JPS6029217B2 - Manufacturing method of semiconductor device - Google Patents

Description

[Detailed description of the invention]

The present invention provides ohmic performance of gold-zinc (Au-Zn) alloy.
The present invention relates to a method suitable for manufacturing a semiconductor device having contact electrodes. Conventionally, if GaAs is n-type, gold-tin (Au-S
n) alloy, and in the case of p-type, an Au-Zn alloy is used. By the way, when the Ga carrier is p-type and an Au-Zn alloy is used, good ohmic contact cannot often be obtained. That is, to form an Au-Zn alloy electrode, a method of vapor depositing an Au-Zn alloy on a GaAs substrate is often used, but generally Au and Zn have significantly different vapor pressures. If it were deposited as is, Zn would be deposited first and then Au would be deposited, so the deposited layer would be separated into two layers. FIG. 1 shows the state, where 1 is a p-type Ga wafer, 2 is a Zn layer, 3 is an Au layer, and 4 is a position where an aluminum Schottky barrier electrode is to be formed.
In addition to the fact that the vapor deposited layer is divided into two layers, if heat treatment is applied to form an ohmic contact as it is, only Zn will be diffused due to the difference in diffusion coefficient with respect to 0aAs. As a result, it is difficult to form a good Au-Zn alloy ohmic contact electrode. Incidentally, the characteristics of Au and Zn are as follows. Boiling point Diffusion coefficient for Ga vessel Au 271
0〇○〕 1.0×10-3Zn 907〔
00] 15 The present invention eliminates the drawbacks of the prior art and makes it possible to form a good ohmic contact electrode of Au-Zn alloy, which will be described in detail below. In the present invention, during the vapor deposition of Au and Zn, the Zn layer is sealed in a sandwich shape with the Au layer, thereby preventing Zm alone from being diffused into the semiconductor wafer during the heat treatment. Homogeneous Au-Zn on top
An alloy is formed, and then Au--Zn is diffused onto the semiconductor surface to form an alloy with the semiconductor to form a good ohmic contact electrode. Next, an embodiment will be described with reference to FIG. First, when performing vapor deposition, an Au source and a Zn source are set separately, and as shown in FIG.
s Au layer 1 2, Zn layer 1 3 on semiconductor wafer 1 1
, Au layers 1 to 4 are formed in this order. Layer 1 of these
The thickness ratio of 2 to 14 may be about 1:1:2. Next, when this was heat-treated for 2 minutes at a temperature of 500 CO in a nitrogen (N2) atmosphere, a good Au-Zn
An alloy layer is formed. In this way, 0.5
It is easy to form an Au-Zn alloy layer having a thickness of approximately [French m]. Thereafter, appropriate heat treatment may be performed to diffuse the Au-Zn alloy onto the surface of the semiconductor wafer 11 to form an ohmic contact electrode. In the above embodiment, there are three vapor deposited layers, but depending on the conditions, it is possible to form a more homogeneous alloy layer by forming more thin layers. However, even in that case, the bottom layer and the top layer must be Au layers. The reason why the lowest layer, that is, the layer closest to the semiconductor wafer 11 is made of Au layer is clear from the above description. The reason why the top layer is an Au layer is that if it is a Zn layer, the Z
This is because n evaporates and an Au-Zn alloy cannot be obtained. FIG. 3 is a diagram for explaining the effects of the present invention, and represents the forward current-voltage characteristics of a Schottky barrier diode. Note that the vertical axis represents the current (1), and the horizontal axis represents the voltage (V). In the figure, A is the characteristic of a Schottky Barrier diode having an ohmic contact electrode of an Au-Zn alloy produced from a three-layer deposited layer of Au+Zn+Au, which is an embodiment of the present invention, and B is a characteristic of a Schottky Barrier diode according to the prior art. This shows the characteristics of a Schottky Barrier diode depending on . The conductivity type of both semiconductors is p.
The alloying temperature was 530 [oC] and the time was 3 [oC].
minutes]. Further, the applied voltage was 0.1 [V] and the current was 10 [mountains A]. As can be seen from the figure, the Schottky barrier diode according to the embodiment of the present invention has excellent start-up characteristics. It has been experimentally confirmed that this is due to the fact that it has a good ohmic contact electrode. FIG. 4 is a diagram showing the relationship between hole concentration and specific contact resistance. In the figure, the black circles (●) are the data regarding the Au-Zn electrode formed by implementing the present invention, and the Au layer with a thickness of 300 [A] and the layer with a thickness of 370 [A] on a p-type GaAs substrate. A Zn layer and an Au layer with a thickness of 2330 [A] are sequentially laminated (this results in the weight [%] of Zn).
, and then heat-treated at a temperature of 350 [° C.] to 400 Co] for 5 [minutes]. Also, in the same figure,
The white square (opening) is Au-Z deposited on the p-type Ga carrier substrate.
n alloy (the weight [%] of Zn is 4 [%]) with a thickness of 6000
[A] and temperature 300

This is data regarding an Au-Zn electrode heat-treated at [00] for 10 [minutes]. Furthermore, in the same figure, the black triangle (▲) indicates p-type Ga.
100 [A] thick Zn layer on As substrate, 1000 [A] thick
The Au layers of [A] are laminated one after another (thereby, the weight [%] of Zn becomes 35 [%]), and then the temperature is 500 [0
0] for 5 [minutes]. Although the conditions for forming each electrode are slightly different, the difference in contact resistance due to the difference in processing conditions is about 5 times at most. Therefore, it can be seen that according to the method of the present invention, an Au-Zn alloy electrode having sufficiently good ohmic contact properties can be obtained. As can be seen from the above explanation, according to the present invention, Au-Zn
When forming an alloy ohmic contact electrode,
A vapor deposition layer is formed such that the bottom layer and the top layer on the semiconductor wafer are Au layers, and a Zn layer is sandwiched between them, and then,
By heat treatment, a good Au-Zn alloy ohmic contact electrode can be obtained, and the characteristics of the semiconductor device are improved. Furthermore, by making the bottom layer of Au, it is possible to improve the adhesion between the semiconductor wafer and the electrode, and by making the top layer of Au, it is possible to prevent so-called ball-up. Fine patterning of electrodes becomes possible.

[Brief explanation of the drawing]

Fig. 1 is an explanatory diagram of a conventional example, Fig. 2 is an explanatory diagram of an embodiment of the present invention, Fig. 3 is a diagram illustrating the current-voltage characteristics of a Schottky Barrier diode, and Fig. 4 is a diagram illustrating the current-voltage characteristics of a Schottky Barrier diode. FIG. 3 is a diagram showing the relationship between concentration and specific contact resistance. In the figure, 11 is a semiconductor wafer, 12 is an Au layer, and 13 is a semiconductor wafer.
indicates a Zn layer, and 14 indicates an Au layer. Figure 1 Figure 2 Figure 3 Figure 4

Claims (1)

[Claims] 1 Au layers and Zn layers are formed in multiple layers on a GaAs semiconductor wafer with at least one Zn layer sandwiched therebetween so that the bottom layer and the top layer are Au layers, and then heat treatment is applied to form an Au-Zn alloy. 1. A method for manufacturing a semiconductor device, comprising the step of obtaining an ohmic contact electrode.