JPS622575A - Semiconductor photo detector - Google Patents

Abstract

PURPOSE:To improve the photo detecting efficiency and the frequency characteristics by forming a plurality of impurity introduced regions on a low impurity concentration semiconductor substrate so that they are adjacent to each other at widths narrower than the depletion layer width which is provided by the voltage used, and applying a voltage only to one impurity region. CONSTITUTION:On an N<+> type high impurity concentration semiconductor substrate 11, a low impurity concentration semiconductor substrate 12 and a P-type impurity introducing region 13 are formed, and the impurity introducing region 13 (photo detecting surface) is divided by distance D1. On the outer peripheral portion of the photo detecting surface, an optical shield film 16 is formed so as to be spaced apart by distance D2 in order that part of the lower impurity concentration semiconductor substrate 12 is exposed on the surface, and an external taking-out lead bonding pad 14 is formed on one P-type impurity introduced region 13. The width D1 between the opposed sides 17 and 18 of the divided P-type impurity introduced regions 13, and the width D2 between the outer sides 19, 20 and the sides 21, 22 of the optical shield film 16 are made less than the depletion layer width which is determined by the voltage used. With this, the junction capacitance is decreased, the photo detecting efficiency is enhanced, and the frequency response characteristics are improved.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to a semiconductor photodetector, and particularly to a photodiode with good light receiving efficiency and frequency response characteristics.

(Prior Art) Conventionally, in a semiconductor device, such as a photodiode, an impurity doped region of a conductivity type opposite to that of a semiconductor substrate is formed over the entire surface of a light receiving portion.

This type of semiconductor photodetection device will be explained with reference to the drawings.

FIG. 3 is a plan view of such a conventional semiconductor photodetecting device, and FIG. 4 is a cross-sectional view taken along the line Vl-VI' in FIG. In these figures, l is a high impurity concentration semiconductor substrate, 2 is a low impurity concentration semiconductor substrate, 3 is an impurity-introduced region of the opposite conductivity type to the semiconductor substrate, 4 is an external lead bonding pad formed of AI or the like, 5 is an insulating film.

As is clear from the figure, if a reverse bias is applied to the PN junction between the impurity-introduced region 3 and the semiconductor substrate and light is applied to the junction surface, a current can be obtained, so light can be emitted. I can do it.

(Problems to be Solved by the Invention) This type of diode has a large impurity-introduced region 3 having a conductivity type opposite to that of the semiconductor substrate. The light-receiving efficiency can be increased because the carriers are collected. However, when the PN junction area becomes large, the junction capacitance increases and the frequency characteristics deteriorate.

An object of the present invention is to eliminate the above-mentioned problems and provide a semiconductor photodetector device with excellent light receiving efficiency and frequency characteristics.

(Means for Solving the Problems) In order to solve the above problems, the present invention introduces a plurality of impurities into a low impurity concentration semiconductor substrate so as to be adjacent to each other with a width narrower than the width of the depletion layer generated at the operating voltage. The impurity regions are formed adjacent to each other by a depletion layer region generated each time a voltage is applied to only one impurity region thus formed. The impurity introduced regions are connected.

(Function) According to the present invention, by using the above means, it is possible to eliminate the influence of junction capacitance generated in the impurity-introduced region to which no voltage is applied, without reducing the effective light-receiving area.

(Example) Hereinafter, an example of the present invention will be described in detail with reference to the drawings.

FIG. 1 is a cross-sectional view (second
FIG. 2 is a plan view of the semiconductor photodetecting device.

In these figures, 11 is a high impurity concentration semiconductor substrate;
12 is a low impurity concentration semiconductor substrate; 13 is an impurity-introduced region having a conductivity type opposite to that of the semiconductor substrate; 14 is an external lead bonding pad formed of AI or the like; 15
is an insulating film. Furthermore, 16 is a light shielding film formed by β etc., 17, 18, 19, 20 is a side surface of the impurity introduced region 13, 21.22 is a side surface of the light shielding film 16, and DI is an adjacent impurity introduced region 13. Opposing sides 17 and 18
D2 is the distance between side surfaces 19 and 2 of the impurity introduced region.
0 and the side surfaces 21 and 22 of the light shielding film 16.

In addition, in this embodiment, the high impurity concentration semiconductor substrate 11 is n-type, the low impurity concentration semiconductor substrate 12 is n-type,
The impurity introduced region 3 is of P type.

The n-type low impurity concentration semiconductor substrate 12 is an epitaxially grown layer with a thickness of about 15 μm and a resistance value of about 1000 cm to 200 Ω(2). The depth of the P-type impurity introduced region 13 is approximately 2 μm. Light receiving surface is low impurity 1 semiconductor substrate 1
2, the impurity-introduced region (light-receiving surface) is divided by a distance #D1, and the sum of the areas of the divided light-receiving surfaces is:
It was set to be the same as that of 0°3 finφ. The outer peripheral portion of the light-receiving surface is spaced apart by a distance D2 so that a part of the low-temperature impurity semiconductor substrate 12 is exposed on the surface, and a light shielding film 16 is formed of A1 or the like. The thickness of the light shielding film 16 was 1.5 μm. The relationship between the impurity introduced region 13 and the exposed region of the low impurity concentration semiconductor substrate 12 is such that the exposed region is at a distance that is equal to or slightly smaller than the depletion layer width at any point on the side surface of the impurity introduced region 13. When the external lead bonding pad 14 is formed on the insulating film 15 on the n-type low impurity concentration semiconductor substrate 12, MO3 capacitance is generated between the n-type low impurity concentration semiconductor substrate 12 and the insulating film 15.
In order to prevent O3 capacitance, it is formed on the P-type impurity introduced region and has a structure without wiring. In this example, the width D 1 between the opposing side surfaces 17 and 18 of the divided P-type impurity doped region 13, and the width D2 between the outer surfaces I9 and 20 of the El region 13 and the side surfaces 21 and 22 of the light shielding film I6. It is also necessary to appropriately select the thickness of the n-type low impurity semiconductor substrate 12. If the above-mentioned widths DI and D2 are carrier diffusion distances, the junction capacitance of only one region to which a voltage is applied is dominant among the P-type impurity introduced regions that are divided into two in a part of the n-type low impurity concentration substrate 12. Therefore, the influence of the junction capacitance in the other region disappears, and the junction capacitance becomes small, but it is affected by the minority carriers generated in the carrier diffusion region, and the frequency response deteriorates. Therefore, in order to improve the frequency response characteristics, the width DI
and D2 need to be the depletion layer width or slightly smaller than it. In this example the widths D1 and D2 are 10μ
It was set as m.

Moreover, by using the n-type low impurity concentration semiconductor substrate 12, the depletion layer region becomes large, and the light receiving efficiency can be improved.

With this configuration, (1) the junction capacitance could be reduced by about 35% compared to the conventional semiconductor photodetector shown in FIGS. 3 and 4.

Furthermore, when receiving infrared light, the light receiving efficiency (light receiving sensitivity) can be improved by about 30% compared to an element with the same junction area.

(2) It is possible to improve frequency response characteristics by about 12% compared to a device with the same light receiving area.

Note that the present invention is not limited to the above embodiments,
Various modifications are possible based on the spirit of the present invention, and these are not excluded from the scope of the present invention.

In particular, although the conductivity type of the semiconductor has been specified in the explanation, it goes without saying that all of these may be of opposite conductivity type. Further, the shape of the impurity introduction region 3 may also be circular, square, or rectangular.

(Effects of the Invention) As described in detail above, according to the present invention, an impurity semiconductor substrate of one conductivity type, a plurality of impurity-introduced regions of the opposite conductivity type to the substrate, and a portion of the entire periphery or peripheral portion. External lead bonding in which an applied voltage is connected to only one of the plurality of impurity-introduced regions, which are formed by diffusion so that they are in contact with each other at a distance less than the depletion layer width determined by the concentration of the substrate and the voltage used. Since the device is provided with a band, it is possible to (1) reduce junction capacitance and increase light receiving efficiency compared to conventional semiconductor photodetecting devices.

(2) It is possible to improve frequency response characteristics.

It has the following advantages, and the effects brought about by it are remarkable.

[Brief explanation of drawings]

FIG. 1 is a sectional view of a semiconductor photodetection device according to the present invention, and FIG.
The figure is a plan view of the same semiconductor photodetection device, FIG. 3 is a plan view of a conventional semiconductor photodetection device, and FIG. 4 is a plan view of the conventional semiconductor photodetection device.
FIG. 11... High impurity concentration semiconductor substrate 12... Low impurity concentration semiconductor substrate 13... Impurity introduction region 1 of the opposite conductivity type to the semiconductor substrate
4... External lead bonding band 15... Insulating film 16... Light shielding film

Claims (2)

[Claims] (1), (a) an impurity semiconductor substrate of one conductivity type, and (b)
(c) a plurality of impurity-introduced regions of opposite conductivity types formed on the substrate by diffusion such that the entire circumference or a part of the peripheral portion thereof are in contact with each other at a distance equal to or less than the depletion layer width determined by the concentration of the substrate and the voltage used; 1. A semiconductor photodetection device comprising: an external lead bonding pad to which an applied voltage is connected to only one of the plurality of impurity-introduced regions. (2) Semiconductor photodetection according to claim 1, characterized in that a portion other than the depletion layer region generated in the plurality of impurity introduced regions and their periphery is covered with a light shielding film. Device.