JPH0342679Y2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to improvements in Darlington transistors.

Most conventional Darlington transistors have a resistor connected between the base and emitter of each transistor, as shown in FIG.
However, since the gain of such a Darlington transistor is determined, there is a need to develop a resistance-free Darlington transistor as shown in FIG. 2, which has a high gain.

The specific structure of such Darlington is shown in FIGS. 3 and 4. 1 is a semiconductor substrate forming a common collector region, 4 and 5 are the base and emitter regions of the first transistor 2, 6 and 7 are the base and emitter regions of the second transistor 3, and 8 is the first transistor 2;
and a guard region of the same conductivity type as both emitter regions 5 and 7 surrounding both base regions 4 and 6 of the second transistors 2 and 3; 9 indicated by a dotted line is a base in ohmic contact with the base region 4 of the first transistor 2; The electrodes 10 are connection electrodes connecting the emitter region 5 of the first transistor 2 and the base region 6 of the second transistor 3, and 11 is an emitter electrode in ohmic contact with the emitter region 7 of the second transistor 3.

In the above transistor, as shown by the dotted line in FIG. 4, the base region 4 of the first transistor 2 and the second
A channel 12 is generated by the connecting electrode 10 on the surface of the collector region 1 between the base regions 6 of the transistors 3, and this channel resistance connects the base of the first transistor 2 and the base of the second transistor 3. The disadvantage was that the current amplification factor (h _FE ) was reduced, making it impossible to obtain a high h _FE Darlington transistor. In order to prevent this, it is conceivable to form the guard region 8 in the collector region 1 described above to stop the channel 12, but this has the disadvantage that a high concentration junction is formed between the channel 12 and the guard region 8, and the withstand voltage deteriorates. It was hot.

Therefore, in order to eliminate both of these drawbacks, the present inventor provided a guard region 8 also in the collector region 1 between both the base regions 4 and 6, as shown in FIG. first coating
A shield electrode 14 is provided which extends over the insulating film 13 and extends to the surface of the collector region 1 between both base regions 4 and 6. Further, in order to prevent the connection electrode 10 from forming a high concentration region on the surface of the base region 4 of the first transistor, a base electrode 9 is provided in ohmic contact with the entire circumference of the base region 4 of the first transistor 2.

However, in such a transistor, the base region 4 of the first transistor 2 is 15 to 20 μm for small signals and 15 to 20 μm for large signals in order to form an electrode hole for contact.
A width of 20 to 40 microns is required, and for this reason, the base region 4 of the first transistor 2 must be formed large, leading to an increase in the pellet area.

The present invention has been devised in view of this point, and aims to provide a Darlington transistor that eliminates such drawbacks. An embodiment of the present invention will be described in detail below with reference to FIG.

The Darlington transistor according to the present invention has a semiconductor substrate 20 and a substrate 20 serving as a common collector region.
First transistor 2 provided by double diffusion on the surface
1, and a second base region 25 and a second base region 25 that constitute a second transistor 24, which is provided adjacent to the first transistor 21 by double diffusion on the surface of the substrate 20. a second emitter region 26; a guard region 27 provided on the surface of the substrate 20 and having the same conductivity type as the first and second emitter regions 23, 26 and completely surrounding the first and second base regions 22, 25; a first shield electrode 29 extending over a first insulating film 28 such as silicon oxide, which is in ohmic contact with and covering the surface of the substrate 20, and extends onto the surface of the collector region 20 between the base regions 22 and 25; A second electrically independent second base region that does not contact the first base region 22 is provided in a portion of the first insulating film 28 on the first base region 22 of the first transistor 21 located below the connection electrode 33, which is a feature of the present invention. a shield electrode 30, first and second shield electrodes 29,
30, which is in ohmic contact with a second insulating film 31 such as a silicon nitride film provided on the first insulating film 29 and the first base region 22 of the first transistor 21, and extends over the second insulating film 31. Base electrode 32
The second base region 2 of the second transistor 24 is in ohmic contact with the first emitter region 23 of the first transistor 21 and extends over the second insulating film 31.
5, and an emitter electrode 34 which is in ohmic contact with the second emitter region 25 of the second transistor 24 and extends over the second insulating film 31.

According to the above configuration, since the second shield electrode 30 only needs to be on the first base region 22, the width of the first base region 22 can be reduced to about 7 μm. Further, since the electric field of the connection electrode 33 is shielded by the second shield electrode 30, no high concentration region is formed on the surface of the first base region 22.

As detailed above, according to the present invention, a high h _FE Darlington transistor can be realized using the guard region and the first and second shield electrodes. Furthermore, by floating the second shield electrode, the area of the first base region of the first transistor can be reduced, and the pellet size can be reduced, contributing to mass production.

[Brief explanation of drawings]

1 and 2 are circuit diagrams explaining the connection of a Darlington transistor, FIGS. 3 and 4 are a top view and a sectional view taken along the line 3-3 of a conventional Darlington transistor, and FIG. 5 is a circuit diagram of a conventional Darlington transistor. FIG. 6 is a sectional view illustrating the improved Darlington transistor. FIG. 6 is a sectional view illustrating the Darlington transistor of the present invention. Explanation of main figure numbers: 20 is a semiconductor substrate serving as a common collector region, 21 and 24 are first and second transistors, 22 and 23 are first base and emitter regions, and 25 and 26 are second base and emitter regions , 27 are guard regions, 28 and 31 are first and second insulating films, and 29 and 30 are first and second insulating films.
32 is a base electrode, 33 is a connection electrode, and 34 is an emitter electrode.

Claims (1)

[Scope of utility model registration request] A semiconductor substrate serving as a common collector region, a first base and emitter region provided on the surface of the substrate constituting a first transistor, and a first base and emitter region provided on the surface of the substrate adjacent to the first transistor constituting a second transistor. a second base and emitter region provided, a guard region completely surrounding the first and second base regions and having the same conductivity type as the emitter region, a base electrode in ohmic contact with the first base region; a connection electrode connecting the first emitter region and the second base region;
In a Darlington transistor comprising an emitter electrode in ohmic contact with the emitter region, and a first shield electrode in ohmic contact with the guard region and provided insulated below the connection electrode, the connection is made on the first base region. A Darlington transistor characterized in that a second shield electrode is provided below the electrode in an insulated manner.