KR820002330B1 - Photosensor - Google Patents

Abstract

In a photosensor having at least a light-transmitting conductive layer which is arranged on the side of light incidence, and a photoconductive layer in which charges are stored in correspondence with the light incidence; a photosensor characterized in that at least a region of said photoconductive layer for storing the charges is made of an amorphous material which contains hydrogen and silicon as indispensable constituent element thereof, in which the silicon amounts to at least 50 atomic % and the hydrogen amounts to at least 10 atomic % and at most 50 atomic %., and whose resistivity is not lower than 1010 -cm.

Description

Light-receiving element

1 is a cross-sectional view of a photoconductive imaging tube that is a representative example of an accumulation type light receiving device.

2 and 3 are explanatory diagrams showing an example of a thin film forming apparatus.

4 to 10 are cross-sectional views showing an imaging tube target using the light receiving element of the present invention.

11 is a view showing spectral sensitivity characteristics of the light receiving device of the present invention.

12 is a diagram showing a relationship between hydrogen concentration in a photoconductive film and its optical response.

13 is a cross-sectional view of an essential part of an apparatus showing another embodiment of the light receiving element of the present invention.

The present invention relates to a structure of a light receiving element that can be used in a light receiving element used in an accumulation mode, namely, a photoconductive imaging tube target or a solid state imaging device.

A typical example of the light receiving apparatus used in the conventional accumulation mode is the light conductive imaging tube of FIG. This consists of a light-transmitting substrate 1, a transparent conductive film 2, an optical conductor layer 3, an electron gun 4, an external atmosphere, and the like 5 which are commonly referred to as face plates.

An optical image formed through the face plate 1 and formed on the photoconductor layer 3 is photoelectrically converted and accumulated on the surface of the photoconductor layer 3 as a charge pattern to form a scanning electron beam 6. It is structured to read time-series by.

At this time, an important characteristic required for the photoconductor layer 3 is that the charge pattern is not dissipated by the diffusion of the charge pattern during the time interval (that is, the accumulation time) at which the specific number of times is scanned by the scanning electron beam 6.

Therefore, as a material of the optical conductor layer 3, a semiconductor having a specific resistance of 10 ¹⁰ Ω · cm or more, for example, Sb ₂ S ₃ P _b O, Se-based chalcogen glass and the like is commonly used.

If a material having a resistivity of less than 1010 Ω · cm, such as Si single crystal, is used, it is necessary to divide the surface on the non-electron imposing side into a mosaic shape to prevent the disappearance of the charge pattern. Among these materials, Si single crystals have a complicated processing process and other high-resistance semiconductors usually contain a high concentration of trap levels that prevent travel of optical carriers. Poor conditions are likely to occur.

The present invention seeks to eliminate the above drawbacks.

The present invention is a light receiving element having the following configuration.

In a light-receiving element having a light-transmitting conductive film disposed on the incident side of light and a light conductor layer having a small amount of electric charges accumulated upon incidence of light, the light conductor layer is composed of a single layer or a plurality of layers of the photoconductive material. At least the charge accumulation region of the body layer is composed of an amorphous material containing hydrogen and silicon as essential constituents, and the amorphous material contains at least 50 atomic% silicon and at least 10 atomic% and at least 50 atomic% hydrogen. And a resistivity of 10 ¹⁰ Ω · cm or more.

SUMMARY OF THE INVENTION An object of the present invention is to provide a light receiving element using a high resolution accumulation mode.

The light-receiving element of the present invention has extremely low bake phenomenon and good afterimage characteristics. Moreover, the manufacturing method is simple.

The light receiving element of the present invention is basically configured as follows. In a light-receiving element having a transmissive conductive film disposed on the incident side of light and an optical conductor layer in which charges are accumulated upon incidence of light, the photoconductor layer is composed of a single layer or a plurality of layers of the photoconductive material, and the photoconductor At least the charge storage region of the layer is an amorphous material containing hydrogen and silicon as essential components, and the amorphous material contains at least 50 atomic% silicon and at least 10 atomic% and at least 50 atomic% hydrogen. The specific resistance is 10 ¹⁰ Ω · cm or more.

The thickness of the optical conductor film is selected within the range of 100 nm to 20 μm.

Means for extracting charges accumulated in the photoconductor layer by the incident of light as electrical signals from the photoconductor layer can be enumerated as follows.

As a representative example, an imaging tube or the like is widely used as a method of scanning an electron beam onto an optical conductor layer.

Another example is the use of solid state image sensors. The accumulated charge is taken out by a semiconductor device such as a MOS transistor or a CCD (charge coupled device) connected to the photoconductor layer.

It was found that the amorphous material containing silicon and hydrogen at the same time can be easily made to have a high resistivity of 10 ¹⁰ Ω · cm or more, and furthermore, it is a high quality optical conductive material with very few traps which hinder the running of the optical carrier.

It is natural that some impurities are contained in the amorphous material simultaneously containing silicon and hydrogen.

Germanium which is a cognate element with silicon may be contained as the remainder in the above-mentioned composition.

Such materials are used in thin films. The thin film sample can be formed by various methods such as diffusion of a silicon alloy in an atmosphere containing hydrogen decomposition by glow discharge of SiH ₄ or electron beam deposition of a silicon alloy in an atmosphere containing active hydrogen. Explanatory drawing of FIG. 2 and FIG. 3 is an example of the typical apparatus.

2 is an example in the case of using a glow discharge.

(20) is a sample, (21) is a container capable of evacuating to vacuum, (22) is a radio frequency coil, (23) is a sample holder, (24) is a thermocouple for temperature measurement, ( 25) is a heater, 26 is an atmosphere gas inlet, 27, such as SiH ₄ is a tank, 28 is the connection port as the exhaust system for mixing the gas.

3 is an example in the case of a sputtering process. Numeral 30 denotes a sample, numeral 31 denotes a container which can be evacuated by vacuum, and numeral 32 uses a silicon sintered body as a sputtering target. Reference numeral 33 denotes an electrode for applying a high frequency voltage, 34 denotes a sample holder, 35 denotes a thermocouple for measurement, 36 denotes a rare gas such as argon, and a gas inlet such as hydrogen, and 37 denotes cooling water. Represents a passage. In order to obtain a high resistance sample, a particularly preferable manufacturing method is a method by reactive sputtering of a silicon alloy in a mixed atmosphere of hydrogen and rare gas such as argon.

The amorphous film produced by using the glow discharge is extremely hard to obtain a resistivity of 10 ¹⁰ Ω · cm. However, in an amorphous film produced using reactive sputtering, a resistivity of 10 ¹⁰ Ω · cm or more can be obtained.

Furthermore, in the imaging characteristics, the amorphous film produced by using reactive ciphering is superior to the amorphous film produced by using glow discharge.

As a sputtering apparatus, a magnetron type low temperature high speed sputtering apparatus is suitable. The amorphous film containing hydrogen and silicon is usually denatured by releasing hydrogen when heated to 350 ° C. or higher, so that the substrate temperature during film formation is preferably maintained at 100 ° C. to 300 ° C. FIG.

In addition, the hydrogen concentration contained in the amorphous film can be varied widely by varying the partial pressure of hydrogen in the pressure of atmosphere 2 × 10 ⁻³ Torr to ¹ × 10 ⁻¹ Torr during discharge from 0% to 100% in various ways. The target for sputtering uses a sintered body of silicon, but if necessary, a rod containing a form impurity, a phosphorus as a form impurity, or a mixed sintered body of silicon and germanium can be used.

Among the amorphous films produced in this way, the resistivity that is particularly suitable for a light-receiving device that functions in the accumulation mode is 10 ¹⁰ Ω · cm or more.

(The specific resistance is preferably 10 ¹² Ω · cm or more for the imaging tube). It is particularly preferable to obtain a film having a low trap concentration when the content of silicon contained in the film is 10 atomic atoms or more, such as 10 to 50 atomic%.

If the hydrogen content is too small, the resistance value is excessively lowered. This causes a decrease in resolution.

If the hydrogen content is excessive, the photoconductivity is lowered and the photoconductive properties are not sufficient. Therefore, this resolution is naturally reduced. In the light-receiving device which operates in the accumulation mode, in order to obtain a high resolution, the high resistance layer for accumulating the charge pattern and maintaining it for a predetermined time is not necessarily the entire photoconductor layer. It may be part of the body layer.

In general, since the rh resistive layer operates as a capacitive component in an equivalent circuit, it is preferable that the rh resistive layer has a thickness of at least 100 nm or more depending on the requirement of the circuit constant.

4 is an example of the case where the above-mentioned high resistance amorphous photoconductor layer is used only for a part of the photoconductor layer 3.

The photoconductor layer 3 has a two-layer structure of the high resistance amorphous photoconductor layer 7 and the other photoconductor layer 8.

In this case, light carriers are generated in the photoconductor layer 8 due to the light incident in the direction of the face plate 1, which is injected into the high-resistance amorphous photoconductor layer 7 to charge the surface of the amorphous layer 7. Accumulate as a pattern.

Since the photoconductor layer 8 does not directly participate in accumulation, it is not necessary to necessarily have a high resistance of 10 ¹⁰ Ω · cm or more, and known photoconductors such as CdS, CdSe, Se, and ZnSe can be used.

A transparent conductor film (2) as generally can be used semi-transparent metal film such as _{S n O 2, I n2 O} 3, T i O 2 , such as a low-resistance oxide film, or Al, Au. In order to reduce the dark current of the light-receiving device and to increase the response speed, it is preferable to form a rectifying contact between the transparent conductive film 2 and the photoconductive layer 3. Injection of holes from the transparent conductive film 2 into the photoconductive layer 3 can be suppressed by interposing a thin n-type oxide layer between the photoconductor layer 3 and the transparent conductive film 2.

It has thus been found that good rectifying contact can be obtained. In such a case, in order to use such a contact as a photodiode, it is preferable to use the transparent conductive film side as a positive electrode and the amorphous layer side as a negative electrode.

5 shows an example of a light receiving surface having such a structure.

An n-type oxide layer 9 is interposed between the transparent conductive film 2 and the amorphous photoconductor layer 3.

6 is a cross-sectional view showing an example of a light receiving surface having an n-type oxide layer. It is similar to the example of FIG. 5 except that the optical conductor layer 3 has a laminated structure of the layers 7 and 8.

Usually, optical conductors sensitive to visible light are semiconductors having a band width of about 2.0 eV. Therefore, in this case, the n-type oxide layer 9 preferably has a prohibition band of 2.0 eV or more so as not to disturb the arrival of light to the photoconductor layer 3. In order to prevent the injection of holes from the transparent conductive film 2, the thickness of the n-type oxide layer 9 is preferably 5 nm to 10 nm.

Suitable materials for this use include compounds such as cerium oxide, tungsten oxide, niobium oxide, germanium oxide, and molybdenum oxide. Since these materials exhibit normal conductivity, photoelectrons generated in the amorphous photoconductor layer 3 by light do not prevent the electrons from flowing toward the transparent conductive film 2.

When using the photoelectric surface of this invention as a target for imaging tubes like FIG. 1, the surface of the optical conductor layer 3 is normally used as a beam landing layer, and an antimony trihydride layer is used. The injection of electrons from the scanning electron beam 6 can be prevented or the generation of secondary electrons from the photoconductor layer 3 can be suppressed. For this purpose, an antimony trisulfide film is deposited in a low pressure argon gas from 1 × 10 ⁻³ Torr to 1 × 10 ⁻² Torr so that the thickness of the film is in the range of 10 nm to 1 μm.

7 is a sectional view showing an example of this structure.

The transparent conductive film 2 and the optical conductor layer 3 are provided on the translucent substrate 1, and the antimony trifluoride film 11 is formed thereon. 8 to 10 are cross-sectional views showing an example in which the antimony trifluoride film 11 is formed on the photoconductor layer 3.

In this case, FIG. 8 is an example in which the laminated structures of the layers 7 and 8 of the optical conductor layer 3 are formed.

9 and 10 show examples suitable for a structure in which an n-type oxide layer is provided between the photoconductor layer 3 and the transparent electrode. In the past, the photoconductor layer 3 has been shown only as an example of a single layer or two layers of layers 7 and 8, but a photoconductor layer may be formed in multiple layers.

In this case, of course, the portion where the charge pattern is accumulated is configured as the high resistance layer as described above.

Moreover, you may change a composition continuously, The structure of the various light receiving surface demonstrated so far may be selected according to the objective.

Next, the features of the light receiving element of the present invention are summarized as follows.

(1) The resolution can realize a high resolution of 800 lines or more per 1 ".

(2) There is no baking phenomenon and this property is extremely good.

(3) Excellent heat resistance and withstands at least 200 degrees.

(4) The mechanical strength is large.

(5) The manufacturing method is easy.

Hereinafter, the present invention will be described in more detail with reference to Examples.

Example 1

On the glass substrate, a transparent oxide film of 300 nm in thickness is formed using a method of thermal decomposition of S ⁿ Cl ⁴ in air.

Next, a 99,999% silicon sintered body was mounted on a target in a high frequency sputtering apparatus and subjected to reactive sputtering of an amorphous silicon film on the transparent conductive film in a mixed atmosphere of argon and hydrogen of 3 × 10 ^-3 Torr under a pressure of 5 × 10 ^-3 Torr. Make.

In this case, the substrate is kept at 200 ° C.

The thickness of the amorphous silicon film is about 2 mu m. The amorphous silicon film thus produced contains about 30 atomic% hydrogen and has a specific resistance of 10 ¹⁴ Ω · cm. In addition, a non-landing layer made of trimony antimony is formed to form a light receiving surface.

When the light receiving surface thus formed is used as the non-cone type imaging tube light receiving surface, an image pickup tube having excellent image pickup characteristics without quenching is obtained. 11 shows the sensitivity characteristics of the non-icon type imaging tube incorporating the above-described light receiving surface.

The basic structure of the image pickup tube other than the light receiving surface is the same as that of FIG. 1 shown as a conventional example. The target voltage is 30V.

It shows the extremely good characteristic which has a peak of a sensitivity near 555 mmicro which has a peak of visibility. FIG. 12 shows the results of measuring the optical response by varying the content of hydrogen in an amorphous material containing hydrogen and silicon as essential components for the light-receiving surface having the structure as described above.

A tungsten lamp is used as the light source to measure the photocurrent flowing through the photoelectric surface. It is understood from this optical response property that an amorphous material of 10 atomic% to 50 atomic% containing hydrogen is preferable for the purpose of the present invention. Moreover, when the hydrogen concentration is 10 atomic% or less, abnormality of the material decreases and high resolution of the device cannot be expected.

For example, when the hydrogen concentration is 10 atomic%, the specific resistance is about 10 ¹² Ω · cm, while when the 5 atomic number is much lower, 10 ¹⁰ Ω · cm.

Example 2

A mixture of S _n O ₂ and I _{n 2} O ₃ is deposited on the glass substrate 1 by known high frequency sputtering to form a transparent conductive film having a thickness of 150 nm. In addition, C _e O ₂ is vacuum-deposited to a thickness of 20 nm using a molybdenum boat to form an n-type oxide layer 9 thereon. Next, an amorphous silicon film 8 is formed on the substrate at a thickness of 10 nm in a hydrogen atmosphere of 3 × 10 ⁻³ Torr using high frequency sputtering with a silicon single crystal doped with 1 ppm of boron.

At this time, the substrate temperature is maintained at 150 ℃.

The amorphous silicon film thus formed contains about 55 atomic% hydrogen in the film.

Subsequently, 6 × 10 ⁻³ Torr of argon is introduced into the sputtering apparatus to form an amorphous silicon film 7 overlapping with a thickness of 3 μm using the silicon target in a mixed atmosphere of hydrogen and argon already present. .

This amorphous silicon film is almost P-type, contains about 25 atomic% hydrogen, and has a specific resistance of 10 ¹² Ω · cm. The light-receiving surface thus formed is used as a target for the non-icon type imaging relationship. The structure of the light receiving surface is the same as that of the conventional imaging tube. Since the light receiving surface has a rectifying contact, the optical response speed is low, the dark current is low, and the light incident surface is close to the incident surface of light, thus having an amorphous silicon film having a high hydrogen concentration, so that the influence of surface recombination can be reduced, and therefore, the blue light region. High sensitivity at.

Similar effects can also be obtained by using tungsten oxide, niobium oxide, germanium oxide, molybdenum oxide, or the like as the n-type oxide layer.

In addition, even if an antimony trifluoride film is formed on the photoconductive film 3 which consists of the non-hard silicon films 8 and 7, it is good as a target of a video cone type imaging tube as mentioned above.

It is preferable to form the trisulfated antimony film as follows.

A substrate having an optical conductor film composed of the composite film of amorphous silicon film described above is provided in a vacuum deposition apparatus. Argon gas is deposited at a pressure of 3 × 10 ⁻³ Torr to form antimony trisulfide with a thickness of 100 nm. This is the structure shown in FIG.

Example 3

This embodiment will be described using FIG.

Oxidation by spraying an aqueous solution of S _n Cl ₄ on a glass substrate 1 is heated to 400 ℃ to form S _n O _2, a transparent conductive film (2).

The substrate is held at 200 ° C. in a vacuum apparatus, and CdS _e is deposited on the transparent conductive film 2 as a photoconductor layer 8 to a thickness of 2 μm. This CdS _e film is then heat treated in air at a temperature of 500 ° C. for 1 hour. The substrate is kept at 250 ° C. in a vacuum apparatus to deposit an amorphous silicon layer 7 to a thickness of 0.5 μm by an electron beam deposition method in an active hydrogen atmosphere of 1 × 10 ⁻³ Torr. Subsequently, the substrate temperature is reduced to room temperature, and deposited in a thickness of 50 nm in an antimony trifluoride film (11) in an argon atmosphere of 5 × 10 ⁻³ Torr to make a beacon-type image tube target.

The light-receiving element thus formed uses a light carrier generated in the CdS _e film, and thus has a high light sensitivity over the entire visible light.

Example 4

This embodiment will be described with reference to FIG.

Metal chromium is deposited on an insulating smooth substrate 12 to a thickness of 100 nm with a vacuum of 1 × 10 ⁻⁶ Torr to form an electrode 10. The substrate was placed in a high frequency sputtering apparatus to form an amorphous silicon film 7 having a thickness of 10 μm using a silicon target in a mixed gas of argon 5 × 10 ^-3 Torr and hydrogen 3 × 10 ^-3 Torr at a substrate temperature of 130 ° C. . This amorphous silicon film 7 has a specific resistance of ˜10 ¹¹ Ω · cm.

The substrate is held at 200 占 폚, and a film of niobium oxide 9 is deposited to a thickness of 50 nm by high frequency sputtering thereon. The substrate is then placed in a vacuum deposition apparatus, and the substrate temperature is maintained at 150 ° C. to deposit metal indium in a thickness of 100 nm in an oxygen atmosphere of 1 × 10 ⁻³ Torr. When the substrate is placed in an atmosphere of 1 atmosphere and subjected to heat treatment at 150 ° C. for 1 hour, the metal indium is changed into the transparent electrode 2 of indium oxide. The light-receiving element thus produced operates as a reverse biased photodiode when a voltage is applied such that the indium oxide transparent electrode is positive and the metal chromium electrode is negative.

In addition, the following light receiving device was manufactured.

Metal chromium is deposited on an insulating smooth substrate 12 to a thickness of 100 nm in a 1 × 10 ⁻⁶ Torr process diagram to form an electrode 10. The substrate was placed in a high frequency sputtering apparatus at a substrate temperature of 130.degree. C. using a target of 90 atomic% silicon and 10 atomic% germanium in a mixed gas of argon 2 × 10 ^-3 Torr and hydrogen 2 × 10 ^-3 Torr. An amorphous hard film 7 is formed.

This amorphous film 7 has a specific resistance of 2 × 10 ¹⁰ Ω.

The substrate is held at 200 占 폚, and a film of niobium oxide 9 is deposited to a thickness of 50 nm by high frequency sputtering thereon. The substrate was then placed in a vacuum deposition apparatus and the substrate temperature was maintained at 150 ° C. to deposit a thickness of 100 nm of metal indium in an oxygen atmosphere of 1 × 10 ⁻³ Torr. When the substrate is taken out from the atmosphere at 1 atmosphere and subjected to heat treatment at 150 ° C. for 1 hour, the metal indium turns into a transparent electrode 2 of indium oxide.

Thus, a light receiving element is made. As described above, it can be operated as a photodiode. This embodiment is an example of a light receiving device. Compared to the case of the imaging tube target described above, the formation order of the multiple films is reversed, but the structure of the light receiving surface has a common part. In addition, the metal chromium electrode on the substrate in this embodiment is divided into a number of small pieces and connected to a circuit which reads out accumulated charges sequentially by an external switch, thereby making it possible to obtain a solid-state image sensor of one or two dimensions. have.

As an external switch, a MOS transistor is used. The MOS transistor is connected to a photodiode using an amorphous film, the drain of the photodiode is connected to the signal output side, and a signal for reading this gate is applied.

Claims (1)

In a light-receiving element having at least a light-transmissive conductive film 2 disposed on the incident side of light and a photoconductor layer 3 in which charge is accumulated upon incidence of light, the photoconductor layer 3 is a single layer of a photoconductive material. Or a plurality of layers, wherein at least one region of the photoconductor layer 3 that accumulates this charge is made of an amorphous material having hydrogen and silicon as essential components, while the amorphous material is 50 atomic percent or more silicon. And hydrogen containing 10 atomic percent or more and 50 atomic percent or less, and having a specific resistance of 10 ¹⁰ Ω · cm or more.

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