JPS62125669A - Manufacture of bipolar transistor - Google Patents

Abstract

PURPOSE:To improve high frequency characteristic and noise characteristic by implanting first conductivity type impurity to an emitter forming region in a predetermined region by removing a mask layer covered on a predetermined region to form an emitter region. CONSTITUTION:A second conductivity type impurity is implanted to the surface of a first conductivity type semiconductor substrate 11 to specify a base forming region 13, a predetermined region is then covered with a mask layer 15 in the base forming region, the impurity is implanted to the region 13 except the predetermined region covered with the mask layer to specify a graft base forming region 17 of high impurity density. After a base region 18 and a graft base region 19 are formed, the mask layer covered with the predetermined region is removed, a first conductivity type impurity is implanted to an emitter forming region 20 in the predetermined region to form an emitter region 21. Thus, the regions 19, 21 are not superposed on each other to obtain a preferable high frequency characteristic and noise resistance.

Description

DETAILED DESCRIPTION OF THE INVENTION <Field of Application in Industry> The present invention relates to a method of manufacturing bipolar devices 1 to transistor devices, and particularly relates to a method for manufacturing bipolar devices 1 to 1 to transistor devices in which a graft base region and an emitter region are formed in a self-aligned manner. The present invention relates to a method of manufacturing a transistor device.

<Prior Art> FIGS. 2(a) to 2(e) are cross-sectional views showing each step of a conventional method for manufacturing a bipolar device 1 to a transistor device. In this manufacturing method, first, an n-type semiconductor substrate 1 is The surface of the silicon dioxide film 2 is grown by thermal oxidation (see Fig. 2).
a)). Subsequently, the silicon dioxide film 2 is selectively removed by photoetching to expose the region from graph 1 to the region where the base is to be formed. A p-type impurity is introduced into this graft base formation region to form a base region z3 in graph 1 (FIG. 2(b)). Thereafter, the silicon dioxide film 2 is selectively removed through a process on the photoresist 1 to expose the region where the base is to be formed, and P-type impurities are introduced to form the base region 4 (FIG. 2(C)). .

When the step of forming the base region 4 is completed, the surface of the semiconductor substrate 1 is covered with silicon dioxide ll'a 2 again, so the silicon dioxide film 2 is selectively removed in step 5 to form the base region. A region in region 4 where an emitter is to be formed is exposed (FIG. 2(d)). In the next step, n-type impurities are introduced into the region where the emitter is to be formed to form the emitter region 5 (FIG. 2(e)), and the bipolar transistor device is then completed through standard steps.

<Problems to be Solved by the Invention> In the conventional manufacturing method described in -1-, the formation of the graft base region 3, the formation of the base region 4, and the formation of the emitter region 5 are performed in independent photoresist steps that have no relation to each other. Since the emitter region 5 was formed over a period of time, a part of the emitter region 5 may extend into the graft base region 3 having a high impurity concentration due to an error in mask alignment, as shown in FIG. As a result, the capacitance between the base and emitter becomes large, resulting in a problem that the high frequency characteristics of the bipolar transistor device deteriorate.In addition, carrier movement between the base and emitter becomes uneven, resulting in noise characteristics. There was also the problem that it worsened.

Therefore, the present invention can produce a bipolar transistor device with excellent high frequency characteristics and noise characteristics by self-aligning the base region and the emitter region and forming the emitter region in the base region outside the graft base region. The purpose is to provide a method.

<Means for solving the problems> The present invention provides a first conductivity type semiconductor,! &Second on the surface of the board
After defining a region where a base is to be formed by introducing a conductivity type impurity, a predetermined region within the region where a base is to be formed is covered with a mask layer, and a layer is formed in the region where a base is to be formed except for the predetermined region covered with the mask layer. 2-conductivity type impurity is introduced to define a high impurity concentration graph 1 to a region where a base is to be formed. After forming the base region and the craft base region, the mask layer covering the predetermined region is removed, and impurities of a first conductivity type are introduced into a predetermined region in the predetermined region where an emitter will be formed to form an emitter region. The gist is that.

<Example> FIGS. 1(a) to 1(g) are cross-sectional views showing each step of the first example of the present invention. First, the surface of an n-type semiconductor substrate 11 is thermally oxidized to form a silicon dioxide film. 12 to about 5,000 people (Figure 1 (a)).

Subsequently, the base formation area 13 is formed by photoetching.
is exposed, and 1013 to 10'4 of boron is implanted at an energy of about 40 to 50 keV (FIG. 1(b)). Thereafter, the polysilicon film 1-4 covering the exposed surface of the semiconductor substrate 11 and the silicon dioxide film 12 is removed by about 1. O
OO layer is applied, and silicon nitride film 1-5 is further applied to approximately 200 mm.
Zero people arrive at the wave (Figure 1 (C)). A photoresist film]-6 is applied on the silicon nitride film 15 and patterned to form a predetermined area in the base formation area 1; It is covered with a resist film 16. After this, the photoresist film 1-6
The silicon nitride film 15 is selectively removed using as a mask,
Approximately 60 to 70k through the exposed polysilicon film 14
1014 to 1015 boron is implanted into the base formation region 17 of the semiconductor substrate]-1 (FIG. 1(d)). After removing the photoresist film 16, the base region 18 and graphs 1 to 19 are formed by heating in a nitrogen atmosphere at about 1000° C. for about 30 minutes (first
Figure (e)). After this, the polysilicon film 1 is heated in an oxidizing atmosphere.
When the polysilicon film 14 is oxidized, the polysilicon film 14 becomes a silicon dioxide film. During the oxidation of this polysilicon film 14, the polysilicon film under the silicon nitride film 15 ]-4 center part 2
0 is not oxidized (FIG. 1(f)). Subsequently, after removing the silicon nitride film 15, about 1016 n-type impurities are removed from the remaining polysilicon film 1 without being oxidized using about 30 keys.
4 to form an emitter region 21. After that, the base electrode 22, emitter electrode 23 and back metal 24 are connected.
A bipolar transistor device is completed (FIG. 1(g)).

In this embodiment, ions are implanted through the central portion 20 of the polysilicon film that remains unoxidized, so that the impurity concentration in the central portion 20 is +7+<, emitter region 21
Good ohmic contact between the emitter electrode 23 and the emitter electrode 23 can be obtained. Furthermore, the emitter region 21 may be formed after removing the polysilicon film 14 in the emitter formation-r constant region 20,
Alternatively, the emitter region 2 may be formed by making the polysilicon film 14 into doped polysilicon by ion implantation while leaving the polysilicon film 14 in the emitter formation region 20. This example shows an NPN type bipolar 1-transistor, but T)
It can also be applied to an NP type bipolar transistor.

<Effects> As explained below, according to the present invention, the base region is formed outside the predetermined region of the base formation region covered by the mask layer in graph 1, and the emitter region is formed within the predetermined region. As a result, there is no overlap between the graft base region and the emitter region, and a bipolar 1-transistor device having good high frequency characteristics and noise characteristics can be obtained.

[Brief explanation of drawings]

1 - Figures (a) to (g) are cross-sectional views showing each process of an embodiment of the present invention, Figures 2 (a) to (e) are cross-sectional views showing each process of a conventional example, and Figure 3. FIG. 2 is a sectional view illustrating problems in the conventional example. 1]... Semiconductor substrate, 13... Base formation area, 15...
...Mask layer, ]7...Graft base formation area, 18
...Base region, 19 ...Graft base region, 20 ...
. . . Emitter formation planned region, 21 . . . Emitter region. Patent Applicant ROHM Co., Ltd. Representative Patent Attorney Kiyoshi Kuwai - (e5) (b) (C) Figure 1 (CI) ce> Figure 1 (↑) Figure 1 (a) (b) (C) Figure B Figure 3

Claims (1)

[Claims] A step of introducing an impurity of a second conductivity type into the surface portion of the semiconductor substrate of the first conductivity type to define a region where a base is to be formed; a step of covering a predetermined region within the region where a base is to be formed with a mask layer; A step of introducing a second conductivity type impurity into a region where a base is to be formed except a predetermined region covered with a mask layer to define a region where a graft base is to be formed with a high impurity concentration, and forming a base region and a graft base region. a step of removing a mask layer covering the predetermined region and introducing an impurity of a first conductivity type into a region where an emitter is to be formed in the predetermined region to form an emitter region. .