JPS62295455A - Semiconductor device - Google Patents

Abstract

PURPOSE:To improve the breakdown strength of a semiconductor device by forming the number of divided emitters per unit area of a transistor of former stage more than that of a transistor of latter stage to accelerate the switching speed. CONSTITUTION:In a semiconductor device 1 having transistors 3, 4 including a split emitter structure coupled in Darlington transistor connection, the number of split emitters 6,.. per unit area of the transistor 3 of former stage is formed more than that of the split emitters 6', ...per unit area of the transistor 4 of latter stage. When with the structures 6, ..., 6',..., unit transistors of many insular split emitter regions 6, ..., 6',... and latticelike base regions 5, 5' are operated in parallel to allow a large current to flow. The breakdown strength can be improved because a resistance generated between the junctions of the emitter and the base is larger than the base contact.

Description

[Detailed description of the invention] 3. Detailed description of the invention (a) Industrial application field The present invention forms a plurality of transistors in a semiconductor substrate,
This invention relates to a semiconductor device formed by Darlington connection, and particularly relates to a semiconductor device with improved operating speed and current capacity when Darlington connection is made.

(b) Conventional technology The Darlington transistor has a high current amplification factor, so it can be used for switching large currents, etc.

In general, the Darlington transistor
As in Publication No. 390 (Figures 2 and 3), the collector and base of the transistor (22) (output transistor) in the subsequent stage are connected between the collector and emitter of the transistor (21) (driver transistor) in the previous stage, Darlington connections were made by forming diffused resistors between the base and emitter of the transistor (21) at the front stage and between the base and emitter of the transistor (z2) at the rear stage.

(c) Problems to be Solved by the Invention In the above-mentioned Darlington transistor, a semiconductor device that allows even higher current to flow is required.

In addition, high-current semiconductor devices are required to have higher switching speeds and improved breakdown resistance.

(d) Means for Solving the Problems The present invention has been made in view of the above problems, and is a semiconductor device (1) equipped with transistors (3) and (4) having a split emitter structure with incorrect Darlington transistor connection. ), the number of divided emitters (6)...(6) per unit area of the transistor (3) in the previous stage is calculated as the number of divided emitters (6')...(6') per unit area of the transistor (4) in the subsequent stage.
- This can be solved by forming more than (6').

(*) Effect Split emitter structure as mentioned above (6)...(6), (6
′)...(6゛), many island-like divided emitter regions (6)...(6), (6')...(6')
The unit transistors of the lattice-shaped base regions (5) and (5') operate in parallel, allowing a large current to flow.

In addition, by increasing the number of divided emitters (6)...(6) in the previous stage, in this case, the number of divided emitters (6)...(6) per unit area, each emitter region (6) (unit transistor ), the traveling distance of the minority carriers becomes shorter and the switching speed can be increased. Therefore, the transistor (4) at the next stage can be brought into the fast<ON state.

Furthermore, by reducing the size of the unit transistor of the transistor (3) in the previous stage, a larger number of unit transistors can be arranged in the previous stage than before, so the emitter peripheral length becomes longer than before and the current capacity improves.

Furthermore, since the transistor (4) in the latter stage has a large unit transistor size, its switching speed is slow, but current concentration is less likely to occur. Furthermore, the resistance to breakdown is improved due to the fact that the resistance generated between the emitter and base junction is greater than that between the base contact and the like.

(F) Example An example of the present invention will be described below with reference to FIG.

A Darlington transistor-connected semiconductor device (1) according to the present invention can be formed by connecting two or more stages of transistors on a silicon semiconductor substrate (2). Here, the explanation will be made in two stages as shown in FIG.

First, the structure of the transistor (3) at the front stage is an N+ type silicon semiconductor substrate, an N type epitaxial layer (2) which acts as a collector and is coated on the semiconductor substrate (2), and a transistor formed on the epitaxial layer (2). P− shown by the dotted line
type base region (5), and N''' type divided emitter regions (6)...(6) provided in the base region (5), and the divided emitter regions (6)...(6). 6) are disposed on almost the entire surface of the base region (5), and are completely surrounded within the base region (5) in the form of multiple islands.

Next, on the silicon oxide film on the surface of the substrate (2), a first
Although not shown in the figure, a first base pole and a first emitter electrode are formed in the first layer, and the first base electrode has a lattice shape with no divided emitter regions (6)...(6) formed. The first emitter electrode is in ohmic contact with substantially the entire surface of the formed base region (5), and the first emitter electrode is in ohmink contact with the divided emitter regions (6), respectively.

Here, in the present invention, the first base/emitter electrode may be omitted. Subsequently, the first base electrode and the first
The emitter electrode is covered with an interlayer insulating film such as a silicon nitride film or polyimide, and on the interlayer insulating film there is a second base electrode (7) in the second layer and a second emitter electrode (8) as shown by the solid line in FIG. ) is formed. The second base electrode (7) is formed in ohmic contact with the first base electrode formed in a lattice shape and extends in one direction in a comb-like shape.

Further, the second emitter electrode (8) is in ohmic contact with the divided first emitter electrode, and extends in a comb-like shape like the second base electrode (7).

On the other hand, the transistor in the latter stage (4) is also the transistor in the former stage (
3), and furthermore, the comb-shaped second emitter electrode (8) at the front stage and the comb-shaped second base electrode (7゛) at the rear stage are electrically connected. As shown in FIG. 1, they are integrally formed by vapor deposition. Also, the base region of the front stage transistor (5) and the rear stage transistor (5°)
Approximately 1/2 of the base area is used in the same area.

This configuration is the first feature of the present invention, and as described above, the divided emitters (6)...(6), (6')...
・If it has a (6') structure, there will be many island-like divided emitter regions (6)...(6), (6゛)...(6') and base regions (5) (5'). Since the device is composed of units, a large number of unit transistors operate in parallel, and the Darlington transistor-connected semiconductor device of the present invention can flow a large current.

Next, the number of divided emitters per unit area of the transistor (3) at the front stage is larger than the number of divided emitters per unit area of the transistor (4) at the rear stage.

This configuration is the second feature of the present invention, and is divided into divided emitter regions (6) of the transistor (3) in the previous stage.
The purpose is to make the dimensions of each of (6) smaller than the dimensions of each of the divided emitter regions (6'), . . . (6') of the subsequent transistor (4), and to form a large number of divided emitters.

For example, here, the dimensions of each of the divided emitter regions (6)...(6) are the dimensions of the subsequent divided emitter regions (6°)...(
6'). Therefore, the traveling distance of minority carriers is shortened, and the switching speed can be increased. Furthermore, by reducing the size of the unit transistor in the front stage, a larger number of unit transistors can be arranged in the front stage than in the past, resulting in a longer emitter peripheral length and improved current capacity. By improving the current capacity of the previous stage, the current capacity of the Darlington transistor also improves.

On the other hand, the latter transistor (4) is a split emitter (6')
...(6゛) is larger than the previous stage, so the switching speed is slow, but current concentration is less likely to occur. Furthermore, the breakdown resistance is improved because the resistance generated between the emitter and base junction is greater than that between the base contact and other reasons. Since the breakdown strength of the Darlington transistor is mainly determined by the breakdown strength of the subsequent transistor (4) through which a large current flows, the breakdown strength of the Darlington transistor is improved. Furthermore, since the vertical profiles of the transistors are the same in both the front and rear stages, they can be formed in the same step, so the number of steps can be kept the same as in the prior art.

(g) Effect of the invention As is clear from the above explanation, the transistor in the previous stage (3
), the number of divided emitters (6)...<6) per unit area is larger than the number of divided emitters (6'>...(6°) per unit area of the subsequent transistor (4). , it is possible to increase the speed of a semiconductor device connected with Darlington transistors, and also to improve current capacity and high breakdown resistance.

[Brief explanation of the drawing]

FIG. 1 is a plan view of a semiconductor device connected with Darlington transistors, which is an embodiment of the present invention, FIG. 2 is a plan view of a conventional semiconductor device connected with Darlington transistors, and FIG. 3 is a plan view of a semiconductor device connected with Darlington transistors. FIG. (1) is a semiconductor device, (2) is a semiconductor substrate, (3
) is the front-stage transistor, (4) is the rear-stage transistor, (5)・(5゛) is the base region, (6)...(6
), (6゛)...(6゛) is the divided emitter region, (7
) and (7') are the second base electrodes, and (8) are the second emitter electrodes.

Claims (1)

[Claims] (1) In a semiconductor device including a transistor having a divided emitter structure connected to a Darlington transistor, the number of divided emitters per unit area of the transistor in the preceding stage is greater than the number of divided emitters per unit area of the transistor in the succeeding stage. A semiconductor device characterized by forming.