JPS6313342B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method of manufacturing a semiconductor device, and particularly to a method of forming an insulating film made of a thick oxide film on the surface of a silicon semiconductor substrate.

FIG. 1 shows a cross-sectional view of a bipolar transistor as an example of a semiconductor device. 1 is a P-type Si semiconductor substrate, 2 is an N-type epitaxial layer and a collector region, 3 is a P-type base region, and 4 is an N-type emitter region. Reference numeral 5 denotes a thick oxide film (SiO ₂ ) 5 of about 4000 Å, on which electrode windows are opened and electrodes 6, 7, and 8 are provided to each region.

By the way, the oxide film 5 is formed thereon.
It insulates wiring such as Al from the substrate, and must have sufficient withstand voltage and film thickness. Therefore, conventionally, in order to increase the breakdown voltage, an oxide film obtained by thermally oxidizing the surface of the substrate (epitaxial layer 2 in FIG. 1) has been used as the denser oxide film 5. However, due to the large thickness of the film, it is necessary to expose it to an oxidizing atmosphere at a high temperature (for example, 1100°C) for a long time of 20 minutes, and such a process may cause warping of the Si wafer, changes in the diffusion region, and the formation of slit lines within the wafer. This was not a desirable method as it caused financial damage.

On the other hand, there is a technique called spin-on glass in which silicon hydroxide containing a solvent is applied and thermally decomposed to form an oxide film. however
When applied as thick as 4,000 to 6,000 Å, the film thickness became uneven and was unsuitable.

An object of the present invention is to form an insulating film without performing thermal oxidation at high temperatures and for a long time.

The method for manufacturing a semiconductor device of the present invention includes the steps of applying a first insulating film made of a solution containing silicon hydroxide to a predetermined thickness on the surface of a silicon semiconductor substrate, and thermally oxidizing the surface of the silicon semiconductor substrate. Then, a second insulating film made of silicon oxide is formed under the first insulating film.
The method is characterized by comprising a step of forming an insulating film.

An embodiment of the present invention will be described in detail below with reference to the drawings.

FIG. 2 is a sectional view illustrating this embodiment.

Refer to FIG. 2a. A first insulating film 10 made of a mixture of silicon hydroxide (Si(OH) ₄ ) and solvent ethanol is formed on a Si semiconductor substrate 1 (epitaxial layer 2 in the example of FIG. 1).
is applied to a film thickness of approximately 2500 Å. Since the film thickness is not so large, the film thickness is uniform.

Refer to Figure 2b. The surface of the substrate 1 is oxidized by exposing it to a high temperature oxidizing atmosphere of about 1000°C for about 10 minutes, and the second insulating film 11 is formed.
Then, an oxide film 11 having a thickness of about 2000 Å is formed.
At the same time, the first insulating film is thermally decomposed to become a SiOx film, further shrinking to about 2000 Å and becoming denser.

As described above, according to this embodiment, there is no need to perform high-temperature thermal oxidation for a long time, and the first insulating film 10 can be coated sufficiently uniformly in the coating process, and both insulating films 10 and 11 can be coated together. , an oxide film with the required thickness (4000 Å) can be obtained. Furthermore, since the etching rates of both insulating films are almost the same, there is no need to make any difference in the subsequent etching process of the electrode window from that of the conventional method.

As explained above, according to the present invention, since a thermal oxidation process at high temperature and for a long time is required, a thick oxide film with high breakdown voltage can be formed without deterioration of the characteristics of the semiconductor device.

[Brief explanation of the drawing]

FIG. 1 is a sectional view of a general bipolar transistor, and FIG. 2 is a sectional view for explaining one embodiment of the present invention. In the figure, 1 is a silicon semiconductor substrate, 10 is a first insulating film, and 11 is a second insulating film.

Claims (1)

[Claims] 1. Applying a first insulating film made of a solution containing silicon hydroxide to a predetermined thickness on the surface of a silicon semiconductor substrate, and thermally oxidizing the surface of the silicon semiconductor substrate to form the first insulating film. 1. A method of manufacturing a semiconductor device, comprising the step of forming a second insulating film made of silicon oxide underneath.