JPS62142375A - Optical semiconductor device - Google Patents

Abstract

PURPOSE:To improve optical sensitivity to a large extent, by providing the optimum reflection preventing film structure against near infrared rays. CONSTITUTION:In order to improve sensitivity for near infrared rays, the thicknesses of an oxide film and a nitride film 5 on the surface of a reverse conductivity type region 3 are controlled, and a reflection preventing film structure is provided. Meanwhile, the thicknesses of oxide films 6 and nitride films 7 on the surface of the same conductivity type region 2 are changed in order that the sensitivity peak does not appear at a part other than the reverse conductivity region 3. Thus a reflecting film structure is obtained. The reflection preventing film is formed by two layers of the oxide film 4(200Angstrom ) and the nitride film 5(850Angstrom ). As the reflecting films, the oxide films 6(4,000Angstrom ) and the nitride films 7(5,000Angstrom ) are formed on the upper surface of the reverse conductivity type region 2. These parts are formed of hour layers.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of the Invention The present invention relates to an optical semiconductor device with improved photosensitivity to light of a specific wavelength.

2. Description of the Related Art A conventional optical semiconductor device has a planar structure and a cross-sectional structure as shown in FIGS. It has two or more shaped regions 3. An oxide film 4 and a nitride film 5 are formed on the surfaces of the first conductive shadow region 2 and the second conductive shadow region 3. Typically, the oxide film has a thickness of 9,000 to 1600 mm, and the nitride film has a thickness of 3,000 to SOO. When light is incident on this optical semiconductor device, the photosensitivity to a specific wavelength may be reduced due to reflection near the surface.

Problems to be Solved by the Invention In such a conventional configuration, it is necessary to select the substrate specifications and form regions of opposite conductivity type in accordance with a predetermined wavelength of light.

Further, if the oxide film and nitride film on the surface have a thickness of 5000 Å or more, there is a reflection effect on near-infrared light, and there is a drawback that sufficient photosensitivity cannot be obtained.

The present invention is intended to solve these problems, and aims to provide an optical semiconductor device that has high photosensitivity to near-infrared light.

Means to Solve the Problem In order to solve this problem, the present invention provides an antireflection film for near-infrared light by controlling the thickness of the oxide film and nitride film on the surface of the opposite conductivity type region. When formed, the oxide film and nitride film on the surface of the same conductivity type region are thickened to form a reflective film, thereby greatly increasing the photosensitivity. The thickness of this antireflection film is 500 Å or less for the oxide film and 500 Å or less for the nitride film.
For 1,600 people, the total thickness of the reflective film of the oxide film and the nitride film is approximately 5008.

Function: The structure of the optical semiconductor device of the present invention reduces reflection of near-infrared light, allowing light to efficiently enter the oppositely conductive region, that is, the junction. Furthermore, the reflection film structure on the surface of the same conductivity type region, that is, the non-junction part, can reduce the light sensitivity to the periphery of the opposite conductivity type region. FIGS. 1A and 1B show an embodiment of the present invention. FIG. 3 is a plan view and a cross-sectional view of a chip in which there are two regions of opposite conductivity type according to an example. 1
is an N-type conductivity type semiconductor substrate, 2 is a region of the same conductivity type as the substrate,
3 is a P-type conductivity type region opposite to the substrate, 4 and 6 are oxide films, and 5
, 7 are nitride films.

In order to improve the sensitivity to near-infrared light, the thickness of the oxide film 4 and nitride film 6 on the surface of the opposite conductivity type region 3 is controlled to form an antireflection film structure. On the other hand, in order to prevent the sensitivity peak from appearing in areas other than the opposite conductivity type area 3,
A reflective film structure is obtained by changing the thickness of the oxide film 6 and the nitride film 7 on the surface.

In this example, oxide film 4 (200 people) was used as an antireflection film.
The oxide film 6 (4000 layers) and nitride film 7 (600 layers) are respectively formed on the upper surface of the opposite conductivity type region 2 as reflective films. is formed of four layers. Note that the lower layer oxide film 4 of this reflective film portion may be left with thousands of anti-diffusion masks used when forming the region 2, and the cross-sectional view of FIG. 1 is an example of this.

FIGS. 2a and 2b are a plan view and a sectional view of a chip in which there are six P shadow areas 3. 1 is an N-type semiconductor substrate, 2 is an N shadow region, 3 is a P shadow region reflecting the substrate, 4 and 6 are oxide films, and 5 and 7 are nitride films.

A nitride film (1000 layers) is formed as an anti-reflection film, and the reflection film is formed of four layers of an oxide film and a nitride film as in FIG. It goes without saying that it is also effective to enhance the reflection effect by attaching a metal such as Ae on the reflective film.

FIG. 3 shows the photosensitivity characteristics of an apparatus according to an embodiment of the present invention in comparison with a conventional apparatus. The broken line 8 shows the photosensitivity distribution of the present invention, and the solid line 9 shows the photosensitivity distribution of the conventional optical semiconductor device.

In the present invention in which a reflective film is formed around the antireflection film, the photosensitivity distribution is flat, and no sensitivity peak occurs on the opposite conductivity type region. Although the embodiments of the present invention have been described using an N-type substrate, the same effect can be obtained by using a P-type substrate with the first conductivity type region being P type and the second conductivity type region being N type. Needless to say.

Effects of the Invention As described above, according to the present invention, the optical sensitivity was significantly improved due to the optimal antireflection film structure for near-infrared light. For example, with respect to a laser beam having a wavelength of 800 nm, the apparatus of this embodiment shown in FIG. 1 was able to achieve an improvement in photosensitivity of about 1.5 times.

[Brief explanation of drawings]

1A and 1B are a plan view and a sectional view of an optical semiconductor device according to an embodiment of the present invention, FIGS. 2A and 2B are a plan view and a sectional view of an optical semiconductor device according to another embodiment, and FIG. Each sensitivity distribution characteristic diagram of the example device and the conventional optical semiconductor device, and FIG. 4 is a plan view and a sectional view of the conventional example device. 1...N type semiconductor substrate, 2...N shadow area,
3...P shadow area, 4,6... Oxide film, 5
,7...Nitride film Q Name of agent Patent attorney Toshio Nakao and 1 other person 2nd
Figure 3 Figure 4

Claims (2)

[Claims] (1) A semiconductor substrate of a predetermined conductivity type has a region of the same conductivity type, and has at least two regions of opposite conductivity type on its surface, and a stack of an oxide film and a nitride film on the surface of the region of the opposite conductivity type. Alternatively, an optical semiconductor device comprising an antireflection film made only of a nitride film and a reflective film provided only on the surface of the same conductivity type region. (2) The anti-reflection film is an oxide film of 500 Å or less and a nitride film of 50 Å or less.
The optical semiconductor device according to claim 1, wherein each thickness is selected in a range of 00 to 1500 Å.