JPH06120234A - Semiconductor device - Google Patents

Abstract

PURPOSE:To prevent defective breakdown strength or short-circuit between a collector and an emitter, and obtain a semiconductor device excellent in high frequency characteristics by reducing base resistance. CONSTITUTION:Periheries of a base diffusion layer 2 of a bipolar transistor is surrounded with a high concentration P-type diffusion layer 4. In a photoresist process, defective breakdown strength or short-circuit failure between a collector and an emitter which failure is caused by alignment deviation or the like of a base diffusion layer 2 or an emitter contact hole 9 is prevented, and high frequency characteristics are improved by reducing base resistance.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a semiconductor device, and more particularly to the structure of a bipolar transistor.

[0002]

2. Description of the Related Art A conventional bipolar transistor is shown in FIG.
As shown in (a) and (b), a transistor in which an N type epitaxial layer 1 is formed on a semiconductor substrate and is partitioned by a field oxide film 10 selectively formed on the main surface of the N type epitaxial layer. A high-concentration P-type diffusion layer 4 connected to the P-type base diffusion layer 2, the N-type emitter diffusion layer 3, and the base diffusion layer 2 for drawing out the base electrode in the formation region.
Form A. The high-concentration P-type diffusion layer 4A is formed for the purpose of reducing the contact resistance with the aluminum wiring generally used as the base electrode wiring. Further, an emitter contact hole 9 is opened in the first insulating film 5 for connecting the emitter electrode 7 and the emitter diffusion layer 3, and an aluminum wiring 8 is connected to the emitter electrode 7.

[0003]

In the structure of this conventional bipolar transistor, when the emitter contact hole 9 and the base diffusion layer 3 are formed laterally displaced due to misalignment of the photoresist process, etc., as shown in FIG. In this case, the lateral distance t ₁ shown in FIG. 4) becomes narrow, and the collector-emitter breakdown voltage of the transistor characteristics often becomes insufficient or short-circuited, and there is a problem that the reliability and yield of the semiconductor device are reduced.

Further, since the base diffusion layer 2 is formed with a dose of about two orders of magnitude lower than that of the high concentration P type diffusion layer 4A,
Distance t between the emitter diffusion layer 3 and the high concentration P-type diffusion layer 4A
_{When 2} becomes long, the base resistance increases and often affects the high frequency characteristics. The commonly defined high frequency cutoff frequency f _max is expressed by the following equation. f _max = (1 / r _b + 1 / r _E ) / (C _E + C _C ), where r _{b is the} base resistance, r _{E is the} emitter resistance, C _{E is the} emitter capacitance, and C _C is the collector capacitance. Therefore, as the base resistance r _b increases, the high frequency cutoff frequency decreases.

An object of the present invention is to provide a semiconductor device which prevents such deterioration of transistor characteristics and improves reliability and yield.

[0006]

The semiconductor device of the present invention comprises:
In a semiconductor device having a collector diffusion layer, a base diffusion layer, and an emitter diffusion layer formed on a main surface of a semiconductor substrate, the base diffusion layer is of the same type as the base diffusion layer and has an impurity concentration higher than that of the base diffusion layer. It is surrounded by a diffusion layer of concentration.

[0007]

Embodiments of the present invention will be described below with reference to the drawings. 1A and 1B are a plan view and a sectional view taken along the line AA of the first embodiment of the present invention.

In FIGS. 1A and 1B, an N type epitaxial layer 1 is formed on a semiconductor substrate, and a transistor is formed which is partitioned by a field oxide film 10 selectively formed on the epitaxial layer 1. The region is a P-type base diffusion layer 2 selectively provided as an impurity-added layer, and a high-concentration P-type diffusion layer 4 provided around the base layer 2.
And an emitter diffusion layer 3 provided in the base layer 2. Then, an emitter contact hole 9 is opened in the first insulating film 5 provided on the epitaxial layer 1 to lead out the emitter wiring, and the emitter electrode 7 is formed of arsenic-added polycrystalline silicon. The emitter diffusion layer 3 is formed by utilizing the diffusion of arsenic added to the polycrystalline silicon of the emitter electrode 7. Reference numeral 6 is a second insulating film, and 8 is an aluminum wiring. The high-concentration P-type diffusion layer 4 is formed by self-aligned ion implantation using the emitter electrode 7 as a mask after forming the emitter electrode 7, so that no special photoresist process is required.

As described above, according to the first embodiment, the lateral distance between the emitter diffusion layer 3 and the high-concentration P-type diffusion layer 4 is determined by the width of the emitter electrode 7. The diffusion layer 2 will not be displaced and the short-circuit or short circuit between the collector and the emitter will not occur.

2 (a) and 2 (b) are a plan view and a sectional view taken along line BB of the second embodiment of the present invention.

In the second embodiment, the major structural difference from the first embodiment is that the first insulating film 5 of FIG. 1 (b) is eliminated and the emitter electrode 7A is formed, and then FIG. 2 (b) is formed. As shown in, the side wall 11 made of an insulating film is formed on the side surface of the emitter electrode 7A. Since the emitter contact hole is not formed, the emitter diffusion layer 3A
Has almost the same width as the emitter electrode 7A. Therefore, a high current type transistor can be formed in the same transistor formation region as in the first embodiment.

Further, the lateral distance between the emitter diffusion layer 3A and the high-concentration P-type diffusion layer 4 is determined by the width of the sidewall 11, so it should be narrower by 1.0 to 1.5 μm than in the first embodiment. You can Therefore, a transistor having higher high frequency characteristics than that of the first embodiment can be obtained.

[0013]

As described above, according to the present invention, the base diffusion layer is surrounded by the diffusion layer having a high impurity concentration.
Insufficient breakdown voltage or short circuit between collector and emitter can be prevented. Therefore, the reliability and yield of the semiconductor device can be improved. Further, since the base resistance can be reduced, there is an effect that the high frequency characteristics of the semiconductor device can be improved.

[Brief description of drawings]

FIG. 1 is a plan view and a sectional view of a first embodiment of the present invention.

FIG. 2 is a plan view and a sectional view of a second embodiment of the present invention.

3A and 3B are a plan view and a cross-sectional view of an example of a conventional semiconductor device.

[Explanation of symbols]

 1 N-type epitaxial layer 2 Base diffusion layer 3, 3A Emitter diffusion layer 4, 4A High-concentration P-type diffusion layer 5 First insulating film 6 Second insulating film 6A Insulating film 7, 7A Emitter electrode 8 Aluminum wiring 9 Emitter contact hole 10 Field oxide film 11 Sidewall

Claims (1)

[Claims] 1. A semiconductor device having a collector diffusion layer, a base diffusion layer, and an emitter diffusion layer formed on a main surface of a semiconductor substrate, wherein the base diffusion layer is an impurity of the same type as the base diffusion layer, A semiconductor device characterized by being surrounded by a diffusion layer having an impurity concentration higher than the impurity concentration.