JPH01117386A - Compound semiconductor thin film manufacturing method - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Field of Application] The present invention relates to a method for selectively forming a superlattice thin film of a ■-■ group compound semiconductor.

[Conventional technology]

Group II-VI compound semiconductors made of zinc selenide (ZnSe), zinc sulfide (ZnS), etc., and their mixed crystals have characteristics that other material systems do not have, such as a wide bandgap, high specific resistance, and low refractive index. Taking advantage of these characteristics, for example, Zn5e thin films are used as current confinement and optical confinement layers in AlGaAs semiconductor laser devices. Figure 4 is a collection of lecture proceedings by the Society of Applied Physics (1939) by Iwano et al.
Zn5e, announced on Spring 2018, 28p-ZH-8)
1 shows a cross-sectional view of the structure of an AlGaAs semiconductor laser device embedded with a thin film layer. A Zn5e thin film layer 402 is formed to bury the lip 401.

In addition, the upper surface 403 of the lip is coated with Zn5e to form an electrode.
It does not form a thin film layer and is exposed in stripes. When it is desired to selectively form a Zn5e thin film layer on a semiconductor substrate as in this structure, in the conventional technology, the Zn5e thin film layer is first deposited on the entire surface.
After depositing the thin film layer, mask it with a resist or the like using a photo-etching method, and then remove the Zn5e in the area that you want to remove.
The thin film layer was removed by etching.

[Problem that the invention seeks to solve]

However, in the case of the above-mentioned prior art, firstly Zn5e and Al
Since there is a large difference in lattice constant and thermal expansion coefficient between the CaAs system and the semiconductor laser active layer, stress is applied to the semiconductor laser active layer, resulting in a shorter lifespan compared to semiconductor lasers manufactured using the AlGaAs system. was there.

Second, it is difficult to form a self-alignment line between the active layer and the electrode stripes, which may cause misalignment, leading to problems such as insufficient reproducibility of the structure and characteristics of the device. Ta. Secondly, etching the Zn5e thin film layer is very difficult, and the process is complicated to achieve good etching, which reduces productivity. Also, the surface after etching has many irregularities, which deteriorates the interface characteristics with the substrate. There were problems such as a decline in

Therefore, in order to solve these problems, the present invention alleviates the stress caused by the difference in lattice constants and thermal expansion coefficients, enables cell fine processing, has good reproducibility, and has a good n-type structure with no surface irregularities. - A method for selectively forming a VII supersuperlattice thin film is provided.

[Means for solving problems]

In order to solve the above problems, the method for growing a semiconductor thin film of the present invention includes means for manufacturing a mask on a part of the surface of a semiconductor substrate, and manufacturing a thin film of a ■-■ group compound semiconductor superlattice on the surface of the semiconductor substrate. It is characterized in that it includes means for.

〔Example〕

The present invention will be further explained in detail based on Examples.

(Example-1) As a first example of the present invention, a Zn5e-embedded AIGaA was used in which the rib formed on the upper part of the double heterojunction was buried with a Zn5ei film layer for current confinement and optical confinement.
A part of the manufacturing process of the S semiconductor laser device will be explained. 1st
Figures (a) to (c) illustrate a first embodiment, and are schematic cross-sectional views of a substrate in the middle of an element manufacturing process. Figure 1 (
a) is a schematic cross-sectional view of a substrate immediately before forming a Zn5e Zn5o, +zSeo, as strained superlattice thin film layer; (1
1.00) on an n-type GaAs substrate 101 with a plane orientation of 1. 5μ
m-thick n-type A 1 o, s G a o, s A S cladding layer 102.0.1 em-thick non-doped A I o
, +sG ao, ssA s active layer 103.1.
5μm thick P type A1o, 5Gao, sAs cladding layer 1
04.0.5 μm thick P-type GaAs contact layer 105
A substrate having a DH structure in which the following are sequentially laminated is prepared. Next, 3,000 5-in.
2 is buried, and a stripe-shaped 5in2 mask 106 with a width of 5 μm is formed by photoetching. After that, 5
Using inz as a mask, the substrate is etched to the middle of the P-shaped rad layer to form ribs 107. A typical rib shape is 5 μm wide at the top, 3.5 μm at the bottom, and 1.6 μm high. Next, to embed this rib, Zn
'5e-ZnSo.

A 1□SeO, 1l11 strained superlattice thin film is epitaxially grown. Z n S e Z n S11 on the rib
．． The 5in2 mask 106 is left as is to prevent deposition of the 12S eo, ea strained superlattice thin film. Zn5
e-ZnSO, l2SeO, l18 strained superlattice is CaAs
Or AI. .

, Ga, , 5As, epitaxial growth is performed on the P-shaped rad surface and the rib side surface exposed by etching. Zn S e Z
n s'o, I! The epitaxial growth of the seo, 118 strained superlattice uses dimethylzinc (DMZn), diethylsulfur (DES), and dimethylselenium (DMSe) as raw materials.
), MOCV using pure hydrogen (H2) as carrier gas
D (Metal-Organic-Chemica
1-Vapor-D'eposition) method was used.

The growth conditions are a substrate temperature of 550°C and a reaction tube pressure of 35To.
r r, 0MZn flow rate 3. OX 10-'mol
e/sin D E S style M1. 6X10-5mo
le/min DMSe flow rate 1, 2 X l O
-'mole/min Gold bullion I1. O3LM,
A strained superlattice is created by turning on and off the DES.

The growth procedure was as follows: insert the substrate shown in FIG. 1(a) into an MOCVD apparatus, heat it to 550'C in a hydrogen atmosphere, perform thermal etching for 15 minutes, and then perform Z n S e Z under the aforementioned conditions. n So, +zS eo, ae
Perform epitaxial growth of strained superlattice thin films. Here D
ES is turned on and off every 20 seconds, one cycle is 6.5 ohm.
(ZnSe3nm-ZnSo, +zSeo, as3,
5 ohm) superlattice structure. At this time, the growth rate is 0.
It is 6 μm/hour.

A schematic cross-sectional view of the substrate after 3 hours of growth is shown in Figure 1 (b).
). Zn5e-ZnSo, +zSeo.

(2) The strained superlattice thin film layer 108 is epitaxially grown almost flat on the DH substrate with ribs buried therein.

On the other hand, Sing? Zn5e-ZnSo on the screen 106
, +□Seo, no adhesion of ao strained superlattice thin film was observed,
Z e S e Z n So, +zS eo, sa
A strained superlattice thin film was selectively formed on the substrate excluding the SiO□ mask portion. Furthermore, since the Si0g mask used for etching the DH substrate is used as is, it is also a self-line. FIG. 1C is a schematic cross-sectional view of a Zn5e-embedded AlGaAs semiconductor laser device obtained by etching away the SiO2 mask, forming a P-type electrode 109 and an N-type electrode 110, and cleaving the device. Z
n5e-ZnSo, +zseo, as strained superlattice thin film layer 1
Since 08 has a high resistance (P >10" Ωcm), it is injected from the P-type electrode. The current flows concentrated in the ribs, forming a complete current confinement layer. This semiconductor laser device is capable of continuous oscillation at room temperature. It exhibited good characteristics with a threshold current of 16 mA and an astigmatism of 1 μm.

In addition, due to the superlattice structure, stress on the active layer is alleviated, resulting in good lifetime characteristics, optical output of 20 mW,
Even when a reliability test was conducted for 5,000 hours at a case temperature of 70'C, the increase in drive current was within 3% compared to the initial value.

(Example 2) As a second example of the present invention, Zn5e-ZnSo was used in the buried layer of a buried (BH) type semiconductor laser device. 1
A method of forming an lset1.92 strained superlattice thin film layer will be described. FIGS. 2(a) to 2(C) explain a second embodiment, and are schematic cross-sectional views of a substrate during the manufacturing process of a BH type semiconductor laser device.

The flow of the manufacturing process is the same as that described in Example-1. FIG. 2(a) is a schematic cross-sectional view of the substrate immediately before forming the buried layer. AlG on the n-type GaAs substrate 201
A striped DH structure 202 made of aAs and S,i
A 0□ mask 203 is formed in the same process as in Example-1. FIG. 2(b) is a schematic cross-sectional view of the substrate after forming the buried layer. Z n S e Z n So, os
S eo, qt strain superlattice forcing layer 204 has a thickness of 3.2
μm, but the side surfaces of the DH structure are well buried. On the other hand, there is no deposit on the SiO□ mask 203 (a buried layer is formed with good selectivity). 1 is a schematic cross-sectional view of the obtained BH type semiconductor laser device.This BH type semiconductor laser is made of Zn5e-ZnSo.

The good crystallinity and high resistivity of the Seo, qz strained superlattice (<10IlΩcm) and the large refractive index difference with GaAs (GaAs23.6, Zn5e-ZnSo, osSeo
, qz strain superlattice 2.5) shows good characteristics, threshold current is 10 mA, and astigmatism is l' from optical output 1 mW.
Ideal characteristics of 1 μm or less were obtained up to QmW.

In addition, in the above examples, Zn5e, Zn5o, oes
Although the eo, qz strained superlattice side has been taken up, the application of the present invention is not limited to this range. That is, the present invention uses Zn
It can be applied to the formation of single crystal and mixed crystal thin films using a combination of group Ⅰ, such as , Cd, Hg, etc., and group ①, such as S, Se, Te, 0, etc. Although methyl-based organometallics were used as raw materials for MOCVD, ethyl-based and other organometallics,
A hydride, a chloride, a mixture thereof, etc. may be used as the raw material.

In addition, although the MOCVD method has been mentioned as a method for growing a thin film, the present invention is also applicable to other methods such as MBE method, MO-MBE method, etc.
It is also possible to use a method such as a gas phase transport method or a gas phase transport method. In addition to GaAs substrates and InP substrates, Si substrates and G
It is possible to use an e-substrate, a GaP substrate, etc., or a semiconductor substrate having a different type of semiconductor layer grown on these substrates. In addition to 5iOz, the mask materials include silicon nitride,
Insulating bands such as alumina, metals such as tungsten, molybdenum, etc. can also be used.

[Effects of the Invention] The method for producing a II-VI group compound semiconductor thin film of the present invention has various effects as described below.

(1) By applying a mask in advance, a thin film can be manufactured using a self-alignment line, so the post-process during device manufacturing can be extremely simplified compared to conventional manufacturing methods.

(2) Using a superlattice relieves stress caused by thermal expansion, coefficient differences, and lattice misalignment, so if it is used in the current confinement layer of a semiconductor laser as in Example 1, stress on the active layer will be reduced. becomes significantly smaller, improving the initial characteristics and reliability of the semiconductor laser. In particular, the improvement in reliability is remarkable, and MT
In TF, an improvement of more than 50% was observed.

In addition, when used in the buried layer of a semiconductor laser as in Example 2, lattice defects are absorbed by the elasticity of the superlattice, resulting in significantly fewer defects than when buried with a normal II-VI group compound semiconductor. A buried layer with good optical properties can be obtained.

(3) Since a flat surface can be obtained, electrode formation is easy;
There is no disconnection of the electrode metal due to the difference in level.

In addition, when used in a semiconductor laser as in Examples 1 and 2, the laser chip is firmly bonded, and the heat generated by the owner when the semiconductor laser is energized can be efficiently dissipated.
(4) Compared to the process of uniformly etching the II-VII superlattice, the process of etching the mask used for selective growth is much easier, resulting in good reproducibility in the etching process. is obtained, and the yield is improved.

[Brief explanation of the drawing]

FIGS. 1(a) to (c) explain the first embodiment of the present invention, and FIG. 1(a) shows Zn5e-Znso, oss
Figure 1(b) is a schematic cross-sectional view of the substrate immediately before forming the eo, qz strained superlattice thin film layer, and Figure 1(b) is a schematic cross-sectional view of the substrate after growth.
C) is a schematic cross-sectional view of a Zn5e-embedded AlGaAs semiconductor laser device. lOl...N-type GaAs substrate 102...N-type rad layer 103...Active layer 104...P-type rad layer 105...P-type contact layer 106...Sin, mask 107...rib 10B...-ZnSe Zn5o , osSeo, *z strained superlattice thin film 109...P-type electrode 110...n-type electrode FIGS. 2(a) to (C) explain the second embodiment of the present invention, and FIG. A) is a schematic cross-sectional view of the substrate immediately before forming the buried layer, FIG. 2(b) is a schematic cross-sectional view after formation, and FIG. 2(C) is a schematic cross-sectional view of the obtained BH type semiconductor laser device. be. 201・-nY3GaAs substrate 202・・DH structure 203・・Stow mask 204・・Zn5e Zn5o, osSeo, qt strained superlattice buried layer 205・・P type electrode 206・・n type electrode and above Applicant Seiko Epson Corporation Agent Patent Attorney Tsutomu Mogami (and 1 other person) -71' (ku) (bn

Claims (1)

[Claims] means for manufacturing a mask on a portion of the surface of the semiconductor substrate;
A method for manufacturing a compound semiconductor thin film, comprising means for manufacturing a II-VI group compound semiconductor superlattice thin film on the surface of the semiconductor substrate other than the mask.