JPH01274420A - Heat treatment method for semiconductor substrate - Google Patents

Abstract

PURPOSE:To restrain generation of slip lines, etc., small so as to maintain electric uniformity under the substrate surface by heating a semiconductor substrate by light irradiation after forming a layer high in light absorption factor, introducing impurity in high concentration, on the surface near the outer fringe of the semiconductor substrate. CONSTITUTION:Before forming an ion implantation layer which has an island-shaped pattern on the surface of a substrate 1, impurity in high concentration is introduced in advance into near the outer fringe of a semiconductor substrate 1 by a heat diffusion method or an ion implantation method so as to form a layer 2 high in light absorption factor. Thereafter, when an ion implantation layer which has an island-shaped pattern is formed and light irradiation heating is executed, since the layer 2 to which impurity in high concentration is introduced by absorption of free carriers is high in light absorption factor in the wave length area of light emitted from a tungsten halogen lamp used widely as a light source, by optimizing the thickness and width of the layer 2 and the carrier concentration, the temperature around the substrate 1 can be made equal to or higher than that at the central part to uniform light irradiation. Accordingly, generation of slip lines resulting from temperature drop at the periphery can be restrained.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a method for 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] A short-time heat treatment method that utilizes heating by light irradiation from a lamp has been known as one of the heat treatment methods for semiconductor substrates. In this method, light from a lamp is irradiated onto one or both sides of the semiconductor substrate, and the substrate is heated by the absorption of light by the semiconductor substrate.It is a heat treatment process for activating ion-implanted impurities as a method suitable for short-time heat treatment. It is used for such things.

In particular, in recent years, due to the improved performance of field effect transistors,
It is important to form a shallow and highly concentrated active layer, and it is necessary to suppress the diffusion of implanted impurities in the depth direction, so a heat treatment method using light irradiation that can rapidly raise and lower the temperature has become essential.

[Problem to be solved by the invention] For example, this heat treatment method
In order to activate silicon (Si) ion-implanted to form an n-type operating layer, heat treatment at 800 to 100° C. for several seconds is required.

However, when the substrate is irradiated with light of uniform intensity to perform such heat treatment by light irradiation heating, the heat dissipation from the outer periphery of the substrate is greater than that from the center. There was a problem in that the temperature was lower than the temperature in the center. Particularly in the case of a GaAs substrate, when the temperature at the periphery of the substrate becomes lower than the temperature at the center of the substrate at a temperature of 800°C or higher, slip dislocation lines called slip lines occur, resulting in uniform electrical characteristics within the substrate surface. There was a problem with the loss of sexuality.

An object of the present invention is to provide a heat treatment method for a semiconductor substrate that can eliminate such conventional drawbacks, suppress the occurrence of slip lines, etc., and maintain electrical uniformity within the substrate surface. There is a particular thing.

[Means for Solving the Problems] The present invention includes a step of forming a layer with high light absorption efficiency by introducing a high degree of impurity into the surface near the outer edge of a semiconductor substrate, and irradiating the semiconductor substrate with light. 1. A method of heat-treating a semiconductor substrate, the method comprising: heating the semiconductor substrate by heating the substrate.

The semiconductor substrate used in the present invention is GaA
In addition to compound semiconductor substrates such as S-substrates, Si substrates, etc. can be mentioned.Applicable heat treatment is not limited to heat treatment for ion-implanted layer activation, but can also be used for other high-temperature, short-time heat treatment. can also be applied.

[Effect] Next, the operation of the present invention will be explained with reference to the drawings.

FIG. 1 and FIG. 2 are a sectional view and a plan view, respectively, of a substrate for explaining the present invention in detail. In the figure, reference numeral 1 denotes a semiconductor substrate, for example, an ion implantation layer is formed in an island pattern on one surface of the substrate 1, and heat treatment is performed to activate this ion implantation layer. When the substrate 1 is heated by irradiating uniform light from a lamp from both sides, the temperature of the peripheral part of the substrate 1 becomes lower than the temperature of the central part for the reason mentioned in the prior art section.
Slip lines occur at temperatures above 0°C.

On the other hand, before forming the ion-implanted layer having the island-like pattern, a highly concentrated impurity is introduced into the vicinity of the outer edge of the semiconductor substrate 1 by thermal diffusion or ion implantation, so that the layer has a high light absorption efficiency. Form 2. After that, as described above, by forming an ion-implanted layer with an island-like pattern and performing light irradiation heating, a high concentration can be achieved due to free carrier absorption in the wavelength range of the emitted light from tungsten halogen lamps, which are widely used as light sources. Since the layer 2 into which impurities is introduced has high light absorption efficiency, by optimizing the thickness and width of the layer 2, as well as the carrier concentration, the temperature at the periphery of the substrate 1 can be adjusted to the temperature at the center for uniform light irradiation. It is possible to make it the same or higher than . Therefore,
It is possible to suppress the occurrence of slip lines due to a decrease in temperature in the peripheral area.

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

A semi-insulating GaAs substrate is used as the semiconductor substrate 1 in FIG. 1, and a layer 2 with high light absorption efficiency is preliminarily formed on both sides near the outer periphery of the substrate 1 by 19S,+ ion implantation to a width of 5 mm and a depth of 2000 layers. , concentration 5X1017cm-
Form it so that it becomes 3. Next, on the surface of one side of the substrate 1, 5×101101 of 19Si+ was applied at 30 keV.
An implanted layer (not shown) having an island pattern is formed by ion implantation at a dose of 2C. Briefly, a silicon nitride (5inx) film (not shown) with a thickness of 500 mm is formed on both surfaces of the substrate 1 by CVD or sputtering as a substrate protection film during heat treatment.

This substrate 1 is placed in a light irradiation heat treatment apparatus, and tungsten is removed from both sides of the substrate 1 in an N2 or inert gas atmosphere.
Heat treatment is performed at 950° C. for 5 seconds by irradiating light with a halogen lamp. At this time, since the light absorption efficiency of the layer 2 is higher than that of the GaAs substrate 1, the temperature of the peripheral portion of the substrate 1 does not decrease with respect to the temperature of the central portion, and the generation of slip lines is suppressed. Here, the SiNx protective film is almost transparent in the wavelength range of the irradiated light, and does not affect the effects of the present invention.

[Effects of the Invention] As explained above, according to the heat treatment method for a semiconductor substrate of the present invention, impurities with a high S degree are introduced in advance near the outer edge of the substrate to form a layer with high light absorption efficiency. It is possible to increase the light absorption efficiency in the peripheral area of the substrate and prevent the temperature drop in that area, so even during high-temperature, short-time heat treatment such as activating ion-implanted impurities, slip lines caused by temperature drop in the peripheral area of the substrate can be prevented. The occurrence of can be suppressed. Therefore, the uniformity of electrical characteristics within the substrate is not impaired, so that by applying the method of the present invention to the semiconductor device manufacturing process, a remarkable improvement in production efficiency can be achieved.

[Brief explanation of the drawing]

1 and 2 are a sectional view and a plan view of a semiconductor substrate, respectively, for explaining the present invention in detail. 1... Semiconductor substrate 2... Layer with high light absorption efficiency

Claims (1)

[Claims] (1) The method comprises a step of introducing impurities at a high concentration into the surface near the outer edge of a semiconductor substrate to form a layer with high light absorption efficiency, and a step of heating the semiconductor substrate by irradiating light. Characteristic heat treatment method for semiconductor substrates.