JPS60216561A - Heat-treating method - Google Patents

Abstract

PURPOSE:To enable a required surface area and the depth of an object to be easily heated to a fixded temperature by a method wherein a surface area to be heated is scanned with a light beam with a wavelength and a light amount selected according to the heating temperature and the heating depth. CONSTITUTION:The Si substrate 1 having a film 11 of diffusion impurity source on the surface is placed in a reaction chamber 2, and N2 gas is introduced after evacuation of the chamber 2 by a vacuum pump 3. Then, a region of the substrate 1 where the impurity is to be reduced is scanned with a near infrared oscillated beam 5 of YAG laser incident onto the substrate 1. Thereby, the surface of the substrate is heated, and the impurity diffuses out of the film 11 into the substrate 1 only at the region irradiated with the beam. This manner enables only the required region to be heated to a fixed temperatue to a fixed depth by changing and controlling the light wavelength and the light amount.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of the Invention] The present invention relates to a heat treatment method for heating a portion of an object to a desired temperature.

[Prior art and its problems]

To heat an object to a desired temperature, the object is usually inserted into a furnace having a high-temperature space, or immersed in a high-temperature liquid. Therefore, the heating temperature is regulated by the temperature of the space or liquid, and in order to change the heating temperature, the temperature must be adjusted each time, which requires a considerably long time depending on the heat capacity. On the other hand, direct heating methods include induction heating in which a conductive object is heated by electromagnetic induction, electrostatic heating in which a dielectric is heated by dielectric loss, and microwave heating in which a non-conductor is heated by microwaves. However, these devices are expensive, and the temperature is often adjusted by adjusting the heating input, making delicate temperature adjustment difficult. Infrared heating, which transmits heat energy through infrared radiation, is also widely used.
The entire surface of the object is heated, and it is difficult to maintain the delicate heating temperature aX. On the other hand, with the development of semiconductor technology, it has become necessary to heat a part of a semiconductor substrate, that is, a predetermined planar region or a predetermined thickness from the surface, in order to diffuse impurities or eliminate surface strain. In this case, if a predetermined heating temperature is not satisfied for a predetermined area, not only will the heating effect not be achieved, but the characteristics of the semiconductor device may be adversely affected.

Electron beam heating is known as a method of locally heating, but in this case as well, there are limits to the adjustment of heating temperature and heating depth, and the device is expensive. □ [Object of the Invention] An object of the present invention is to eliminate the above-mentioned drawbacks and provide a heat treatment method that can easily heat a predetermined surface area and a predetermined depth of an object to a predetermined temperature. .

[Key points of the invention]

According to the present invention, the above object is achieved by scanning the surface area to be heated with a beam of light having a wavelength and light intensity selected according to the desired heating temperature and heating depth.

[Embodiments of the invention]

Embodiments of the present invention will be described below with reference to the drawings. In FIG. 1, a silicon substrate l having a diffused impurity source film 11 on its surface due to precipitation from the gas phase is placed at the bottom of a reaction chamber 2, and after the inside of the reaction chamber 2 is evacuated by a vacuum pump 3, a nitrogen cylinder 4 is evacuated. N2 gas is introduced, and near-infrared oscillation light 5 of a wavelength of 1.064 m from a NdYAG laser is made incident on the substrate 1 via a mirror 6 and a lens 7 to scan the region of the substrate 1 into which impurities are to be introduced. When the energy density of the laser beam on the substrate is set to 1.751/cIa,
The surface of the substrate 1 is heated to 1400-1500°C. As a result, impurities from the impurity film 11 are diffused into the substrate only in the light irradiation region. COz, which oscillates mid-infrared light with a wavelength of 10.6 μm, is used for heating for impurity diffusion.
Gas lasers are also suitable. As the frequency decreases, it directly excites lattice vibrations and improves the efficiency of conversion into thermal energy.

In the MO8 structure, heat treatment to eliminate dangling bonds at the interface between the gate oxide film and the silicon substrate, that is, annealing, is performed using KvF with a wavelength of 2490A, for example.
It is preferable to use excimer laser oscillation light or ruby laser oscillation light with a wavelength of 6940 k.

Furthermore, it is also possible to irradiate light with an appropriate wavelength by controlling the wavelength using one light source. Examples of this include a dye laser whose oscillation light has a wide wavelength range and whose band is narrowed by using an optical element such as a diffraction grating, prism, etalon, or filter as a resonator, or a dye laser that uses synchrotron radiation (80R light) and a diffraction grating. It is effective to use combinations such as

The depth of the heated layer depends on the penetration distance of the irradiated light into the object. The penetration distance is inversely proportional to the object's absorption coefficient for the light. FIG. 2 shows the wavelength dependence of the light absorption coefficient of silicon and the penetration distance of light in silicon at 25°C. It is therefore possible to heat thick layers by using light with a long wavelength. Thereby, for example, the diffusion depth of impurities can be precisely adjusted.

〔Effect of the invention〕

When heating an object by thermal radiation using light, the present invention irradiates the object with a beam, and by changing and controlling the wavelength and intensity of the light, only a predetermined area is heated to a predetermined temperature to a predetermined thickness. It heats and can be extremely effectively applied to impurity diffusion in semiconductor substrates or annealing to eliminate surface strain, which requires particularly delicate control.

[Brief explanation of the drawing]

FIG. 181 is a sectional view of a device according to an embodiment of the present invention, and FIG. 2 is a diagram showing the relationship between the penetration distance of light into silicon and the absorption coefficient of light in silicon and wavelength. 1... Silicon substrate, 11... Impurity source film, 2...
-Reaction chamber, 4...Nitrogen cylinder, 5...YAG laser light. 7 length (pre)

Claims (1)

[Claims] 1) A method of heating a predetermined surface area of an object to a predetermined temperature to a predetermined depth, in which the surface area to be heated is heated by a beam of light with a wavelength and light intensity selected according to the heating temperature and heating depth. A heat treatment method characterized by scanning.