JPH02241066A - Semiconductor photodetector - Google Patents

Abstract

PURPOSE:To operate an Si PIN photodiode having a small dark current and high speed response of low cost type by etching necessary parts of front and rear faces of low concentration Si board having good crystallinity to form an I-type layer thickness. CONSTITUTION:A semiconductor photodetector for converting a light radiated from various types of light emitting elements into electric signals has an I-type layer thickness formed by etching necessary parts of front and rear faces of a low concentration Si board 10 having high crystallinity, N<+> type or P<+> type layers 12 formed at least on the I-type layer thickness of the rear face, P<+> type or N<+> type layer 13 formed on the at least I-type layer thickness of the front face to become a photodetecting face, electrodes 7, 4 and a reflection preventive film 6 formed on the layers 12, 13 formed thereon. For example, an etching mask 11 is formed on the necessary parts of the front and rear face so the board 10, and so anisotropically etched as to become the I-type layer thickness of tau = several 10mum. Thereafter, an N<+> layer 12 is formed on the rear face, a P<+> layer 13 and a guard ring 9 are formed on the front face to become a photodetecting face by ion implanting method, etc.

Description

DETAILED DESCRIPTION OF THE INVENTION <Industrial Application Field> The present invention relates to a semiconductor photodetection element (semiconductor photosensor) used as an element that converts light into an electrical signal and detects it.

<Prior art> Semiconductor photodetectors that convert light into electrical signals and detect them are used, for example, to measure optical loss in optical communications, to optical disk systems, and to evaluate the characteristics of semiconductor lasers. SL photodiodes are known.

There are two types of Sj photodiodes: a PN type and a PIN type, and the type shown in FIG. 3 is conventionally known as the PIN type.

It is characterized by fast response.

FIG. 3 is a structural diagram of a conventional PIN type Sj photodiode.

In FIG. 3, the symbols and names of each part are as follows.

Reference numeral 1 indicates an N-type Si substrate (n'') consisting of a high impurity concentration.
2 indicates one layer, 3 indicates high concentration 2
The code 4 and 7 indicate the layer (P+), the code 4 and 7 indicate the electrode layer (Alt pole), and the code 5 indicates the positive electrode (AIt pole) to which the high bias voltage taken out from above the electrode layer 4 is applied. , numeral 6 indicates an antireflection film made of an oxide film, numeral 8 indicates a negative electrode, and numeral 9 indicates a guard ring (n+) provided to prevent surface leakage.

Here, this type of PIN type Si photodiode is manufactured as follows.

(2): First, on the surface of the N-type Si substrate 1, one layer 2 of an epitaxial layer (so-called insulating S9 layer) with a low impurity concentration S is formed by epitaxial growth to a required thickness.

■Secondly, layer 3 is added to layer 2 by thermal diffusion or ion implantation. Then, a guard ring 9, which is an n+ layer, is formed.

■: The surface of the I layer 2 has a mirror finish, so it reflects a lot of light. Therefore, in order to reduce this reflection and increase the sensitivity on the surface of the light receiving part, a reflective layer with an appropriate thickness is applied. need to be formed. That is, after forming layer 1 and layer 2,
An antireflection film 6, such as an oxide film, is formed on the surface that will become the light-receiving portion in order to increase sensitivity.

(2) Next, an electrode layer <AI electrode) 4.7 is formed on the front surface (P layer/I layer) and the back surface (N substrate).

■: Take out the positive terminal 5 and negative terminal 8 from above the electrode layer 4.7 by wire bonding. At this time, basically the P layer 3
The inside of the plane becomes a light receiving part for spatial beam light.

<Problems to be Solved by the Invention> By the way, such a PIN type S photodiode has good crystallinity that contains almost no impurities on the surface of the N substrate 1, that is, there are no defects that cause the dark current. It is difficult to form a low impurity concentration 84 layer with a low recombination center density by epitaxial growth, and it is also difficult to maintain the manufacturing equipment to solve this problem, which results in an increase in costs. There was a problem.

The present invention has been made in view of the above-mentioned problems of the conventional technology, and its purpose is to provide a low-cost type that has low dark current and is capable of high-speed response.
The present invention provides a semiconductor detection element that can be operated as an S, PIN type photodiode.

Means for Solving the Problems> In order to achieve the above object, the semiconductor photodetecting element of the present invention converts light emitted from various light emitting elements into electrical signals. Good low concentration S
, (2) layer thickness formed by etching on required portions of the front and back surfaces of the substrate, an n+ layer or P middle layer formed on at least the one layer thick portion of the back surface, and at least the I layer on the front surface that will become the light-receiving surface. P middle layer or n formed in the thick layer part
It is characterized in that it consists of a + layer, and an electrode and an antireflection film formed on these layers.

Etching mask is applied to the necessary parts of the front and back surfaces of a low impurity concentration N-type (or P-type) S substrate with good crystallinity, and then one layer (■ layer thickness) of the optimum thickness for the design is applied. An n medium layer (a P medium layer in the case of a low impurity concentration P type) is formed on the back surface of at least the etched part of the ■ layer thickness, and at least the etched said ■ layer on the surface that will become the light-receiving surface. A P medium layer (an n+ layer in the case of a low impurity concentration P type) is formed in the thick portion, and an antireflection film and an electrode are formed on these formed layers. In addition, here, the low impurity concentration N
A type Si substrate will be explained below.

<Example> An example will be described with reference to the drawings. In the following drawings, parts that overlap with those in FIG. 3 are designated by the same reference numerals, and detailed explanation thereof will be omitted.

FIG. 1 is a diagram for explaining the semiconductor photodetecting element of the present invention.

The reference numeral 10 shown in FIG. 1 (1) indicates a low impurity concentration S of about 10"cm"3 that contains almost no impurities and has good crystallinity.
This is an i-substrate, that is, an S substrate with a low density of defects and recombination centers.

(2) In the figure (11), reference numeral 11 is an etching mask. This etching mask 11 is shown in the same figure (+).
It is applied to the required portions of the front and back surfaces of the 81 substrate 10 shown in .

(2) Then, anisotropic etching is performed so that the thickness of the I layer becomes optimum for the design, for example, τ=R10 μm.

■: After that, the etching mask 11 is removed.

(2) Next, as shown in the same figure (lif), an N medium layer 12 is formed on the back surface, and a P medium layer 13 and a guard link 9 are formed on the surface that will become the light receiving surface, for example, by ion implantation. In addition, n4″
The layer 12 and the P intermediate layer 13 can also be formed, for example, by selective epitaxial growth or thermal diffusion.

(2): Next, as shown in the same figure (transfer), an anti-reflection film 6 is formed on the n+N12, and Al electrodes 4 and 7 are formed thereon.

■: Finally 1. '181#14, Take out the positive and negative terminals 5°8 from above 7.

The semiconductor detection element obtained by such a manufacturing method is 5i
If it is operated as a PIN type photodiode, a low-cost type with small dark current and high-speed response can be manufactured.

By the way, the structure of the semiconductor detection device shown in FIG. 1 is not limited to this.

For example, a structure as shown in FIG. 2 is also possible.

FIG. 2 is a diagram showing an applied example of FIG. 1.

FIG. 2 shows that a circuit 14 such as an amplifier is also mounted within the same -Si substrate. Note that the n+10 layer 2a is formed by, for example, ion implantation. At this time, with the guard ring 9,
A circuit 14 such as an amplifier such as a transistor can be formed within the substrate 10 completely separate from the light receiving element.

With this configuration, the amplifier W! A semiconductor photodetector element built in a tank can be realized, and a small #I structure that is not affected by wiring capacitance etc. is possible.

Note that the antireflection film may have a single layer, but in order to further increase sensitivity, it may have a two-layer structure (particularly on the light-receiving surface III). In this case, for example, a thermal oxide film is used in consideration of the interface level, etc., but if a protective resin is applied on top of this thermal oxide film, the refractive index is almost the same, so the anti-reflection conditions are broken and sensitivity is reduced. Since a decrease occurs, for example, by employing a nitride film whose refractive index is higher than that of a thermal oxide film, this can be prevented and the sensitivity can be improved. However, in view of the stability of the S1 surface, a thermal oxide film can be formed as a buffer layer, and a nitride film can be formed thereon.

<Effects of the Invention> Since the present invention is configured as described above, it produces the following effects.

By manufacturing using a Si substrate with good crystallinity that contains almost no impurities, it is possible to stably manufacture a low-cost semiconductor photodetector element with lower dark current, faster response, and lower cost than one formed by epitaxial growth. I can do it.

Furthermore, by forming the anti-reflection film into a multi-layered structure, in addition to the above-mentioned effects, higher sensitivity can be achieved.

[Brief explanation of drawings]

FIG. 1 is a diagram for explaining the semiconductor photodetecting element of the present invention;
FIG. 2 is a diagram showing an applied example of FIG. 1, and FIG. 3 is a structural diagram of a conventional PIN type Si photodiode. DESCRIPTION OF SYMBOLS 1...Si substrate, 4,7...electrode layer, 5...positive terminal, 6...antireflection film, 8...negative terminal, 9...guard ring, 10...low Impurity concentration Sl substrate. (i) Figure 1 “17-10 Figure J

Claims (1)

[Claims] In a semiconductor photodetector element that converts light emitted from various light emitting elements into an electrical signal, the thickness of the I layer formed by etching on the required parts of the front and back surfaces of a low concentration Si substrate with good crystallinity, and the thickness of the back surface. an n^+ layer or p^+ layer formed at least in the I layer thickness portion; a p^+ layer or n^+ layer formed in at least the I layer thickness portion of the surface serving as a light-receiving surface; 1. A semiconductor photodetecting element comprising an electrode and an antireflection film formed on a layer formed in the same manner.