JPH0348653B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION (A) Field of Industrial Application The present invention relates to improvements in power transistors, particularly power transistors having a ring-shaped emitter region.

(b) Prior Art When a power amplifier or the like is incorporated into a semiconductor integrated circuit, the power transistor occupies most of the chip, so it is desired to realize a highly efficient power transistor with as small an area as possible. Since a power transistor having a ring-shaped emitter region can have the longest emitter-base junction facing the base electrode, it is efficient in terms of area and is optimal as a power transistor to be incorporated into a semiconductor integrated circuit.

A conventionally used power transistor having a ring-shaped emitter region will be explained with reference to FIGS. 1 and 2. In this power transistor, an N-type epitaxial layer 2 serving as a collector region is provided on a P-type semiconductor substrate 1, and a layer is formed on the bottom surface of the epitaxial layer 2 to lower the extraction resistance of the collector region.
An N ⁺ type buried layer 3 is provided, an N ⁺ type collector contact region 4 is provided in a strip shape in parallel on the surface of the epitaxial layer 2, and a P type base is provided in a strip shape on the surface of the epitaxial layer 2 between the collector contact regions 4. A region 5 is provided, and a continuous N ⁺ is formed on the surface of the base region 5.
A ring-shaped emitter region 6 is provided, and a collector electrode 7, a base electrode 8, and an emitter electrode 9 shown by dotted lines are provided in ohmic contact with the collector contact region 4, base region 5, and emitter region 6, respectively.

However, in the above-mentioned power transistor having a ring-shaped emitter region of single-layer wiring, the emitter electrode 9 must be placed between the base electrode 8 and the collector electrode 7, and the ring-shaped emitter region 6 in this part must be made wide. It was necessary to form. As a result, the base bias is well applied to the narrow emitter region 6 where the emitter electrode 9 is not provided, making it extremely active, whereas the base bias is not well applied to the wide emitter region 6 where the emitter electrode 9 is provided, making it inactive. becomes. For this reason, there are parts of the emitter region 6 that do not work well, resulting in area loss. Furthermore, due to the unbalanced working of the emitter region 6, the safe operation area (A, S, O,) is narrower than that of a stripe-type power transistor, making it vulnerable to destruction.

(c) Object of the Invention The present invention has been made in view of the above points, and an object of the present invention is to realize a power transistor having a ring-shaped emitter region that greatly improves the conventional drawbacks.

(d) Structure of the invention According to the present invention, as shown in FIGS. 3 to 5,
A semiconductor substrate 11 of one conductivity type, an epitaxial layer 12 of the opposite conductivity type provided on the substrate 11 and serving as a collector region, a collector contact region 14 of the opposite conductivity type provided on the surface of the epitaxial layer 12, and a collector contact region 14 of the opposite conductivity type provided on the surface of the epitaxial layer 12. A base region 16 , a ring-shaped emitter region 17 of opposite conductivity type, a first insulating film 18 covering the surface of the epitaxial layer 12 , a first collector electrode 19 in ohmic contact with the collector contact region 14 , and a first collector electrode 19 in ohmic contact with the emitter region 17 . A first emitter electrode 20 in ohmic contact, a base electrode 21 in ohmic contact with the base region 16 surrounded by the emitter region 17 and extending over the first insulating film 18, and a first collector electrode 19. 20 and a second insulating film 22 covering the base electrode 21;
First collector electrode 19 and first emitter electrode 2
The second collector electrode 23 and the second emitter electrode 24 are connected to each other and extend on the second insulating film 22.

(E) Embodiment According to the present invention, a P-type semiconductor substrate 11, an epitaxial layer 12 provided on the substrate 11 and serving as a collector region, and an N ⁺ type buried layer provided on the bottom surface of the epitaxial layer 12. 13, an N ⁺ type collector contact region 14 provided parallel to the surface of the epitaxial layer 12 in a strip shape, an N ⁺ type collector lead-out region 15 connecting the collector contact region 14 and the buried layer 13, and a collector contact region. 14, a P-type base region 16 provided in a belt shape on the surface of the epitaxial layer 12 and parallel to the collector contact region 14, and a continuous ring-shaped emitter having hollow portions at equal intervals provided on the surface of the base region 16. Region 17 and epitaxial layer 1
a first insulating film 18 made of a silicon oxide film covering two surfaces; a first collector electrode 19 and a first emitter electrode 20 in ohmic contact with the collector contact region 14 and the emitter region 17;
A first collector electrode 19 and a first emitter electrode 2 are in ohmic contact with the base region 16 surrounded by the ring-shaped emitter region 17 and are on the first insulating film 18 .
The base electrode 21 is extended so as not to be short-circuited with 0.
and a second insulating film 22 made of polyimide or the like that covers the first collector electrode 19, first emitter electrode 20, and base electrode 21 of the first layer to provide interlayer insulation.
and a second collector electrode 23 and a second emitter electrode 24 that connect the plurality of first collector electrodes 19 and first emitter electrodes 20 and extend on the second insulating film 22 .

One of the features of the present invention is that the electrode has a two-layer structure. That is, the first collector electrode 19, the first emitter electrode 20, and the base electrode 21 are the electrodes of the first layer (indicated by dotted lines in FIG. 3), and the second collector electrode 23 and the second emitter electrode 24 are the electrodes of the second layer. This is an electrode (indicated by a dotted line in FIG. 3). As is clear from FIG. 3, the first collector electrodes 19 are scattered at regular intervals on the collector contact region 14.
The first emitter electrodes 20 are scattered at regular intervals between the portions of the ring-shaped emitter region 17 where the base region 16 is exposed. Also, the first collector electrode 19
and the first emitter electrode 20 are provided adjacently at the same interval. A base electrode 2 is provided on each base region 16 exposed in the center from the ring-shaped emitter region 17.
1 in ohmic contact and the first collector electrode 19
All the base regions 16 are connected by extending the gap between the first emitter electrodes 20 in a stripe shape in one direction on the first insulating film 18 . The second collector electrode 23 and the second emitter electrode 24 extend in a stripe shape in one direction on the second insulating film 22, and connect the first collector electrode 19 and the first emitter electrode 20 which are scattered. As a result, the base electrode 21, the second collector electrode 23, and the second emitter electrode 24 are connected to the second insulating film 22, as shown in FIG.
electrically insulated by Further, in terms of pattern design, it is desirable that the extending direction of the base electrode 21 and the extending directions of the second collector electrode 23 and the second emitter electrode 24 be perpendicular or nearly so.

According to the present invention, since the base electrode 21, the second collector electrode 23, and the second emitter electrode 24 can cross in their extending directions, the ring-shaped emitter region 1
7 can be formed to have an even width. As a result, the ring-shaped emitter region 17 all works uniformly and efficiently, making it possible to improve the overall effect more than ever before and eliminate imbalances in the way it works.

Furthermore, in the present invention, by adjusting the size of the through hole provided in the second insulating film 22 that connects with the first emitter electrode 20, a resistance can be created in series between the first emitter electrode 20 and the second emitter electrode 24. Can be formed. This resistor acts as an emitter resistor, and can play the role of a ballast resistor that expands the safe operating area of the power transistor. Furthermore, the emitter resistance value can be arbitrarily selected depending on the size of the through hole.

(F) Effects of the Invention According to the present invention, by adopting a two-layer wiring structure, the width of the ring-shaped emitter region 17 can be formed uniformly,
The efficiency of power transistors has been improved compared to conventional ones. As a result, the power transistor can be formed in a smaller area than before, and the degree of integration of the integrated circuit can be improved.

Furthermore, it is possible to eliminate the imbalance in the way the ring-shaped emitter region of the power transistor works, and to expand the safe operating area of the power transistor. Furthermore, by selecting the shape of the through hole in the second insulating film 22, a ballast resistor can be incorporated, and the safe operation area of the power transistor can be further expanded.

[Brief explanation of drawings]

FIG. 1 is a top view of a conventional power transistor having a ring-shaped emitter region, FIG. 2 is a sectional view taken along the line -- in FIG. 1, FIG. 3 is a top view of the power transistor of the present invention, and FIG. FIG. 5 is a cross-sectional view taken along the line -- in FIG. 3. Description of main figure numbers 11 is a semiconductor substrate, 12 is an epitaxial layer, 14 is a collector contact region,
16 is a base region, 17 is a ring-shaped emitter region, 18 is a first insulating film, 19 is a first collector electrode, 20 is a first emitter electrode, 21 is a base electrode, 22 is a second insulating film, 23 is a The second collector electrode 24 is a second emitter electrode.

Claims (1)

[Claims] 1 A semiconductor substrate of one conductivity type, an epitaxial layer of the opposite conductivity type provided on the substrate and serving as a collector region, a collector contact region of the opposite conductivity type provided on the surface of the epitaxial layer, and a collector contact region of the opposite conductivity type provided on the surface of the epitaxial layer, and a collector contact region of the opposite conductivity type provided on the surface of the epitaxial layer. It has a base region of one conductivity type that extends between the base regions, and openings provided on the surface of the base region to expose the base regions at regular intervals, and the widths of the emitter regions at the openings are approximately equal. a ring-shaped emitter region of opposite conductivity type; a first insulating film covering the surface of the epitaxial layer; and an emitter region extending over the first insulating film in ohmic contact with the opening of the base region. A base electrode, a first collector electrode in ohmic contact with the collector contact region and extending over the first insulating film, and an ohmic contact with an emitter region sandwiched between openings of the ring-shaped emitter region. and a first emitter electrode extending over the first insulating film, a second insulating film covering each of the electrodes, and a second insulating film extending over the second insulating film connecting the first collector electrode. a second collector electrode in a second layer; a second emitter electrode in a second layer extending on the second insulating film and connecting the first emitter electrode; A power transistor characterized in that the direction and the extending direction of the second collector electrode and the second emitter electrode are substantially perpendicular to each other.