JP3320039B2 - Bipolar transistor manufacturing method - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to an improvement in the structure of a bipolar transistor, and more particularly, to a bipolar transistor having a high amplification factor, a bipolar transistor having a high withstand voltage, and a bipolar transistor having a small power loss.

[0002]

2. Description of the Related Art Bipolar transistors are widely used for signal amplification and digital signal processing. As shown in FIGS. 3A and 3B, for example, a conventional bipolar transistor has an emitter E made of an n-type or p-type semiconductor and a base joined to the emitter E and made of a p-type or n-type semiconductor. B, a collector C joined to the base B and made of an n-type or p-type semiconductor, and external contacts tE, tB and tC connected to the emitter E, the base B and the collector C. .

In the bipolar transistor shown in FIGS. 3A and 3B, when a base current is supplied to the base B from an external signal source, a current having a magnitude substantially proportional to the base current is applied between the collector C and the emitter E. The current path including the collector C and the emitter E is controlled so as to flow through the current path.

In the bipolar transistors shown in FIGS. 3A and 3B, a base B is formed by diffusing a p-type impurity or an n-type impurity into a semiconductor substrate made of an n-type semiconductor or a p-type semiconductor constituting a collector C. It is manufactured by forming an emitter E by diffusing an n-type impurity or a p-type impurity into the base B.

[0005]

The current amplification factor of a bipolar transistor (ie, the ratio of the magnitude of the current flowing between the collector and the emitter to the magnitude of the base current)
Increases as the area of the junction surface between the base and the emitter increases. The breakdown voltage of the base of the bipolar transistor increases as the impurity concentration of the semiconductor forming the base decreases. The power loss that occurs when a current flows between the emitter and the collector of a bipolar transistor increases as the resistance (on-resistance) between the emitter and the collector when the current flows between the emitter and the collector.

However, the volume of the entire bipolar transistor increases as the area of the junction between the base and the emitter increases. Therefore, a bipolar transistor having a higher current amplification factor has a larger overall volume, and when the volume is limited to a predetermined range, a desired current amplification factor may not be obtained.

On the other hand, the lower the impurity concentration of the semiconductor constituting the base, the higher the resistance of the base and the higher the on-resistance. Therefore, the power generated when a current flows between the emitter and the collector of the bipolar transistor is reduced. The loss increases. In other words, when the impurity concentration of the base is increased in order to reduce the power loss that occurs when a current flows between the emitter and the collector of the bipolar transistor, the breakdown voltage of the bipolar transistor decreases.

Furthermore, the lower the impurity concentration of the semiconductor constituting the base, the lower the probability that majority carriers emitted from the emitter reach the collector via the base, so that the current amplification factor also decreases.

The present invention has been made in view of the above circumstances, and provides a bipolar transistor manufacturing method for realizing a bipolar transistor having a high current amplification factor per volume and a bipolar transistor having a high withstand voltage and a low on-resistance. The purpose is to:

[0010]

To achieve the above object, according to an aspect of the bipolar transistor fabrication process of this invention, base
A semiconductor substrate having a first conductivity type region serving as a source region;
Preparing an emitter region formed in the first conductivity type region;
Region and the collector region are connected at one end to each other.
It has a comb-like shape with multiple projections
Projection forms a gap formed by the first conductivity type region.
Through, so as to be sandwiched by the plurality of protrusions provided on the other
Emitter region and collector region formation as arranged
Forming a mask for the first conductive layer using the mask.
By diffusing impurities of the second conductivity type into the region of the mold,
Forming an emitter region and a collector region .

A method for manufacturing such a bipolar transistor
In the bipolar transistor manufactured by the method, the area of the junction between the base and the collector and the area of the junction between the base and the emitter are larger than those of the conventional configuration. Therefore, the resistance value of the base between these two joining surfaces becomes small,
The on-resistance of such a bipolar transistor is lower than the on-resistance in the conventional configuration. If the probability that the majority carriers emitted from the emitter reach the collector is the same as the probability in the conventional configuration, the current amplification factor will be larger than in the conventional configuration. On the other hand, even if the impurity concentration of the base is lower than the impurity concentration in the conventional configuration and the probability that the majority carriers emitted from the emitter reach the collector is lower than the probability in the conventional configuration, the current amplification factor is maintained at the same level as the conventional configuration. It becomes possible. Therefore, the withstand voltage of the base is maintained higher than the withstand voltage of the conventional configuration while the current amplification factor is maintained at about the same level as that of the conventional configuration. Also this
In a bipolar transistor manufacturing method, an emitter and a core are used.
Lector is simply manufactured in one diffusion step.

If the area of the junction between the base and the emitter is smaller than the area of the junction between the base and the collector, the amount of carriers injected from the emitter to the collector via the base is small. It can be controlled by an appropriate base current. That is, the input impedance of the base of the bipolar transistor increases, and the current amplification factor increases.

The base is made of, for example, a p-type semiconductor. In this case, the emitter and the collector are made of an n-type semiconductor. Further, the base may be composed of an n-type semiconductor, and in this case, the emitter and the collector are composed of a p-type semiconductor.

[0014]

[0015]

[0016]

[0017]

Embodiments of the present invention will be described below with reference to the drawings. FIG. 1A is a diagram schematically showing a configuration of a bipolar transistor according to an embodiment of the present invention. FIG. 1B is a cross-sectional view of the bipolar transistor shown in FIG. 1A taken along a plane perpendicular to the plane of the drawing, including a straight line connecting two points indicated by “α” in FIG. It is a figure which shows typically. As shown, the bipolar transistor includes a collector C, a collector terminal tC, a base B, a base terminal tB, an emitter E, and an emitter terminal tE.

The base B comprises a p-type semiconductor region (hereinafter, referred to as a p-type region) formed in a p-type semiconductor substrate or an n-type semiconductor substrate. A base terminal tB for external connection is connected to the base B.

The collector C has an n-type semiconductor region (hereinafter referred to as n-type semiconductor region).
Arsenic or any other n-type impurity is thermally diffused or ion-implanted on the base B. A collector terminal tC for external connection is connected to the collector C.

The emitter E is composed of an n-type region and the base B
An n-type impurity is formed so as not to be in contact with the collector C by thermal diffusion, ion implantation, or the like. The emitter E is connected to an emitter terminal tE for external connection.

As shown in FIGS. 1 (a) and 1 (b), the collector C and the emitter E have a comb shape, and are arranged so as to be intertwined with each other.

That is, in the collector C, a cross section parallel to the main surface of the substrate is connected in common to a plurality of rod-shaped projections (comb-shaped portions) substantially parallel to each other and to the base end of each comb-shaped portion. And a single rod-shaped base.

Further, the emitter E is, like the collector C,
A cross section parallel to the main surface of the substrate includes a plurality of protrusions (a plurality of rod-like protrusions substantially parallel to each other) corresponding to comb teeth, and a base commonly connected to base ends of the comb teeth. It is comb-shaped. The comb teeth of the emitter E and the comb teeth of the collector C are substantially parallel to each other, and the adjacent comb teeth of the emitter E are arranged so as to sandwich the comb teeth of the collector C.

Further, the distance between the two comb teeth adjacent to the emitter E and the comb tooth of the collector C, which is interposed between the two comb teeth, is set at a distance from the emitter E. They are arranged sufficiently close together so that majority carriers emitted towards the collector C can reach the collector C.

The collector C and the emitter E are, for example,
(1) A semiconductor substrate having a base B (an n region functioning as a base) is prepared. (2) A photoresist is applied on the semiconductor substrate, and the photoresist is patterned to form a comb between an emitter formation region and a collector formation region. Exposed like a tooth (3)
Using a patterned resist as a mask, an n-type impurity is diffused and ion-implanted into the substrate surface to activate the substrate, and the like. According to this manufacturing process, the emitter and the collector can be manufactured in substantially one diffusion step.

The bipolar transistor according to the present embodiment having the above-described configuration has the same size as the base B as compared with the conventional configuration shown in FIGS. 3A and 3B. And the area of the junction between the collector C and the base B and the emitter E also increases. Therefore, the resistance value of the base B is changed to the collector C
When viewed between a point on the junction surface of the base B and a point on the junction surface of the emitter E-base B, the resistance value decreases.

If the probability that the majority carrier emitted from the emitter E passes through the base B and reaches the collector C is the same as that in the conventional configuration, the majority carrier is emitted from the emitter E and reaches the collector C. The ratio of the total amount of majority carriers per unit time to the magnitude of the base current flowing into the base B from the outside (that is, the current amplification factor) also increases. In other words, even if the probability that the majority carriers emitted from the emitter E pass through the base B and reach the collector C is lower than the probability in the conventional configuration, it is possible to maintain the current amplification factor at the same level as the conventional configuration. Become.

Therefore, even when the distance between the emitter E and the collector C is wider than that of the conventional configuration, or when the p-type impurity concentration of the base B is lower than that of the conventional configuration, it is possible to maintain the current amplification factor at the level of the conventional configuration. Become. Therefore, it is possible to maintain the current amplification factor at about the same level as the conventional configuration while increasing the breakdown voltage of the base B by lowering the p-type impurity concentration of the base B.

The structure of the bipolar transistor according to the embodiment of the present invention is not limited to the above-described structure.
For example, the conductivity types (impurity types) of the collector C, the base B, and the emitter E need not be n-type, p-type, and n-type, respectively, but may be p-type, n-type, and p-type, respectively. The operation of the bipolar transistor in this case is such that the direction of the current flowing between the collector C, the base B and the emitter E and the outside is reversed, and that the carriers accumulated in the base B are electrons instead of holes. Except for the above, the operation is substantially the same as that of the bipolar transistor having the above-described configuration.

Further, among the comb teeth of the collector C, there may be one which is not located between the comb teeth of the emitter E. In addition, among the comb-tooth portions of the emitter E, there may be one that is not positioned so as to sandwich the comb-tooth portion of the collector C.

FIG. 2A shows a top view of this bipolar transistor, and FIG.
May be provided. That is, base B-
The area of the junction surface between the emitter E and the base B-collector C
It may be smaller than the area of the joint surface between them. In addition,
FIG. 2B schematically shows a cross section of the bipolar transistor shown in FIG. 2A cut along a plane perpendicular to the plane of the drawing, including a straight line connecting two points indicated by “α” in FIG. 2A. FIG.

Thus, the amount of carriers injected from the emitter E to the collector C via the base B can be controlled by a small base current. That is, the input impedance of the base B of the bipolar transistor increases, and the current amplification factor increases. The minority carriers flowing from the emitter E into the base B diffuse widely into the base B and are absorbed as a collector current flowing through the collector C.

By reducing the area of the junction surface between the base B and the emitter E, the junction capacitance of the capacitor formed by these portions also decreases. For this reason,
In this bipolar transistor, good frequency characteristics can be obtained (that is, a high transition frequency can be obtained). The conventional high power bipolar transistor has a drawback that the current amplification factor is small and the frequency characteristics are poor. On the other hand, the bipolar transistor shown in FIGS. 2A and 2B can be used widely for power control because it can be easily controlled for low power as well as for high power.

[0034]

As described above, according to the present invention, a bipolar transistor manufacturing method for realizing a bipolar transistor having a high current amplification factor per volume and a bipolar transistor having a high withstand voltage and a low on-resistance is realized. You.

[Brief description of the drawings]

FIG. 1A is a schematic diagram showing a configuration of a bipolar transistor according to an embodiment of the present invention, and FIG.
FIG. 2 is a schematic cross-sectional view showing a cross section of the bipolar transistor shown in FIG.

FIG. 2A is a schematic diagram showing a configuration of a modification of the bipolar transistor of FIG. 1A, and FIG.
FIG. 3A is a schematic cross-sectional view illustrating a cross section of the bipolar transistor of FIG.

FIGS. 3A and 3B are schematic cross-sectional views showing a configuration of a conventional bipolar transistor.

[Explanation of symbols]

 B Base C Collector E Emitter tB Base terminal tC Collector terminal tE Emitter terminal

Claims (4)

(57) [Claims] (1)A first conductivity type region serving as a base region;
Prepare a semiconductor substrate The emitter region formed in the first conductivity type region and the collector region;
Are connected to each other at one end.
It has a comb shape with projections, and one of the projections
Through a gap constituted by the region of the first conductivity type.
And arranged so as to be sandwiched by the plurality of protrusions provided on the other side.
For forming the emitter region and the collector region.
Form a mask, Using the mask, a region of the second conductivity type is formed in the region of the first conductivity type.
Diffuses the impurity of the
Data area and  Bipolar transistor characterized by the following:Production method. 2. A surface of a junction between the base and the emitter.
The product is based on the area of the junction between the base and the collector.
smallFormed to be  The bipolar transistor according to claim 1, wherein:
StarProduction method. 3. The method according to claim 1, wherein the base is made of a p-type semiconductor, and the emitter and the collector are made of an n-type semiconductor . 4. The method according to claim 1, wherein the base is made of an n-type semiconductor, and the emitter and the collector are made of a p-type semiconductor .