JPH0658975B2 - Incident position detection semiconductor device - Google Patents

Description

The present invention relates to an incident position detecting semiconductor device capable of outputting information about the incident position of light or a particle beam as a current or the like.

[Conventional technology]

Conventionally, as a technique in such a field, for example, Japanese Patent Laid-Open No.
There was a thing shown by 9-17288 gazette. In this conventional example, first, a pair of position signal electrodes are provided on both ends of an n-type rectangular semiconductor substrate. Then, in the center of the incident surface between them, p with a uniform cross-sectional area and a uniform impurity concentration is formed.
A p-type branched conductive layer is formed so as to extend from the basic conductive layer to the incident surface.

According to this conventional example, the charges generated on the incident surface by the incidence of light or particle beam are collected by the branched conductive layer and resistance-divided by the basic conductive layer. Here, since the basic conductive layer is formed thin, its resistance value is sufficiently high and can be set with high accuracy, and therefore the detection sensitivity can be improved.

[Problems to be solved by the invention]

However, this conventional example cannot be used for a rotation angle detector or a rotary encoder. A conventional rotary encoder or the like uses a rotating disk having slits formed along its circumference, and detects light passing through the slits with a pair of a light emitting element and a light receiving element. For this reason, it is difficult to miniaturize the device, and due to the dimensional limit of slit formation, the resolution remains within a fixed range.

Therefore, an object of the present invention is to provide a semiconductor device for detecting an incident position, which can be applied to a small angle detector having a high resolution and a small rotary encoder.

[Means for solving problems]

The semiconductor device for incident position detection according to the present invention is a semiconductor substrate of one conductivity type, and an electrode provided on the semiconductor substrate for collecting one of hole-electron pairs excited by incidence of light or particle beam, A pair of position signal electrodes provided on both ends of the incident surface of the semiconductor substrate for collecting the other of the hole-electron pairs, and a predetermined point on the semiconductor substrate so as to connect the pair of position signal electrodes with high resistance And a basic conductive layer formed along the circumference of a circle having a predetermined radius, and a plurality of components containing impurities of opposite conductivity type formed so as to extend in the radial direction of the circle from the basic conductive layer to the incident surface. And a branch conductive layer.

[Action]

According to the present invention, carriers generated by incidence of light or particle beams are collected in the branched conductive layer and flow into the backbone conductive layer,
The resistance is divided according to the ratio of the length of the basic conductive layer up to the position detection electrode. Therefore, it becomes possible to accurately detect the information about the rotation angle.

〔Example〕

Embodiments of the present invention will be described below with reference to FIGS. 1 to 5 of the accompanying drawings. In the description of the drawings, the same elements will be denoted by the same reference symbols, without redundant description.

FIG. 1 is a plan view of a semiconductor device for detecting an incident position according to this embodiment. As shown in the figure, a pair of position signal electrodes 2a and 2b are provided at both ends of the donut-shaped incident surface on the front surface side of the semiconductor substrate 1, and the core conductive layer 3 is provided at the outer end of the incident surface between them. Are formed. This basic conductive layer 3
Is along the circumference of a circle centered on the point P in the figure. The branched conductive layers 4 are formed in the radial direction so as to extend from the basic conductive layer 3 in the direction of the incident surface, and the branched conductive layers 4 are arranged at equal angular intervals.

The detailed configuration of the apparatus of the above embodiment will be described with reference to the plan view of FIG. 2 and the sectional view taken along the line AA.

For example, 1 × 10 ¹³ to 1 × 10 ¹⁴ is provided on the front surface side of the semiconductor substrate 1 made of n-type silicon having each side of 1 to 50 mm.
The backbone conductive layer 3 in which a p-type impurity is implanted to about cm ⁻³ is formed in a ring shape, and the branched conductive layer 4 is formed by 5 in the same process.
It is formed with a pitch of about μm and a depth of about 0.5 to 1 μm. The ohmic contact regions 6 in which p-type impurities are incident at about 1 × 10 ¹⁸ to 10 ¹⁹ cm ⁻³ at both ends of the incident surface.
a and 6b are formed, and these are connected to the above-mentioned basic conductive layer 3. On these, for example, thermally oxidized SiO ₂
Is formed, and ohmic contact is made with the position signal electrodes 2a and 2b made of, for example, aluminum through the openings of the insulating film 7 on the ohmic contact regions 6a and 6b. A surface protective layer 8 made of, for example, an epoxy resin is applied and formed on these, and wires (not shown) are bonded to the position signal electrodes 2a and 2b through the openings (not shown). On the back surface side of the semiconductor substrate 1, for example, 1 × 10 ¹⁹ to 10 ²⁰ cm
Ohmic contact layer 10 containing about ⁻³ n-type impurities
Is formed, and the back surface electrode 11 is provided on this surface in ohmic contact.

Next, the operation of the apparatus of the above embodiment will be described.

For example, when an infrared spot is incident from the front surface side, it passes through the surface protective layer 8 and the insulating film 7 and reaches the incident surface of the semiconductor substrate 1. As a result, the semiconductor substrate 1
When a hole pair is generated, the electron is in ohmic contact layer 1
0 and the back electrode 11 side, and the holes flow into the p-type branched conductive layer 4. Then, the photocurrent due to the holes flows through the branch conductive layer 4 into the basic conductive layer 3 and is divided by the resistance ratio according to the ratio of the distance (angle) from the inflow point to the position signal electrodes 2a and 2b. It Therefore, this semiconductor substrate 1
If a spot light is made incident on this incident surface by attaching the to the object to be measured, a signal according to the rotation angle is generated by the position signal electrodes 2a and 2a.
It will be obtained from b.

Next, a modification of this embodiment will be described with reference to FIG.

In FIG. 1A, the size of the semiconductor substrate 1 is halved,
In this example, an angle of 0 ° can be detected. With this configuration, the device can be installed on the object to be measured that does not rotate 180 ° or more, and thus can be used for an inclination sensor or the like.

In the same figure (b), the branch conductive layer 4 is applied to the part where the spot light does not reach.
This is an example in which is not provided. In this way, the semiconductor substrate 1, the backbone conductive layer 3 and the branched conductive layer 4 have p
Since the total area of the n-junction can be reduced, the leak current can be suppressed and the sensitivity can be improved. Further, since the pn junction capacitance is reduced, it is suitable for high speed and high frequency detection.

Next, another modification will be described with reference to FIGS. 4 and 5.

FIG. 4 is a plan view thereof, and FIG. 5 is an enlarged view thereof and a sectional view taken along line BB and CC. As shown in the figure, the basic conductive layer 3 is provided on the outer end of the incident surface, and the shield films 5a, 5b are integrally formed on the basic conductive layer 3 and the position signal electrodes 2a, 2b.
b is provided. The shield films 5a and 5b need to have conductivity, and are separated at the central portion. The effective incident area where the branched conductive layer 4 is formed is only in the left half of the incident surface, and spot light is not incident on the other invalid incident areas. Therefore, in this example, the p-type carrier trapping layer 20a is formed on the semiconductor substrate 1 in the invalid incident region, and the light shielding film 21b made of, for example, aluminum is further formed thereon. On the other hand, the carrier trapping layer 20 a and the light-shielding film 2 are also provided outside the basic conductive layer 3.
1a is formed, and the carrier trapping layer 20a and the carrier trapping layer 20b are short-circuited to the semiconductor substrate 1 by the contact electrodes 22a and 22b.

FIG. 5 (a) is an enlarged plan view of the vicinity of the position signal electrodes 2a, 2b of FIG. 4, and FIGS. 5 (b), (c) respectively show B-.
It is a B line and CC sectional view. As shown in the figure, the shield films 5a and 5b, the carrier trapping layers 20a and 20b, and the light shielding films 21a and 21b are laminated via the insulating film 7, respectively. Then, the semiconductor substrate 1 and the carrier trapping layers 20a and 20b are short-circuited by the contact electrodes 22a and 22b through the opening of the insulating film 7. Further, a surface protection layer 8 made of epoxy resin or the like is laminated on the uppermost part.

Next, the operation of the above modification will be described.

The holes generated by the spot light incident on the effective incident area are collected by the branched conductive layer 4 and flow into the backbone conductive layer 3. Therefore, the photocurrent is divided by the resistance ratio according to the angle of the inflow point.

On the other hand, electron / hole pairs are also generated in the semiconductor substrate 1 other than the effective incident region due to thermal excitation or the like. However,
The holes due to this thermal excitation are carrier trapping layers 20a and 20b.
Are captured by the semiconductor substrate 1 and flow into the semiconductor substrate 1 through the contact electrodes 22a and 22b. Then, similarly, electrons generated by thermal excitation and holes that have flowed in are recombined, and as a result, carriers do not exist. Therefore, so-called thermal noise can be significantly reduced.

Further, the light-shielding films 21a, 21
Since b is provided, all light incident on it can be eliminated. Therefore, also in this respect, the noise component can be significantly reduced.

Further, since the shield films 5a and 5b are provided on the basic conductive layer 3 with the insulating film 7 interposed therebetween, the influence of the charges contained in the surface protective layer 8 can be eliminated. Specifically, the epoxy resin or the like that constitutes the surface protective layer 8 often contains sodium ions (Na ⁺ ), and the presence of this causes the effective cross-sectional area of the core conductive layer 3 to change. This variation of the cross-sectional area becomes more remarkable as the impurity concentration of the basic conductive layer 3 is lowered in order to increase the resistance of the basic conductive layer 3 and improve the detection accuracy. However, in the above example, the basic conductive layer 3 is shielded by the conductive shield films 5a and 5b, so that the above inconvenience does not occur.

Next, another example having the same principle as the present invention will be described with reference to FIG.

FIG. 6 (a) is a plan view thereof, and FIG. 6 (b) is BB.
It is a line sectional view. As illustrated, seven conductive layers 31 to 37 are formed on the semiconductor substrate 1. These conductive layers 3
Nos. 1 to 37 have the same conductivity type impurity concentration at the same concentration, and the thickness thereof gradually decreases toward the inside. Therefore, the resistances between both ends of the conductive layers 31 to 37 are the same.

According to this example, the holes generated by the incidence of the spot light flow into the p-type conductive layers 31 to 37 and are divided into the position signal electrodes 2a and 2b at a resistance ratio according to the angle of the inflow point. Therefore, it can be used as an angle sensor, an inclination sensor, or the like.

The present invention is not limited to the above-mentioned embodiments and modified examples, and various modes are possible.

For example, the shield films 5a and 5b are used as the position signal electrodes 2a and 2b.
Instead of connecting to b, it may be connected to the semiconductor substrate 1 or may be connected to an external ground via a separate electrode. In addition, the material concentrations of the semiconductor substrate 1 and the like, and the impurity concentrations of the basic conductive layer 3 and the branched conductive layer 4 are not limited to those illustrated. Further, the basic conductive layer 3 can also be realized by depositing polysilicon on the surface of the semiconductor substrate 1 or forming a metal thin film of SnO ₂ or the like. Then, if the branch conductive layer 4 is connected to the basic conductive layer 3 formed of the polysilicon film or the metal thin film, the photocurrent is resistance-divided as in the embodiment. Also, the use of polysilicon or a metal thin film in this way is the same as in FIG.

〔The invention's effect〕

As described above in detail, in the present invention, carriers generated by the incidence of light or particle beam are collected in the branched conductive layer and flow into the basic conductive layer, and the ratio of the length of the basic conductive layer to the position detection electrode is compared. It is divided according to the resistance. Therefore, it becomes possible to accurately detect the information about the rotation angle,
It can be applied to a small angle detector with high resolution and a small rotary encoder.

[Brief description of drawings]

FIG. 1 is a plan view of a semiconductor device for detecting an incident position according to an embodiment of the present invention, FIG. 2 is an enlarged view and a sectional view of FIG. 1, FIG. 3 is a plan view of a modified example, and FIG. A plan view of a modified example of
FIG. 5 is an enlarged view and a sectional view thereof, and FIG. 6 is a plan view and a sectional view of another example having the same principle as the present invention. DESCRIPTION OF SYMBOLS 1 ... Semiconductor substrate, 2a, 2b ... Position signal electrode, 3 ... Basic conductive layer, 4 ... Branched conductive layer, 5a, 5b ... Shield film,
6a, 6b ... Ohmic contact region, 7 ... Insulating film,
8 ... Surface protective layer, 10 ... Ohmic contact layer, 11
... Backside electrodes, 20a, 20b ... Carrier trapping layer, 21
a, 21b ... Shading film, 22a, 22b ... Contact electrodes, 31-37 ... Conductive layer.

Claims (2)

[Claims] 1. A semiconductor substrate of one conductivity type and one of a hole electron pair excited by the incidence of light or a particle beam,
The electrodes provided on the semiconductor substrate, a pair of position signal electrodes provided on both ends of the incident surface of the semiconductor substrate for collecting the other of the hole-electron pairs, and the pair of position signal electrodes are connected with high resistance. As described above, a basic conductive layer formed along the circumference of a circle having a predetermined radius centered on a predetermined point on the semiconductor substrate, and extending from the basic conductive layer to the incident surface in the radial direction of the circle. And a plurality of branch conductive layers containing impurities of opposite conductivity type formed as described above. 2. The semiconductor device for incident position detection according to claim 1, wherein the incident surface includes an effective incident region and an invalid incident region, and the branched conductive layer is provided only in the effective incident region. .