JPS58192348A - Manufacture of semiconductor device - Google Patents

Abstract

PURPOSE:To shrink a section between a buried layer and a channel cut region without lowering dielectric resistance, and to integrate the device by thinning an epitaxial layer by a thick oxide film before an impurity is added to the channel cut region, eliminating the need for deep diffusion and preventing diffusion in the lateral direction. CONSTITUTION:The epitaxial layer 12 is superposed to a Si substrate 11 with the buried layer 13, and an oxide film 16, thickness thereof is approximately half the layer 12, is formed by a double mask of SiO2 14 and Si3N4 15. The film 16 is bored 17 selectively and the impurity is added, and channel cuts 18 are formed. The film 16 is removed by a buffer fluoric acid solution, the epitaxial layer 12 is changed into SiO2 19 while using the film 15 as a mask, and the channel cuts 18 are diffused into the substrate 11 to completely isolate element regions. The Si3N4 mask 15 is removed, and the element regions are completed. According to the constitution, sections among the buried layer and the channel cuts are fined without having an effect on the characteristics of the device, and the device can be integrated without lowering dielectric resistance.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method of manufacturing a semiconductor device, and particularly relates to the formation of a channel cut region.

In a bipolar semiconductor device, the dielectric strength of the device is one of the important characteristics. The dielectric strength voltage is
It is determined by the distance between the buried layer region and the channel cut region, and the longer the distance, the higher the dielectric breakdown voltage. However, if the distance between the buried layer region and the channel cut region is long, the degree of integration of the semiconductor device will decrease, which is not preferable.

Conventionally, when forming a bipolar source semiconductor device, impurities are added to the surface of the epitaxial layer in advance to the p-channel region and the p-channel region, and then a thick oxide film is formed by selective oxidation, and at the same time the impurities are added to the desired depth. spread to
The channel cut area was formed. however,
In this formation method, the impurity added to the channel cut region is also diffused in the lateral direction, and the distance of the diffusion is approximately the same as in the depth direction. That is, the epitaxial layer is 2.
In the case of 0 μm, the impurities in the channel cut region will also diffuse in the lateral direction by about 2.0 μm. Therefore, when manufacturing semiconductor devices, in order to prevent a drop in dielectric strength voltage, masks must be designed taking into account the lateral extent of the channel cut region, and the distance between device regions must be reduced by 1 lli. The purpose of the present invention is to eliminate the above-mentioned drawback, shorten the distance between the buried layer region on the mask and the channel cut region compared to the conventional method, and provide insulation. An object of the present invention is to provide an anti-oxidation method for a semiconductor device that does not reduce the withstand voltage.

The present invention includes a process of oxidizing the surface of a semiconductor substrate using a selectively provided thin film of an oxidation-resistant material as a mask to form a relatively thick oxide film on one surface of the semiconductor substrate, and a process of forming a relatively thick oxide film in a channel cut region. selectively removing the oxide film;
The method includes a step of adding impurities using the remaining thick oxide film and the thin film as a mask, a step of removing the remaining thick oxide film, and a step of forming a thick oxide film again using the remaining thin film as a mask. It is characterized by

That is, before adding impurities to the channel cut region, a part of the epitaxial layer is converted into an oxide film by forming a thick oxide film using a selective oxidation method. The epitaxial layer is thinner, so it is not necessary to diffuse impurities as deeply to provide insulation between elements, and at the same time, it is possible to prevent lateral diffusion, so it is possible to close the buried layer region and channel without lowering the dielectric strength. It is possible to shorten the distance of the cut area.

Next, the present invention will be explained by examples.

1 to 6 are cross-sectional views of the main manufacturing steps when the present invention is applied to manufacturing a bipolar type semiconductor device.

First, an epitaxial layer 12 is formed on the surface of the semiconductor substrate 11 on which the buried layer region 13 is formed, and a thermal oxide film 14 and a silicon nitride film 15 are formed on the epitaxial layer 12. The thermal oxide film and silicon nitride film each have a thickness of 50
0A and 100OA are suitable (Fig. 1).
(Next, the silicon nitride film 15 and the thermal oxide film 14 are selectively removed so that they remain only in the element region (FIG. 2). Next, the remaining silicon nitride film 15 is used as a mask to remove the exposed epitaxial film. Converting layer 12 to an oxide film 16 by approximately 1/2 the thickness of the epitaxial layer (FIG. 3).
0 Next, using the photoresist film as a mask, the oxide film 16 in a portion that will become a channel cut region in the future is removed to form an opening 17. Further, the photoresist film is removed, and using the remaining oxide film 16 and silicon nitride film 15t as a mask, impurities are added through the opening 17 to form a channel cut region 18 (FIG. 4).

Next, the remaining oxide film 16 is completely removed using a Fard hydrofluoric acid solution (FIG. 5). Next, using the remaining silicon nitride film 15 as a mask, all of the exposed epitaxial layer 12 is removed again. It is converted into a thermal oxide film 19. At this time,
The channel cut region 18 is diffused into the interior of the semiconductor substrate 11 and completely isolates the device regions (FIG. 6).
0 Next, the remaining silicon nitride film 15 is removed, a transistor is formed inside the element region by a conventional method, and metal wiring is further formed to complete the formation of the device.

As explained in the above embodiments, according to the present invention, before adding impurities to the channel cut region 18, approximately 1/2 of the thickness of the epitaxial layer 12 is converted into an oxide film 16 to form a future channel cut region. Since the epitaxial layer 12 that forms the layer is approximately 1/2 the thickness of the conventional one, the distance over which the impurity doped into the channel cut region is diffused to completely separate the device regions is longer than that of the conventional one. is also about 1/2 less. Therefore, the diffusion spread in the lateral direction is also smaller than in the conventional case.

This reduces the buried layer area and channel forces without any significant effect on the characteristics of the semiconductor device.

It is possible to form a fine gap between the contact regions without reducing the dielectric strength.

Although nine cases have been described above in which the present invention is applied to a bipolar source semiconductor device, it can also be applied to an integrated circuit device including a diode or the like.

[Brief explanation of the drawing]

1 to 6 are cross-sectional views showing main manufacturing steps of an embodiment of the method for manufacturing a semiconductor device of the present invention. In the same figure, 11...semiconductor substrate 12.
...Epitaxial layer, 13...Buried layer region, 14°16.19...Oxide film, 15...
...Silicon nitride film, 17...Opening part, 1
8...Channel cut area. Atsushi 5 Mouth 8 /3 X 61. ￥]

Claims (1)

[Claims] The surface of the C'P conductor substrate (t) is compared by using a thin layer (g) of at least a corrosion-resistant material selectively provided on one surface of the semiconductor substrate as a mask. a step of forming a thick oxide film; a step of selectively removing the -11th thick oxide film in the channel region; and a step of removing impurities from the semiconductor substrate using the remaining thick oxide film and the thin film as a mask. Manufacture of a four-body cow device comprising the steps of: adding to the channel cut region; removing the remaining thick oxide film; and forming a thick oxide film again using the remaining thin film as a mask. Method.