JPH07249595A - Method for manufacturing semiconductor device - Google Patents

Abstract

(57) [Summary] [Object] To provide a method for manufacturing a semiconductor device that enables ohmic contact between a p-type layer made of a II-VI group compound semiconductor epitaxial crystal and an electrode. A high-concentration p-type ohmic layer formed between a p-type layer made of a II-VI compound semiconductor epitaxial crystal and an electrode layer is formed by the MOCVD method. Due to the different energy states and the possibility of a large tunnel current, an ohmic contact can be easily obtained between the two with a simple manufacturing method. Further, by forming the p-type ohmic layer with the same crystal as that of the p-type layer, lattice matching can be achieved between the p-type layer and the p-type ohmic layer, so that no crystal defect occurs. Furthermore, by forming the p-type ohmic layer by MOCVD, the adhesion between the two layers can be secured, the subsequent heat treatment can be omitted, the process can be simplified, and the adverse effect of heat on the entire semiconductor device can be avoided.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method of manufacturing a semiconductor device having a p-type layer made of a II-VI group compound semiconductor epitaxial crystal on a substrate, and more particularly to the contact portion between the p-type layer and the electrode layer. The present invention relates to a method for manufacturing a semiconductor device having the above.

[0002]

2. Description of the Related Art A molecular beam epitaxy method (hereinafter abbreviated as MBE method in the present specification) is well known as an epitaxial crystal growth method for compound semiconductors.

On the other hand, as a II-VI group epitaxial crystal, a crystal of zinc selenide (ZnSe) is grown on a gallium arsenide (GaAs) substrate, and nitrogen (N) is further introduced as a dopant to obtain a blue laser. A method and an apparatus for forming a p-type crystal have recently been attracting attention and are disclosed in Japanese Patent Laid-Open No.
An example is disclosed in Japanese Patent Publication No. 2-88329.
Also, DePuydt et al. Of the US have proposed a method of generating an active nitrogen beam by an rf plasma excitation cell by the MBE method and realizing nitrogen doping of 10 ¹⁸ cm ⁻³ (Appl.Phys.Lett). .57, 2127 (1991)), which suggests that a low-resistance p-type crystal can be obtained.

At this time, for example, when a p-type layer made of a II-VI group epitaxial crystal such as ZnSe is formed by the MBE method, the gold (A
u) and other electrodes have a large interfacial potential barrier (2 V to
It is conceivable that ohmic contact cannot be obtained and the electrical characteristics thereof deteriorate. This issue is MOMB
The same occurs when the E method or the CBE method is used.

Therefore, for example, a multiple quantum well structure is formed by stacking zinc telluride (ZnTe) and ZnSe on the upper layer of a ZnSe p-type layer by gradually changing the thickness thereof, and forming the multiple quantum well structure on the upper layer. A method of forming an electrode layer has been proposed (see F. Hiei et al. Electron Lett. 29,878 (1993)).

However, the lattice mismatch between ZnSe and ZnTe is different (about 7%).
Therefore, when a multi-quantum well structure is formed, distortion due to stress is caused between layers to cause crystal defects, and not only the durability thereof becomes a problem, but the multi-quantum well structure is complicated, There is also a problem that it is difficult to mass-produce because it is difficult to form.

[0007]

SUMMARY OF THE INVENTION The present invention has been made in view of the problems of the prior art described above, and its main purpose is to provide a p-type layer made of a II-VI compound semiconductor epitaxial crystal and an electrode. It is to provide a method for manufacturing a semiconductor device that enables ohmic contact with the semiconductor device.

[0008]

According to the present invention, the above-mentioned object is achieved by a step of forming a p-type layer made of a II-VI compound semiconductor epitaxial crystal on a substrate and a metal organic chemical vapor deposition (MOCVD) method. Forming a heavily doped p-type ohmic layer on top of the p-type layer;
This is achieved by providing a method for manufacturing a semiconductor device, which comprises, in this order, a step of forming an electrode layer on the upper layer of the p-type ohmic layer.

[0009]

As described above, a highly doped p-type ohmic layer is formed between the electrode layer and the p-type layer made of the II-VI group compound semiconductor epitaxial crystal by the MOCVD method, and is formed by the MBE method or the like. When the energy state of the acceptor is different from that in the above case, and a large amount of tunnel current can be expected due to inclusion of carbon in the crystal, an ohmic contact can be obtained between the two. Also, the p-type ohmic layer has the same II-V as the p-type layer.
By forming the I-group compound semiconductor epitaxial crystal, the original p-type layer and the p-type ohmic layer can be lattice-matched with each other, so that no crystal defect is generated. Furthermore, M
The surface of the p-type ohmic layer formed by the OCVD method is M
Adhesion during electrode layer deposition is better than in the case of forming by the BE method and the subsequent heat treatment can be omitted, so the process can be simplified and adverse effects of heat on the entire semiconductor device can be avoided.

[0010]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT A preferred embodiment of the present invention will be described below with reference to the accompanying drawings.

FIG. 1 is a sectional view of the main part of a semiconductor laser device manufactured by the method of the present invention. Gallium arsenide
As) a n-type ZnSe buffer layer 2 and n
A ZnZe-type cladding layer 3, an active layer 4 made of CdZnSe, a p-type ZnSSe cladding layer 5, and a heavily-doped p-type ZnSe layer 6 are formed in this order by the MBE method and stacked. In addition, heavily doped p-type Z
A p-type ohmic ZnSe layer 7 is stacked on the nSe layer 6 by the MOCVD method, and an Au electrode layer 8 is further formed on the p-type ohmic ZnSe layer 7 by vapor deposition. GaAs substrate 1
An Au / Ge (germanium) electrode layer 9 is formed on the back surface side of the. It should be noted that chlorine (Cl) is used as a dopant for each of the above n-type layers, and nitrogen (N) is used as a dopant for the p-type layers.
Was used.

Here, the p-type ohmic ZnSe layer 7 is
According to the MOCVD method, the crystal growth temperature is 300 ° C., the growth pressure is 76 torr, and dimethyl zinc is 6 × as a source gas.
10 ⁻⁵ mol / min, 1.2 × 10 dimethyl selenium
^-4 mol / min, t-butylamine 6 × 10 ^-5 mo
The crystal growth rate was controlled to 2.5 μm / h while irradiating the substrate 1 with an ultrahigh pressure mercury lamp at 1 / min and H ₂ as a carrier gas at 1 / min, the film thickness was 2000 angstroms, and the carrier (nitrogen) concentration was It was formed to have a size of 2 × 10 ¹⁸ cm ⁻³ .

In practice, the film thickness may be set between 10 angstroms and 2000 angstroms by an applied voltage, and the nitrogen concentration as a carrier is 1 × 1.
It may be set to be between 0 ¹⁶ cm ^{-3 and} 1 × 10 ¹⁹ cm ^-3 .

The Au electrode layer 8 is made of p-type ohmic Zn.
A film was formed on the surface of the Se layer 7 by vapor deposition. Where MO
The surface of the p-type ohmic layer formed by the CVD method is MB
Adhesion during electrode layer deposition is better than when formed by the E method and the like, and adhesion between both layers can be secured without performing subsequent heat treatment.

In the semiconductor device manufactured in this manner, p-type ZnSSe, which has a large interfacial potential barrier, is conventionally used.
Between the cladding layer 5 and the Au electrode layer 8, a p-type ohmic Z
With the nSe layer 7 interposed, ohmic contact between both layers becomes possible. Further, between the p-type ZnSSe cladding layer 5 and the p-type ohmic ZnSe layer 7, a highly-doped p-type ZnSe layer 6 is formed.
The interfacial potential barrier between these layers is reduced by interposing.

In this embodiment, the n-type ZnSe buffer layer 2, the n-type ZnSSe cladding layer 3 and the CdZnS are used.
e active layer 4 and p-type ZnSSe cladding layer 5
And the heavily doped p-type ZnSe layer 6 were formed by the MBE method, but it goes without saying that the same applies when the MONBE method or the CBE method is used. Further, although the crystal growth temperature of the heavily doped p-type layer is set to 300 ° C. in this embodiment, it may be arbitrarily set between 100 ° C. and 400 ° C. within the range permitted by other conditions. Further, in this embodiment, as a raw material for forming the heavily doped p-type layer and the p-type ohmic ZnSe layer 7, I
Although Zn was used as the group I element and Se was used as the group VI element, any of cadmium (Cd), zinc (Zn), magnesium (Mg) manganese (Mn) as the group II element, and sulfur ( S), Selenium (S
Similar results can be obtained by using a raw material selected from among e) and tellurium (Te) as desired. However, it is desirable to use the same material for the heavily doped p-type layer and the p-type ohmic layer because of the problem of the lattice constant. In addition, in this embodiment, gallium arsenide (GaAs) is used as the crystal growth substrate.
Although a substrate is used, a suitable thin film crystal (for example, a gallium arsenide film grown by epitaxial crystal growth) may be formed on a ZnSe, GaP, or gallium arsenide (GaAs) substrate, and the electrode may be other than Au. Platinum (P
t), aluminum (Al), zinc (Zn), palladium (Pd), or a laminated film or alloy in which these are combined may be used.

[0017]

As is apparent from the above description, according to the method of manufacturing a semiconductor device of the present invention, II-V
MBE is formed by forming a highly-doped p-type ohmic layer between the p-type layer made of a Group I compound semiconductor epitaxial crystal and the ohmic electrode layer by the MOCVD method.
Since the energy state of the acceptor is different and the tunnel current can be expected to be large compared with the case where it is formed by the method etc., an ohmic contact can be easily obtained between the two by a simple manufacturing method and a simple structure. Further, by forming the p-type ohmic layer also from the II-VI group compound semiconductor epitaxial crystal similar to the above-mentioned p-type layer, lattice matching can be achieved between the original p-type layer and the p-type ohmic layer, and thus the crystal is formed. No defects will occur. Furthermore, the semiconductor device to which the present invention is applied is not desirable for heat treatment at 300 ° C. for more than 5 minutes,
By forming the p-type ohmic layer by MOCVD, adhesion between both layers can be secured, the subsequent heat treatment (usually 400 ° C., 1 to 2 min) can be omitted, the process can be simplified, and the entire semiconductor device can be formed. The adverse effect of heat can be avoided. From the above, a semiconductor device having good electrical characteristics and high reliability can be manufactured with high yield.

[Brief description of drawings]

FIG. 1 is a cross-sectional view of essential parts of a semiconductor laser manufactured by a manufacturing method according to the present invention.

[Explanation of symbols]

 1 GaAs substrate 2 n-type ZnSe buffer layer 3 n-type ZnSSe clad layer 4 CdZnSe active layer 5 p-type ZnSSe clad layer 6 heavily doped p-type ZnSe layer 7 p-type ohmic ZnSe layer 8 Au electrode layer 9 Au / Ge electrode layer

 ─────────────────────────────────────────────────── ─── Continuation of front page (72) Inventor Tetsuya Suzuki 5-10-1 Fuchinobe, Sagamihara-shi Nippon Steel Corp. Electronics Research Laboratories

Claims (4)

[Claims] 1. A process of forming a p-type layer made of a II-VI group compound semiconductor epitaxial crystal on a substrate, and a p-type layer highly doped in the upper layer of the p-type layer by a metal organic chemical vapor deposition (MOCVD) method. A method of manufacturing a semiconductor device, comprising: a step of forming a type ohmic layer and a step of forming an electrode layer on the p-type ohmic layer in this order. 2. The semiconductor according to claim 1, wherein the p-type layer made of the II-VI compound semiconductor epitaxial crystal is formed by any one of the MBE method, the MONBE method and the CBE method. Device manufacturing method. 3. The II-type p-type ohmic layer
3. The method for manufacturing a semiconductor device according to claim 1, wherein the p-type layer made of a Group VI compound semiconductor epitaxial crystal is formed of a II-VI group compound semiconductor epitaxial crystal made of the same element. 4. The p-type layer made of the II-VI compound semiconductor epitaxial crystal is composed of a plurality of layers, and the layer on the p-type ohmic layer side is more highly doped than the layer on the substrate side. The method for manufacturing a semiconductor device according to claim 1, wherein