JPS6177385A - Manufacture of photosemiconductor device - Google Patents

Abstract

PURPOSE:To locate the cleavage surface, produced by breaking a beam part, almost as designed, by a method wherein, in forming the photo emission surfce of the title device by micro cleavage, a beam part to be removed by cleavage is so shaped as to be narrower toward the photo emission surface of a photo conductor semiconductor element, and as to be wider on the farther side. CONSTITUTION:The width at the joint of a beam pat 10A, i.e on the closer side to the photo emission surface of a semiconductor laser is narrower, and the width on the farther side is wider. Here, a larger width means a width enough to have no trouble in pressure application, regardless of either mechanical force or ultrasonic waves, at the time of breaking the beam part 10A, whereas a small width may be a width to give no allowance for abuttment of e.g. a jig which applies pressure. Such a formation of the beam pat 10A enables the position 10q of the cleavage surface to be reproduced always as designed. The shape of the beam pat 10A can be obtained by forming the mask film pattern in such a manner, and the other processes are the same as by the conventional technique.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention is applicable to the production of optical semiconductor devices that require a step of forming a light emitting surface of a semiconductor laser, an edge-emitting light emitting diode, etc. by local cleavage. Regarding the method.

[Conventional technology]

In recent years, development and research on optical integrated circuits has been active.
In that case, a semiconductor laser is naturally incorporated into the optical integrated circuit.

Conventionally, the light emitting surface (mirror surface) in a discrete type semiconductor laser has been formed by cleavage, and at present, the mirror surface formed by this technique has shown the best performance.

However, in the case of optical integrated circuits, semiconductor elements having other functions in addition to the semiconductor laser are monolithically integrated.

Therefore, if the cleavage technology applied to individual type semiconductor lasers is used for such optical integrated circuits, the substrate would be separated, so it would be impossible to implement it, or it would only be possible to use it on a very small scale. I can't get it.

Therefore, the light emitting surface was subjected to reactive ion etching (reactive ion etching).
active ton etching (RIE)
Attempts have been made to form the film by applying a dry etching method, such as the method, or a wet etching method, using a chemical mixture, etc., but it is not possible to obtain a mirror surface of good quality as in the case of cleavage.

In order to overcome these drawbacks of the prior art, a technique called micro-creep has been developed, and it has become possible to locally cleave a semiconductor laser.

2 to 5 are a cut-away side view and a cut-away oblique view of the main parts of an optical semiconductor device at key points in the process for explaining the conventional technology, and the explanation will be given below with reference to these figures. do.

See Figure 2fal Liquid phase epitaxial growth
phase epitaxy (LPE) method, vapor phase epitaxial growth (vapor phase epitaxy)
xy:VPE) method, organometallic chemical vapor deposition (metal
organics chemical vapor
r deposition: MOCVD) method, molecular beam epitaxial growth (molecular beam epitaxial growth)
By selecting and applying an appropriate technique such as epitaxy (MBE) method, an n+ type GaAs buffer layer 2 with a thickness of about 3 [μm] is formed on an n+ type GaAs substrate 1.
, n-type A7 with a thickness of about 3 [μm]! GaAs cladding layer 3, n-type GaAs active layer 4 with a thickness of about 0°2 [μm], p-type A with a thickness of about 3 [μm] 7! o1s
Gao, 55A s cladding layer 5, thickness approximately 0.
A p+ type GaAs contact layer 6 of about 3 [μm] is grown.

In addition, since the purpose of FIG. 2 is to explain the layer structure of each semiconductor layer, the semiconductor layer is shown not as a wafer but as a single unit.

fbl By applying ordinary techniques, various electrodes and the like are formed, and a wafer on which an optical semiconductor device is fabricated is completed.

Refer to FIG. 3 (C) A mask film 9 is formed to cover the portion of the semiconductor laser that requires opening and other portions that require protection. Note that as this mask film 9, photoresist or silicon dioxide (Si02) can be used.

Here, the symbol 8 is, for example, gold (Au), zinc (Zn
), and symbol 10 represents a double hetero structure (double
A heterostructure (DH) portion, that is, a DH portion is shown.

! The DH portion 10 is etched by applying a chemical etching method in which the dl etchant is, for example, 8H202+IH, 2SO4+1'H20.

By applying a selective chemical etching method using (el etchant as, for example, 20 H202+ I N H40H), see FIG.
The n-type GaAS substrate 1 is selectively etched.

As a result, a beam portion 10A to be removed by cleavage is formed in the DH portion 10.

ff) Remove the mask film 9.

Refer to FIG. 5 (gl) Cleavage is performed by applying pressure to the beam portion 10A using a suitable jig.

As a result, the DH portion 10 has a laser beam emitting end face 10B.
(light emitting surface) is formed.

[Problem that the invention seeks to solve]

In the conventional micro-creep method explained above,
Depending on the shape of the mask film 9 shown in FIG. 3, the shape of the portion indicated by the symbol 10P in the same figure is likely to change, and as a result, the etched surface IP of the n1 type GaAs substrate 1 shown in FIG. The shape becomes uncertain, and in that state the beam portion 10
When A is folded and cleaved, the laser beam emitting end face 10B shown in FIG. 5 also becomes uncertain, and a cleavage plane is formed in the part that bites into the laser body, or a part of the beam part 10A remains. do.

In the present invention, when performing cleavage using the micro-creep method, a cleavage plane is always formed at a predetermined portion when a beam portion is broken.

Means for Solving and Resolving Problem C] In the method for manufacturing an optical semiconductor device of the present invention, an active layer portion including an active layer is epitaxially grown on a semiconductor substrate, and then an optical layer on the optical semiconductor element and the optical semiconductor element of the optical semiconductor element are grown epitaxially. A mask film is formed to cover the beam portion which is narrow on the side close to the portion to become the radiation surface and wide on the side remote from it, and then
The active layer portion is etched along the mask film to expose a part of the surface of the semiconductor substrate, and then the semiconductor substrate is selectively etched so that a void is formed at least under the beam portion. The method includes the steps of removing the semiconductor substrate, then folding the beam portion to form a light emitting surface of the optical semiconductor element by cleaving.

[Effect]

According to the above means, the beam portion removed by the micro-creep method has a narrow width on the side close to the light emitting surface of the optical semiconductor element and a wide width on the far side. As a result, the position of the cleavage plane generated when the beam portion is folded is approximately determined, and the manufacturing yield is improved.

〔Example〕

FIG. 1 shows a cut-away perspective view of the main parts of an optical semiconductor device at key points in the process for explaining one embodiment of the present invention, and the same parts as those explained with reference to FIGS. 2 to 5 are designated by the same symbols. It is an instruction.

FIG. 1 corresponds to FIG. 4 in the explanation of the prior art, and the difference from the conventional example is the shape of the beam portion 10A.

As can be seen from the figure, the width of the original portion of the beam portion 10A, that is, the side close to the light emitting surface of the semiconductor laser is narrow, and the width of the side farther from it is wide. here,
Wide means that the width is such that there is no problem in applying pressure, whether by mechanical force or ultrasonic, when folding the beam part 1°A. This means that, for example, the width may be such that there is no margin for contact with a jig that applies pressure.

By shaping the beam portion 10A as described above, it is possible to always reproduce the position 10Q of the cleavage plane as designed.

The shape of the beam portion 10 as shown in FIG. 1 is obtained by forming the pattern of the mask film 9 shown in FIG. 3 in this way, and the other steps are as shown in FIGS. This is similar to the prior art described above.

An example of the dimensions shown in FIG. 1 is as follows.

DI=20 Cμm] D2=50 Cμm] D3=15 Cμm] D4=10 Cμm] In addition, the width of the p-side stripe electrode 8 was set to 3 [μm], the length was set to 200 [μm], and the second By removing the portion 7 shown in broken lines in the figure, a ridge is obtained, namely the p+ type GaAs contact layer 6 and the p type A
j! o, a, G a o, ssA When a semiconductor laser was completed with a structure including a stripe portion consisting of a part of the S cladding layer 5, a high performance with a threshold current Ith of 30 (mA) was obtained. .

Note that the ridge is formed in step (b) explained with reference to FIG.
In this process, we reused the mask used to form the p-side stripe electrode and applied, for example, an ion beam etching method, so that D shown in Figure 2 was approximately 0.3 [μ
It can be formed by etching and removing the portion 7 so as to have a thickness of about 100 m.

〔Effect of the invention〕

In the method for manufacturing an optical semiconductor device of the present invention, when forming the light emitting surface of the optical semiconductor device by the micro-creep method, the shape of the beam portion to be removed by cleavage is such that the light emitting surface of the optical semiconductor device is The width on the side closer to the radiation surface is narrower, and the width on the side farther from the radiation surface is wider.

Therefore, the position of the cleavage plane generated when the beam portion is folded is determined approximately as designed, and the manufacturing yield is improved.

[Brief explanation of drawings]

FIG. 1 is a cut-away perspective view of the main parts of an optical semiconductor device at key points in the process for explaining one embodiment of the present invention, FIG. 2 is a cut-away side view of the main parts of the optical semiconductor device, and FIGS. The figures each represent a cut-away oblique view of a main part of an optical semiconductor device at key points in the process for explaining the conventional technology. In the figure, 1 is an n1 type GaAs substrate, 2 is an n+ type GaAs substrate, and 2 is an n+ type GaAs substrate.
As buffer layer, 3 is n-type A#GaAs cladding layer, 4
is an n-type GaAs active layer, 5 is a p-type A (lo, 4S
Gao, ssA S cladding layer, 6 is p+ type Ga
An As contact layer, 7 a portion to be removed to form a ridge, 8 a p-side stripe electrode, 9 a mask film,
10 indicates the DH portion, IOA the beam portion, and 10Q the position of the cleavage plane.

Claims (1)

[Claims] An active layer portion including an active layer is epitaxially grown on a semiconductor substrate, and then a beam portion is formed which has a narrow width on the side close to the optical semiconductor element and the portion that is to become the light emitting surface of the optical semiconductor element and a wider width on the side away from the optical semiconductor element. A mask film is formed to cover the active layer, and then the active layer portion is etched to expose a part of the surface of the semiconductor substrate, and the semiconductor substrate is selectively etched to remove at least the area under the beam portion. A method for manufacturing an optical semiconductor device, comprising the steps of removing a semiconductor substrate, then folding the beam portion to form a light emitting surface of the optical semiconductor element by cleaving.