JPH0212941A - Manufacture of semiconductor device - Google Patents

Abstract

PURPOSE:To prevent boron from diffusing in the sidewall of a groove and to obtain a semiconductor device in which its quality and yield are improved by forming an insulating film on the surface of the groove formed in a semiconductor substrate, removing the film on the bottom surface of the groove, and then implanting the boron to form a channel stopper layer. CONSTITUTION:An N-type impurity layer 2 is formed by an epitaxially growing method on the surface of a P-type semiconductor substrate 1, and a silicon oxide film 4, a silicon nitride film 5, an insulating film of the silicon oxide film 4 are sequentially formed thereon. Then, a thin silicon oxide film 4A is formed on a groove 3 by thermally oxidizing, and the film 4A in the bottom of the groove 3 is removed by a reactive ion etching method. Then, boron is ion implanted, heat treated to form a thin silicon oxide film and a P-type impurity layer 6 of a channel stopper on the bottom of the groove, a polycrystalline silicon film 7 is grown, and a dielectric isolation groove is formed. Since the layer 6 is formed after the film 4A is formed on the side face of the groove 3, boron is not diffused in the silicon layer on the side face of the groove 3.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a method for manufacturing a semiconductor device, and more particularly to a method for forming an isolation trench.

[Conventional technology]

Conventionally, the manufacturing method for this type of semiconductor device first began with the method shown in Fig. 3 (
As shown in a), for example, a P-type semiconductor substrate made of silicon has an N-type impurity layer 2 on the surface and an insulating film formed with a silicon oxide film 4 on the upper and lower surfaces of a silicon nitride film 5 used as a mask during ion implantation. 1, a predetermined pattern of grooves 3
form.

Next, as shown in FIG. 3(b), boron ions are implanted to form a P-type impurity layer 6 as a channel stopper at the bottom of the trench.

Next, as shown in FIG. 3(c), after forming a silicon oxide film 4A by thermal oxidation or CVD, a polycrystalline silicon film 7 is grown inside the trench to form an insulating isolation trench. .

[Problem to be solved by the invention]

In the conventional semiconductor device manufacturing method described above, boron ions for a channel stopper are ion-implanted after trench formation, so that boron out-diffusions depending on the oxidation conditions when oxidizing the silicon surface. Therefore, boron is diffused into the sidewall of fi3 and a P-type impurity layer is formed on the sidewall.
This has the disadvantage that the characteristics of the transistor deteriorate.

[Means to solve the problem]

The method for manufacturing a semiconductor device of the present invention includes the steps of forming a groove for insulation isolation in a semiconductor substrate, forming an insulating film on the surface of the groove and then removing the insulating film at the bottom of the groove, and removing the insulating film from the bottom of the groove. The method includes a step of introducing boron into the bottom of the removed groove to form a channel stopper layer.

〔Example〕

Next, embodiments of the present invention will be described with reference to the drawings.

FIGS. 1(a) to 1(d) are cross-sectional views of semiconductor chips arranged in the order of steps for explaining a first embodiment of the present invention.

First, as shown in FIG. 1(a), an N-type impurity N2 is formed on the surface of a P-type semiconductor substrate 1 by epitaxial growth, and then a silicon oxide film 4. Silicon nitride film 5. An insulating film having a three-layer structure of silicon oxide film 4 is formed. Next, a groove 3 for insulation isolation reaching the inside of the P-type semiconductor substrate 1 and having a width of 1 μm is formed using photolithography and etching techniques.

Next, as shown in FIG. 1(b), a thin silicon oxide film 4A is formed on the surface of the groove 3 by thermal oxidation.

Next, as shown in FIG. 1(c), a thin silicon oxide film 4 at the bottom of the groove 3 is etched using a reactive ion etching method.
Etch and remove A.

Next, as shown in FIG. 1(d), boron ions are implanted, and then the temperature is 900°C to 1000°C in an oxidizing atmosphere.
A heat treatment is performed at .degree. C. to form a thin silicon oxide film and a P-type impurity layer 6 serving as a channel stopper on the bottom surface of the trench.

Next, a polycrystalline silicon film 7 is grown to fill the trench 3, thereby completing the insulation isolation trench.

According to the first embodiment, ? Since the P-type impurity layer 6 is formed by boron ion implantation after forming the silicon oxide film 4A on the side surface of the trench s3, boron is not diffused into the silicon layer on the side surface of the groove 3.

FIG. 2 is a cross-sectional view of a semiconductor chip shown in the order of steps for explaining a second embodiment of the present invention.

First, as shown in FIG. 2(a), an N-type impurity layer 2, a silicon oxide film 4, and a silicon nitride film 5 are formed on a P-type semiconductor substrate 1 by the same process as in the first embodiment, and then trenches are formed. form 3. Next, after forming a thin silicon oxide film 4A in the trench 3, the silicon oxide film 4A at the bottom of the trench is removed.

Next, as shown in FIG. 2(b), boron is diffused using a diffusion method to form a P-type impurity layer 6 and a boron-containing glass M8.

Next, as shown in FIG. 2(C), the boron-containing glass layer 8 formed by the diffusion method is removed by etching with a hydrofluoric acid aqueous solution, and then heat treated at 900 to 1000°C in an oxidizing atmosphere. Then, a thin silicon oxide film is formed on the bottom surface of the groove 3.

Next, as shown in FIG. 2(d), a polycrystalline silicon film 7 is grown to fill the trench 3, thereby completing the insulation isolation trench.

According to the second embodiment, since the P-type impurity N6 as a channel stopper is formed by the diffusion method, the first
This method has the advantage that damage to the silicon crystal layer can be reduced compared to the ion implantation method of the embodiment.

〔Effect of the invention〕

As explained above, the present invention forms an insulating film on the surface of a trench formed in a semiconductor substrate, removes the insulating film at the bottom of the trench, and then introduces boron to form a channel stopper layer. This can prevent boron from diffusing into the wall. Therefore, since the characteristics of the transistor can be stabilized, a semiconductor device with improved quality and yield can be obtained.

[Brief explanation of the drawing]

1(a)-(d) and FIG. 2(a)-(d) are cross-sectional views of semiconductor chips arranged in process steps for explaining the first and second embodiments of the present invention. Figure 3 (a) to (c)
1 is a cross-sectional view of a semiconductor chip for explaining a conventional method of manufacturing a semiconductor device. DESCRIPTION OF SYMBOLS 1... P-type semiconductor substrate, 2... N-type impurity layer, 3...
... Groove, 4, 4A... Silicon oxide film, 5... Silicon nitride film, 6... P-type impurity layer, 7... Polycrystalline silicon film, 8... Boron-containing glass layer.

Claims (1)

[Claims] A step of forming a trench for insulation isolation in a semiconductor substrate, a step of forming an insulating film on the surface of the trench and then removing the insulating film at the bottom of the trench, and a step of applying boron to the bottom of the trench from which the insulating film has been removed. A method for manufacturing a semiconductor device, comprising the step of forming a channel stopper layer.