JPH0644640B2 - 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, when this conventional example is put into practical use, since the incident surface where the branched conductive layer exists is rectangular, the area that is not used as the detection area is also included in the incident surface, and thermal excitation etc. It was easy for noise to appear. Further, when mounting a light emitting element such as a laser diode, the incident surface (semiconductor substrate) in an unused area is an obstacle.

Therefore, an object of the present invention is to provide a semiconductor device for incident position detection, which can be widely applied to various uses.

[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 to collect the other of the hole-electron pairs, and a basic conductive layer formed on the semiconductor substrate so as to connect the pair of position signal electrodes with high resistance. And a plurality of branch conductive layers containing impurities of opposite conductivity type formed so as to extend from the basic conductive layer to the incident surface, and at least one of the plurality of branch conductive layers is the other branch conductive layer. Characterized by different lengths from at least one of the layers.

[Action]

According to the present invention, since the incident surface on which the branched conductive layer is present can have various shapes, it is possible to provide a notch or the like on the semiconductor substrate, and it is possible to apply to various uses.

〔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 an incident position detecting semiconductor device according to an embodiment. As shown in the figure, a pair of position signal electrodes 2a and 2b are provided at both ends of the short side of the incident surface, which is the front side of the semiconductor substrate 1.
Are provided, and the basic conductive layer 3 is formed in the center of the incident surface between them. The branch conductive layers 4 are formed from the basic conductive layer 3 so as to extend in the direction of the incident surface. The central conductive layer 3 has a shorter length in the central portion, and a cutout 20 is formed in the semiconductor substrate 1 in that portion.

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 10 ¹⁴ cm ⁻³ 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 basic conductive layer 3 in which p-type impurities are implanted to a degree of 0.5 to
The branch conductive layers 4 are formed to a depth of about 1.0 μm, and the branched conductive layers 4 are formed at a pitch of about 5 μm by 0.5 to 1.0 μm by the same process.
It is formed to a certain depth. 1 × 10 on both sides of the entrance surface
Ohmic contact regions 6a and 6b in which a p-type impurity is implanted are formed at about ¹⁸ to 10 ¹⁹ cm ^-3 , and these are connected to the above-mentioned basic conductive layer 3. Above these are
The insulating film 7 made of, for example, thermally oxidized SiO ₂ is formed, and the position signal electrode 2 made of, for example, aluminum is formed through the opening of the insulating film 7 on the ohmic contact regions 6a and 6b.
Ohmic contact with a and 2b is made. And
A surface protection layer 8 made of, for example, an epoxy resin is applied and formed on these, and wires 9a and 9b are bonded to the position signal electrodes 2a and 2b through openings (not shown). On the back side of the semiconductor substrate 1, for example, 1 × 1
An ohmic contact layer 10 containing an n-type impurity of about 0 ¹⁹ to 10 ²⁰ cm ⁻³ is formed, and a 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 from the inflow point to the position signal electrodes 2a and 2b.

Here, the length of the branched conductive layer 4 is short in the upper center portion of the incident surface, and the notch 20 is formed therein. Therefore, since a laser diode or the like can be attached here, the emission optical axis from the light source to the DUT (not shown) and the incident optical axis from the DUT to the incident surface can be close to each other. As a result, for example, when the apparatus of FIG. 1 is used for the tilt sensor, even if the distance between the object to be measured and the sensor changes, this can reduce the error given to the tilt detection result.

Next, a modified example will be described with reference to FIG.

FIG. 6A shows an example in which the branch conductive layer 4 is not provided in a portion that is not exposed to the spot light. By doing so, the total area of the pn junction formed by the semiconductor substrate 1, the backbone conductive layer 3 and the branched conductive layer 4 can be reduced, so that the leak current can be suppressed and the sensitivity can be improved. Further, since the pn junction capacitance is correspondingly reduced, it is suitable for high speed and high frequency detection. Note that the semiconductor substrate 1 may be cut off at a portion where the branched conductive layer 4 is not provided.

FIG. 3B is an example in which the basic conductive layer 3 is provided at the lower end of the incident surface in the semiconductor device for incident position detection of FIG. Further, FIG. 3C is an example in which the opening 21 is provided in the semiconductor substrate 1 in the central portion of the incident surface. By these,
Since a light source such as a laser diode is provided in the cutout 20 or the opening 21, the same effect as that of FIG. 1 can be obtained.

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

FIG. 4 is a plan view showing the overall structure. As shown in the figure, the basic conductive layer 3 is provided at the lower end of the incident surface, and the shield films 5a and 5b made of, for example, aluminum are provided thereon. This shield film 5a, 5
b is required to have conductivity, and is formed integrally with the position signal electrodes 2a and 2b, respectively, and is separated at the central portion. The branched conductive layer 4 is gradually shortened from the leftmost one in the drawing toward the right side, and an ineffective incident region that is not used as an effective incident surface exists in the upper part thereof. Then, the p-type carrier trapping layer 2 is formed in the invalid incident region.
2 is provided, and the carrier trapping layer 22 is in ohmic contact with the semiconductor substrate 1 by the contact electrode 23.

FIG. 5 is an enlarged view of FIG. 4 and a sectional view taken along the line AA.
As shown in the drawing, shield films 5a and 5b are integrally formed with the position signal electrodes 2a and 2b on the basic conductive layer 3 with an insulating film 7 interposed therebetween. Further, the carrier trapping layer 22 in the invalid incident region is formed by containing the same impurities and the same concentration as the main conductive layer 3 and the branched conductive layer 4.

Next, the operation of the device shown in FIGS. 4 and 5 will be described.

For example, when an electron / hole pair is generated by incidence of infrared rays, only holes are collected in the branched conductive layer 4 and the basic conductive layer 3
Flow into. Thereby, the photocurrent is resistance-divided according to the ratio of the distances from both ends of the basic conductive layer 3, and the position is detected. At this time, the core conductive layer 3 has the shield films 5a and 5b.
Since it is covered with, the influence of the electric charge (for example, sodium ion) of the surface protection layer 8 does not appear in the basic conductive layer 3, and therefore the basic conductive layer 3 can be made to have a high resistance and highly accurate measurement can be performed. .

Further, when infrared light is incident on the invalid incident region or when electron / hole pairs are generated by thermal excitation, holes are captured by the carrier capture layer 22. Here, since the carrier trapping layer 22 is short-circuited to the semiconductor substrate 1 by the contact electrode 23, holes in the carrier trapping layer 22 flow into the semiconductor substrate 1 and recombine with electrons. Therefore, these do not become noise components.

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

For example, the shield films 5a and 5b are used as the position signal electrodes 2a and 2b.
It may be connected to the semiconductor substrate 1 without being in contact with b, or may be connected to an external earth 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.

〔The invention's effect〕

As described above in detail, in the present invention, since the incident surface on which the branched conductive layer is present can have various shapes, it is possible to provide a notch or the like in the semiconductor substrate, so that it can be widely applied to various applications. There is an effect that can be.

[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 of another modification of FIG. 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, 9a, 9b ...... Wire, 10 ...... Ohmic contact layer, 11 ...... Back electrode, 20 ...... Notch, 21 ...... Open hole, 22 ...... Carrier trapping layer 22.

Claims (1)

[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. A plurality of branched conductive layers containing impurities of opposite conductivity type formed so as to extend from the basic conductive layer to the incident surface, and the plurality of branch conductive layers formed on the semiconductor substrate. At least one of the branched conductive layers
One is a semiconductor device for detecting an incident position, which is different in length from at least one of the other branched conductive layers.