the gas flow rate increases, the film formation rate increases, but if the gas flow rate is out of this range, the film quality may change as shown in the examples below. This is because it deteriorates significantly, which poses a problem in practical use as various photoelectric conversion devices. Furthermore, no particular relationship has been found between the shape and dimensions of the substrate on which the a-Si-:H:F film is formed on the surface of this gas flow rate, and almost all substrates of various photoelectric conversion devices This can be said to apply to roses.

Furthermore, the fluorine-containing silicon compound according to the present invention includes SiF.
There are various compounds such as +, 5isFa, and 5iaFs, and the hydrogen-containing silicon compound according to the present invention is S.
There are various compounds such as iH4°Si, 2Ha, and 5isHs.

Furthermore, the present invention is characterized in that the silicon compound gas is mixed with a carrier gas consisting of H2 gas or a rare gas such as Ar or He to form the a-81 layer forming gas. In order to improve this, it is desirable to set the gas volume ratio in the total gas to a range of 50 to 90%. Through various experiments, the present inventors have confirmed that the use of H9 gas or He gas in particular significantly improves the film quality for charge conversion elements.

Next, a-8l-:
An inductively coupled glow discharge decomposition apparatus for producing an H:F film will be described with reference to FIG.

In Figure 1, 1. Second. 3rd tank il) (2113
1 contains H2, SiF4. SiH4 is sealed and hydrogen is used as carrier gas. These gases correspond to the first. Second. Third regulating valve 14+1
51 +61 is released, and its flow rate is regulated by the mass flow controller +7118+ +9) l, and the first, second, and first iGa tanks +11
+21 (The gas from 31 is sent to the gas introduction pipe Ql. Note that a11t121 is a stop valve. The gas flowing through the gas introduction pipe bend is sent to the reaction chamber (13,
A resonant vibration coil (14) is wound around the reaction chamber 3, and its high frequency power is 50 watts.
s ~3 ki, 1OWatt8, and the frequency is IM
Hz to several tens of MH2 is one. Inside the reaction chamber 03, an inner cylindrical substrate 15, such as an aluminum plate or a NESA glass plate, on which an a-Si:H:F film is formed, is provided with a turn-chip luminaire rotatable by a motor 161. The substrate α9 itself is uniformly heated to a temperature of about 100 to 400°C, preferably about 150 to 250°C, by an appropriate heating means.

In addition, the interior of the reaction chamber (131) requires a high vacuum state (discharge voltage 02 to 3 TOrr-) when forming the a-Si:E(:F film), so the rotary pump a& and the diffusion pump αI
This is connected.

In the glow discharge decomposition device having the above configuration, the first and second
．． The third regulating valve f4+ +51161 is opened and the first regulating valve f4+ +51161 is opened. 2nd and 3rd tanks [1+2) (H2 gas from 31, S
iF4 gas.

5YH4 gas is released, and the amount released is determined by mass flow control)
Troller f7) fs) f9) t is regulated. In this way, the gas composition ratio is set within a predetermined range, the total gas flow rate is specified, and the gas is fed into the reaction chamber (13).

Thus, the reaction chamber (13 interior is 0.2~3'1'or
r vacuum state, substrate temperature is 100-400℃, resonance vibration coil (141 high frequency power is 5Q watts ~ 3
kilowatts, whose frequency ranges from 1 to several tens of M
The reaction chamber (131
When the internal gas flow rate is set within a predetermined range and a glow discharge is generated, the a-8i:H:F film becomes 1
The film is formed at a film formation rate of several tens of micrometers/hour.

Further, in the present invention, a capacitively coupled glow discharge decomposition apparatus may be used to produce the a-8i:H:F film, and this apparatus is shown in FIG. In FIG. 2, the same parts as in FIG. 1 are given the same reference numerals.

In Fig. 2, the gas flowing through the gas introduction pipe Ql is sent into the reaction chamber (13A), and a capacitively coupled discharge electrode (4) is arranged around the base inside this reaction chamber. , which itself generates plasma by applying high-frequency power. In the glow discharge decomposition apparatus having this configuration, the capacitively coupled discharge electrode (to) was heated to 50 watts to 3 klO according to the same procedure as described for the inductively coupled glow discharge decomposition apparatus shown in FIG.
Apply high-frequency power of WattE+ to the reaction chamber (13A)
A glow discharge is generated between the inner substrate (15+) and an a-Si, :f(:F film is formed on the substrate at a constant film formation rate by gas decomposition.

Hereinafter, the drum for electrophotographic photoreceptor Ikoa-Si, :H,
A specific explanation will be given using an example in which a :F film is produced.

[Example 1] A-Si-:H:Fl was deposited on a drum-shaped aluminum substrate using the inductively coupled glow discharge decomposition apparatus shown in FIG.
il was formed and the film formation condition was tested.

That is, in this example, a Pyrex tube with an inner diameter of 600J11 is used as the reaction chamber (131), and a drum-shaped aluminum substrate A5 is placed on a turntable +171 inside the reaction chamber (131).
1. Second. 3rd tank (11+21 +3
H2 gas, SLE'4 gas, and SiH+ gas are released from +, and the gas composition ratio of the glow discharge atmosphere is determined depending on the ratio of these gas flow rates.

The glow discharge decomposition region inside the Pyrex tube is determined by the setting range of the resonant vibration coil I, but in this example, if the height of the glow discharge decomposition region is set to lQQgmi, the volume of that region is 785] becomes. Therefore, SiF4. When the flow rate of all the gases in SiH+, E(2) is set to 88 sec.I, the amount of gas for forming the a-81 layer per unit time introduced into the glow discharge decomposition region is 347 minutes with respect to the volume of this region.

In addition, the high frequency power is 200W, the substrate temperature is 200℃, and 5L.
1F4 gas and 5iE (ti scan the sum of the flow rates of 4 gases)
The total gas pressure and SiF4 gas composition ratio (R31F4=
SiF! / (SiF4-1-5iE(4)) When the experiment was repeated using l as a variable, the results shown in FIG. 3 were obtained.

In FIG. 3, the ○ mark indicates that a uniform and good quality film was formed, the Δ mark indicates that the film peeled off, and the X mark indicates that no film was formed.

As is clear from the figure, it can be seen that a uniform and high-quality film could be formed when the total gas pressure inside the reaction chamber (131) and the SiF'+ gas composition ratio were within the range of the present invention.

[Example 2] Based on Example 1, when the high frequency power was set to 200 W, the gas pressure inside the reaction chamber was set to 2.5'rorr, and the gas flow rate was set to 34/min and 68/min, 5i -fj″
When the film formation rate was investigated by changing the 4-gas composition ratio R8tF+, the results shown in FIG. 4 were obtained. In the figure, marks ``mu'' and ``-'' indicate plots of gas flow rates of 34/min and 68/min, respectively, and curves a and b indicate corresponding dependence characteristic curves.

As is clear from FIG. 4, it can be seen that the film forming rate for R8IF4 is higher when the gas flow rate is higher θ/min. In addition, in both cases, the decrease in the film formation rate due to the increase in R8V4 is due to the decrease in the SiH4 gas flow rate.
This is due to an increase in the iF4 gas flow rate, and as described above, since SiF'+ gas has an etching effect in plasma, it can be seen that an increase in the S j h'4 gas flow value decreases the film formation rate.

[Example 3] In this example, an experiment was conducted to examine the effect of gas flow rate on the film quality of an a-Si:H:F film.

That is, according to Example II, the high frequency power was 200 W, the gas inside the reaction chamber was 2.5'T'O,t''r, "SiF4
was set at 40%, and the film formation rate and film quality were measured while changing the gas flow rate, and the results shown in FIG. 5 were obtained.

As a means of evaluating this film quality, the production rate of dangling bonds is examined by measuring the intensity of photoluminescence, and the greater the intensity, the less dangling bonds are produced, which indicates that the film quality is excellent.

This photoluminescence measurement was carried out at 80k using liquid nitrogen.
c Temperature set a-Si:E(:F film + co-ETe
-('a Laser light (441, 611) is projected, and its photoluminescence emission intensity is measured. In the figure, the intensity is expressed as a relative value with the maximum value being 1.

In the figure, marks O and Δ indicate plots of the film formation rate and relative photoluminescence intensity, respectively, and curves c and d indicate the corresponding dependence characteristic curves.

As is clear from Fig. 5, as the gas flow rate increases, the film formation rate slows down (although it is desirable to set the gas flow rate in the range of 20 to 150/min for photoelectric conversion devices). I understand..

As shown in the above example, when applying the a-6i:H:F film to a photoelectric conversion element, if the gas pressure of the glow discharge atmosphere, its gas components, and their composition ratios are set within a predetermined range, the number of photoelectric conversion elements used can be improved. The film formation rate can be increased while maintaining the quality of the a-83-:H:F film, and in order to obtain a higher quality a-8IE (:F film), the gas flow rate according to the indication of the present invention can be increased. It is recommended to rub it in a predetermined range G.

[Brief explanation of the drawing]

Figures 1 and 2 are a glow discharge decomposition device for forming a fluorinated amorphous silicon film, Figure 3 is a graph showing the film formation status as a function of glow discharge gas pressure and SiF4 gas composition ratio, and Figure 4 is a graph showing the fluorinated amorphous silicon film. FIG. 5 is a graph showing a characteristic curve of the film formation rate of a fluorinated amorphous silicon film depending on the SiF4 gas composition ratio. FIG. . a, b... SiF of fluorinated amorphous silicon film
4 Gas composition ratio dependence characteristic curve C... Gas flow rate dependence characteristic curve d of film formation rate of fluorinated amorphous silicon film... Gas flow rate dependence characteristic curve Patent applicant: Kyocera Corporation Takao Kawamura Figure 8 Full force, month = (Torr) RstF+ (%)

Claims (8)

[Claims] (1) In a manufacturing method in which an amorphous silicon layer forming gas is introduced into a reaction chamber and a glow discharge is generated inside the reaction chamber to form an amorphous silicon photoelectric conversion layer containing hydrogen and fluorine on a substrate, glow discharge is The pressure of the amorphous silicon layer forming gas is set at 0.2 to 3 Torr, and the amorphous silicon layer forming gas is composed of a fluorine-containing silicon compound, a hydrogen-containing silicon compound, and a carrier gas. A method for manufacturing a photoelectric conversion element, characterized in that the gas volume of the fluorine-containing silicon compound is set to 20 to 50% of the gas volume of the silicon compound containing hydrogen and the silicon compound containing hydrogen. (2) The amount of amorphous silicon layer forming gas introduced into the glow discharge decomposition region inside the reaction chamber per unit time is set in the range of 20 to 150/min with respect to the volume of the glow discharge decomposition region. Claim 1:
2. Method for manufacturing a photoelectric conversion element described in Section 1. (3) The method for manufacturing a photoelectric conversion element according to claim 1, wherein the carrier gas is hydrogen gas. (4) The method for manufacturing a photoelectric conversion element according to claim 1, wherein the carrier gas is a rare gas. (5) The method for manufacturing a photoelectric conversion element according to claim 4, wherein the rare gas is helium gas. (6) The method for manufacturing a photoelectric conversion element according to claim 1, wherein the carrier gas occupies 50 to 90% of the gas volume ratio in the amorphous silicon layer forming gas. (7) The method for manufacturing a photoelectric conversion element according to claim 1, wherein the fluorine-containing silicon compound is 5i-F+. (8) The method for manufacturing a photoelectric conversion element according to claim 1, wherein the hydrogen-containing silicon compound is SiH+.