JPH0226083A - Planar photodetector and manufacture of same - Google Patents

Abstract

PURPOSE:To diminish contact resistance by providing at least one electrode for picking out a second signal which is formed on a second conductive crystal growth layer. CONSTITUTION:A diffusion area S in which a p-type impurity is thermally diffused is formed on a substrate 7. A recessed groove of a reverse trapezoid shape is formed on the diffusion area 8 and an undoped GaInAs light-absorbing layer 9 is formed along the inner surface of the recessed groove. Further, an n-type crystal growth layer 10 of GaInAs is buried in the light-absorbing layer 9, and the surface of the substrate 7 is flattened. On the diffusion area 8 and the crystal growth layer 10 is formed a p-type electrode 11 and an n-type electrode 12. Therefore, the area in which the electrode 11 is formed can be made larger and the electrode can be made larger. As a result, the resistance value can be diminished.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a planar semiconductor light-receiving element formed on a substrate and a method for manufacturing the same.

[Prior art]

Semiconductor light-receiving elements are small and lightweight, and can follow changes in optical signals at high speed, so they are essential for optical communication and optical information processing. Recently, in order to improve the degree of integration, miniaturization is progressing more and more.

FIG. 3 is a sectional view showing a conventional Brehner type light receiving element. An inverted trapezoidal groove is formed in the InP substrate 1 having a high resistance. For example, p
A first crystal growth layer 2 of the type is embedded. This first crystal growth layer 2 is made of GaInAs, and forms a groove smaller than the groove described above. A light absorption layer 3 is formed along the inner surface of this groove. This light absorption layer 3 is made of undoped InGaAs,
The groove is smaller than the groove described above. For example, an n-type second crystal growth layer 4 is buried in this groove to planarize the substrate surface. A pair of signal extraction electrodes 5.6 are formed on this flattened surface.

According to this technique, since there is no step on the substrate surface, it is suitable for integration and is excellent for integration with electronic devices such as FETs.

Next, a method of manufacturing this Brehner type light receiving element will be explained.

This Brehner type photodetector is composed of 3@ crystal growth layers. The embedding of these crystal growth layers is achieved using a selective growth technique using organic metal vapor phase epitaxy (OMVPE) (Journal of Crystal Growth).
f'Crystal Growth) 77(19
8B), pp. 297-302), and a technique for flattening the surface by performing ion beam etching after forming a groove and burying a crystal growth layer (JOURNAL 0FLIG).
ITWAVE TPCIINOLOGY), VOL
,LT-5,NO,10°0CTOBIER1987,
pp. 1371-1376).

[Problem to be solved by the invention]

However, the Brehner type photodetector according to the prior art is
In both cases, since the crystal growth layer is buried in the groove, the first crystal growth layer 2 is hardly exposed on the surface of the substrate 1, and the area of the signal extraction electrode 6 (current path area) is reduced. Therefore, there was a drawback that contact resistance was increased and reliability was poor.

In addition, during the manufacturing process, the signal extraction electrode 6 is formed on the first crystal growth layer 2 buried inside the groove, so the electrode should not be formed in a region that is not exposed on the surface of the substrate 1. It was difficult to form electrodes because the electrodes did not shatter. As a result, there was a drawback that production efficiency was low.

Therefore, the present invention aims to reduce contact resistance and improve reliability.

Another purpose is to improve production efficiency by making it easier to take out the electrodes.

[Means to solve the problem]

In order to achieve the above-mentioned problems, this invention (a Brehner type photodetector) has a first conductivity type region doped with a first conductivity type impurity on a highly resistive substrate, and a signal extraction within this first conductivity type region. A light absorbing layer is embedded along the inner surface of the groove, which is formed by exposing at least a width for forming the electrode. a second conductivity type crystal growth layer;
It is configured to include at least one signal extraction electrode formed on the conductivity type region and at least one signal extraction electrode formed on the second conductivity type crystal growth layer.

In addition, this invention (method for manufacturing a Brehner type light receiving element)
A first step of doping a first conductivity type impurity into a highly resistive substrate, and a second step of forming a groove portion by exposing at least a width for forming a signal extraction electrode in the first conductivity type region. a third step of embedding a light absorption layer along the inner surface of the groove and embedding a second conductivity type crystal growth layer thereon to flatten the surface of the substrate; and a fourth step of forming at least one signal extraction electrode on the second conductivity type crystal growth layer.

[Effect]

Since the present invention (Brehner type light receiving element) is configured as described above, the area in which the signal extraction electrode is formed can be widened.

In addition, this invention (method for manufacturing a Brehner type light receiving element)
It becomes easy to widen the area in which the signal extraction electrode is formed.

〔Example〕

DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the Brehner type light receiving element and its manufacturing method according to the present invention will be described below with reference to the accompanying drawings. In addition, in the description, the same reference numerals are used for the same elements, and redundant description will be omitted.

FIG. 1 is a cross-sectional view showing one embodiment of the Brehner type light receiving element according to the present invention. A diffusion region 8 in which a p-type (first conductivity type) impurity such as Zn is thermally diffused (doped) is formed in a substrate 7 made of InP or the like whose resistance has been increased by doping with Fe or the like. In this diffusion region 8, an inverted trapezoidal groove is formed, and an undoped Ga1nA groove is formed.
A light absorption layer 9 of s is formed along the inner surface of the groove. Furthermore, on this light absorption layer 9, Ga 1 n A s
An n-type (second conductivity type) crystal growth layer 10 is buried therein, and the surface of the substrate 7 is flattened. The material of the light absorption layer 9 is selected depending on the wavelength of light to be absorbed.
It is not limited to Ga1nAs. For example, 1.
When absorbing light having a wavelength other than 3 μm or 1.55 μm, Q a A s 5AI GaAs can also be used.

On the diffusion region 8 and the crystal growth layer 10 described above, a p-type electrode (first signal extraction electrode) 11 and an n-type electrode (second
A signal extraction electrode) 12 is formed.

According to this embodiment, since the area in which the electrode 11 is formed can be made wider, the electrode can be made larger.

Therefore, resistance value can be reduced and reliability can be improved.

Next, an embodiment of a method for manufacturing a Brehner-type light receiving element according to the present invention will be described with reference to FIG.

First, in the first step, impurities of the first conductivity type are diffused into the substrate 71 having a high resistance. Specifically, a silicon nitride film (SiNx) (or silicon oxide film (Si02)) 1 is formed on the entire surface of an InP substrate 7 doped with Fe or the like to have a high resistance.
B is cyclotron resonance plasma or plasma CV
It is formed by the D method etc. ((b) in the same figure). Next, a diffusion mask is formed using photolithography technology (see the same figure).
C)). Aperture without diffusion mask A I: p of Z n, etc.
type (first conductivity type) impurity is thermally diffused ((d) in the same figure,
(e)).

In the second step, a groove C is formed in this diffusion region 8.

Specifically, as described above, a resist film 14 is applied to a part of the diffusion region 8 (FIG. 2(f)). For example, a silicon nitride film (SiNx) 15 is formed on the entire surface of the substrate 7 by CVD or the like (FIG. Figure (g)). Next, the above-mentioned resist film 14 is removed by a lift-off method, and an opening B is formed which is narrower than the area (opening A) of the diffusion region 8 on the substrate 7 (FIG. 6(h)).
). Anisotropic etching is performed through this opening B to form an inverted trapezoidal groove C in the diffusion region 8 (FIG. 1(i)).
).

In the third step, a light absorption layer 9 and an n-type (second conductivity type) crystal growth layer 10 are buried along the inner surface of the groove C, and the substrate surface is flattened ((j), (k) in the same figure). (1)). Here, the light absorption layer 9 is made of undoped Ga1nAs or the like, and the n-type (second conductivity type) crystal growth layer 10 is made of, for example, Ga1nAs. These embeddings can be performed using a selective embedding growth technique using metal organic vapor phase epitaxy, similar to the conventional technique.

In the fourth step, a p-type electrode (first signal extraction electrode) 11 is formed on the diffusion region 8, and the n-type (first signal extraction electrode) 11 is formed on the diffusion region 8.
N-type electrodes (second signal extraction electrodes) 12 are formed on the crystal growth layer 10 (second conductivity type) ((m) in the same figure)
. These electrodes 11.12 are formed in ohmic contact.

According to this embodiment, unlike the prior art, the electrodes can be formed over a wide area, and the electrodes can be formed easily. Therefore, production efficiency can be improved.

Note that in the above embodiments, p type is used as the first conductivity type and n type is used as the second conductivity type, but n type may be used as the first conductivity type and p type is used as the second conductivity type. . In this case, Si or the like can be used as the n-type impurity.

Further, although thermal diffusion is used as a method of mixing the first conductivity type impurity into the substrate, ion implantation may also be used. What is important is that the first conductivity type region is formed broadly by introducing impurities into the substrate.

Further, the step (first step) of mixing the first conductivity type impurity into the substrate may be performed after forming the groove portion C (see FIG. 2(i)).

Note that the substrate is not limited to InP.

For example, GaAs, Si, etc. may be used.

〔Effect of the invention〕

Since the present invention (Brehner type light receiving element) is configured as described above, the electrode can be configured to be sufficiently large. Therefore, contact resistance can be lowered,
Reliability can be improved.

In addition, this invention (method for manufacturing a Brehner type light receiving element)
With the configuration as described above, it becomes easier to take out the electrodes on the surface of the substrate.

[Brief explanation of the drawing]

FIG. 1 is a sectional view showing an embodiment of the Brehner type light receiving element according to the present invention, FIG. 2 is a process diagram showing an example of the method for manufacturing the Brehner type light receiving element according to the present invention, and FIG. FIG. 1 is a sectional view showing a Brehner-type light receiving element according to the prior art. 1.7...Substrate 2...First crystal growth layer 3.9...Light absorption layer 4...Second crystal growth layer 5.6...Signal extraction electrode 8...Diffusion region 10...N-type crystal growth layer 11...P-type electrode 12...N-type electrode 13...Silicon nitride film Patent applicant Sumitomo Electric Industries, Ltd. Representative patent attorney Yoshiki Hase Yoshikima
Mountain 1) Row - Bushina type light receiving element Fig. 1 Conventional technique cup〒 Fig. 3 Fig. 2

Claims (1)

[Claims] 1. A first conductivity type region doped with a first conductivity type impurity on a highly resistive substrate, and a space for forming a signal extraction electrode in the first conductivity type region. a second conductivity type crystal growth layer buried along the upper surface of the light absorption layer and flattening the substrate surface; , at least one first signal extraction electrode formed on the first conductivity type region, and at least one second signal extraction electrode formed on the second conductivity type crystal growth layer. A planar light receiving element characterized by: 2. A first step of doping a high resistance substrate with a first conductivity type impurity to form a first conductivity type region, and a widening step to form a signal extraction electrode in the first conductivity type region. a second step of forming a groove by exposing at least the substrate surface; and a second step of embedding a light absorption layer along the inner surface of the groove, and embedding a second conductivity type crystal growth layer thereon to planarize the surface of the substrate. 3 and a fourth step of forming a first signal extraction electrode on the first conductivity type region and forming a second signal extraction electrode on the second conductivity type crystal growth layer, respectively. 1. A method for manufacturing a planar light-receiving element, comprising: