JPH0481349B2 - - Google Patents

Description

[Detailed description of the invention]

INDUSTRIAL APPLICATION FIELD The present invention relates to a photoconductor, particularly for use in image devices such as image pickup tube target solid-state imaging devices and electrophotographic photosensitive plates, and a method for manufacturing the same. Structure and Problems of Conventional Example The present inventors proposed a hydrogen-containing method for realizing a photoconductive film of amorphous hydrogenated silicon suitable for image devices with low dark current and photosensitivity. A structure using a large amount of a wide bandgap amorphous hydrogenated photoconductive film as a blocking layer was demonstrated, and it was shown that it could be realized by reactive sputtering.
A layer with a large amount of hydrogen is particularly effective as a hole blocking layer, and it is necessary to introduce acceptor impurities to reduce electron injection. However, even a layer with a large amount of hydrogen into which impurities were introduced was insufficient to prevent electron injection. Therefore, it was necessary to further reduce the dark current in storage type image devices. Purpose of the Invention The purpose of the present invention is to provide a photoconductor provided with a photoconductive film that uses amorphous hydrogenated silicon that has high resolution and high sensitivity and achieves low dark current, and a method for manufacturing the same. do. Structure of the Invention The present invention provides a photoconductor comprising first and second layers mainly composed of amorphous silicon hydride and having a resistivity of 10 ¹⁰ Ωcm or more, and wherein the second layer is
characterized in that a first layer of a hole injection blocking layer having a higher hydrogen content than that of the layer is successively formed on the substrate so as to be sandwiched between the second layer and the electron injection blocking layer,
The manufacturing method uses silicon as the main component, and forms a first layer with a hydrogen content of 10 10 Ωcm or more by a reactive sputtering method in an atmosphere containing hydrogen as a reactive gas, and a first layer with a hydrogen content of 10 ¹⁰ Ωcm or more. the second most
It consists of step A of forming a layer of , step B, and step C of forming a silicon nitride layer or a silicon oxide layer (hereinafter referred to as oxide layer) by a reactive sputtering method in an atmosphere containing nitrogen or oxygen as a reactive gas, The first layer is sandwiched between the second layer and an oxide layer, and is formed on the substrate in the configured lamination order, and a part of one surface of the first layer is nitrided. It consists in changing to a silicon layer or a silicon oxide layer. DESCRIPTION OF EMBODIMENTS The photoconductor of the present invention has a substrate 1 as shown in FIG.
2 with specific resistances of ¹⁰ Ωcm or more with different hydrogen contents on the top
The layer consists of amorphous hydrogenated silicon layers 2, 3 and a silicon nitride or silicon oxide layer 4. Said 2
The amorphous silicon hydride having a high hydrogen content acts as a hole injection blocking layer, and the silicon nitride or silicon oxide layer 4 acts as an electron injection blocking layer. One example of a specific method for manufacturing a photoconductor will be described below. As shown in FIG. 2a, a Mo film 12 is formed on a single crystal Si wafer 11 as a substrate by a sputtering method. The substrate body A thus formed was placed in a magnetron sputtering device, and after being evacuated to 2 × 10 ^-6 Torr, the substrate body A was kept at 250°C, and polycrystalline silicon was targeted, and an argon pressure of 4.5 ×
10 ^-3 Torr, hydrogen pressure 5×10 ^-4 Torr atmosphere
With a discharge power of 100 W, an amorphous hydrogenated silicon layer 13 with a thickness of 0.2 to 0.3 μm containing a large amount of hydrogen was formed in 60 minutes, and the discharge power was continuously changed to 200 W to form an amorphous hydrogenated silicon layer 13 with a thickness of 0.2 to 0.3 μm in 60 minutes.
Amorphous hydrogenated silicon 14 having a small amount of hydrogen and having a thickness of 1.5 to 1.8 μm is formed in minutes. Next, the surface is anodized in oxygen plasma to form silicon oxide 15 on the surface. Next, about 1000 In ₂ O ₃ 16 was added using the sputtering method.
Å form. This amorphous hydrogenated silicon layer 13,
No. 14 has a specific resistance of 10 ¹⁰ Ωcm or more.
Figure 3 21 shows the dark current when a voltage is applied with the transparent electrode 16 of negative polarity and the Mo film 12 of positive polarity, and the dark current when the dark current is irradiated with light with a wavelength of 435 nm (0.5 μw/cm ² ). The current is shown at 22. For comparison ^, after the formation of the layer 14 in the example instead of the silicon oxide 15 as shown in the cross-sectional view of FIG.
×10 ^-3 Torr, diborane (B ₂ H ₆ ), pressure 1×
Amorphous silicon 1 with increased hydrogen content and doped with boron at 10 ^-5 Torr with a discharge power of 200W
7 is formed with a thickness of 0.1 μm, and then a transparent electrode 16 is formed.
The dark current and photocurrent are shown as 23 and 24, respectively. It can be seen that the dark current was reduced by adding the surface silicon oxide layer. Next, a sectional view of an electrophotographic photoreceptor according to a second embodiment of the present invention is shown in FIG. 4, in which figure a shows an initial state and figure b shows a state diagram of changes in the surface layer. An amorphous hydrogenated silicon layer 32 with a large amount of hydrogen is formed on the Al substrate 31 under the same conditions as the layer 13 of the first embodiment.
Then, under the same conditions as the first embodiment layer 14, an amorphous hydrogenated silicon layer 33 having a small amount of hydrogen is formed to a thickness of 5 to 6 μm. When negative charges are repeatedly applied to this using a corona charger, the initial charging potential gradually increases as shown in FIG. Auger analysis of this revealed that there was a lot of oxygen and silicon oxide on the surface. This oxidation is thought to be due to the amorphous hydrogenated silicon on the surface being oxidized by ozone accompanying negative charging. This silicon oxide layer reduced electron injection and increased the initial charging potential. The above embodiments are examples in which the surface layer of amorphous hydrogenated silicon is changed to a silicon oxide layer. FIG. 6 shows a sectional view of a third embodiment of the present invention. The amorphous hydrogenated silicon layer 13 in the first embodiment is placed on a stainless steel substrate 41 whose surface has been mirror-finished.
Argon pressure 4×13 ^-3 Torr, hydrogen pressure 1×
The layer 42 with a high hydrogen content is formed under the same conditions except that it is formed in an atmosphere of 10 ^-3 Torr. Next, argon pressure 4.5×10 ^-3 Torr, hydrogen pressure 5×
Create an atmosphere of 10 ^-4 Torr and reduce the discharge power.
An amorphous hydrogenated silicon layer 43 with a low hydrogen content of 5 to 6 μm is formed at 300 W for 4 hours. Additionally, Ar pressure is 1×10 ^-3 Torr, and nitrogen pressure is 2×10 ^-3 Torr.
Then, the discharge power was set to 400W and the silicon nitride film 44 was
Forms over 100 Å. Table 1 shows the initial charging potential and dark decay time of this photosensitive plate, which was corona charged to -6 KV using a charging tester. For comparison, the characteristics when there is no silicon nitride film are also shown. Improvements are seen in both the initial charging potential and dark decay characteristics. The optical attenuation characteristics are good with no significant difference. FIG. 7 shows the structure of the third embodiment reversed, with silicon nitride 44 on the substrate, amorphous silicon hydride 43 with a small amount of hydrogen, and amorphous silicon hydride 42 with a large amount of hydrogen on the substrate. are formed sequentially. The conditions are the same as in the third example. When this film is used as a photosensitive plate, it becomes positively charged.

[Table] In the above embodiments, forming an electron injection blocking layer using silicon nitride and silicon oxide has the effect of reducing dark current, increasing the charging potential of the photoreceptor, and reducing dark decay. The layer that blocks this electron injection can have a similar effect even if it has an intermediate composition of SiNxOy. Amorphous hydrogenated silicon produced by the sputtering method has a higher resistance than that produced by the glow discharge method due to the decomposition of _SiH4 , and even if a denser, higher resistance, high quality silicon nitride or silicon oxide is used, the amorphous hydrogenated silicon layer There is sufficient voltage distribution, and the deterioration of optical attenuation characteristics and increase in residual potential are not large. Further, due to the same effect, silicon nitride or silicon oxide can be made thicker than amorphous hydrogenated silicon produced by glow discharge method, and the surface stability and wear resistance are excellent. Such a structure increases the charging potential even if it is thin, and is advantageous in terms of productivity. Effects of the Invention According to the above configuration, the present invention prevents injection of holes by using high-resistance amorphous silicon hydride with a large hydrogen composition and a wide band gap, or by providing a silicon nitride or silicon oxide layer to prevent electrons from being injected. Since the structure prevents the injection of , it produces effects of high resolution, high sensitivity, and low dark current. On the other hand, it has excellent stability and abrasion resistance as an electrophotographic photoreceptor. The manufacturing method of the present invention has a resistance of 10 ¹⁰ Ω even without doping.
It is possible to obtain amorphous silicon hydride with a size of 1 cm or more, and the amount of hydrogen can be easily controlled. Moreover, silicon nitride and silicon oxide can be easily formed by simply changing the reaction gas using the reactive sputtering method. can be easily realized by reacting amorphous hydrogenated silicon in nitrogen or oxygen activated by plasma or the like.

[Brief explanation of drawings]

Figure 1 is an explanatory diagram of the structure of the photoconductor of the present invention, Figure 2a is a sectional view of the first embodiment of the photoconductor of the present invention, and Figure b is a comparison of characteristics with the first embodiment. 3 is a V-1 characteristic diagram of the first embodiment of the present invention and the comparative example, and FIG. 4 is a cross-sectional view of a photoconductor (hereinafter referred to as a comparative example) for the purpose of implementing the present invention. A cross-sectional view of the electrophotographic photoreceptor according to the second embodiment of the present invention, FIG. 5 shows the initial state, FIG. FIG. 6 is a sectional view of an electrophotographic photosensitive plate according to a third embodiment of the present invention, and FIG. 7 is a reversed sectional view of the structure of the third embodiment of the present invention. 1, 11, 31, 41: substrate, 2, 3, 13,
14, 32, 33, 42, 44: amorphous hydrogen silicon layer, 4: silicon nitride or silicon oxide layer.

Claims (1)

[Claims] 1. A first layer formed on a substrate and mainly composed of amorphous hydrogenated silicon and having a specific resistance of 10 ¹⁰ Ωcm or more;
A second layer formed on the first layer and having a specific resistance of 10 ¹⁰ Ωcm or more and mainly composed of amorphous hydrogenated silicon, and silicon nitride or silicon oxide formed on the second layer. and an electron injection blocking layer as a main component, wherein the first layer has a hydrogen content higher than the second layer and serves as a hole injection blocking layer. body. 2 A first layer with a hydrogen content of 10 ¹⁰ Ωcm or more and a second layer with a hydrogen content higher than that of the first layer are formed by reactive sputtering in an atmosphere containing silicon as a main component and hydrogen as a reactive gas. It consists of Step A of forming a layer of , Step B, and Step C of forming a silicon nitride layer or a silicon oxide layer (hereinafter referred to as an oxide layer) by a reactive sputtering method in an atmosphere containing nitrogen or oxygen as a reactive gas, A method for manufacturing a photoconductor, characterized in that the first layer is sandwiched between the second layer and an oxide layer, and the layers are formed on a substrate in the configured lamination order.