JP2925169B2 - Bipolar transistor - Google Patents

Description

The present invention relates to a structure of a bipolar transistor.

Conventionally, as a bipolar transistor, a transistor as shown in the sectional view of FIG. 1 is generally used.

In Figure 1, 1 is N ^- consists type semiconductor substrate, the first region 2 is comprised of a base layer P-type semiconductor, 3 second region serving as an emitter layer with N ⁺ type semiconductor, the base electrode 4 , 5
Is an emitter electrode.

Although not shown, a collector electrode is provided below. In FIG. 1, the switching time, breakdown voltage, and current amplification factor (h _FE ), which are important characteristics of the bipolar transistor, are closely related to the formation conditions such as the depth and impurity concentration of the first region 2 and the second region 3. There is. For example, in order to increase the withstand voltage, the first region 2 needs to be deepened, but this degrades the characteristic values of _hFE and switching time. To increase _hFE , it is necessary to reduce the distance a between the first region 2 and the second region 3,
As a result, the breakdown voltage decreases. In addition, in order to shorten the switching time, measures are taken by diffusion of heavy metals such as platinum and gold, but it is difficult to control the diffusion,
There is a disadvantage that _hFE decreases. SUMMARY OF THE INVENTION It is an object of the present invention to provide a bipolar transistor structure having a simple structure and improved switching characteristics without deteriorating other important transistor characteristics. In addition, the present invention also provides a bipolar transistor structure that improves switching characteristics, breakdown voltage, and _hFE .

Next, the present invention will be described with reference to the sectional structural view of the embodiment shown in FIG. Although the same reference numerals as those in FIG. 1 indicate the same parts, the N ⁻ type semiconductor substrate 1 is formed of an epitaxial layer on an N ⁺ type semiconductor bulk. The first region 2 is formed of a deep portion made of P ⁺ type and a shallow portion made of P type. Reference numeral 6 denotes a third region made of a P ⁻ -type, which is formed separately between the plurality of first regions 2 formed on the semiconductor substrate 1. Lower than the impurity concentration. The emitter electrode 5 is formed of a metal such as aluminum to electrically connect the P ⁻ -type semiconductor in the second region 3 and the third region 6 serving as the emitter via the insulating film 7. The third region 6, at the time on, the injected minority carriers is withdrawn rapidly disappear as a result can be shortened off-time of the switching characteristics (t _s). The depth of the peripheral portion of each first region 2 is smaller than that of the central portion, and the impurity concentration of the peripheral portion is lower than that of the central portion. As a result, the base width is reduced in the shallow peripheral portion of the first region 2 and the impurity concentration is low, so that the current amplification factor (h _FE ) can be increased and the deep region of the first region 2 can be deepened. Prevents crackling in the center,
High withstand voltage has been achieved.

Therefore, the switching characteristics are improved by forming the third region 6, and furthermore, the depth of the first region 2 is locally increased, or a portion having a high impurity concentration is used in combination. , Breakdown voltage and _hFE can also be improved.

According to experimental examples, V according to the prior structure _{CEO 450~500V,} h _FE
6-10, the structure of the bipolar Tonranjisuta of t _s 1~2μsec Figure _{2, V CEO 450~500V, h FE 20~30} , t s 0.
It could be improved to 3 to 0.5 μsec.

In the practice of the present invention, it is free to relatively change the conductivity type of the semiconductor, and other means for improving characteristics,
For example, guard ring structure, field plate structure,
It can be used in combination with various improved structures such as the EQR structure.
Further, in the formation of each conductivity type, a manufacturing process such as a diffusion method or an implantation method can be arbitrarily selected as necessary. The conversion of other materials, modification of the structure, and partial addition are also included in the present right within the scope of the present invention.

As described above, it is possible to provide a bipolar transistor having a simple structure capable of improving the switching characteristics and improving the breakdown voltage and the current amplification factor. It is a great thing.

[Brief description of the drawings]

FIG. 1 is a cross-sectional view of a conventional type, and FIG. 2 is a cross-sectional view of an embodiment of the present invention, wherein 1 is a semiconductor substrate, 2 is a first area, 3 is a second area, and 4 is a base. The poles, 5 are emitter electrodes, 6 is a third region, 7 is an insulating film, and a is a specified distance.

Claims (1)

(57) [Claims] A semiconductor device according to claim 1, wherein a plurality of first regions of another conductivity type are formed on a semiconductor layer having one conductivity type.
A second region 3 having the one conductivity type shallower than the first region 2 is formed on the second region 3, and a third region 6 having the other conductivity type and a lower impurity concentration than the first region 2 is formed. Are formed separately between the first regions 2 to electrically connect the second region 3 and the third region 6 and to locally increase the depth of the region in the first region 2. A bipolar transistor, which is formed or provided with a portion having a high impurity concentration.