JPH01274421A - Heat treatment method for semiconductor substrate - Google Patents

Abstract

PURPOSE:To enable heat treatment excellent in under-surface uniformity of temperature and in reproducibility by irradiating light from a lamp after covering the whole face of a substrate with metal film so as to heat. CONSTITUTION:For example, to alloy n type GaAs layer (first film) 2 and an electrode metal film (second film) 3 so as to obtain low-resistant ohmic contact, prior to heat treatment, an intermediate layer 4 consisting of SiO2 film is accumulated, by a spatter method, etc., such that is covers the film formed face of a substrate 1, and subsequently a metal film 5 consisting of tungsten (W) film is accumulated by the sputter method, etc., over the entire both faces of the substrate 1. This substrate 1 is put in a light irradiation heat treatment device, and is irradiated and heated in the atmosphere of N2 or inactive gas from both sides of the substrate 1 with a tungsten halogen lamp for heat treatment.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Field of Application] The present invention relates to a method of heat treatment of a semiconductor substrate, and more particularly to a method of heat treatment of a semiconductor substrate for a short time by heating by light irradiation.

[Prior Art] As one of the heat treatment methods for semiconductor substrates, a short time heat treatment method using heating by light irradiation from a lamp has been known. This method irradiates light from a lamp onto one or both sides of a semiconductor substrate, and heats the substrate by absorption of light by the semiconductor substrate, and is used in the manufacturing process of semiconductor devices as a method suitable for short-time heat treatment.

By the way, I! of semiconductor devices! In the manufacturing process, a thin film having a pattern is often formed on the surface of the semiconductor substrate when the semiconductor substrate is subjected to heat treatment. Conventionally, heat treatment by light irradiation heating of a semiconductor substrate having a thin film pattern on its surface has been carried out with the surface of the semiconductor substrate including the thin film pattern exposed, or these semiconductor substrates are heated with silicon dioxide (5i02) or silicon nitride (5iNx). ) and other protective films.

[Problems to be Solved by the Invention] However, in such conventional heat treatment methods, if there is a difference in light absorption efficiency between the semiconductor substrate and the thin film material, selective heating occurs depending on the pattern, causing damage within the substrate surface. Variations occur in the heating temperature.

For example, in the wavelength range of emitted light from a tungsten halogen lamp, which is widely used as a light source for heat treatment, the light absorption efficiency of semiconductor crystal substrates such as silicon (Si) and gallium arsenide (GaAs) is low; Light absorption efficiency increases in the order of crystal and metal. Also,
5i02. The light absorption efficiency of SiNx is extremely low.

Therefore, when a patterned metal film or an impurity-doped semiconductor layer is present on the surface of a semiconductor substrate, there is a problem in that selective heating causes temperature distribution within the substrate surface, impairing the uniformity of the heat treatment effect. Furthermore, for this reason, the local temperature and temperature distribution change depending on the size, shape, and density of the pattern, which poses a major problem in terms of the effectiveness, uniformity, and reproducibility of heat treatment.

SUMMARY OF THE INVENTION An object of the present invention is to provide a method for heat-treating a semiconductor substrate, which eliminates such conventional drawbacks and can heat-treat a semiconductor substrate with good uniformity and reproducibility.

[Means for Solving the Problems] The present invention provides a method for heat treatment by light irradiation of a semiconductor substrate on which a thin film having an arbitrary pattern is formed, in which at least the surface of the semiconductor substrate on the side to be irradiated with light during heat treatment is heated. A method for heat-treating a semiconductor substrate, comprising a step of covering the entire surface with a metal film, and a step of heating the semiconductor substrate by irradiating light.

In the present invention, the metal film to be coated on the entire surface of the substrate may react with the underlying semiconductor substrate or thin film material, or the underlying semiconductor substrate or thin film material may be easily damaged when the metal film is removed after heat treatment. In this case, it is desirable to form an intermediate layer as a protective film over the entire surface of the substrate prior to coating with the metal film. Examples of materials used for such an intermediate layer include 5
i02 is mentioned.

[Function] When the entire surface of the substrate is coated with a metal film and then irradiated with light from a lamp and heated, the temperature rise of the substrate is dominated by the heating caused by the light absorption of the metal film with high light absorption efficiency formed on the entire surface. , non-uniformity in temperature within the plane of the substrate does not occur due to selective heating of the thin film formed on the substrate. At this time, when the temperature of the substrate increases, the effect of heat conduction from the metal film increases, but if the metal film is brought into close contact with the substrate via an intermediate layer, the in-plane uniformity of heat conduction is sufficiently guaranteed. Furthermore, since the thickness of the metal film is sufficiently smaller than the thickness of the semiconductor substrate, there is almost no increase in heat capacity, and the temperature increase/decrease rate, which is important for short-time heat treatment, is not affected.

From the above, according to the present invention, it is possible to perform heat treatment with good in-plane temperature uniformity and reproducibility, regardless of differences in material, size, shape, density, etc. of thin film patterns formed on the surface of a semiconductor substrate. become.

[Example] Next, examples of the present invention will be described.

FIG. 1 is a partial sectional view of a semiconductor substrate for explaining an embodiment in which the method of the present invention is applied to heat treatment for forming an ohmic contact to an n-type GaAs layer.

In FIG. 1, 1 is a semiconductor substrate made of semi-insulating GaAS crystal, and a first thin film 2 made of an n-type GaAs layer having a thickness of 1500 nm and having an island-like pattern on its surface is formed by ion implantation. has been done. Furthermore, an electrode metal film having a two-layer structure of a gold-germanium (AuGe) eutectic alloy film and a nickel (Ni) film having an island-like pattern in contact with a part of the surface of the n-type GaAs layer 2 is used. A second thin film 3 is formed by vacuum evaporation.

In this example, the heat treatment by light irradiation is performed on the n-type GaA
s layer (first thin film) 2 and the electrode metal film (second thin film)
This is done to obtain a low resistance ohmic contact. Before the heat treatment, an intermediate layer 4 made of a 5i02 film with a thickness of 2000 μm is deposited by sputtering or the like so as to cover the thin film formation surface of the substrate 1, and then a tungsten layer with a thickness of about 1 μm is deposited over the entire surface of both sides of the substrate 1. (W) Metal film 5 made of film
is deposited by sputtering or the like. This substrate 1 is placed in a light irradiation heat treatment apparatus, and is heated by light irradiation from both sides of the substrate 1 with a tungsten halogen lamp in an atmosphere of N2 or inert gas, and heat treatment is performed at approximately 450°C for several seconds to achieve a low resistance. Ohmic contact is obtained.

At this time, the temperature rise of the substrate 1 is dominated by the effect of heat generation due to light absorption by the W film 5, and there is a problem of in-plane temperature non-uniformity caused by selective heating in the electrode metal film 3 and the n-type GaAs layer 2. does not occur. Therefore, even if the pattern shape, dimensions, density, etc. of the electrode metal film 3 and the n-type GaAS layer 2 change, ohmic contact can be formed with good reproducibility under the same heat treatment conditions.

Roughly speaking, due to the presence of the 5i02 film as the intermediate layer 4, the electrode metal film 3, the n-type GaAS layer 2 or the GaAs substrate 1
The reaction between the tungsten and the W film 5 is prevented. Furthermore, the 5i02 film 4 becomes a protective film when the W film 5 is removed by etching after heat treatment.
The removal of the 5i02 film 4 can be performed without damaging the GaAs substrate 1, the n-type GaAS layer 2, and the electrode metal film 3. Therefore, the subsequent manufacturing steps can be carried out in the same manner as before.

Although one embodiment of the present invention has been described above, the semiconductor substrate 1 is not limited to GaAs, but may be other compound semiconductors or Si. Furthermore, the purpose of the heat treatment is not limited to forming ohmic contact.

[Effects of the Invention] As explained above, according to the method for heat treatment of a semiconductor substrate of the present invention, a metal film with high light absorption efficiency is formed on at least the surface of the semiconductor substrate on the light irradiation side before heat treatment by light irradiation. Accordingly, it is possible to suppress the occurrence of in-plane temperature non-uniformity caused by the thin film pattern formed on the surface of the semiconductor substrate. Therefore, the pattern size, shape,
Since heat treatment can be performed without deterioration of temperature uniformity or reproducibility due to changes in density, it has a remarkable effect on improving the efficiency in manufacturing semiconductor devices.

[Brief explanation of the drawing]

FIG. 1 is a partial sectional view of a semiconductor substrate for explaining one embodiment of the present invention. 1... Semiconductor substrate 2... First thin film 3...
・Second thin film 4...Intermediate layer 5...Metal film

Claims (1)

[Claims] (1) In a method of heat treatment by light irradiation of a semiconductor substrate on which a thin film having an arbitrary pattern is formed, a step of covering the entire surface of the semiconductor substrate with a metal film at least on the side that is irradiated with light during heat treatment; A method for heat treatment of a semiconductor substrate, comprising the step of heating the semiconductor substrate by irradiating light.