JP2778068B2 - Heat treatment method for semiconductor device - Google Patents

Description

The present invention relates to a method for manufacturing a semiconductor device, and more particularly to a method for heat-treating a semiconductor substrate.

[Conventional technology]

In a manufacturing process of a semiconductor device, heat treatments such as formation of a thermal oxide film on a semiconductor substrate, activation of a dopant after ion implantation, and reflow of a passivation film are performed. Usually, this heat treatment is performed using a horizontal electric furnace, but in recent years, a lamp heating device has been used to increase the diameter of a wafer and to shorten the processing time. As shown in FIG. 4, the conventional lamp heating apparatus has a structure in which a quartz halogen lamp 1 is disposed above and below a processing chamber 2. The figure shows a cross-sectional view when the GaAs substrate 6 is being heat-treated. The GaAs substrate 6 is placed on the susceptor 3 and the periphery of the wafer is fixed by the guard ring 7.

[Problems to be solved by the invention]

In the above description, the reason why the periphery of the wafer is fixed by using the guard ring 7 is to prevent the GaAs substrate 6 from warping due to the heat treatment and generating internal strain. The guard ring 7 is made of a GaAs material and clamps the wafer with the same expansion coefficient. If the temperature rise of the semiconductor substrate is uniform on the substrate surface, the warpage of the substrate is small. In a horizontal electric furnace, the air in the plane and the periphery of the substrate, that is, the temperature of the substrate is uniformly increased over a relatively long time, so that the warpage of the substrate is small. However, in the lamp heating, only the portion irradiated with the lamp is rapidly heated, so that the peripheral portion also has heat dissipation, the temperature is not uniform unlike the central portion, and warpage is likely to occur.

In order to solve the above problem, it is better not to make the amount of light irradiated to the semiconductor substrate uniform but to change it appropriately in place. In some cases, a process for heating only a part of the semiconductor substrate may be required.

An object of the present invention is to provide an improved heat treatment method for lamp heating in view of the above circumstances.

[Means for solving the problem]

According to the present invention, in a heat treatment step by lamp heating, a filter means for locally changing an infrared transmittance depending on a silicon oxide film thickness is provided between an infrared light source and a semiconductor substrate, and a light amount irradiated on the semiconductor substrate from the infrared light source is provided. Is adjusted.

(Operation)

Depending on the purpose of the heat treatment, the infrared transmittance of the filter is locally changed. For example, when a thermal oxide film is formed on a silicon flat plate disposed between a lamp above and below a heat treatment chamber and a wafer to be heated, the peripheral portion of the wafer has a large heat dissipation outside the peripheral portion when the lamp is heated. When light is irradiated in this manner, the temperature of the peripheral portion becomes lower than that of the central portion. Therefore, the thickness of the silicon oxide film in that portion of the filter is designed to be thin so that the light amount corresponding to the portion corresponding to the peripheral portion is increased. As a result, the temperature of the semiconductor substrate rises uniformly, and there is no warpage, and a thermal oxide film having a uniform thickness can be formed.

〔Example〕

An embodiment of the present invention will be described below with reference to the drawings. FIG. 1 is a longitudinal sectional view of the lamp heating apparatus according to the present embodiment. The semiconductor substrate 5 carried by a belt or the like is placed on the susceptor 3 and loaded into the processing chamber 2. Above and below the processing chamber 2, there are quartz halogen lamps 1, and the semiconductor substrate 5 is rapidly heated by light emitted therefrom. A silicon flat plate 4 is arranged between the quartz halogen lamp 1 and the semiconductor substrate 5. As shown in the sectional view of FIG. 2, the silicon flat plate 4 has a silicon oxide film 8 on the surface of silicon 9 and is formed so that the thickness of the oxide film becomes large at the center. Since the silicon oxide film 8 has a lower transmittance in the infrared region than the silicon 9, the silicon oxide film 8 acts as a kind of infrared filter. The transmittance is high at the periphery and low at the center. Characteristics. Therefore, the intensity of infrared light generated from the quartz halogen lamp 1 is modulated by the silicon flat plate 4 and emitted to the semiconductor substrate 5.

FIG. 3 is a longitudinal sectional view of a reference example of the present invention. In implementing this reference example, in addition to providing a filter separately from the semiconductor substrate as in the above-described embodiment, an oxide film is formed on the semiconductor substrate itself, and the thickness of the oxide film is locally changed. Thus, the heat treatment can be performed by operating as a filter. This filter means is suitable for the case where the element specific region of the semiconductor device is subjected to heat treatment at a temperature different from that of the other specific region. As shown in the figure, the silicon oxide films 8, 8 'depend on the location so that the transmittance is different.
Is formed by changing the thickness.

A thick silicon oxide film 8 having a low transmittance is formed on the P-type diffusion layer 10 which has already been pressed, and a thin silicon oxide film 8 'is formed on the N-type diffusion layer 11 to be pressed. The amount of transmitted heat is increased from the region of the P-type diffusion layer 10. With this method, the N-type diffusion layer 11 can be formed by heat treatment without affecting the impurity distribution of the P-type diffusion layer 10.

〔The invention's effect〕

As described above, in the heat treatment method of the present invention, a semiconductor substrate is subjected to heat treatment by lamp heating. However, the thickness of a silicon oxide film provided on a silicon flat plate is locally changed so that transmission in an infrared region is performed. The filter was used as an infrared filter having spatial characteristics. In the reference example, when the lamp is heated from each of the semiconductor devices, the entire surface of the semiconductor substrate is uniformly heated to the periphery to prevent warping or to provide a heating effect only to a specific region of the semiconductor device. it can.

[Brief description of the drawings]

FIG. 1 is a longitudinal sectional view of a lamp heating apparatus for carrying out an embodiment of the present invention, FIG. 2 is a view showing a silicon flat plate used as a filter means, and FIG. 3 is a longitudinal sectional view of a semiconductor integrated circuit showing a reference example. FIG. 4 is a longitudinal sectional view of a conventional lamp heating apparatus. 1. Quartz halogen lamp, 2. Processing chamber, 3. Susceptor, 4. Silicon flat plate (filter), 5. Semiconductor substrate, 8, 8 'Silicon oxide film.

──────────────────────────────────────────────────続 き Continued on the front page (58) Field surveyed (Int.Cl. ⁶ , DB name) H01L 21/26

Claims (1)

(57) [Claims] In a manufacturing process of a semiconductor device, a filter means for locally changing an infrared transmittance according to a silicon oxide film thickness is provided between an infrared light source and a semiconductor substrate, and the semiconductor substrate is irradiated from the infrared light source. A heat treatment method by lamp heating, which comprises adjusting a light amount.