JPS59155959A - power transistor - 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 [Technical Field of the Invention] The present invention relates to a power transistor capable of increasing the amount of one needle broken during use.

[Technical Background of the Invention and Problems Therewith J'One of the defects in acid transistors is the 'current concentration breakdown phenomenon' caused by thermal positive feedback. This phenomenon limits the conditions for positive use and requires extra margin in the design of the device. For this reason, various methods have been proposed to increase the breakdown resistance of transistors. For example, a balance resistor is interposed in the emitter region of a transistor, and an example thereof will be explained with reference to FIG.

Figure 1 (N is a plan view of a power transistor in which a balance resistor is inserted in the emitter region, Figure 1 ω) is
) is a sectional view taken along line AA' of the plan view shown in FIG.

In FIG. 1, 1 is a Nu collector layer, 2 is a P-type base layer, 3 is a plurality of emitter layers formed separately on the base layer 2, 4 is an insulating film, and 5 is the emitter layer on the insulating film 4. 3 is in contact with a balance resistor made of polysilicon, for example; 6 is a three-mitter electrode that commonly connects each balance resistor 5 on the insulating film 4; 7 is an emitter layer 3;
8 is a pace electrode and 9 is a collector electrode. In the power transistor shown in FIG. 1, a large number of separately formed emitter layers 3 are commonly connected through a parasitic resistor 5, so that the emitter current is evenly distributed and current concentration is prevented. As a result, a large amount of destruction resistance can be obtained.

However, from a manufacturing technology point of view, by providing the resistor 5, a step is created between the resistor 5 and the insulator 4.

Therefore, there is a drawback that wiring breaks are likely to occur during aluminum evaporation to form the 'rR pole 6. Therefore, the balance resistor 5 made of polysilicon
cannot be made very thick for the reasons mentioned above. Because of this,
Even if the current is divided into many parts and the current is written as 9+1, there is a problem in that the resistance of the resistance layer is limited by its size.

Furthermore, a power transistor in which the balance resistor 5 shown in FIG. 1 is formed by diffusion is also being considered. I will explain about such a transistor]. In FIG. 2, 11 is an N-type collector layer, 12 is a P-type base layer, 13 is a plurality of emitter layers formed separately on the base layer 12, 14 is an insulation layer, and 15 is connected to a plurality of emitter layers I3. N-type resistor ry5,1 formed by
Reference numeral e designates an emitter electrode commonly connected to the resistance layer 15, 17 a base' electrode, and 1B a collector electrode.

The power transistor shown in FIG. 2 is considered to have the same effect as the power transistor shown in FIG. 1. However, in the power transistor shown in FIG. 2, when the transistor is in operation, the resistance layer 15 generates heat due to a large current, and a phenomenon occurs in which the resistance layer 15 itself starts to be injected as an emitter.

For this reason, there was a drawback that the function as a resistor was reduced by half, and the expected effect could not be obtained.

Furthermore, another method for increasing the breakdown resistance of a power transistor is to insert a balance resistor into the base and control the base current. FIG. 3 is a sectional view showing a power transistor controlling the base current in this manner. In FIG. 3, 21 is an N-type collector layer, 22 is b
a type base layer; 23 is an emitter layer; 24 is an insulating film; 25 is an N-type base separation layer formed on the base layer 22 and located between the emitter layer 23 and the base electrode 27;
6 is an emitter electrode in contact with the emitter layer 23; 2;
7 is a base electrode, and 28 is a collector electrode. In a transistor like the one shown in Fig. 3, the N-type component FBI i
@25 ii The underlying base layer 22 acts as a balance resistor for the base l-flow and can distribute the current uniformly across the emitter.

However, in the large power transistor shown in FIG. 3, the base layer 22 is directly used as a resistor, so in order to further increase the effect, the base layer 22
Increasing the resistance of , the hole f3 degree in the base decreases.

This has the disadvantage of causing conduction modulation quickly and lowering the current gain. Furthermore, reduction in current gain at high currents often poses a problem in 1♀- transistors for acupuncture.

[Purpose of the invention]

This invention was made in view of the above points, and its purpose is to separate and form a balance resistor in the base layer, so that the emitter current is uniformly distributed during transistor operation, and the damage allowance is increased. The purpose of the present invention is to provide a power transistor.

[Summary of the invention]

A balance resistor is formed separately in the base layer to uniformly distribute emitter current during transistor operation and increase breakdown resistance.

[Embodiments of the invention]

Hereinafter, one embodiment of the present invention will be described with reference to the drawings.

FIG. 4 shows a power transistor according to an embodiment of the present invention, FIG. 4(A) is a plan view, and FIG. 4(B) is a top view.
is a sectional view taken along the A-p! line of the plan view shown in FIG. 31 was oxidized at high temperature in a steam atmosphere to give 5i0
Two layers 34 are formed. Then, holes for selective diffusion are formed in the 5i04 layer 34 by photolithography to form a base region, and boron atoms are diffused to form a P-type paste I@32. The diffusion in this case is carried out in an oxidizing atmosphere, and at the same time as the boron atoms are diffused, 5i024 is again deposited on the main surface of the base layer 32.
to form. Next, an N-type emitter layer 33 and an n-type resistance layer 35 are formed in the base layer 32 by selective diffusion of phosphorus atoms. The emitter layer 33 and the resistance layer 35 O11
6 was formed, and the 8102 layer was again opened by the photolithography method, and then aluminum was vacuum-deposited. Then, by photolithography, emitter electrode 36, pace electrode 5337
, a base contact electrode 371 is formed separately. This improved and divided emitter layer 33 and resistance layer 35
are distributed to 4) k, which are co-traced connected. Further, the collector electrode 38 is formed by plating nickel metal or by vapor deposition.

〔Effect of the invention〕

As described in detail above, according to the present invention, the balance resistor is formed at a distance of 5+ from the base layer, and the emitter electrodes are evenly distributed during temporary operation of the transistor, so that the breakdown resistance can be improved. Furthermore, it is possible to provide a power transistor in which conductivity modulation in the base layer is less likely to occur.

[Brief explanation of the drawing]

Figure 1 (10 is a plan view of a conventional power transistor, Figure 1 (B) is a sectional view taken along line A-A' in Figure 1 (4), Figures 2 and 3 are respectively FIG. 4 is a cross-sectional view of a conventional power transistor, FIG. 4 is a plan view of a power transistor according to an embodiment of the present invention, and FIG. 31... N-type semiconductor substrate, 32... Base J-shaped, 3
3...Emitsuta layer, 34...5i02 layer, 35...
・Resistance layer. Applicant's Representative Patent Attorney Takehiko Suzue Figure 1 Figure 2 Figure 3 Figure 8 Figure 4

Claims (1)

[Claims] A plurality of emitter regions and a plurality of diffused resistance layers of the same conductivity type as the emitter regions are formed separately in a pace region opposite to the emitter regions, and the paste 1! A power transistor characterized by having a pole removed.