JPS60105280A - Amorphous semiconductor device - Google Patents

Abstract

PURPOSE:To obtain the titled device, charge potential thereof is sufficient, residual potential thereof does not rise and which has excellent repetitive characteristics and is particularly proper as a photosensitive body for electrophotograph, by forming an amorphous film containing silicon in four layer structure and giving the specific resistance values of each layer specific relationship. CONSTITUTION:An amorphous film 12 containing silicon is formed on a substrate 11, and the film 12 is formed in multilayer structure, and has a first layer 13, a second layer 14, a third layer 15 and a fourth layer 16 in the direction of film thickness from the substrate 11 side. When the specific resistance values of these each layer 13, 14, 15, 16 are represented by rho I , rhoII, rhoIII, rhoIV, the relationship of rho I <rhoIII<rhoII<rhoIV is satisfied. Said amorphous film 12 shall contain elements such as hydrogen or hydrogen and a halogen element, and the layers except the third layer 15 shall contain one or more of elements of IIIa group elements, Va group elements, nitrogen, carbon and oxygen and the third layer 15 one or more of elements of the IIIa group elements.

Description

DETAILED DESCRIPTION OF THE INVENTION [Technical Field of the Invention] The present invention relates to an amorphous semiconductor device in which an amorphous film containing silicon is formed on a support.

[Technical background of the invention and its problems]

In recent years, amorphous materials containing silicon have been attracting attention as materials on which images are formed in electrophotographic devices such as copying machines and laser beam printers, replacing conventional amorphous selenium, zinc oxide, cadmium sulfide, etc. . This'i1.
For example, it has excellent mechanical strength and heat resistance, and has high photosensitivity over the visible region.

However, on the other hand, this amorphous material containing silicon only has a low resistivity at room temperature, so
In electrophotographic applications, there has been a problem in that the charge retention ability on the surface is insufficient.

Therefore, the amorphous film containing silicon is made into a multilayer structure, and in order to prevent the neutralization of charges held on the film surface, p-type or n-type
It has been considered to form a charge injection blocking layer using a semiconductor layer of one conductivity type, or to provide a high resistance film doped with carbon, nitrogen, or oxygen.

However, although the former type provided with a charge injection blocking layer can withstand repeated use without generating residual potential, it has the disadvantage that a sufficient charging potential cannot be obtained. However, the latter case provided with a resistance film also blocked the free movement of charge carriers caused by light irradiation, resulting in an increase in residual potential and a drawback that it could not withstand repeated use.

Therefore, when conventional amorphous films containing silicon were used, they were not suitable for electrophotographic applications.

[Object of the Invention] The present invention has been made based on the above-mentioned circumstances, and provides a non-contact material particularly suitable as a photoreceptor for electrophotography, which has a sufficient charging potential, does not cause an increase in residual potential, and has excellent repeatability. The purpose is to provide a crystalline semiconductor device.

[Summary of the invention]

In order to achieve the above-mentioned object, the present invention provides an amorphous semiconductor device comprising an amorphous film containing silicon formed on a support, in which the amorphous film containing silicon substantially has a film thickness of The first layer, the second layer, the third layer and the fourth layer from the support side in the direction
It has a multilayer structure of layers, and these first layer, second layer, third layer
The specific resistance values of the layer and the fourth layer are respectively ρI.

When ρ■1ρ■, ρ■, ρ■kuρ■u＜ρII＜
ρIV.

[Embodiments of the invention]

Generally, the specific resistance value of an amorphous film containing silicon can be controlled by incorporating various elements into the film.

For example, in the film, there is a group 111a or va of the periodic table
When it contains group elements, it becomes a p-type or n-type semiconductor, and its specific resistance value decreases depending on the amount of these elements added. Furthermore, when the film contains carbon, nitrogen, or oxygen, its forbidden band width increases and its specific resistance value increases.

Furthermore, the specific resistance value of the film can be controlled by containing carbon, nitrogen, or oxygen in addition to the elements that belong to either Group A or Group Va of the periodic table mentioned above. . In this case, the specific resistance value decreases or increases depending on the content of each element.

Now, FIG. 1 shows a cross-sectional view of an electrophotographic photoreceptor 10 in which an amorphous semiconductor device according to the present invention is applied.

As the support 11, a cylindrical or flat conductive substrate made of aluminum, stainless steel, etc. is used, but its shape is arbitrary depending on the purpose of use.

An amorphous film 12 containing silicon is formed on this support 11. This film 12 has a substantially multilayer structure, with first layers 13 . 2nd I Threat 14. It has a third layer 15 and a fourth layer Δ16.

Each of these layers 13, 14, 15.16 has a specific resistance value of ρ1. ρ■, ρ+n > and ρIV
Then, the relationship ρl×ρ1m<ρ■<ρ■ is satisfied.

The first layer 13 with the lowest specific resistance value (ρI) is
Contains at least one element belonging to Group 1a or Group Ⅰa of the periodic table in an amount of 10 or more atoms, and is p-type or i
It is an n-type low-resistance amorphous silicon film, and the support 11
Gold plays a role in blocking the injection of electrons or holes from the surface.

In addition, in this 17th song 12, at least one element selected from carbon, nitrogen, or oxygen is further added! :9, the specific resistance value can be easily controlled.

- Also, No. 47 16, which has the highest specific resistance value, contains at least one or more elements selected from carbon, nitrogen, or oxygen, and carbonizes, oxidizes, or oxidizes the silicon in the film. Increasing the optical width of the lateral band,
It has the function of increasing the stability and mechanical strength of the film in free space, and also has the role of sufficiently increasing the transmittance of visible light to reduce the reflection of unnecessary light.

Note that it is also effective to contain a trace amount (10 atoms or less) of an element belonging to group nTa or group Va of the periodic table in this fourth layer.

Furthermore, the specific resistance value is larger than that of the first layer 13 and smaller than that of the fourth layer 16. The second scrap 14 and the third layer 15 have a resistance value ρ■ by ρ■ depending on the magnitude relationship of their resistance values.

Of these, the third layer 15 is generally in the intrinsic region, and either contains no additives for controlling valence electrons, or contains a trace amount (10' atoms or less) of an element of group IV of the periodic table. In addition, the second layer 14 contains one or more elements selected from carbon, nitrogen, or oxygen in the film, and its specific resistance value ρ■ is the same as that of the fourth layer 16. The resistance (needs to be less than 1 fptv and more than the specific resistance value ρ■ of the third layer 15).

Note that it is also effective to contain an element belonging to Group 111a or Group Va of the periodic table in this second layer 14.

Now, when this amorphous film 12 is used as an electrophotographic photoreceptor, these second layer 14 and third layer 15 are elements that determine the charging ability and photoelectric characteristics of the photoreceptor. .

In other words, the charging potential is determined by the series sum of the dielectric strength voltages of the second layer 4 and the third layer 15, and the photoelectric characteristics and repeatability are determined by the number of charge carriers generated by light irradiation and their transport ability. Ru.

Among these, the second layer 14 containing at least one element selected from carbon, nitrogen, or oxygen has a higher dielectric strength voltage, and as a result, the dielectric strength voltage increases and the charging potential increases.

In addition, the transport ability of charge carriers caused by light irradiation is
Layer 15 is larger. This transport ability increases as the specific resistance value of the second J-Hyoku 14 increases to 7.1.

On the other hand, the fourth layer 16 may simply be a high-resistance film without discussing the charge carrier transport ability.

Therefore, in order to obtain an electrophotographic photoreceptor with a high charging potential, a low residual potential, and good repeatability, the second layer 14, the third layer 15, and the fourth layer 16 should have their respective specific resistance values determined. It is necessary that ρ■ ρ■〈ρIV, and if we consider including the first layer 13, ρI kuρ■
Must be iv.

In the above description, the second layer 14 and the third layer 15 are both described as having a function as a charge generation layer, but the second layer 14 is used to prevent charge injection in the same way as the first layer 13. It can also be thought of as having the function of a layer.

However, in either case, the third layer 15 generates charges when irradiated with light.

Further, as the support 11, although a conductive substrate is exemplified, it is also possible to use an FC substrate in which a layer of chromium or the like is provided on an insulating material such as glass or a polymer film, or a substrate in which a semiconductor layer is provided.

Now, considering the above-mentioned amorphous semiconductor device, the appropriate thickness of each layer is as follows.

First layer 13-・-0,05~5 (μm) Second layer 1
4...0.5-10 [μm] Third layer 15...3-2
0 [μm] Fourth layer 16·−0,01 to 1 (μm) Next, a method for forming the amorphous film 12 as described above will be described.

Film formation of amorphous silicon is S i H4, S i 2H61
A glow discharge decomposition method using a gas containing silicon atoms such as SiF4, a reactive sputtering method in a hydrogen atmosphere, a vacuum evaporation method, an ion blating method, and a photoCVD method are known.

Here, a glow discharge decomposition method using a gas containing silicon atoms will be explained.

The closed reaction vessel 2o is connected to an exhaust device 22 via a pulp 21, and is in a reduced pressure state. Also,
The reaction vessel 20 includes a gas supply device 2 containing a flow rate control device.
3 is connected so that a desired gas can flow into the reaction vessel 20 at a predetermined flow rate.

A support susceptor 24 is provided within the reaction vessel 20 and is configured to support the support 11. The support susceptor 24 is equipped with a heater 25 to heat the support 11 to an appropriate temperature.

Note that the support susceptor 24 is electrically connected to the reaction vessel 20, and the support 11 is grounded.

In fact, in the reaction vessel 20, an electrode 26 for generating a discharge is provided with an insulator 27 interposed therebetween, facing the support 11. This electrode 26 is connected to a high frequency power source 28 provided outside the reaction container 20 via a matching box 29.

This matching box 29 is for efficiently supplying power from the high frequency power source 28 to the load.

The electrode 26 also serves as a spout for blowing gas supplied from the gas supply device 23 into the reaction vessel 20 .

Note that an insulating joint 28 is interposed between the electrode 26 and the gas supply device 23 to electrically insulate the electrode 26.

Further, since one side of the high frequency power source 28 is grounded, high frequency power is applied between the support body 11 and the electrode 26.

In addition, the surface of the electrode 26 facing the reaction vessel 20 is covered by a shield plate 29 with a gap of several millimeters. This prevents discharge between the electrode 26 and the reaction vessel 20 when the full power is applied.

In such a film forming apparatus, first, the pressure inside the reaction vessel 20 is reduced to below klO'Torr using the exhaust device 22, and at the same time, the heater 25 is operated to raise the support 11 to 20
Heat to 0-300°C.

Next, the raw material gas is fed into the reaction vessel 20 at a predetermined flow rate from the gas supply device 23K, while the exhaust device 22
The pressure inside the reaction vessel 20 is adjusted to 0.1 to 3 Torr by 4. Then, the power of the high frequency power source 28 is applied to the electrode 26.

The raw material gas used here is first SiH4゜5t2HO
, SiF4 and other silicon-containing gases are living organisms;
A diluting gas and a dosing gas are used. As the diluent gas, hydrogen or an inert gas such as helium, neon, or argon is used1.As the impurity addition gas, when adding all the elements of group IV or Va of the periodic table, n BFa is used. , B2H61PHa, As
1a etc. is used and when carbon, nitrogen or oxygen is added, CH41C2H4+ C2H6,N21NH
3°N 20 + 02 or the like is used.

Using the above film forming apparatus, all amorphous semiconductor devices of samples A to E shown in Table 1 were fabricated.

Here, as the discharge power, the output of the power source 28 is set to 120 W, and the pressure inside the reaction vessel 20 is measured with a Pirani vacuum gauge.
．． It was set to 0 Torr.

In addition, between each layer during film formation, the discharge was stopped after the film formation of one layer, and the discharge for the formation of the next layer was started after the gas flow rate and pressure became constant. Film formation may be performed continuously between layers. In this case, by continuously decreasing or increasing the inflow amount of the gas containing the elements contained in each layer, it is possible to add the required type and amount of additives to each layer.

In addition, the fixed resistivity values of each layer shown in Table 1 are for a cell in which a single layer is formed on a glass substrate under the same conditions and with the same configuration, and a chromium electrode is deposited on the surface at room temperature. This is what was measured.

In addition, using 5iH4 (100 articles) as the raw material gas,
The additive gas is B2H6 (2000PPM/H2
), CH4 (100%) and NH3 (100%) were used.

This value is taken as the layer thickness of each layer.

In addition, the film formation time refers to the time during which the power supply 28 is operated and discharge is generated with the interior of the reaction vessel 20 set to predetermined conditions. The sample was set in a measuring device to measure electrophotographic properties.

This is done by using a corona discharger to charge the surface of each sample in the dark, and using a halogen lamp to charge the sample surface with an illuminance of 2io.
The operation of irradiating the sample surface with light as w is repeated. The corona discharger has a corona electrode applied with a DC voltage of 6 KV. Table 2 shows the surface potential and photosensitivity when charging and light irradiation are carried out using such a device.

In Table 2, the initial potential is the surface potential of the sample surface immediately after being charged, and the residual potential is the surface potential of the sample after being irradiated with light after being charged.

-The number of repetitions is the number of times the series of steps of charging and light irradiation are repeated.

(Leaving space below) Table 2 Therefore, when considering the results of Tables 1 and 2, it is found that samples A to C have a specific resistance value of ρI.
〈ρ■ ρ■〈ρ1v, whereas sample D
Uρ■〈ρ■〈ρ■〈ρ■, and sample E is ρ■〈ρ■
〈ρ■〈ρ■.

And, for both samples A-C, the initial potential is 1st and 5th.
There is almost no change from the 00th time, and no increase in residual potential is observed. Also, the photosensitivity is sufficient.

On the other hand, sample E has an initial potential of 500% compared to the first time.
There is a difference of 30 to 40 degrees from the second time.Furthermore, the residual potential is one order of magnitude larger than that of samples A-C, and the photosensitivity is also higher than that of sample A.
-C, specific resistance values of each layer ρI, ρ■, ρ■, ρI
When V satisfies the relationship ρ■ ρm < ρ■ ρ■, it is possible to obtain an electrophotographic photoreceptor with high charging ability, low residual potential, and excellent photosensitivity in repeatability. In the above description of the embodiment, the present invention was applied to an electrophotographic photoreceptor, but the present invention can equally be applied to other devices such as an optical sensor.

In addition, the layer structure of each layer is substantially the first layer, the second layer, and the third layer.
It suffices if it has a multilayer structure consisting of a layer and a fourth layer,
There is no problem in providing a separate boundary layer between each layer.Furthermore, each layer does not have to be configured completely independently, and as mentioned above, by continuously changing the concentration and flow rate of the raw material gas, a clear layer can be formed. There is no problem even if the structure has no boundaries.

In short, the film has a first layer, a second layer, a third layer, and a fourth layer in the film thickness direction from the support side, and the specific resistance value of these layers is calculated by ρ.
[Effects of the Invention] According to the present invention, an amorphous material having a sufficient charging potential, a low residual potential, and excellent repeatability characteristics is particularly suitable as an electrophotographic photoreceptor. A semiconductor device can be provided.

In particular, since the silicon-containing amorphous film contains hydrogen or hydrogen and a halogen element, a device with excellent electrical characteristics can be obtained in which the dangling bonds of silicon atoms can be fully compensated for.

In addition, an amorphous film containing silicon belongs to Group 1IIa of the periodic law.

By fully containing at least one of Group Va elements, nitrogen, carbon, and oxygen, the specific resistance value can be easily controlled.

Furthermore, by including an element belonging to Group 11 Ja of the periodic table in the 3N, the transport function of charge carriers in this layer can be changed, and when an amorphous film is used as an electrophotographic photoreceptor, It is possible to eliminate the so-called "image blurring" phenomenon.

[Brief explanation of drawings]

FIG. 1 is a cross-sectional view of an amorphous semiconductor device showing an embodiment of the present invention, and FIG. 2 is a schematic configuration diagram showing a film forming apparatus suitable for manufacturing the amorphous semiconductor device on the same side. 0 11... Support, 12... Amorphous film, 13... First layer, 14... Second layer, 15... Third layer, 16...
・4th layer Q Representative Patent Attorney Noriyuki Chika (and 1 other person) Figure 2 Figure 1

Claims (4)

[Claims] (1) In an amorphous semiconductor device in which an amorphous film containing silicon is formed on a support, the amorphous film containing silicon has a first N, It has a multilayer structure of a second layer, a third layer and a fourth layer, and these 1N and 2nd layers. The specific resistance values of the third and fourth layers are ρ■, respectively. When ρ■, ρ■, ρ1■, ρ■〈ρ■kuρ■〈ρ
(2) An amorphous semiconductor device characterized by: (2) Claim 1, characterized in that the amorphous film containing silicon contains hydrogen or hydrogen and a halogen element.
The amorphous semiconductor device described in . (3) The amorphous film containing silicon, except for its third layer, contains at least one element selected from elements of group 111a of the periodic table, elements of group Ⅰa, nitrogen, carbon, and oxygen. An amorphous semiconductor device according to claim 1 or 2, characterized in that the device includes: (4) The amorphous film containing silicon contains in its third layer at least one element selected from group 1 [a] elements of the periodic table. The amorphous semiconductor device according to any one of the ranges 1 to 3.