JPS5917288A - Semiconductor device for incident position detection - Google Patents

Abstract

PURPOSE:To enable to perform positional operation at a small optical input signal by a method wherein the titled device is constructed of a one conductive type semiconductor substrate, a pair of positional signal electrodes, the conductive layer of an incident face, a base conductive layer and an incident light volume signal electrode. CONSTITUTION:A first and a second positional signal electrodes 12, 13 are formed by forming P type conductive layers of high concentration doping boron from one face of the semiconductor substrate 11, and by evaporating aluminum on the surface thereof. A first and a second lead wires 14, 15 are connected to the respective positional signal electrodes 12, 13. A P type conductive layer 16 is formed on the incident face side of the semiconductor substrate 11. The P type conductive layer 16 thereof is constructed of a main trank part 16a to connect linearly the centers of the electrodes 12, 13, and branch parts 16b, 16c,... 16n of the plural number to cross perpendicularly the main trank part 16a. Phosphorus is doped to another face of the semiconductor substrate 11 to form the base conductive layer 17 of N type conductive layer of high concentration, gold is evaporated to the surface thereof to form the incident light volume signal electrode 18, and a third lead wire is connected thereto.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a semiconductor device for detecting an incident position that can output a current, etc. that includes information regarding the incident position of light or particle beam;
More specifically, the present invention relates to an incident position detection semiconductor device suitable for extracting one-dimensional information on the incident position of light or particle beams.

2. Description of the Related Art A semiconductor device for detecting an incident position that can output a current or the like that includes information regarding the incident position of light or a particle beam is known.

First, this semiconductor device for detecting an incident position will be briefly explained.

FIG. 1 is a plan view of a semiconductor device capable of outputting one-dimensional information on the incident position of light, etc., and FIG. 2 is a schematic cross-sectional view.

The semiconductor substrate 5 of this semiconductor device may be of any conductivity type.

A conductive layer 4 having a conductivity type different from that of the semiconductor substrate 5 is formed on one surface of the semiconductor substrate 5 (the upper surface in FIG. 2). This layer 4 has a uniform thickness so that the sheet resistance remains uniform. The surface of this entrance surface conductive layer 4 forms the light receiving surface 1 of this device.

Both ends 4a and 4b of the entrance surface conductive layer 4 are doped with impurities at a particularly high concentration, and metal layers 2a and 3a are formed on their respective upper surfaces.
is formed. These metal layers 2a, 3a and the portions doped with impurities at a high concentration are the first
A position signal electrode 2 and a second position signal electrode 3 are formed.

A bottom conductive layer 6 is formed on the bottom surface of the semiconductor substrate 5 by doping impurities of the same conductivity type as the semiconductor substrate 5 at a high concentration. A metal layer is provided on the surface of this bottom conductive layer 6, and an incident light amount signal electrode 7 is formed by this metal layer.

Lead wires 8a, 8b and 8c are connected to the first and second position signal electrodes 2.3 and the incident light amount signal electrode 7, respectively.

The operation of the semiconductor device with the above configuration is as follows.

First, a power supply is connected to apply an equal reverse bias voltage between the incident light amount signal electrode 7 and the first and second signal electrodes 2.3. In this state, when light is incident on any position on the light receiving surface l of the device, an electromotive force is generated at the PN junction formed by the substrate 5 and the conductive layer 4 near the point of incidence.

This electromotive force causes the light quantity electrode 7 to move from the first position signal electrode 2 to the first position signal electrode 2.
A photocurrent flows from the light quantity signal electrode 7 to the second position signal electrode 3 . If the polarity of the bias voltage is reversed, the current will flow in the opposite direction to the aforementioned direction. In any case, the first
The ratio of the magnitude of the current flowing through the position signal electrode 2 and the current flowing through the second position signal electrode 3 is determined by the electrical resistance of the layer 4 between the first position signal electrode 2 and the light incident point and the second position signal electrode 3. It is proportional to the reciprocal of the ratio of the electrical resistances of the incident surface conductive layer 4 between the light incident points. From this, the magnitude of the current flowing through the first position signal electrode 2 can be determined as 11. The magnitude of the current flowing through the second position signal electrode 3 is I2, and the first position signal electrode 2 is at the coordinates 1.
In one-dimensional coordinates with the second position signal electrode 3 as the coordinate -1, the incident point of the light is (II 12)/(II
+12) can be found by performing an analog calculation.

If the semiconductor device for detecting the incident position of the type described above is miniaturized and applied to a distance needle of a camera, etc., there is a problem that the resistance between the position signal electrodes becomes low and the semiconductor device cannot be used.

In the above application, under certain conditions the resistance between the position signal electrodes is 20
It is strongly required that the resistance be greater than 0Ω. The reason is as follows.

Thermal noise current of the semiconductor device is inversely proportional to the square root of the electrical resistance between the two position signal electrodes. That is, when the electrical resistance between the electrodes is small, the thermal noise current becomes large. Therefore, if the resistance between the electrodes is small, the photocurrent for weak incident light will be buried in thermal noise current, making it difficult to detect the position of the light incident point.

The output currents from the two position signal electrodes of the semiconductor device are typically amplified by separate operational amplifiers.

The input offset voltages of the two operational amplifiers do not exactly match. If the electrical resistance between the two position electrodes is small, a current will flow due to the difference between the two input offset voltages. When the incident light is weak and the photocurrent is small, 2
This current causes the ratio of the currents sent out by the two position electrodes to deviate greatly from the ratio of the currents due to the original incidence of light.

This problem will be further explained using an example of a semiconductor device for detecting an incident position using an N-type silicon semiconductor substrate, with a distance between two position signal electrodes of 2 mm, and a width of a light receiving surface of 1 mm.

A P-type conductive layer obtained by implanting boron ions into the N-type conductive silicon substrate reduces the electrical resistance to 200.
In order to make the resistance more than Ω, the amount of boron implanted must be less than 4×10/−. Therefore, the thickness of the conductor layer is 1 μm.
, the impurity concentration must be 4×10/et4. It is difficult to actually form a uniform, high-resistance layer using impurities at such a low concentration for the following reasons.

First, due to non-uniform impurity concentration in the substrate, a uniform electrical resistance layer cannot be obtained even if boron is uniformly implanted. For example, the impurity concentration of the substrate is 4×10/cn! 20% of that
When there is a variation in boron concentration, a variation of 1% occurs. This causes a 1% variation in electrical resistance. This variation in electrical resistance may cause an unsatisfactory result as a position signal, depending on the distribution on the light-receiving surface or the point of incidence of the light.

Next, since a non-uniform inversion layer is formed in the P-type groove conductive layer, a uniform electrical resistance layer cannot be obtained. That is, a silicon oxide layer is provided on the surface of the P-type conductive layer to protect the P-type groove conductive layer and to prevent reflection of incident light. At this time, if the impurity concentration of the P-type groove conductive layer is low,
An inversion layer is formed on the surface of the P-type groove conductive layer. Furthermore, when dirt adheres to the surface of the oxidized layer, an inversion layer corresponding to the pattern of the dirt is formed. This inversion layer acts as a layer with higher resistance among the layers with P-type groove conductivity, so that the non-uniformity of electrical resistance corresponding to the dirt pattern on the surface of the oxide layer results in the layer with P-type groove conductivity. It will occur inside.

An object of the present invention is to increase the resistance between two position signal electrodes without lowering the concentration of impurities of different conductivity formed on a semiconductor substrate, so that even when weak light is incident, the incident point of the light can be improved. An object of the present invention is to provide a semiconductor device for detecting an incident position, which is capable of detecting the position of an incident position.

In order to achieve the above object, a semiconductor device for detecting an incident position according to the present invention includes a semiconductor substrate of one conductivity type, and a pair of positions provided parallel to each other along the short side of a rectangular incident surface of the semiconductor substrate. a signal electrode and a conductive layer different from the conductive layer and having a uniform impurity concentration so as to divide the rectangular incident surface of the semiconductor substrate at equal intervals in a direction parallel to or perpendicular to the pair of position signal electrodes; an entrance surface conductive layer formed to have a narrow uniform width and connect the pair of position signal electrodes with high resistance; and a high concentration semiconductor substrate formed on a surface opposite to the rectangular entrance surface of the semiconductor substrate. It is composed of a bottom conductive layer of the same conductivity type as the bottom conductive layer, and an incident light amount signal electrode connected to the bottom conductive layer.

Note that according to the above configuration, a considerable portion of the entrance surface is not covered with the entrance surface conductive layer. However, if the interval between the entrance surface conductive layers is shorter than the diffusion length of the minority carriers, the minority carriers generated on the substrate due to the incidence of light will reach the entrance surface conductive layer, leaving the portions of the entrance surface conductive layer that are not covered. There is no problem at all in detecting light incident on the device. With this configuration, the resistance of the two position signal electrodes can be increased, and the object of the present invention can be completely achieved.

The semiconductor device for detecting an incident position according to the present invention will be described in more detail below with reference to the drawings.

FIG. 3 is a schematic plan view of a semiconductor device for detecting an incident position according to an embodiment of the present invention, and FIG. 4 is a schematic cross-sectional view. The semiconductor substrate 11 is an N-type semiconductor doped with 10/Cta of phosphorus as an impurity and has a thickness of about 250 μm. 1st and 2nd
The position signal electrodes 12 and 13 are formed by doping boron at 4 x 10/cta from one side of the semiconductor substrate 11 to form a highly concentrated P-type groove conductive layer, and coating the surface with aluminum at a concentration of 4 x 10/cta.
It is formed by vapor deposition to a thickness of 8 μm. Each position signal electrode 12
First and second lead wires 14, 15 are connected to and 13 by wire bonding.

A P-type conductive layer 16 is provided on the incident surface side of the semiconductor substrate 11.
form. This P-type conductive layer 16 is connected to the electrodes 12 and 1.
A core portion 16a linearly connecting the midpoints of 3 and a plurality of core portions 16b, 16c perpendicularly intersecting the core portion 16a.
...16n. The other surface (bottom surface) of the semiconductor substrate 11 is doped with phosphorus to form a bottom conductive layer 17 of a highly concentrated N-type groove conductive layer, and gold is deposited on the surface to form an incident light amount signal electrode 18. Then, the third lead wire is connected.

The width of the semiconductor substrate 11 is one square, and the distance between the two electrodes 12 and 13 is two squares. The width of the P-type groove conductor layer is 100 μm for both the core portion 16a and the core portions 16b, 16cm16n, and the interval between the adjacent core portions 16b, 16C, . . . , 16n is 100 μm.
μm, the length of the core portions 16b, 16c, --16n is 90
(This is given as lum.) The interval of 100 μm between the core portions is smaller than the diffusion length of minority carriers in the semiconductor substrate 11 of 300 μm.

When the electric resistance between the position signal electrode 13 and the electrode 14 of the above-mentioned embodiment device was measured, a high resistance of 250Ω was obtained.

When a conductive layer was formed on the entire incident surface of the semiconductor substrate 110 of this example device under the same conditions, the voltage between the electrodes could not exceed 50Ω.

As described above in detail, in the device according to the present invention, the resistance between the position signal electrodes can be increased, so position calculation can be performed using a small optical input signal, and a wide range of applications can be expected.

[Brief explanation of drawings]

FIG. 1 is a plan view of a semiconductor device capable of outputting one-dimensional information on the incident position of light, etc., and FIG. 2 is a schematic cross-sectional view. FIG. 3 is a plan view of an embodiment of the semiconductor device for detecting an incident position according to the present invention, and FIG. 4 is a schematic cross-sectional view. 2...First electrical signal electrodes 2a, 3a...Metal layer 3...Second electrical signal electrode 4...Incidence surface conductor layer 4a, 4b...Dose portion 5... Semiconductor substrate 6... Bottom conductor layer 7... Incident light amount signal electrode 11... Semiconductor substrate 12... First electrical signal electrode 13... Second electrical signal electrode 14. ...First lead wire 15...Second lead wire 16...Incidence surface conductive layer (P-type groove layer) 16a...Main conductive layer 16b, 16b to 16n...Branch groove Conductive layer 17...Bottom conductive layer (P-type groove conductive layer) 18...Light level signal electrode 19...Third lead wire procedural amendment form Commissioner of the Japan Patent Office Kazuo Wakasugi 1, Incident Display ■Total Patent Application No. 126242 of 1957 2, Name of the invention: Semiconductor device for detecting incident position 3, Relationship with the person making the amendment: Patent applicant 4, Contents of the amendment by the agent (Patent Application No. 126242, 1982) ( 11 Specification page 6 line 17 r4X10/cjJ is r4X10
6 (2) r 4 X 1 (1
/ctJJ is corrected to r 4 X 10'/c+(J. (3) [4×i
Correct 0/cnJ to r4X10'nd'. (4) “1” from page 9, line 16 to line 17 of the specification
0/ctJJ as “101ncJ”? 1st floor. (5) [4] from line 19 to line 20 on page 9 of the specification
Correct X10/Jl to r4X10'nd. that's all

Claims (1)

[Claims] +11 - A conductive type semiconductor substrate, a pair of position signal electrodes provided parallel to each other along the short side of a rectangular incident surface of the semiconductor substrate, and the pair of position signal electrodes. The conductive layer has a uniform impurity concentration and has a uniform impurity concentration such that the rectangular incident surface of the semiconductor substrate is divided at equal intervals in a direction parallel to or perpendicular to the pair of position signal electrodes. an entrance surface conductive layer of different conductivity types and formed to have a narrow and uniform width; and a highly concentrated bottom conductive layer of the same conductivity type as the semiconductor substrate formed on a surface opposite to the rectangular entrance surface of the semiconductor substrate. . A semiconductor device for detecting an incident position, comprising an incident light amount signal electrode connected to the bottom conductive layer. (2) The incident surface conductive layer is composed of a main conductive layer directly connecting the pair of position signal electrodes, and a plurality of branch conductive layers connected at right angles to the main conductive layer. The semiconductor device for detecting the incident position according to the scope 11. (3) A semiconductor device for detecting an incident position according to claim 1, wherein the width of the semiconductor substrate divided by the incident surface conductive layer is equal to or less than the mean free path of fractional carriers in the semiconductor substrate. .