JPH01278077A - Photosensor - Google Patents

Abstract

PURPOSE:To detect the intensity of detected light of the central part and the peripheral part of a substrate by using one substrate, by forming one laminated member at the central part of the substrate, and forming the other laminated member on the peripheral part, so as to surround the central member. CONSTITUTION:On the central part A and the peripheral part B of a rectangular transparent substrate 1, laminated members (a), (b) composed of an amorphous semiconductor 3 of PIN junction are formed and constituted, respectively. The layer 3 is sandwiched by a transparent common electrode 2 and conducting films 4a, 4b for applying a bias voltage. When the light to be detected enters, the polarity of the bias voltage applied to the conducting films 4a, 4b is inverted. Thereby, the light quantity intensities of light flux of the central part A and the peripheral part B are independently and simultaneously measured, and a highly precise photosensor is realized. Further, the external circuit of an equipment to mount the photosensor also is simplified.

Description

DETAILED DESCRIPTION OF THE INVENTION [Background of the Invention] The present inventor first developed a laminated layer consisting of an amorphous semiconductor layer and a metal electrode that were P-1-N bonded on a transparent substrate coated with a transparent conductive film. He proposed an optical sensor composed of a plurality of bodies (Japanese Patent Application No. 331620/1983). That is, 8J has an amorphous semiconductor layer connected by P-I-N on a transparent substrate.
It had a structure in which three diodes were tied together in opposite directions.

FIGS. 5(a) and 5(b) are a sectional view and a plan view showing the structure of the optical sensor.

The transparent substrate 51 is made of glass, translucent ceramic, or the like, and a transparent conductive film 52 is adhered to the entire surface of the transparent substrate 51.

The transparent conductive film 52 is formed of a metal oxide film such as tin oxide, indium oxide, indium tin oxide, etc., and is made of a metal oxide film such as tin oxide, indium oxide, indium tin oxide, etc. is formed.

The amorphous semiconductor layer 53 has at least metal electrodes 54X, 5
P-I-
An N junction is formed.

The metal electrodes 54x, 54y are formed on the amorphous semiconductor layer 53 in a rectangular shape and spaced apart from each other by a predetermined distance.

Then, a constant bias voltage is applied between the metal electrodes 54x and 54y from an external circuit (not shown).

The optical sensor having the above-mentioned structure has a structure in which diodes, which are P-1-N junction laminated bodies x and y, are tied together.

Now, if a + bias voltage is applied to the metal electrode 54x of the laminate X and a - bias voltage is applied to the metal electrode 54y of the laminate y, the laminate
A reverse bias is applied to the y side of the stack, and a forward bias is applied to the y side of the stack.

The current due to the bias application is applied to the metal electrode 54x of the laminate X.
-N layer 53N-I layer 531-2 layer 53 of the amorphous semiconductor layer
P-transparent conductive film 52-two layers of amorphous semiconductor layer of stacked body y 53P-I layer 53I-N layer 53N-metal electrode 54y. That is, the resistance between the metal electrodes 54x and 54y is
is the sum of the reverse resistance of y and the forward resistance of laminate y, but in the bright state, a reverse photocurrent is generated in laminate X,
Since the stacked body y is forward biased, a change in the reverse photocurrent of the stacked body X acts as a resistance change of the optical sensor. Therefore, the resistance of the entire optical sensor is reduced by the apparent principal light irradiation, and it functions like a photoconductive sensor. This makes the illuminance-resistance value characteristic linear.

That is, in the bright state, among the stacked bodies x and y, only the stacked body X in the reverse bias direction contributes to the resistance change of the optical sensor, and the stacked body y is thick (does not contribute).

However, since the above-mentioned optical sensor has a structure in which diodes, which are P-I-N junctioned stacked bodies x and y, are tied together, both stacked bodies X and Y are stacked together.

Although it was possible to detect the intensity of the incident light that irradiated light onto y, the intensity distribution of the incident light could not be detected. For example, in the case of a camera's exposure light sensor, it can only detect the light flux (imaging light) introduced into the camera through the viewfinder, and when metering a subject in strong ambient light, the exposure will be affected by the strong ambient light. The subject was sometimes darkened.

[Object of the present invention]

The present invention was devised in view of the background of the above-mentioned optical sensor, and its purpose is to detect the central part of the incident light to be detected,
This provides a more accurate optical sensor that detects the amount and intensity of light at the peripheral edge.

[Specific means for solving the problem] According to the present invention, in order to achieve the above-mentioned object, two conductive films are formed on the amorphous semiconductor layer corresponding to the portion and the peripheral portion, and , there is provided an optical sensor characterized in that a bias voltage is applied between the two conductive legs, and the polarity of the bias voltage is reversed at the time of light detection.

[Effect]

By the above-mentioned means, the center portion and the peripheral portion of the substrate are separated.
Among the two stacked bodies, one stacked body that is reverse biased with respect to the bias voltage contributes to the resistance change of the optical sensor, and if the direction of application of the bias voltage, that is, the bias voltage is reversed, the other stacked body will contribute to the resistance change of the optical sensor. For this reason, one ME body is formed in the center of the substrate, and the other laminate is formed at the peripheral edge so as to surround the laminate, so that the bias voltage can be reversed when detection light is incident on the substrate. As a result, the intensity of the detection light at the center portion and the peripheral portion of the substrate can be detected using a single substrate.

〔Example〕

Hereinafter, the optical sensor of the present invention will be explained in detail based on the drawings.

FIGS. 1(a) and 1(b) are a cross-sectional structural diagram and a plan view showing the structure of an optical sensor according to the present invention.

In the optical sensor of the present invention, a transparent conductive film 2 is shared between a central portion A and a peripheral portion B of a rectangular transparent substrate 1, and a conductive film 4a to which a bias voltage is applied; Laminated bodies a and b each consisting of the amorphous semiconductor layer 3 of the P-I-N junction sandwiched by the amorphous semiconductor layer 4b are formed and configured.

Then, when the detection light is incident, the conductive film 4a.

This is to invert the polarity of the bias voltage applied to 4b.

The insulating substrate 1 is made of glass, translucent ceramic, etc.
A transparent conductive film 2, which is a first conductive film, is adhered to the whole surface of the insulating substrate 1.

The transparent conductive film 2, which is the first conductive film, is formed of a metal oxide film such as tin oxide, indium oxide, or indium tin oxide. It is formed to be a film common to the laminate of part B. Specifically, after a mask is attached to one main surface of the transparent substrate 1, the above-mentioned fully curved oxide film is deposited. After a metal oxide film is deposited on one main surface of the insulating substrate 1, it is formed into a predetermined shape by resist etching.

The amorphous semiconductor layer 3 has a first conductivity type, a second conductivity type, and a third conductivity type bonded, that is, P- An I-N junction is formed. Specifically, the amorphous semiconductor layer 3 is made of amorphous silicon or the like deposited by a plasma CVD method or a photo CVD method in which a silicon compound gas such as silane or disilane is decomposed by glow discharge. is formed with a reactive gas of silane gas mixed with a P-type doping gas such as diborane, the first layer 32 is formed with silane gas as a reactive gas, and the eighth layer 33 is formed with a reactive gas of silane gas mixed with an N-type doping gas such as phosphine. It is formed.

Note that the portions of the amorphous semiconductor layer 3 where the conductors 11!24a and 4b are not formed do not need to be in a P-I-N junction.

The conductive films 4a and 4b have a predetermined shape on the amorphous semiconductor layer 3.
They are formed at predetermined intervals, that is, the laminate a in the central portion A and the laminate in the peripheral portion B. Specifically, the conductive films 4a and 4b are formed by attaching a mask to the amorphous semiconductor layer 3 and then depositing metal such as nickel, aluminum, titanium, chromium, etc., or depositing nickel on the amorphous semiconductor layer 3. After depositing a metal film of aluminum, titanium, chromium, etc., a predetermined pattern is formed by resist etching, laser cutting with a YAG laser, or the like.

That is, as shown in FIG. 1(b), the conductive films 4a, 4b
The conductive film 4a to which a bias on the + side is applied is placed in the center part A of the substrate 1, and the conductive film 4b to which a bias is applied in the negative side is placed in the peripheral part B of the substrate 1 so as to surround the conductive film 4a. It is formed.

The optical sensor having the above-mentioned configuration has a structure in which diodes, which are a stacked body aXb connected to a P-I-N junction, are tied together.

Equivalently, between the conductive film 4a and the conductive film 4b, the resistance Ra of the laminate a and the resistance Rb of the laminate A are connected in series, and furthermore, the resistance Ra and the resistance Rb are connected in series. The resistance Rx in the amorphous semiconductor layer 3 between the laminate a and the laminate is connected in parallel to the resistance.

Then, when a + bias voltage is applied to the laminate a in the center part A of the substrate 1 and a negative bias voltage is applied to the laminate in the peripheral part B of the substrate l, the amorphous semiconductor layer 3 on the side of the laminate a has the opposite bias voltage. A forward bias is applied to the amorphous semiconductor layer on the side of the stack.

In the dark state, the bias current flowing between the conductive films 4a and 4b corresponds to the combined resistance value - of the reverse resistance Ra of the laminate a, the forward resistance Rb of the laminate A, and the resistance Rx.

In the bright state where light is irradiated from the insulating substrate 1 side of the above-mentioned photosensor, a photovoltaic force is generated in each of the laminate a and the laminate, but since the potentials are opposite to each other, unless the intensity of light irradiation is significantly different, Although this photovoltaic force is canceled out and almost no photocurrent flows, since a positive bias voltage is applied to the conductive film 4a and a negative bias voltage is applied to the conductive film 4b, a reverse photocurrent is generated in the laminated body a. Note that the laminated body serves as a resistor for the forward resistance of the diode. Then, the current due to the application of the bias voltage flows between the conductive film 4a of the laminate a - the 8 layers of the amorphous semiconductor layer 33 - 1 layer 32 - 2 layer 31 - the conductive film 2 - the amorphous semiconductor layer of the laminate. 2 layers 31-1. It flows from layer 32 to N layer 33 to conductive film 4b. Here, in order for the laminate to become equivalent to the forward resistance of a diode, a bias voltage higher than the open circuit voltage generated by the P-1-N junction amorphous semiconductor layer must be applied to the conductive films 4a and 4b. It is important to apply the voltage in between.

Therefore, in the optical sensor, the WFi body a functions like a photodiode due to the reverse photocurrent in the WFi body a generated by light irradiation on the central portion A of the substrate 1. This results in
The illuminance-bright current characteristic becomes linear, and the T value becomes approximately 1.

Furthermore, the polarity of the piezoelectric pressure applied to the conductive films 4a and 4b is reversed, that is, the polarity of the piezoelectric pressure applied to the conductive films 4a and 4b is
When a bias voltage of 10 is applied to the laminate in the peripheral portion B of the base @1, a forward bias is applied to the amorphous semiconductor layer 3 on the laminate a side, and a reverse bias is applied to the amorphous semiconductor layer 3 on the laminate side. The operation is completely opposite to the above-mentioned operation, and it functions like a photodiode as a photosensor due to the reverse direction photocurrent of the laminated body generated by the irradiation of the peripheral edge portion B of the substrate 1 with light.

As described above, according to the present invention, a voltage is applied between the conductive film 4a of the laminate a in the central portion A of the substrate and the conductive film 4b of the laminate in the peripheral portion B of the substrate 1 surrounding the laminate a. By inverting the polarity of the bias voltage, it is possible to easily detect the intensity of the detection light irradiated onto the substrate 1 at the central portion and the peripheral portion.

Note that the resistance Rx between the second conductive films 4a and 4b is determined by the resistance Rx between the second conductive films 4a and 4b, which
However, the resistance in the lateral direction (gap of 0.1 to several mm) of the amorphous semiconductor layer 3 between the second conductive films 4a and 4b is sufficiently larger than that in the thickness direction (thickness of about 1 to several μm). Therefore, unless a high bias voltage such as IOV or higher is applied, leakage current will not occur.

Next, an external circuit for effectively operating the optical sensor of the present invention will be explained based on FIG. 2.

The external circuit includes at least a bias voltage power supply 21, a stack a, a switching means 22 for reversing the polarity of the bias voltage applied to the stack, and a detection means for detecting the current flowing between the stacks a and b. 23, and an output means 24 for comparing the signal from the detection means 23 and the reference signal.

A bias voltage power supply 21 is constantly applied to the stacked bodies a and b through a switching means 22 while it is desired to detect the irradiated light.

The switching means 22 includes an oscillation means such as a multi-by-break, operates at least at the moment of light detection, and inverts the polarity of the bias voltage applied from the bias power supply 21 to the laminated bodies a and b.

The detection means 23 detects the bright current flowing through the laminated bodies a and b, and provides its output signal to the output means 24 for comparison processing.

The output means 24 compares the signal from the detection means 23 with an internally generated reference signal, and quantitatively measures the intensity of the irradiated light. Further, the output means 24 is supplied with an inversion operation signal from the switching means 22, and compares and processes the signal of the detection means 23 in synchronization with the inversion operation of the polarity of the bias voltage. As a result, the intensity of the light irradiating the laminate a in the central portion A of the substrate and the intensity of the light irradiating the laminate A in the peripheral portion B of the substrate 1 can be extracted without confusion.

Note that the external circuit shown in Figure 2 is just an example.
For example, a high-frequency power source that integrates the bias power source 21 and the switching means 22 may be used, a plurality of output means 24 may be installed and the output means 24 may be switched according to the reversal of the polarity of the bias voltage, or a microcomputer may be used to simplify the process. However, it is important to synchronize the operation of reversing the polarity of the bias voltage and the comparison process of the tongue care detection signal.

Furthermore, as shown in FIG. 3, corresponding to IJ bodies a and b,
Terminal portion 41a to which bias voltage is applied from an external circuit
, 41b are exposed. Specifically, an insulating resin paste is formed by adding a light-shielding pigment, a black colored pigment, etc. to a base material such as epoxy resin, acrylic resin, or phenol resin using a thick film method. Specifically, the bias voltage is applied to the laminate a in which the terminal portion 41a on the back surface of the substrate l is formed in the center portion A, and the bias voltage is applied to the laminate in which the terminal portion 41b is formed in the peripheral portion B. It becomes the terminal of And this terminal 4
Solder lead wires from the external circuit to 1a and 41b.

FIGS. 4(a) and 4(b) are a sectional view and a plan view of an embodiment further developed from FIG. 3.

In this embodiment, second conductive films 6a, 6b and a second insulating film 7 are further provided in the embodiment shown in FIG. As a result, an optical sensor that can be easily connected to external circuits and made into a chip component can be achieved.

The second conductive films 6a and 6b are formed in a predetermined pattern on the insulating film 5, and terminals 41 are exposed corresponding to the stacked bodies a and b.
It is formed into a predetermined shape so as to extend from a and 41b to the corner of the substrate 1. Specifically, it is desirable that a conductive paste containing a solderable metal such as nickel be formed by a thick film method such as screen printing. Another possibility is to form a metal such as nickel that can be soldered using a resistance heating method, but in order to make it into a chip component, a solder dip process is required. , 6b from being eaten by solder.

The second insulating film 7 is a laminate a, b formed of the insulating films 5.
The terminals 41a, 41b corresponding to the second conductive films 6a, 6
b extends to the corner of the board 1, but is this a terminal that actually connects to an external circuit? In order to form the insulating film 5 and the second conductive films 6a, 6 except for the terminals 7a, 7b,
formed on b.

Specifically, in consideration of the bonding strength between the insulating film 5 and the second conductive films 6a and 6b, and the heat resistance during solder dip processing, a thick film of insulating resin paste such as epoxy resin, acrylic resin, or phenol resin is used. Formed by method.

In addition, in FIG. 4(b), terminals 7a are provided at the corners of the board 1.

7b is formed, but there is also a terminal on only one end of the board 1? The patterns of the second conductive films 6a, 6b and the second insulating film 7 may be appropriately set depending on the connection conditions with the external circuit, such as concentrating the second conductive films 6a and 7b.

As in the above configuration, an electric current is applied between the conductive film 4a of the laminate a in the central portion A of the transparent substrate 1 and the conductive film 4b of the laminate in the peripheral portion B of the substrate 1 surrounding the laminate a. By inverting the polarity of the bias voltage, the central part and the peripheral part of the light beam irradiated onto the transparent substrate 1 can be measured independently and simultaneously, resulting in a more accurate optical sensor.

In addition, since the photodetection cells a and b have a structure in which a photodiode in the opposite direction and a photodiode in the forward direction are tied together, even if a high voltage is applied compared to a single photodiode, the amorphous semiconductor The P-I-N junction of the layers is not destroyed, and the resistance value changes linearly over a wide range of illuminance changes.

For example, when a bias voltage of 1 to 10 volts was applied to one photodetection cell, a good linear response was obtained with respect to the change in resistance value over a wide illuminance range of 0.1 to 100,000 Lx.

〔Effect of the invention〕

As described above, the present invention provides a photodetector comprising a P-I-N junction amorphous semiconductor layer that has a common transparent conductive film and is sandwiched between the transparent conductive film and two conductive films to which a bias voltage is applied. Since the cells are formed in the central part and the peripheral part of the transparent substrate, the central part of the light beam irradiated on the transparent substrate,
The light intensity and the peripheral edge can be measured independently and simultaneously, resulting in a more accurate optical sensor. This also simplifies the external circuitry of the device that mounts the optical sensor.

In addition, the amount of light detected at the center and at the periphery is performed over the entire surface of the substrate, improving the light-receiving area with respect to the substrate.

Furthermore, since one photodetection cell has a structure in which a reverse direction photodiode and a forward direction photodiode are tied together, even if a high voltage is applied, the amorphous semiconductor layer with P-I-N junction It is not destroyed, and a linear response with good resistance change over a wide range of illuminance changes is obtained, with a T value of about 1.

[Brief explanation of the drawing]

FIGS. 1(a) and 1(b) are a sectional view and a plan view of the non-light receiving surface side showing the structure of the optical sensor according to the present invention. FIG. 2 is a block circuit diagram of an external circuit for effectively operating the optical sensor of the present invention. FIG. 3 is a plan view of the non-light receiving surface side showing an advanced structure of the optical sensor of the present invention. FIGS. 4(a) and 4(b) are a sectional view and a plan view of the non-light-receiving surface side of an embodiment further developed from FIG. 3. FIGS. 5(a) and 5(b) are a cross-sectional view and a plan view showing the structure of a conventional photodiode-combined optical sensor. 1. Transparent substrate 2. ...Transparent conductive film 3...Amorphous semiconductor layers 4a, 4b...
...Conductive film 5...Insulating films a, b...Laminated body

Claims (1)

[Claims] A transparent conductive film and a P-I-N bonded amorphous semiconductor layer are formed on a transparent substrate, and two conductive films are further formed on the amorphous semiconductor layer corresponding to the center portion and peripheral portion of the substrate. An optical sensor characterized in that a bias voltage is applied between the two conductive films, and the polarity of the bias voltage is reversed at least when detecting light.