JPH0644641B2 - 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 detection electrodes is provided at the end of an n-type rectangular semiconductor substrate. Then, a p-type basic conductive layer having a uniform cross-sectional area and a uniform impurity concentration is formed in the center of the incident surface between them, and a plurality of p-type conductive layers are formed so as to extend from the basic conductive layer to the incident surface. A branch conductive layer is formed.

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 it is practically used for the conventional autofocus of a camera, for example, only a part of the incident surface is an effective incident area, and light or particle beam may not be incident on the other invalid incident areas. At this time, if a branched conductive layer is provided in the invalid incident region as in the conventional device, holes generated by thermal excitation flow into the basic conductive layer and become noise. Further, since the pn junction capacitance due to the branched conductive layer appears even in the invalid incident region, it becomes unsuitable for high-speed response. Furthermore, the photocurrent generated by the reflection of the lens (provided in front of the incident surface) that entered the invalid incident area, or the photocurrent generated by the light that entered the effective incident area and reached the invalid incident area. Occurs, which lowers the position detection accuracy.

Therefore, an object of the present invention is to provide a semiconductor device for detecting an incident position, in which the invalid incident region does not cause noise of the detection signal or lower the detection accuracy.

[Means for solving problems]

The incident position detecting semiconductor device according to the first invention of the present application is a semiconductor substrate of one conductivity type in which an incident surface including an effective incident region and an invalid incident region is set, and a positive electrode excited by incidence of light or particle beam. An electrode provided on the semiconductor substrate for collecting one of the hole-electron pairs, a pair of position signal electrodes provided at 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. A basic conductive layer formed on the semiconductor substrate so as to connect the position signal electrodes with high resistance, and a plurality of components containing impurities of opposite conductivity type formed so as to extend from the basic conductive layer to the effective incident area of the incident surface. And a branch conductive layer.

Further, the incident position detecting semiconductor device according to the second invention of the present application is excited by one-conductivity type semiconductor substrate having an incident surface including an effective incident region and an invalid incident region and incident by light or particle beam. An electrode provided on the semiconductor substrate for collecting one of the hole-electron pairs, and 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. Of the main conductive layer formed on the semiconductor substrate so as to connect the position signal electrodes with high resistance, and a plurality of impurities containing opposite conductivity types formed so as to extend from the main conductive layer to the effective incident region of the incident surface. It is characterized by comprising a branched conductive layer and a conductive shield film which is formed so as to cover the basic conductive layer via an insulating film and shields the basic conductive layer from the influence of charges of the surface protective layer.

Further, an incident position detecting semiconductor device according to a third invention of the present application is a semiconductor substrate of one conductivity type in which an incident surface including an effective incident region and an invalid incident region is set, and is excited by incidence of light or a particle beam. To collect one of the paired hole-electrons
The electrodes provided on the semiconductor substrate, the pair of position detection 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 to each other with high resistance to form a semiconductor. A basic conductive layer formed on the substrate, a plurality of branched conductive layers containing impurities of opposite conductivity type formed so as to extend from the basic conductive layer to the effective incident area of the incident surface, and a reactive incident area of the incident surface. And a carrier trap layer containing impurities of opposite conductivity type formed.

Further, the semiconductor device for incident position detection according to the fourth invention of the present application is a semiconductor substrate of one conductivity type in which an incident surface including an effective incident region and an invalid incident region is set, and is excited by incidence of light or particle beam. To collect one of the paired hole-electrons
The electrodes provided on the semiconductor substrate, the pair of position signal electrodes provided at 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 basic conductive layer formed on a semiconductor substrate, a plurality of branched conductive layers containing impurities of opposite conductivity type formed so as to extend from the basic conductive layer to an effective incident area of the incident surface, and an invalid incident area of the incident surface. And a light-shielding film formed so as to cover the.

Further, the semiconductor device for incident position detection according to the fifth invention of the present application is a semiconductor substrate of one conductivity type in which an incident surface including an effective incident region and an invalid incident region is set, and is excited by incidence of light or a particle beam. To collect one of the paired hole-electrons
The electrodes provided on the semiconductor substrate, the pair of position signal electrodes provided at 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 main conductive layer formed on the semiconductor substrate, a plurality of branched conductive layers containing impurities of opposite conductivity type formed so as to extend from the main conductive layer to the effective incident area of the incident surface, and invalid incident light of the incident surface. A light-shielding film formed so as to cover the region, and a conductive shield film formed so as to cover the core conductive layer via an insulating film and shielding the core conductive layer from the influence of the electric charge of the surface protective layer. Is characterized by.

[Action]

According to the first aspect of the invention, since the branched conductive layer does not exist in the invalid incident region, even if an electron / hole pair is generated here, the probability of flowing into the basic conductive layer is low. Further, the pn junction capacitance is also reduced because the branch conductive layer is not provided.

According to the second aspect of the invention, since the core conductive layer is covered with the shield film, the core conductive layer can be protected from the electric charge of the surface protective layer.

According to the third aspect of the present invention, since the carrier trapping layer having a conductivity type opposite to that of the substrate is provided in the invalid incident region, electron / hole pairs generated by thermal excitation or reflected light from the lens or the effective incident region. The electron-hole pairs that have been generated in 1 and have reached the invalid incident region are not captured and flow into the basic conductive layer. Further, when the carrier trapping layer is electrically short-circuited with the semiconductor substrate, these electrons and holes are recombined so that they do not become a noise component of the detection signal.

According to the fourth invention, since the light-shielding film is provided in the invalid incident area, even if there is reflected light from the lens,
No photocurrent is generated in the ineffective region.

According to the fifth aspect, since the light-shielding film is provided in the invalid incident area, even if there is reflected light from the lens,
No photocurrent is generated in the ineffective region, and since the core conductive layer is covered with the shield film, the core conductive layer can be protected from the charges of the surface protective layer.

〔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 the first embodiment. As shown in the figure, a pair of position signal electrodes 2a and 2b are provided at the end of the incident surface, which is the surface side of the semiconductor substrate 1, and the central conductive layer 3 is provided at the center of the incident surface between them.
Are formed. The branched conductive layers 4 are formed only in the effective incident region B so as to extend from the basic conductive layer 3 in the incident surface direction, but a plurality of branched conductive layers 4 are formed at equal intervals. Further, no branched conductive layer is formed in the invalid incident region C on the right half.

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 branched conductive layer 4 is formed to have a depth of about 1.0 μm, and in the effective incident region B excluding the invalid incident region C, the branched conductive layer 4 contains the same impurities as the trunk conductive layer 3 at a pitch of about 5 μm to 200 μm. It is formed to a depth of about 0.5 to 1 μm. Ohmic contact regions 6a and 6b are formed at the ends of the incident surface, and these are connected to the above-mentioned basic conductive layer 3. An insulating film 7 made of, for example, thermally oxidized SiO ₂ is formed on these, and ohmic contact regions 6a, 6 are formed.
An ohmic contact is made with the position signal electrodes 2a and 2b made of, for example, aluminum through the opening of the insulating film 7 on b. Then, a surface protection layer 8 made of, for example, an epoxy resin is applied and formed on these, and the wires 9a and 9b are connected to the position signal electrode 2 through openings (not shown).
Bonded to a and 2b. An ohmic contact layer 10 containing, for example, an n-type impurity is formed on the back surface side of the semiconductor substrate 1, and a back surface electrode 11 is provided in ohmic contact with this surface.

Next, the operation of the device of the first embodiment will be described.

For example, when an infrared spot is incident on the effective incident area B 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, when electron / hole pairs are generated in the semiconductor substrate 1, electrons flow toward the ohmic contact layer 10 and the back electrode 11 side, and 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 reciprocal of the resistance ratio from the inflow point to the position signal electrodes 2a and 2b.

Here, since the p-type branch conductive layer is not provided in the invalid incident region C, an electron / hole pair is generated here by thermal excitation or an electron / hole pair generated by reflection of a lens or the like. Alternatively, most of the electron / hole pairs generated in the effective incident region and reaching the invalid incident region are recombined in the invalid incident region C. Therefore, it is possible to prevent the detection accuracy from being lowered due to the noise included in the detection signal.

In addition, the semiconductor substrate 1, the core conductive layer 3 and the branched conductive layer 4
The total area of the pn junction due to can be reduced by the amount that the branch conductive layer is not formed in the invalid incident region C, so that the leak current can be suppressed. Further, since the pn junction capacitance is correspondingly reduced, it is suitable for high speed and high frequency detection.

Next, a second embodiment will be described with reference to FIG.

FIG. 3 is a plan view thereof, and a point different from that in FIG. 1 is that the carrier trapping layer 20 is formed in the invalid incident region. This carrier trapping layer 20 can be formed, for example, by implanting a p-type impurity through the opening of the mask when forming the basic conductive layer 3 and the branched conductive layer 4. The carrier trapping layer 20 is connected to a potential lower than that of the semiconductor substrate 1 or the external substrate 1 (not shown).

By doing so, the electron / hole pairs generated by thermal excitation or reflection of the lens, or the electron / hole pairs generated in the effective incident area and reaching the invalid incident area are respectively captured by the semiconductor substrate 1 and carrier trap. Pour into layer 20. Here, when the semiconductor substrate 1 and the carrier trapping layer 20 are short-circuited as described above, these electrons and holes are recombined, so that they do not become a noise component of the detection signal.

Next, a third embodiment will be described with reference to FIG.

FIG. 4 is a plan view thereof, and different from the first embodiment,
That is, the light shielding film 21 is provided in the invalid incident region. The light shielding film 21 is formed of a material that does not transmit light to be detected or particle beams, and when aluminum is used, for example, an insulating film is interposed between the light shielding film 21 and the semiconductor substrate 1. The carrier trapping layer 20 as shown in FIG. 3 may be provided below the light shielding film 21.

In this way, the incidence of light or particle beam on the invalid incident area is completely prevented. For example, when a lens is disposed on the front surface of the incident surface and used, even when the light reflected in the effective incident area is reflected again in the lens and returns to the invalid incident area, the effect is completely eliminated. It can be lost. Therefore, the incident position can be detected with extremely high accuracy. When the resistance value of the basic conductive layer 3 is affected by the light shielding film 21, the detection accuracy itself is lowered. Therefore, for example, the impurity concentration of the basic conductive layer 3 is 1 × 10 ¹³ cm 2.
^-3 or more is desirable.

Next, an example of an apparatus to which the second and third embodiments are applied will be described with reference to FIG.

FIG. 5 (a) is a plan view, and FIG. 5 (b) is its A-A.
It is a line sectional view. As shown in the figure, the p-type trunk conductive layer 3 is disposed at the lower end of the incident surface, and the branch conductive layer 4 extends in parallel only from the trunk conductive layer 3 to the effective incident region B. The semiconductor substrate 1 in the ineffective incident region C is provided with a p-type carrier trapping layer 20 formed in the same step as the basic conductive layer 3 and the branched conductive layer 4, and an insulating film 7 is interposed thereabove. A light shielding film 21 made of aluminum is formed. And
A contact electrode 23 is provided at an end of the carrier trapping layer 20 through an opening of the insulating film 7, and is short-circuited by making ohmic contact with each of the semiconductor substrate 1 and the carrier trapping layer 20. On the other hand, the position signal electrodes 2a, 2
b extends on the basic conductive layer 3 through the insulating film 7 to form a pair of shield films 22a and 22b.

Next, the operation of the device shown in FIG. 5 will be described.

When, for example, an infrared spot is incident on the effective incident region B, an electron / hole pair is generated in the semiconductor substrate 1, and only the hole flows into the branched conductive layer 4 and becomes a photocurrent. This photocurrent is resistance-divided by the basic conductive layer 3, and therefore the incident position of the infrared spot is detected.

At this time, a part of the incident infrared spot is reflected by the surface of the semiconductor substrate 1 in the effective incident area and the like, and is reflected again by the front objective lens and the like and returns to the invalid incident area C. However, the returned light is blocked by the light shielding film 21, and therefore, electron / hole pairs are not generated. If an antireflection film (not shown) is provided on the light shielding film 21, the reflected light of the light shielding film 21 will not return to the effective incident area B again via the objective lens.

Further, in the invalid incident region C of the semiconductor substrate 1, electron / hole pairs are generated by thermal excitation. However, since the holes flow into the carrier trapping layer 20 and recombine with the electrons in the semiconductor substrate 1 through the contact electrode 23, thermal noise can be significantly reduced. The carrier trapping layer 20 is the core conductive layer 3
Also, since it is not connected to the branched conductive layer 4, the pn junction capacitance is not increased.

Further, since the position signal electrodes 2a and 2b are made of aluminum and extend over the basic conductive layer 3 via the insulating film 7 to form the shield films 22a and 22b, the detection accuracy can be improved. That is, even when the surface protective layer 8 contains ions, the influence of this charge is due to the shield film 22a,
It is blocked by 22b and does not reach the basic conductive layer 3. Therefore, even if the impurity concentration is lowered in order to increase the resistance of the basic conductive layer 3, the effective cross-sectional area of the basic conductive layer 3 does not change and the resistance value does not change microscopically with time, so that the detection accuracy is improved. Can be expected.

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

For example, the shield films 22a and 22b are used as the position signal electrode 2
Instead of connecting to a and 2b, it may be opened or connected to an external potential through a separate electrode. Further, 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 distance between the branched conductive layers 4 may be different depending on the position on the incident surface, and in this case, the resolution can be used when the required resolution differs depending on the incident position. 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 first invention, since the branched conductive layer does not exist in the invalid incident region, even if an electron / hole pair is generated here, the probability of flowing into the basic conductive layer is low. Further, the pn junction capacitance is also reduced because the branch conductive layer is not provided. Therefore, the invalid incident area does not cause noise in the detection signal and does not deteriorate the detection accuracy.

In addition, in the second invention, the invalid incident region does not cause noise in the detection signal and does not reduce the detection sensitivity. In particular, since the core conductive layer is covered with the shield film, the core conductive layer can be protected from the electric charge of the surface protective layer.

Further, in the third invention, since the carrier trapping layer having a conductivity type opposite to that of the substrate is provided in the invalid incident region, even if an electron / hole pair is generated due to thermal excitation or reflected light from the lens,
These carriers are not captured and flow into the basic conductive layer.

Further, in the fourth aspect of the invention, since the light shielding film is provided in the invalid incident area, even if there is light reflected from the lens, no photocurrent is generated in the invalid area. For this reason,
The noise component included in the detection signal is reduced, and it becomes unnecessary to pay particular attention to the reflectance of the lens.

Further, in the fifth invention, even if there is light reflected from the lens, no photocurrent is generated in the ineffective region, and since the core conductive layer is covered with the shield film, the charge of the surface protective layer is changed to the core. The conductive layer can be protected.

[Brief description of drawings]

FIG. 1 is a plan view of a semiconductor device for detecting an incident position according to a first embodiment of the present invention, FIG. 2 is an enlarged view and a sectional view of FIG. 1, and FIGS. 3 and 4 are second and third views. FIG. 5 is a plan view of the embodiment, and FIG. 5 is a configuration diagram of an apparatus to which the second and third embodiments are applied. DESCRIPTION OF SYMBOLS 1 ... Semiconductor substrate, 2a, 2b ... Position signal electrode, 3 ... Basic conductive layer, 4 ... Branch conductive layer, 6a, 6b ... Ohmic contact region, 7 ... Insulating film, 8 ... Surface protective layer, 9a, 9b
... wire, 10 ... ohmic contact layer, 11 ... back electrode, 20 ... carrier trapping layer, 21 ... light-shielding film, 22a,
22b ... Shield layer, 23 ... Contact electrode.

Claims (6)

[Claims] 1. A semiconductor substrate of one conductivity type in which an incident surface including an effective incident area and an invalid incident area is set, and one of a hole electron pair excited by the incidence of light or a particle beam, for collecting one of The electrodes provided on the semiconductor substrate, the pair of position signal electrodes provided at 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. And a plurality of branched conductive layers containing impurities of opposite conductivity type formed so as to extend from the basic conductive layer to the effective incident area of the incident surface. A semiconductor device for detecting an incident position, characterized by: 2. A semiconductor substrate of one conductivity type in which an incident surface including an effective incident region and an invalid incident region is set, and one of a hole electron pair excited by the incidence of light or a particle beam, in order to collect one of the pairs. The electrodes provided on the semiconductor substrate, the pair of position signal electrodes provided at 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 trunk conductive layer formed on the semiconductor substrate, a plurality of branch conductive layers containing impurities of opposite conductivity type formed so as to extend from the trunk conductive layer to the effective incident area of the incident surface, and an insulating film Is formed so as to cover the basic conductive layer through
An incident position detecting semiconductor device, comprising: a conductive shield film that shields the core conductive layer from the influence of charges of the surface protective layer. 3. A semiconductor substrate of one conductivity type in which an incident surface including an effective incident area and an invalid incident area is set, and one of a hole-electron pair excited by the incidence of light or a particle beam, in order to collect one of the pairs. The electrodes provided on the semiconductor substrate, the pair of position signal electrodes provided at 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 trunk conductive layer formed on the semiconductor substrate, a plurality of branched conductive layers containing impurities of opposite conductivity type formed so as to extend from the trunk conductive layer to the effective incident region of the incident surface, and An incident position detecting semiconductor device, comprising: a carrier trapping layer containing an impurity of opposite conductivity type formed in an ineffective incident region of the surface. 4. The semiconductor device for incident position detection according to claim 3, wherein the carrier trapping layer is electrically short-circuited with the semiconductor substrate. 5. A semiconductor substrate of one conductivity type in which an incident surface including an effective incident area and an invalid incident area is set, and one of a hole electron pair excited by the incidence of light or a particle beam, for collecting one of the electron pairs. The electrodes provided on the semiconductor substrate, the pair of position signal electrodes provided at 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 trunk conductive layer formed on the semiconductor substrate, a plurality of branched conductive layers containing impurities of opposite conductivity type formed so as to extend from the trunk conductive layer to the effective incident region of the incident surface, and A light-shielding film formed so as to cover the invalid incident area of the surface. 6. A semiconductor substrate of one conductivity type in which an incident surface including an effective incident area and an invalid incident area is set, and one of a hole electron pair excited by the incidence of light or a particle beam, for collecting one of the pairs. The electrodes provided on the semiconductor substrate, the pair of position signal electrodes provided at 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 trunk conductive layer formed on the semiconductor substrate, a plurality of branched conductive layers containing impurities of opposite conductivity type formed so as to extend from the trunk conductive layer to the effective incident region of the incident surface, and A light-shielding film formed so as to cover the invalid incident area of the surface, and formed so as to cover the core conductive layer via an insulating film,
An incident position detecting semiconductor device, comprising: a conductive shield film that shields the core conductive layer from the influence of charges of the surface protective layer.