JPS6037122A - Annealing method of semiconductor substrate - Google Patents

Abstract

PURPOSE:To inhibit the generation of a slip line based on the temperature gradients of the central section and peripheral section of a semiconductor substrate, and to anneal the whole surface of the substrate homogeneously by heating the substrate under the state in which the periphery of the substrate is surrounded by an infrared absorber. CONSTITUTION:A smiconductor sample is surrounded by a carbon thin sheet 7, heat dissipation in the lateral direction from the end surface section of the semiconductor substrate 3 is offset by heat dissipation from the carbon thin sheet 7, the temperature-rise characteristics of the central section and peripheral section of the substrate 7 are made the same, and the generation of slip lines in the peripheral section of the substrate is prevented. Carbon can be processed easily to a circle or a D-shape while being fitted to the substrate because it has excellent workability, and it is desirable that the surface is coated previously with SiC.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for annealing a semiconductor substrate, and more specifically, slip lines (dislocation lines running along the valve opening direction of a crystal) caused by thermal stress applied during high temperature and short time annealing using infrared irradiation.
The present invention relates to a semiconductor substrate annealing method that makes it possible to suppress the occurrence of .

In recent years, development of highly integrated and high-performance integrated circuits on silicon substrates and gallium arsenide (hereinafter referred to as GaAs) substrates has been progressing using ion implantation technology.

These integrated circuits are manufactured by integrating basic elements such as field effect transistors and diodes on an n-type or p-type conductive layer formed on a semiconductor substrate. In order to improve performance, it is essential to form an impurity concentration distribution controlled by the linesman.

Recently, a high-temperature, short-time annealing method using infrared irradiation from a halogen lamp or the like has been studied as an annealing method after ion implantation. By using this annealing method, thermal diffusion of impurities in a semiconductor can be suppressed to a lower level than in the conventional electric furnace annealing method, and a steep impurity distribution can be formed.

However, in this short-time annealing with infrared irradiation, a thermal gradient occurs between the center and the periphery of the semiconductor substrate during the rapid temperature rising process, and the resulting thermal stress causes slip lines at the periphery of the semiconductor substrate. This phenomenon is often observed.

Thermal gradient between semiconductor substrates occurs because heat is absorbed and heat is dissipated differently in the central and peripheral areas of the semiconductor substrate.

FIG. 1 schematically shows how heat is absorbed and dissipated within the plane of a semiconductor substrate. 1 indicates incident heat, 2 indicates dissipated heat, and 3 indicates a semiconductor substrate. Most of the incident heat is supplied by parallel infrared rays that are incident perpendicularly to the sample surface, so heat absorption mainly occurs at the main plane of the semiconductor substrate, and heat absorption from the edge of the substrate is caused by heat incident from the lateral direction. There are very few, very few.

On the other hand, heat dissipation occurs uniformly over the entire surface of the semiconductor substrate, regardless of whether it is a main plane or an end surface. In short-time annealing using infrared irradiation, the temperature increase due to annealing occurs selectively in the annealed sample, and the temperature increase in the annealing atmosphere is very small, so that almost no heat is absorbed from the annealing atmosphere by the semiconductor substrate. Therefore, the difference in the state of heat absorption and heat dissipation between the main plane part and the end face part of the semiconductor substrate directly appears as non-uniformity of coverage within the plane of the semiconductor substrate.

As a result, as shown in Figure 2, when a semiconductor substrate is annealed by short-time annealing using infrared irradiation, the temperature rise at the periphery is smaller than that at the center of the semiconductor substrate, and thermal stress due to the temperature gradient causes a rise in temperature at the periphery of the substrate. A slip line occurs.

An object of the present invention is to provide a method for annealing a semiconductor substrate, which makes it possible to suppress the occurrence of slip lines due to the temperature gradient between the center and periphery of the semiconductor substrate and to perform uniform annealing over the entire surface of the semiconductor substrate. There is a particular thing.

A feature of the present invention resides in that, in the process of performing high-temperature, short-time heat treatment on a semiconductor substrate by infrared irradiation, the semiconductor substrate is heated while being surrounded by an infrared absorber.

The content of the present invention will be explained below using experimental facts and examples.

FIG. 3 is a diagram for explaining the conventional method, and FIG. 4 is a diagram for explaining the method according to the present invention. In FIGS. 3 and 4, 4 is an infrared lamp, 5 is an infrared reflector, 6 is a substrate holder, and 7 is a thin carbon plate. By surrounding the semiconductor sample with a carbon thin plate, the lateral heat dissipation from the edge of the semiconductor substrate is offset by the heat dissipation from the contacting carbon thin plate, so the temperature rise characteristic within the semiconductor substrate plane is reduced to the center of the substrate. This makes it possible to make the area and the peripheral area the same, and it is possible to prevent the occurrence of slip lines at the peripheral area of the substrate. The reason why carbon is used as a material surrounding the semiconductor substrate is because it has good processability.
The advantage is that it can be easily processed into a circular or D-shape to match the shape of the substrate. The thickness of the carbon thin plate is 1 to 1.5.
The surface is preferably coated with 8iC.

As a result of short-time annealing at 950° C. for 4 seconds on a 21-nchφ GaAs substrate using the method of the present invention, slip lines of more than 5 lines were observed on the substrate surface after annealing using the conventional method. No slip lines were detected even when observed using an optical microscope (Wt) or a mirror, demonstrating the usefulness of this method.

By using the annealing method of the present invention, it is possible to improve the uniformity of characteristics within the plane of the semiconductor substrate, and to increase the effective area within the plane of one semiconductor substrate.

[Brief explanation of drawings]

Figure 1 shows how heat is absorbed and dissipated in the plane of a semiconductor substrate, Figure 2 shows the temperature LW gradient that occurs in the plane of the semiconductor substrate during short-time annealing with infrared irradiation, and Figure 3 shows the conventional method. FIG. 4 is a sectional view showing a holding part for a semiconductor substrate in an annealing method according to the present invention. In the figure, 1 indicates incident heat, 2 indicates dissipated heat, 3 indicates a semiconductor substrate, 4 indicates an infrared lamp, 5 indicates a substrate holder with 6 infrared reflectors, and 7 indicates a thin carbon plate. Figure 3 Cow diagram

Claims (1)

[Claims] 1. A method of annealing a semiconductor substrate, characterized in that, in the step of subjecting a semiconductor substrate to high-temperature, short-time heat treatment by infrared irradiation, the semiconductor substrate is heated while being surrounded by an infrared absorber.