JPS6146071B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention is useful for detecting the position of a laser beam spot in a semiconductor device, for example, where it is desired to arrange semiconductor elements such as photodiodes in close proximity on a common semiconductor substrate. Related to detection equipment.

For example, a semiconductor device as a detection device used for detecting the position of a laser beam spot includes, for example, four photodiodes 2 separated by a separation region 7 on a common semiconductor substrate 1, as shown in FIG. , when the laser beam spot is in the normal position, the center of the four photodiodes 2 is positioned diagonally to each other, as shown by the chain line b in FIG. The outputs of the two diodes 2 are summed, and the deviation of the beam spot b is detected from the difference between the summed outputs.

As shown in FIG. 1, such a semiconductor device has
For example, a semiconductor substrate 6 is prepared in which a silicon semiconductor layer 5 of the same conductivity type and higher resistivity is provided on an N-type silicon semiconductor layer 4 of low resistivity. A low resistivity isolation region 7 of the N type of the same conductivity type as the substrate 6, that is, a high impurity concentration, is provided in the depth of the entire thickness W of the layer 5 by selective diffusion, for example, in a cross pattern. A P-type high impurity concentration region 8 is provided in each portion of the semiconductor layer 5 separated by the isolation region 7 by selective diffusion, ion implantation, etc. so as to be separated from the high concentration isolation region 7. diodes 2 are constructed respectively. Reference numeral 9 represents an electrode ohmicly applied to each region 8, and 10 represents an anti-reflection film for the laser beam.

In the case of such a structure, the thickness W of the semiconductor layer 5 is determined to improve the electrical signal conversion efficiency of incident light.
a certain thickness, for example 6000 Å if this is silicon
For light with a wavelength of It becomes big because it is D2W. Moreover, due to problems such as withstand voltage, region 8 is
Since it is required to avoid contact with the high concentration separation region 7, the above-mentioned width D
In addition to this, there is also a required spacing l between regions 7 and 8, and the spacing between each element 2 must be at least D+2 l. And this interval l is the area 7 and 8
For example, distances are required that take into account mutual errors in the alignment of each exposure mask during photoetching for opening a window in a diffusion mask during selective diffusion of each impurity to form a mask. Therefore, with this configuration, the distance between the diodes 2 cannot be made sufficiently small, and the ineffective portion with respect to the beam spot becomes large, resulting in a small amount of detected signal. Furthermore, in the above-described configuration, if the width D of the isolation region 7 is made small, crosstalk between the diodes 2 becomes a problem.

In the present invention, these drawbacks are solved,
It is an object of the present invention to provide a semiconductor device that can sufficiently reduce the distance between semiconductor elements, that is, the distance between diodes, and can avoid crosstalk.

The present invention will be described in detail below with reference to FIGS. 2 and 3. For example, as described above, the present invention may be implemented by forming a plurality of diodes on a common semiconductor substrate to detect the position of a beam spot. An example of application to a semiconductor device will be explained together with an example of its manufacturing method to facilitate understanding.

In the present invention, as shown in FIG. 3, a semiconductor layer 11 having a low resistivity of one conductivity type, that is, a high impurity concentration, is formed on a semiconductor layer 11 of the same conductivity type and having a high impurity concentration, for example, an N-type silicon substrate. A first semiconductor layer 12 having a high specific resistance, for example an N-type silicon layer, is formed by epitaxial growth. Then, by, for example, selective diffusion, the first semiconductor layer 12 is made to have a depth that spans the entire thickness of the semiconductor layer 12, has the same conductivity type as the semiconductor layer 12, and has a sufficiently high conductivity compared to the first semiconductor layer 12. An isolation region 13 having an impurity concentration is formed in a cross pattern corresponding to, for example, the isolation region 7 explained in FIG. (only two are shown). Further, on this first semiconductor layer 12, a second semiconductor layer 14 having the same conductivity type and also having a low specific resistance,
For example, an N-type silicon layer is formed by epitaxial growth. Then, this second semiconductor layer 1
A relatively high concentration region 15 of another conductivity type, eg, P type, is formed on the entire surface of 4 by, eg, a diffusion method. Each thickness of each of the first and second semiconductor layers 12 and 16 of the semiconductor substrate 16 formed in this way
W ₁ and W ₂ are selected such that W ₁ >>W ₂ .

Then, as shown in FIG. 4, along the pattern of the isolation region 7, it is applied to the isolation region 7 across the entire thickness of the region 15 of the base body 16 and the second semiconductor layer 14 therebelow. A groove 17 is formed, for example, by etching, and the groove 17 divides the second semiconductor layer 14 and the region 15 into a plurality of portions 14a and 15a, respectively. Here, the separation trench 17 as a separation means for the second semiconductor layer 16 is
The width D ₂ of the separation groove 17 is selected to be as small as possible, and the width D ₁ of the separation area 13 is selected to be sufficiently large. Therefore, the tolerance for positioning the groove 17 with respect to the separation region 13 can be sufficiently large.

Then, on the surface of the base body 16 having the region 15,
For example, an anti-reflection film 18 having optical transparency and electrical insulation is coated on the inside of the separation groove 17 . Furthermore, 1
Reference numeral 9 designates one electrode of each diode element ohmicly adhered to each divided portion 15a of the region 15, which is an anode electrode in the illustrated example.

As described above, according to the device of the present invention, the regions 15 divided by the separating means, that is, the separating regions 13 and the separating grooves 17, and the regions 15a and 14a of the semiconductor layer 14 are formed on the common semiconductor substrate 16, respectively. For example, a plurality of 4
The semiconductor elements 20, ie, photodiodes, are formed separately.

According to the configuration of the present invention described above, each semiconductor element, in this example, the photodiode 20 is
Since the parts having the PN junctions j are separated by widthwise separating means, e.g. grooves 17, they are arranged sufficiently close to each other, so that the ineffective parts can be made small, for example as illustrated in FIG. In detecting the spot position of the laser beam, the signal amount can be made sufficiently large. Since the isolation region 13 does not directly affect the isolation of the PN junction j, that is, the setting of the spacing between the elements 20, its width D ₁ can be selected to be sufficiently large.
This avoids the possibility of crosstalk between the elements 20, and since the width D ₁ can be selected to be sufficiently large, the thickness W ₁ of the semiconductor layer 12 can also be selected to be sufficiently large. It can efficiently absorb the incident beam and convert it into an electrical signal.

In the example described above, the present invention is applied to a semiconductor device that detects the position of a laser beam in which four diodes are arranged, but it is possible to arrange a plurality of semiconductor elements close to each other on a common semiconductor substrate. The present invention can also be applied to various desired semiconductor devices.

[Brief explanation of the drawing]

FIG. 1 is a schematic enlarged plan view of a conventional semiconductor device, FIG. 2 is an enlarged cross-sectional view of the main part along line A-A, and FIGS. 3 and 4 are fabrication of an example of a semiconductor device according to the present invention. It is a process diagram. 16 is a semiconductor substrate; 12 and 14 are first and second semiconductor layers of the first conductivity type; 13 is an isolation region; 17 is an isolation trench; 15 is a region of a second conductivity type;
0 is a semiconductor element.

Claims (1)

[Claims] 1 A first semiconductor layer of a first conductivity type on a semiconductor substrate, and a second semiconductor layer of the same conductivity type formed thereon.
a semiconductor layer is provided, means is provided for separating the first and second semiconductor layers into a plurality of regions, the second semiconductor layer is separated by a smaller interval than the first semiconductor layer, and the second semiconductor layer is separated by a smaller interval than the first semiconductor layer; A semiconductor device comprising a second conductivity type region spaced apart from the separation means of the first semiconductor layer on the surface of the second semiconductor layer.