JPS62150772A - Bipolar transistor device and its manufacturing method - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

DETAILED DESCRIPTION OF THE INVENTION <Field of Industrial Application> The present invention relates to a bipolar transistor device and a method for manufacturing the same, and more particularly to a bipolar transistor device with excellent high frequency characteristics and a method for manufacturing the same.

<Prior Art> FIGS. 2(a) to 2(e) are cross-sectional views showing each step of a conventional method for manufacturing a bipolar transistor device. is thermally oxidized to grow a silicon dioxide film 2 (see Fig. 2(a)
)). Subsequently, the silicon dioxide film 2 is selectively removed by photoetching to expose the region where the graft base is to be formed. A p-type impurity is introduced into this region where the graft base is to be formed to form the graft base region 3 (second
Figure (b)). Thereafter, the silicon dioxide film 2 is selectively removed through a photoresist process to expose a region where a base is to be formed, and a p-type impurity is introduced to form a 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 the silicon dioxide film 2 again, so the silicon dioxide film 2 is selectively removed by the photoresist step again, and the area in the base region 4 where the emitter is to be formed is removed. (Fig. 2(d)).

In the next step, an n-type impurity is introduced into the region where the emitter is to be formed to form the emitter region 5 (FIG. 2(e)), and then standard electrode forming steps are carried out to complete the pie/polar transistor device.

<Problems to be Solved by the Invention> However, in the conventional bipolar transistor device described above, since the emitter region 5 is formed on the surface of the base region 4, the area of the base-emitter junction becomes large. There is a problem in that the parasitic capacitance caused by the base-emitter junction also increases, making it impossible to improve the high frequency characteristics of the bipolar transistor. Moreover, forming the emitter region 5 on the surface of the base region 5 has a problem in that the influence of surface recombination in the base region 4 is large, and it is difficult to obtain good linearity between the emitter voltage and the emitter grounded current gain h f e. There were also points.

In addition, in the conventional method for manufacturing a bipolar transistor device, the formation of the graft base region 3, the formation of the base region 4, and the formation of the emitter region 5 were formed through independent photoresist processes that had no relation to each other. Due to mask alignment errors in each photoresist process, a part of the emitter region 5 may extend into the graft base region 3 with a high impurity concentration. 4 had to be widened to separate the graft base region 3 and emitter region 5 from each other. As a result, in bipolar transistor devices formed by conventional manufacturing methods, the area occupied by each element increases, and as the emitter region 3 becomes shallower, the base parasitic resistance rbb' increases and noise characteristics deteriorate. There were also points.

Therefore, a first object of the present invention is to provide a structure of a bipolar transistor device that is excellent in high frequency characteristics, noise characteristics, and linearity of current gain hfe. The object is to provide a method for manufacturing a bipolar transistor device in which the graft base region 3 and the emitter region 5 do not overlap even when the distance between the graft base region 3 and the emitter region 5 is reduced.

<Means for Solving the Problems> The first invention of the present application includes an active base region formed by introducing a low concentration of second conductivity type impurity into the surface portion of a first conductivity type semiconductor substrate; an inactive base region formed by introducing impurities of a second conductivity type at a high concentration into the outer periphery of the region; and an emitter region formed by introducing impurities of a first conductivity type into a surface portion of the active base region. The gist of the bipolar transistor device is that an insulating film is provided to cover the surfaces of the active base region and the inactive base region and the side surfaces of the emitter region. A step of introducing impurities of a second conductivity type into the surface portion of the substrate to form an active base region with a low impurity concentration, and forming an inactive base continuous to the periphery of the active base region and the periphery of the active base region. a step of selectively removing a surface portion with a planned region to form a moat shallower than the active base region; a step of oxidizing the wall surface of the moat I- to form an oxidation +11J thinner than the depth of the moat; A step of ion-implanting impurities of a second conductivity type into a region where an inactive base is to be formed through a film to form an inactive base region, and implanting a first conductive type into a surface portion of the active base region surrounded by the oxide film. The method is intended to include a step of introducing type impurities and forming an emitter region.

<Operations and Effects> In the first invention of the present application, the surfaces of the active base region and the inactive base region of the bipolar transistor device and the side surfaces of the emitter region are covered with an insulating film, and the active base region and the emitter region are separated. Since the junction was made only at the bottom of the active base region, the area of the base-emitter junction could be reduced, and the parasitic capacitance could be reduced.

Therefore, the charging time of the parasitic capacitance is shortened, and it is possible to follow high frequency signals applied to the active base region. Furthermore, by covering the sides of the emitter region with an insulating film, recombination at the surface of the active base region can be reduced and a linear voltage-current gain relationship can be formed.

In addition, in the second invention of the present application, after oxidizing the wall surface of the moat shallower than the active base region to form an oxide film thinner than the depth of the moat, impurities of the second conductivity type are inactivated through the oxide film. Since ions are implanted into the region where the base is to be formed to form an inactive base region, the thickness of the oxide film through which ions must pass differs between the bottom and side surfaces of the moat. As a result, by adjusting the energy given to the ions, the second conductivity type impurity was implanted only under the bottom surface of the moat.
It is possible to prevent impurities from reaching under the oxide film formed on the side surface of the moat. Therefore, after ion implantation, the first
When forming an emitter region by grooving conductivity type impurities,
An active base region having a width approximately equal to the thickness of the oxide film is interposed between the emitter region and the inactive base region.

Because the oxide thickness can be controlled much more precisely than mask alignment, it is possible to reduce the spacing between the emitter and passive base regions without creating overlap between the emitter and passive base regions. Therefore, it is possible to reduce the area occupied by the element and improve noise characteristics by lowering the parasitic base resistance rbb'.

<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 grow to about 5,000 people. Subsequently, the region where the base is to be formed is exposed by photoetching, and 1013 to 1014 boron is implanted at an energy of about 40 to 50kav to form the base region 13.
(Fig. 1(a)). After the silicon dioxide film is completely removed to expose the surface of the semiconductor substrate 11.

The polysilicon film 14 covering the surface of the semiconductor substrate 11 is
000 people arrived, and approximately 200 silicon nitride films were deposited.
0 people arrive (No. ill (b)). A photoresist film is applied on the silicon nitride film 15 and patterned to form a mask covering the center of the base region 13. Using this photoresist film as a mask, the silicon nitride film 1 is
5, polysilicon 1114, and the semiconductor substrate 11 including the peripheral portion of the base region 13 are sequentially removed by etching. By such etching, a moat 16 shallower than the base region 13 is formed on the surface of the semiconductor substrate 11 (FIG. 1(c)).
), then, using the silicon nitride film 15 as a mask, the surface of the semiconductor substrate 11 including the peripheral part of the base region 13 and the side surface of the polysilicon film 14 are thermally oxidized to form an oxide film 17 thinner than the depth of the moat 16. (Figure 1(d)). Subsequently, 1014 to 1015 boron is implanted into the region of the semiconductor substrate 11 where the graft base is to be formed at approximately 60 to 70 keV to form the graft base region 18 (see FIG. 1(e)).
)). In this ion implantation, the oxide film 17 grown on the bottom surface of the moat 16 is replaced by the oxide film 17 grown on the side surface of the moat 16.
(i.e., the thickness of oxidation +1'J 17 is thinner than the depth of the moat after thermal oxidation), the implanted boron passes through the oxide film 17 grown on the bottom of the moat 16 and into the semiconductor substrate 11. However, the BHX 11 cannot pass through the oxide film 17 grown on the side surface of the moat 16. In the subsequent step, the silicon nitride film 15 in the center of the base region 13 is removed, and an n-type impurity of about 1011' in about 30 keys is introduced into the center of the base region 13 to form an emitter region (see FIG. 1). f)). As mentioned above, since boron does not reach under the oxide film 17 grown on the side surface of the moat 16, the impurity concentration in this region is not increased, and therefore the emitter region 19 and the graft base region 18 overlap. There's nothing to do. Moreover, since the thickness of the oxide film 17 can be controlled within the range of angstroms, the distance between the emitter region 19 and the graft base region 18 can be made extremely small. After forming the emitter region 19, a contact hole is made in the oxide film 17, aluminum is deposited on the entire surface, and then patterned to form a base electrode 20 and an emitter electrode 21 (see FIG. 1). g)).

In the bipolar transistor device formed through such a manufacturing process, the side walls of the emitter region 19 are covered with the oxide film 17, and the junction area between the base region 13 and the emitter region 19 is reduced. A reduction in the junction area between the base region 13 and the emitter region 19 results in a reduction in parasitic capacitance, and it is possible to improve the high frequency characteristics of the bipolar transistor device. Further, the side walls of the emitter region 19 are covered with an oxide film 17 and a silicon film 1.
4 reduces recombination on the surface of the base region and improves the linearity of the current gain with respect to the applied voltage. Further, in the manufacturing method of the above embodiment, the distance between the emitter region 19 and the graft base region 18 can be made extremely small, so that the parasitic resistance of the base region 13 can be reduced and the noise characteristics can be improved.

[Brief explanation of drawings]

FIGS. 1(a) to 1(g) are sectional views showing each step of an embodiment of the present invention, and FIGS. 2(a) to 2(e) are sectional views showing each step of a conventional example. 11...Semiconductor substrate, 13...Active base region, 16...Moat, 18...
...Inactive base region, (graft base region) 19...Emitter region. Patent Applicant: ROHM Co., Ltd. Agent, Patent Attorney Kiyoshi Kuwai - (a) (b) (C) Figure 1 17: Acid Ichimichi (CI)] 7 Hair] 8: An ode to Imashii Divination (e) Figure 1 one: 15/So9 negative relation (f) Figure 1 (a) Cb) (C) Figure 2 Figure 2

Claims (2)

[Claims] (1) A low concentration of second conductivity is applied to the surface of the first conductivity type semiconductor substrate.
an active base region formed by introducing conductivity type impurities;
an inactive base region formed by introducing impurities of a second conductivity type at a high concentration into the outer periphery of the active base region; and an emitter formed by introducing impurities of a first conductivity type into the surface portion of the active base region. 1. A bipolar transistor device comprising: an insulating film covering surfaces of the active base region and the inactive base region and side surfaces of the emitter region. (2) A step of introducing impurities of a second conductivity type into the surface portion of the semiconductor substrate of the first conductivity type to form an active base region with a low impurity concentration; a step of selectively removing a surface portion of an inert base formation planned region that is continuous with the peripheral portion to form a moat shallower than the active base region; and a step of oxidizing the wall surface of the moat to form an oxide film thinner than the depth of the active moat. a step of forming an inactive base region by ion-implanting a second conductivity type impurity into a region where an inactive base is to be formed through the oxide film, and a step of forming an inactive base region surrounded by the oxide film. A method for manufacturing a bipolar transistor device, comprising the step of introducing impurities of a first conductivity type into a surface portion to form an emitter region.