JPS6159869A - Manufacture of semiconductor device - Google Patents

Abstract

PURPOSE:To stabilize the steps by growing the first polysilicon layer after recessing an oxide film of a silicon substrate, selectively removing the polysilicon layer, and growing the second polysilicon layer on the single crystal silicon and polysilicon layer of the substrate. CONSTITUTION:With a mask 31 an oxide film 30 is selectively etched to form in a structure that the surface of the film 30 is recessed on the surface of a silicon substrate 11, and a polysilicon layer 32 is grown on the entire upper surface of the substrate 11. When the upper surface is then etched, the layer 32 is selectively retained on the same plane as the mask 31 in the stage of exposing the mask 31. Subsequently, the remaining mask 31 is removed, and, when then epitaxially grown, a polysilicon layer 34 is grown on the layer 32, and a single crystal silicon 33 is grown on the substrate 11. Then, a base and an emitter are formed.

Description

DETAILED DESCRIPTION OF THE INVENTION (Industrial Field of Application) The present invention relates to a method for manufacturing a semiconductor device, and more specifically, to making an external base contact on the side surface of an internal base using polysilicon.

The present invention relates to a method of manufacturing a semiconductor device including a step of forming a pieral transistor.

(Conventional technology) Pie? - Since the planar structure of the transistor has a very large base area, there is a problem that the base-collector capacitance and base resistance become large. In order to solve this problem, U.S. Patent No. 3,600,6
According to the specification of No. 51, a bipolar transistor as shown in FIG. 7 is proposed. That is, all 12 SiO□ films 12 are formed on the N-type silicon substrate 10, and the SiO
□A single-crystal silicon layer 14 is epitaxially grown on all 12 parts of the film 12, a silicon IC 16 is grown on the 5IO2 film 12, and these silicon layers 14 and 16 are doped with L) type. A monocrystalline silicon layer 14 of type P, on the other hand, serves as an internal base region, j?
The IJ silicon layer 16 is used as an external base contact to provide electrical conduction to the side surface of the base region.

5 selectively formed on the silicon layer 14.16
The opening on the single crystal silicon layer (base region) 14 of the IO2 film 18 is doped with N-type impurities to form the emitter region 20, while the opening 22 on the silicon layer 16
is used as a base contact window. According to such a bipolar transistor structure, an increase in switching speed is expected because the base-collector capacitance is reduced. However, it is difficult to form a polysilicon layer that serves as an external base on the field insulating film that is formed in the LOCO8 process used in the IC manufacturing process, and a step is formed between the internal base and the external base. Therefore, there is a risk that poor conduction may occur at the stepped portion.

(Problems to be Solved by the Invention) In the method of the above-mentioned US patent, it is difficult to grow silicon on StO□@12 under the conditions in which epitaxial growth of single crystal silicon 14 is achieved.
If there are no nuclei for polysilicon growth on the O2 film, growth of the polysilicon layer 16 cannot be expected. 1st
As shown in the figure, LOCO8, which is often used in general IC manufacturing.
11 on the silicon substrate using the nitride film 31 as a mask.
Since there is no nucleus for polysilicon growth on the field oxide film 30 formed in the field oxide film 30, it is difficult to grow polysilicon for the external base under epitaxial growth conditions for forming the internal base.

(Means and effects for solving the problems) The present invention has the following features:
A pie that uses polysilicon to make external base contacts to the sides of the internal base? - In a method of manufacturing a semiconductor device including a step of forming a transistor, an oxide film selectively formed on the surface of a silicon substrate using an oxidation-resistant mask is recessed on the surface of the silicon substrate, and then the oxide film is formed on the silicon substrate. 1st to
After growing a polysilicon layer of the first polysilicon layer and then selectively removing this first polysilicon layer to expose the mask, the single crystal silicon of the substrate exposed by this mask removal and the first polysilicon layer (1C) By growing a second polysilicon layer on the polysilicon layer, single crystal silicon for forming an internal base is formed on the single crystal silicon, and /IJ silicon for forming an external base is formed on the first polysilicon. This feature allows the first polysilicon layer to be grown on the selective oxide film to serve as the nucleus for the growth of polysilicon for the external base, thereby forming single crystal silicon for the internal base and single crystal silicon for the external base. This allows polycrystalline silicon to be formed simultaneously under normal epitaxial growth conditions.

(Example) Hereinafter, an example of the present invention will be described with reference to FIGS. 1 to 6.

In Figure 1, 30 is a normal LOCO8 or ROX
An oxide film for element isolation, such as 5IO2,
31 is a mask for selective oxidation such as 513N4. Second
The process of forming polysilicon for forming an external base on the oxide film 30 and forming an internal base and emitter on the n-type collector region covered by the mask 31 will be described with reference to the subsequent drawings. Incidentally, the n-type collector region is formed of an epitaxial T6Jll including a high concentration n-type buried layer and a collector reach-through region 37 on the p-type substrate 10, as is generally well known.

In the process shown in FIG. 2, the oxide film 30 is selectively etched using a mask 31 by a wet method using buffered hydrofluoric acid, so that the surface of the oxide film 30 is etched onto the silicon substrate 1.
A concave structure is obtained with respect to the surface. Although the depth of this depression is not particularly limited, it is preferably 0.3 microns or more.

Next, in the process shown in Figure 3, the first
A polysilicon layer 32 is grown over the entire upper surface of the silicon substrate 11. The conditions for CvD growth are silane (5 in.
4) at 600-700℃, 1-50pa (z?skull)
If CVD is used to decompose under reduced pressure conditions, polysilicon with excellent growth properties can be grown.

Next, in the process shown in Figure 4, the top surface is machined.

When etching, polishing, or lapping is performed, removal of the first polysilicon layer 32 is stopped when the mask 31 is exposed, and the first polysilicon layer 32 is selectively left in the same plane as the mask 31. It will be done. However, when etching is performed, it is necessary to control the etching time to selectively remove the polysilicon layer 32. On the other hand? In the case of ridging, etc., the mask 31 made of hard S 1 3N4 serves as a stopper for polishing, etc. Subsequently, when the remaining mask 31 is removed when the process shown in FIG. This means that d IJ silicon nuclei are generated in the external base formation region.

Subsequently, when silicon is grown under normal epitaxial growth conditions in the process shown in FIG. 33 each grow. Since polysilicon nuclei have not yet been generated in the preceding process of this growth process, polysilicon grows as shown at 34 even under normal epitaxial growth conditions for obtaining single crystal silicon 33 with good crystallinity.

Note that this growth condition is, for example, 1000 to 1100°C,
The conditions may be 1 to 100 Pa.

Subsequently, in order to obtain a structure similar to that shown in FIG. 7, the υ base and emitter are formed by a conventional method in the process shown in FIG. That is, after forming an oxide film 41 using selective oxidation or the like on polysilicon that is not used as an active region such as a base region and a collector contact region, p-type impurities such as boron are added to the base region 40 using an appropriate mask. Implant ions. At this time, a thermal oxide film 4 is formed on the surface of the active region.
2 is formed. If necessary, it is also possible to implant p-type impurities at a high concentration into only the base contact portion using an appropriate mask after forming the base region. After that, after opening an emitter window 39, a base contact window 38, and a collector contact window 43 in this thermal oxide film, using an appropriate mask, can impurities such as 1S are implanted into the emitter window and collector contact window by ion implantation, etc. form,
Form an emitter region and a collector contact compensation diffusion region.

(Effects) According to the present invention, since polysilicon for an external base contact is formed on a selective oxide film formed by LoCO8 or ROX, an external base contact is formed on the side surface of an internal base in a semiconductor device fffi structure that involves a LOCO8 or ROX process. It is possible to manufacture a bipolar transistor that takes

Further, in the above semiconductor device, when selective epitaxial growth is performed after forming polysilicon growth nuclei by low pressure CVD in forming polysilicon for an external base contact, selective epitaxial growth can be performed stably.

Furthermore, since the polysilicon layer and the single-crystal silicon layer are planarized during selective epitaxial growth, the connection between the external base and the internal base does not follow the step of the oxide film, which reduces the risk of wire breakage.

[Brief explanation of the drawing]

1 to 6 are process diagrams illustrating an embodiment of the method according to the present invention, and FIG. 7 is a sectional view of a conventional bipolar transistor. 11... Silicon substrate, 30... Oxide film, 31...
-Mask, 32...first polysilicon layer, 33...
- Single crystal silicon, 34... second capital silicon layer. Patent volume, applicant Mujitsu Co., Ltd. Patent Depth Agent

Claims (1)

[Claims] 1. A method for manufacturing a semiconductor device including the step of forming a bipolar transistor with an external base contact on the side surface of an internal base using polysilicon, the method comprising: using an oxidation-resistant mask on the surface of a silicon substrate; After recessing the selectively formed oxide film relative to the substrate surface, a first polysilicon layer is grown on the silicon substrate, and then this first polysilicon layer is selectively removed to form the mask. After exposing the mask, a second polysilicon layer is grown on the single crystal silicon of the substrate exposed by removing the mask and the first polysilicon layer, so that a second polysilicon layer is grown on the single crystal silicon for forming an internal base. A method of manufacturing a semiconductor device, comprising forming single crystal silicon and polysilicon for forming an external base on the first polysilicon.