JPH0232550A - Manufacture of semiconductor device - Google Patents

Abstract

PURPOSE:To improve integration by forming an oxide film on a foundation before forming an epitaxial growth layer and by forming a polysilicon layer on the oxide film during epitaxial growth. CONSTITUTION:A buried layer 2 is formed by diffusing n-type impurity at a specified area on a P-type Si substrate 1 and, at the same time, P<+> diffusion layer 4a is formed by diffusing P-type impurity of high concentration on a periphery of the layer 2 to enclose the layer 2. Then an n-type epitaxial growth layer 3 is formed on a part of the layer 2 and all over the substrate 1 which includes the layer 4a. Of the layer 3, poly-Si layers 4b, 6b are made to grow respectively on the oxide film 7. P-type impurity is diffused from the upper part of the layer 4b, and impurity if diffused from the layer 4a at the same time. A P-type dispersion and diffusion region 4 is thereby formed by simultaneous diffusion from both the upper and lower sides of the layer 3. Since an impurity diffusion coefficient against poly-Si is much larger than that against single crystal Si, diffusion to a rock crystal Si layer, that is, transverse diffusion is controlled, thus reducing a width of the region 4.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a method of manufacturing a semiconductor device, and particularly to a method of manufacturing a semiconductor device having an isolation diffusion region, a collector all region, and the like.

(Prior Art) Fig. 2 is a sectional view showing a part of a bipolar integrated circuit obtained by a conventional manufacturing method.
An n-type epitaxial growth layer 11f3 is formed over the entire surface of the type silicon substrate 1. An n-type buried layer 2 is formed at a predetermined portion of the interface between the p-type silicon substrate 1 and the n-type epitaxial growth layer 3, and this buried layer 2
A p-type isolation diffusion region 4 is formed in the n-type epitaxial growth layer 3 so as to surround it. This isolation diffusion region 4 is formed by simultaneously diffusing p-type impurities from the upper and lower surfaces of the n-type epitaxy 1 fully grown layer 3. By this isolation diffusion region 4, a desired region of the n-type epitaxial growth layer 3 is isolated from other parts in an island-like pn
The junction is separated. On the upper surface of the separated n-type epitaxial growth layer 3, a base region 5 is formed by selectively diffusing n-type impurities, and a collector all region 6 is also formed by diffusing n-type impurities.

[Problem to be solved by the invention]

In the conventional manufacturing method described above, in the process of forming the isolation diffusion region 4 and the collector all region 6, impurities are
Since the diffusion occurs not only in the vertical direction (depth direction) of the type epitaxial growth layer 3 but also in the horizontal direction, the width of the resulting isolation diffusion region 4 and collector all region 6 inevitably becomes large. Therefore, there is a problem in that the degree of integration of the integrated circuit becomes low, and the number of chips that can be obtained from one semiconductor substrate is also limited.

The present invention has been made to solve these problems, and an object of the present invention is to provide a method of manufacturing a semiconductor device that can reduce the width of the isolation diffusion region and the collector all region.

[Means to solve the problem]

A method for manufacturing a semiconductor device according to the present invention is a method for manufacturing a semiconductor device in which impurities are selectively diffused into an epitaxial growth layer to form a diffusion region penetrating the epitaxial growth layer, the method comprising: forming a diffusion region that penetrates the epitaxial growth layer; A polysilicon layer is provided in the diffusion region by selectively forming an oxide film in a portion corresponding to the diffusion region and then forming an epitaxial growth layer.

[Effect]

In this invention, since a polysilicon layer is formed on the oxide film during epitaxial growth, impurities are then diffused into the epitaxial growth layer to form diffusion regions that penetrate the epitaxial growth layer, such as isolation diffusion regions and collector all regions. During formation, the impurity diffuses into the polysilicon layer faster than into the single crystal silicon layer, so that the lateral expansion of the diffusion region is kept small.

〔Example〕

FIGS. 1A to 1D are cross-sectional views showing steps in an embodiment of the method for manufacturing a semiconductor device according to the present invention, in which the steps for manufacturing a bipolar integrated circuit are shown.

In this manufacturing method, first, in the step shown in FIG. A p-expansion layer 4a is formed by diffusing a high concentration of n-type impurity around it so as to surround it.

Next, as shown in FIG. 1B, an oxide film 7 is formed on a part of the upper surface of the buried M2 and almost the entire upper surface of the p+ diffusion layer 4a.
is formed.

Thereafter, as shown in FIG. 1C, an n-type epitaxial growth layer 3 is formed over the entire surface of the n-type silicon substrate 1, including the buried layer 2 and the p+ diffusion layer 4a. At this time, of the n-type epitaxial growth layer 3 formed,
Polysilicon layers 4b and 6b are grown on the oxide film 7, respectively.

Next, n-type impurities are diffused from above polysilicon layer 4b. At this time, impurities are also diffused from the p+ diffusion layer 4a at the same time, so that the n-type isolation diffusion region 4 is formed by simultaneous diffusion from both the upper surface and the lower surface of the n-type 1 bitaxial growth layer 3.

At this time, F T, 1. amins et al.
J, ^p1. phys, 43°83 (1972) J
As disclosed in the literature, the diffusion coefficient of impurities to polysilicon is approximately 100 times larger than that to single-crystal silicon, so that n-type impurities enter polysilicon l1db faster than the surrounding single-crystal silicon layer. The impurity is diffused, and therefore the diffusion into the single crystal silicon layer, that is, the diffusion in the lateral direction, is suppressed to a small level, and the width dimension of the formed isolation diffusion region 4 is reduced. Further, the diffusion treatment at this time can be performed at a lower temperature and at a higher speed than in the past. In this case, the isolation diffusion region 4 is connected to the p" diffusion layer 4a through both ends 8 of the p+ diffusion layer 4a which are not covered with the oxide film 7.

By the isolation expansion r11 region 4 thus formed, a desired region of the n-type epitaxial growth layer 3 is isolated from other parts by a pn junction in the form of an island.

An n-type impurity is diffused into a part of the upper surface of the separated n-type epitaxial growth layer 3, thereby forming a base region 145 as shown in FIG. 1(D). In addition, collector all region 6 is formed by diffusing high concentration n-type impurities from above polysilicon IIU 6b. In this collector all region 6, as in the case of the isolation diffusion region 4 described above, the n-type impurity diffuses into the polysilicon layer 6b faster than into the surrounding single crystal silicon layer, and the collector all region is formed. 6 can be kept small. Collector all region 6 and buried layer 2 are bonded via both ends 9 of oxide film 7 .

〔Effect of the invention〕

As described above, according to the present invention, an oxide film is formed on the base before forming an epitaxial growth layer, and a polysilicon layer is grown on this oxide film during epitaxial growth, so that an epitaxial growth layer including this polysilicon layer is formed. When an impurity is diffused into a region to form a diffusion region penetrating the epitaxial growth layer, such as an isolation diffusion region or a collector all region, the width dimension of the diffusion region becomes smaller, which increases the degree of integration of the semiconductor device obtained. It can be made higher.

[Brief explanation of the drawing]

FIGS. 1A to 1D are cross-sectional views showing the steps of an embodiment of the method for manufacturing a semiconductor device according to the present invention, and FIG. 2 is a cross-sectional view showing a semiconductor device obtained by a conventional manufacturing method. . In the figure, 1 is a p-type silicon substrate, 3 is an n-type epitaxial growth layer, 4 is an isolation diffusion region, 6 is a collector all region, 4b and 6b are polysilicon layers, and 7 is an oxide film. Note that the same reference numerals in each figure indicate the same or corresponding parts.

Claims (1)

[Claims] (1) In a method for manufacturing a semiconductor device in which impurities are selectively diffused into an epitaxial growth layer to form a diffusion region penetrating the epitaxial growth layer, a portion corresponding to the diffusion region on a base before formation of the epitaxial growth layer is A method of manufacturing a semiconductor device, characterized in that a polysilicon layer is provided in the diffusion region by selectively forming an oxide film and then forming the epitaxial growth layer.