JPH081895B2 - Method for forming amorphous silicon film - Google Patents

Description

TECHNICAL FIELD The present invention relates to a method for forming an amorphous silicon film on a substrate such as a conductive substrate.

2. Description of the Related Art Amorphous silicon films containing halogen atoms (hereinafter a-Si:
Abbreviated as X: H film. However, X = F, Cl, Br) is superior in heat resistance to an amorphous silicon film containing only hydrogen (hereinafter abbreviated as a-Si: H film), and is a film formed by light irradiation. Since it has advantages such as little change in structure, it is actively developed into a solar cell or an electrophotographic photoreceptor. Above all, SiF _4, which is a raw material gas, is easily available at a low price, and since the electric characteristics and stability of the film are excellent, researches on the a-Si: F: H film are most actively conducted. .

Conventionally, the glow discharge decomposition method has been most widely used as a method for forming an a-Si: X: H (X = F, Cl, Br) film. According to this method, as shown in FIG. 2, a source gas such as a mixed gas of SiF ₄ and H ₂ or a mixed gas of SiF ₄ and SiH ₄ is opened in a vacuum vessel 21 from a gas inlet 22 in a shower shape. Is introduced through the electrode 23, and high frequency power is applied from the high frequency power source 25 to the electrode 23 arranged to face the substrate 24 to generate plasma and decompose the raw material gas.
An a-Si: F: H film is formed on the surface of the substrate 24 heated to 350 ° C.

Problems to be Solved by the Invention In the glow discharge decomposition method using a mixed gas of SiF ₄ and H ₂ as a raw material gas, which is a conventional method for forming an a-Si: F: H film, fluorine radicals in plasma have an etching action. Therefore, the conditions under which film formation is possible are limited to a very narrow region, and even when film formation is possible, the film formation rate is as low as 1 to 2 μm / h. In order to broaden the film formation conditions and increase the film formation speed,
Instead of using a mixed gas of F ₄ and H _2, a mixed gas of SiF ₄ and SiH ₄ or a mixed gas of SiF ₄ and SiH ₄ and H ₂ or SiH ₂ F ₂
However, the film forming rate is as small as 2 to 3 μm / h, and the film forming rate of the a-Si: F: H film has not been significantly improved. Therefore, it takes 5 hours or more to form an a-Si: F: H film having a thickness of 15 μm or more, which is required for the electrophotographic photoconductor, and enables rapid mass production of the electrophotographic photoconductor. Can not. Further, when the SiF ₄ flow rate is increased to increase the film formation rate, a large amount of powdery silicon is generated due to the gas phase reaction in the raw material gas, which causes a problem that the exhaust system in the film formation apparatus is clogged.

Further, in the glow discharge decomposition method, a part of the energy consumed for film formation is carried by the thermal energy of the substrate heating,
Since the bond energy between Si atoms and F atoms is larger than the bond energy between Si atoms and H atoms, the substrate temperature at the time of forming the a-Si: F: H film is higher than that in the case of the a-Si: H film. Must also be raised and is usually set at 250 ° C or higher. Therefore, in the glow discharge decomposition method, a-Si:
It has a drawback that it is difficult to form an F: H film.

Further, a major problem of the a-Si: F: H film produced by the glow discharge decomposition method is that the film is easily contaminated during film formation.
In the a-Si: F: H film produced by the glow discharge decomposition method, C atoms, O atoms, and N atoms are mixed in as 10 ¹⁸ to 10 ²⁰ (pieces / cm ³ ) impurities. It has been revealed by probe analysis (IMA) and secondary ion mass spectrometry (SIMS). It is considered that the fluorine radicals in the plasma react with the walls of the vacuum container and the electrodes, the impurities bound to the F atoms are taken into the plasma, and are mixed in the film. In addition, the impurities thus mixed in the film cause deterioration of the electrical characteristics of the film, and thus the electrical characteristics of the a-Si: F: H film are inferior to those of the a-Si: H film. It is also becoming.

The present invention is to solve the above-mentioned problems, can form a film at a high speed without generating powder, suppress mixing of impurities into the film, and set the substrate temperature to room temperature. The present invention relates to a method for forming an a-Si: X: H (X = F, Cl, Br) film that enables film formation.

Means for Solving the Problems A film formation chamber and a plasma generation chamber are provided separately in a vacuum container, and both chambers are connected via a plasma flow passage window. A predetermined gas for plasma generation is introduced into the plasma generation chamber, microwave power is applied to the plasma generation chamber, and a magnetic field is formed in the plasma generation chamber to generate electron cyclotron resonance in the plasma generation chamber and generate plasma. It has a molecule containing silicon atoms and halogen atoms, which is introduced into the film formation chamber by guiding the gas into the plasma formation chamber by using a magnetic field in which the magnetic field strength decreases from the plasma generation chamber toward the film formation chamber. The gas and plasma are brought into contact with each other to form a- on the substrate placed in the film forming chamber.
A Si: X: H (X = F, Cl, Br) film is formed.

Action The plasma generation chamber in the vacuum container is a chamber that generates plasma by microwave power and magnetic field, and by setting the conditions for generating electron cyclotron resonance,
Discharge can be sustained even at low pressure of 2 × 10 ^-5 〜 0.1 Torr. The film formation chamber in which the substrate is arranged and the plasma generation chamber are separated by a wall provided with a window for transporting the plasma flow from the plasma generation chamber to the substrate. Further, since the magnetic force lines spread from this window toward the substrate of the film formation chamber, the electrons in the plasma generation chamber are extracted to the substrate along the magnetic force lines. As the electrons move, gas molecules in the film forming chamber are dissociated, so that plasma having a high ionization degree is transported only onto the surface of the substrate under a low pressure. In other words, high-density ions and radicals are formed on the surface of the substrate. Therefore, the film can be grown at high speed only on the surface of the substrate, and the film is not attached to other portions except the substrate and the powder is not generated. In addition, plasma in the film formation chamber
Since there is no contact with other parts except the substrate, there is no problem that impurities are mixed into the plasma from the wall of the film forming chamber or the gas introduction pipe to contaminate the film.

Since the energy consumed for forming the film is given by the energy of the ions incident on the substrate, the film can be formed even when the substrate temperature is set to around room temperature.

Example FIG. 1 shows a-Si used in the examples of the present invention:
X: H (X = F, Cl, Br) film forming apparatus. The vacuum container is composed of a film forming chamber 2 in which a substrate 1 is arranged and a plasma generating chamber 5 to which a magnetron power source 3 is connected by a waveguide 4. A magnetic coil 7 is installed around the plasma generation chamber 5 to induce electron cyclotron resonance in the plasma and to form a magnetic field for extracting the plasma from the window 6 on the substrate 1 in the film formation chamber 2. There is. The substrate 1 can be cooled by heating with the heater 8 or by circulating cooling water through the water supply / drainage port 9. The gas for plasma generation supplied from the first gas inlet 10 to the plasma generation chamber 5 includes H ₂ , NO ₂ , NO, N ₂ ONH ₃ , N ₂ , O ₂ , Cl ₂ , HCl, HBr, SO.
_It is preferable to use a mixed gas composed of any one of ₂ , ₂ , H ₂ S, CO, CO ₂ , He, Ar, Ne, Kr, Xe, CH ₄ , and C ₂ H ₆ , or a combination thereof. In addition, a-Si: X: H (X = F, Cl, B
r) The raw material gas for the film is supplied to the film forming chamber 2 through a ring-shaped second gas introduction pipe 11 provided between the window 6 and the substrate 1. As the raw material gas, specifically, SiF ₄ , Si ₂ F ₆ , SiH
It is preferable to use one of F ₃ , SiH ₂ F ₂ , and SiH ₃ F, or a mixed gas thereof, and to use these gases, SiCl ₄ , SiHCl ₃ , SiH ₂ Cl ₂ , and SiH ₃ Cl. , SiH ₃ Br,
It is preferable to use a gas in which SiH ₂ Br ₂ , SiHBr ₃ , SiCl ₃ Br, SiCl ₂ Br ₂ , SiClBr _{3 and the} like are mixed. Here, the above-mentioned source gases are SiH ₄ , Si ₂ H ₆ , Si ₃ H ₈ , and Si in order to increase the film formation rate.
Silane gas such as ₄ H ₁₀ may be mixed, and H ₂ , H
It is also possible to use it after diluting it with a gas such as e, Ne, Ar or N ₂ .

Impurity doping is necessary for pn control of an a-Si: X: H (X = F, Cl, Br) film, and in the case of a p-type amorphous silicon film, B ₂ H ₆ and BF _{3 are used} as a doping gas. , BCl ₃ , BBr ₃ , (CH
₃ ) ₃ Al, (C ₂ H ₅ ) ₃ Al, (iC ₄ H ₉ ) ₃ Al, (C ₂ H ₅ ) ₃ In, (CH ₃ ) ₃ G
It is preferable to use a, (C ₂ H ₅ ) ₃ Ga, and in the case of an n-type amorphous silicon film, PH ₃ , PF ₃ , PF ₅ , PCl ₂ F, PCl ₂ F ₃ , PCl ₃ , PBr ₃ ,
AsH ₃ , AsF ₃ , AsF ₅ , AsCl ₃ , AsBr ₃ , SbH ₃ , SbF ₃ , SbC
l ₃ and H ₂ Se can be used as a doping gas. These doping gases are mixed with the above-mentioned plasma generating gas and introduced from the first gas inlet 10. Alternatively, it is mixed with the above-mentioned raw material gas through the second gas introduction port 11 and introduced into the film forming chamber 2.

In order to increase the resistance of the film, a-Si: X: H (X =
When carbon is added to the F, Cl, Br) film, CnH _{2n + 2} , CnH
_2n (n = 1,2,3,4,5), CH ₃ F, CH ₃ Cl, C ₂ H ₅ Cl, CH ₃ Br, C
_A mixed gas composed of any one of ₂ H ₅ Br (CH ₃ ) ₄ Si or a combination thereof is mixed with the above-mentioned plasma generating gas and introduced from the first gas inlet 10. Alternatively, it is mixed with the raw material gas and introduced into the film forming chamber 2 through the second gas inlet 11.

Example 1 The first plasma generation chamber 5 was evacuated shown in FIG hydrogen diluted 800ppm concentration of B ₂ H _6: 20sccm and N ₂ O: 1 sccm was introduced from the first gas inlet 10, SiF _4: 40 sccm Was introduced into the film forming chamber 2 through the second gas inlet 11, and the exhaust valve was adjusted so that the pressure in the film forming chamber 2 was 1 × 10 ⁻² to 10 ⁻⁴ Torr. An electric current is applied to the magnetic coil 7 to generate a magnetic field in the plasma generation chamber 5, and microwave power of 100 to 600 W and 2.45 GHz is applied to the plasma generation chamber 5 to generate plasma, which is heated to 50 to 250 ° C. A p-type a-Si: F: H film having a thickness of 0.5 to 2.0 μm was formed on the Al substrate 1. Then, for compensating hydrogen diluted 2ppm concentration
B ₂ H ₆ : 20sccm was introduced from the first gas inlet 10 and SiF ₄ : 40sc
cm is introduced from the second gas inlet 11 and the pressure is 1 × 10 ^-2 to 1 ×
I-type aS under the conditions of 10 ^-4 Torr and microwave power 100-600W
An i: F: H film was deposited to a thickness of 15 to 20 μm. Next, H ₂ : 20sccm is introduced from the first gas introduction port 10, SiF ₄ : 20sccm, CH ₄ : 20sccm is introduced from the second gas introduction port 11, and the pressure is 1 × 10 ^{−2 to} 5 × 10.
^A carbon-added a-Si: F: H film was prepared as a surface layer under the conditions of ^-4 Torr and microwave power of 300 to 500 W by 500 to 2000Å to form an electrophotographic photoreceptor.

The electrophotographic photosensitive member obtained as described above has a charge potential of +600 to +950 V and a half-exposure amount of surface potential in white light (hereinafter, referred to as photosensitivity E ₅₀ ) of 0.55 to 1.20 lux-sec, which is excellent. It showed various characteristics.

Example 2 PH ₃ : 20 having a concentration of 400 ppm diluted with hydrogen in the plasma generation chamber 5
sccm was introduced through the first gas inlet 10, SiH ₂ : 40 sccm was introduced through the second gas inlet 11 into the film forming chamber 2, and the pressure inside the film forming chamber 2 was 1 × 10 ⁻² to 10 ⁻⁴ Torr. Adjust the exhaust valve so that 100 ~ 600W, 2.45GHz microwave power is applied to the plasma generation chamber 5, current is passed through the magnetic coil 7, 50 ~
On the Al substrate 1 heated to 250 ° C., an n-type a-Si: F: H film of 0.5 is formed.
To 2.0 μm, and then H ₂ : 20 sccm is added to the first gas inlet 10
From which SiH ₂ F ₂ : 40 sccm was introduced through the second gas inlet 11.
Pressure 1 × 10 ^-2 〜 1 × 10 ^-4 Torr, microwave power 100〜600
A non-doped a-Si: F: H film was formed with W to a thickness of 15 to 20 μm. Then, N ₂ : 20 sccm is fed from the first gas inlet 10 to SiH ₂ F ₂ : 15 sc
cm is introduced from the second gas inlet 11 and the pressure is 1 × 10 ^-2 to 1 ×
An electrophotographic photosensitive member was formed by depositing a silicon nitride film as a surface protective layer at 600 to 1500Å at 10 ^-4 Torr and microwave power of 300 to 500 W.

The electrophotographic photosensitive member obtained as described above has a charging potential of −650 to −940 V and a photosensitivity E ₅₀ in white light of 0.64 to 1,
It was 20 lux-sec and showed good characteristics.

Example 3 Coating of 1-phenyl-3- (P-diethylaminostyryl) -5- (P-diethylaminophenyl) pyrazoline: 1 g, polycarbonate: 1 g, methylene chloride: 1 g on a glass plate on which an ITO transparent electrode was deposited. Apply the liquid and dry,
Annealing was performed in vacuum at 80 ° C. to form an organic semiconductor layer having a thickness of 10 to 20 μm. The glass plate 1 having the organic semiconductor layer formed on the ITO electrode is placed in the film forming chamber 2 and evacuated,
H ₂ : 20secm was introduced into the plasma generation chamber 5 through the first gas inlet 10, and SiF ₄ : 20sccm and SiH ₄ : 5sccm were introduced into the film forming chamber 2 through the second gas inlet 11, and the pressure was 1 ×. 10 ^-2 ~ 1 x 10 ^-4
A non-doped amorphous silicon film of 0.5 to 2 μm was formed on the organic semiconductor layer with Torr and microwave power of 100 to 600 W. Then, Ar: 20 sccm was placed in the plasma generation chamber 5 at the first gas inlet 1
0F, SiF ₄ : 10sccm, CH ₄ : 10sccm are introduced into the film forming chamber 2 through the second gas inlet 11, and the pressure is 1 × 10 ^-2 to 1 × 10 ^-4.
Torr, microwave power 300-500W, 5 as surface protection layer
A silicon carbide film of 00 to 2000 Å was deposited to form a function-separated electrophotographic photoreceptor. However, the substrate temperature during the formation of the amorphous silicon film and the silicon carbide film was always kept at room temperature by circulating cooling water from the water supply / drain port 9. Therefore, even if the amorphous silicon film and the silicon carbide film were formed on the organic semiconductor film, the surface of the organic semiconductor layer was not deformed or deteriorated.

The electrophotographic photosensitive member obtained as described above has a charged position of +500 to +900 V and a photosensitivity E ₅₀ in white light of 1.2 to
It was 3.6 lux · sec.

The film formation rate of the a-Si: F: H film formed in Examples 1 to 8 is 8.
˜16 μm / h, which is 2 to 4 times the film formation rate obtained by the glow discharge decomposition method, and a high film formation rate was obtained. Furthermore, almost no silicon powder was generated. Also, C, O, N
When the densities of C, O, and N atoms contained in the film of the a-Si: F: H film in which the atoms were not intentionally doped were measured by secondary ion mass spectrometry (SINS), ~ 10 ¹⁷ (pieces / cm ³ )
And a-Si: F: H film obtained by glow discharge decomposition method
A value smaller than an order of magnitude is obtained, and aS produced by the present invention is used.
It was revealed that the i: F: H film was less contaminated with impurities. Further, in Examples 1 to 3, a flat-plate electrophotographic photosensitive member was manufactured. However, even when the substrate has a cylindrical shape, if the film is formed while rotating about the axis of the cylinder, the electrophotographic photosensitive drum can be easily formed. Can be manufactured.

EFFECTS OF THE INVENTION The present invention separates the interior of a vacuum chamber into a plasma generation chamber and a film formation chamber, takes out the plasma generated in the plasma generation chamber onto a substrate arranged in the film formation chamber, and efficiently removes ions and ions on the substrate surface. Radicals are transported and a-Si:
This is a method of forming an X: H (X = F, Cl, Br) film, which allows the film to be deposited at a high speed without generating powder, and has little contamination of the film with impurities, and a substrate at room temperature. Since it is possible to form a film having a high photoconductivity on the top, mass productivity of a device using an amorphous silicon film can be improved and manufacturing cost can be reduced.

[Brief description of drawings]

FIG. 1 shows a-Si: X: H (X =
F, Cl, Br) cross-sectional schematic diagram showing the method of forming the film,
It is a cross-sectional schematic diagram which shows the formation method of the conventional a-Si: X: H (X = F, Cl, Br) film. 1 ... Substrate, 2 ... Film forming chamber, 3 ... Microwave power source,
4 ... Microwave waveguide, 5 ... Plasma generation chamber, 6 ...
... window, 7 ... magnetic coil, 8 ... heater, 9 ... water supply / drainage port, 10 ... first gas inlet, 11 ... second gas inlet.

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Shin Tadashi 1006 Kadoma, Kadoma City, Osaka Prefecture Matsushita Electric Industrial Co., Ltd. (72) Akio Takimoto 1006 Kadoma, Kadoma City, Osaka Matsushita Electric Industrial Co., Ltd. (56) References JP-A-59-131511 (JP, A) JP-A-55-102237 (JP, A)

Claims (3)

[Claims] 1. A vacuum chamber is divided into a plasma generating chamber and a film forming chamber, a predetermined plasma generating gas is introduced into the plasma generating chamber, microwave power is applied to the plasma generating gas, and the plasma is generated. A magnetic coil provided around the generation chamber forms a magnetic field that causes electron cyclotron resonance in the plasma generation chamber, plasma is generated in the plasma generation chamber, and the plasma is generated using the magnetic field formed by the magnetic coil to form a substrate. Is introduced into the film forming chamber, the silicon compound gas containing a fluorine atom is introduced into the film forming chamber, the plasma and the silicon compound gas containing a fluorine atom are brought into contact with each other, and at least fluorine on the substrate is introduced. A method for forming an amorphous silicon film, which comprises forming an amorphous silicon film containing atoms. 2. A gas having a molecule containing a carbon atom is mixed with at least one of a silicon compound gas containing a fluorine atom and a gas for plasma generation. Method for forming amorphous sillin film. 3. A gas containing a molecule containing an element of Group IIIb, Vb or VIb in the periodic table, in at least one of a silicon compound gas containing a fluorine atom and a plasma generating gas. The method for forming an amorphous sillin film according to claim 1, characterized in that: