JPH0466103B2 - - Google Patents

Description

[Detailed Description of the Invention] [Field of Industrial Application] The present invention relates to a high-voltage semiconductor device, and particularly to a bipolar transistor that can obtain a high collector-emitter breakdown voltage in a semiconductor device that operates under an inductive load. It is.

[Conventional technology]

Conventionally, the structure shown in FIG. 3 is known as this type of bipolar transistor. That is,
A large number of emitters 1 are provided on the base 2, and these are connected in parallel.In order to equalize these characteristics, a resistor (for example, a polycrystalline silicon resistor) 11 is inserted in series with the emitters to control local current concentration by negative feedback. Measures are being taken to expand the safe operating range. In the figure, 4 is the collector low concentration layer, and 5 is the collector low concentration layer.
6 is a collector high concentration layer, 6 is a base electrode, 7 is an emitter electrode, 8 is a collector electrode, and 9 is a surface protective film.

[Problem that the invention seeks to solve]

Although the above-mentioned conventional bipolar transistors are certainly useful in preventing local current concentration, they have the drawback of high collector-emitter saturation voltage and base-emitter saturation voltage because a resistor is inserted in series with the element.

In order to eliminate the drawbacks of the above-mentioned prior art, the present invention has the following features:
It is an object of the present invention to provide a high breakdown voltage semiconductor device that can prevent concentration of collector current without using a negative feedback resistor and achieves high breakdown voltage as a result.

[Means for solving problems]

A high voltage semiconductor device of the present invention includes a collector region of a first conductivity type, a base region of a second conductivity type in contact with the collector region, and an emitter of a first conductivity type in contact with the base region and spaced apart from the collector region. In a semiconductor device comprising a region, the first conductivity type semiconductor substrate serving as the collector is partially provided with a buried layer of a second conductivity type and having a higher concentration than the collector substrate, spaced apart from the base region. .

〔Example〕

Next, the present invention will be explained with reference to the drawings. FIG. 1 is a cross-sectional view of one embodiment of the present invention, showing a vertical bipolar transistor. In FIG. 1, 1 is an emitter region, 2 is a base region, and 3 is an emitter region.
is a buried layer for preventing current concentration, which is partially formed in the collector low concentration layer 4 at a higher concentration than this layer and has an opposite conductivity type and is spaced apart from the base region. Also 5
is a collector high concentration layer, 6 is a base electrode, 7 is an emitter electrode, 8 is a collector electrode, 9 is a surface protective film,
10 is the center portion of the base.

The buried layer 3 for preventing concentration of collector current is formed by, for example, impurities having a conductivity type opposite to that of the epitaxial layer during the epitaxial growth process of the collector low concentration layer 4 by ion implantation or gas diffusion. It can be formed by introducing Further, the collector current concentration prevention region 3 is formed within the base pattern as viewed from the element surface so as not to deteriorate the characteristics during forward bias.

FIG. 2 is a cross-sectional view of another embodiment of the present invention, showing a horizontal bipolar transistor. This embodiment is the same except that the positions and structures of the collector high concentration layer 5a and the collector electrode 8a are different, and in particular, the main parts of the invention are the same. In addition, to explain the reason why preventing current concentration improves the breakdown resistance of the element, generally speaking, when a transistor changes from an operating state to a desensitized state, the central part of the base 10, which is a long distance from the base electrode 6, The drift current due to the high electric field caused by poor carrier sweeping or breakage is large in the center part 10 of the base, and the energy P per unit time and unit volume consumed in this part is approximately expressed as P=E・J( E: electric field vector, J: current density vector), and J≒qμNE (q:
elementary charge, μ: mobility, N: majority carrier density)
Therefore, P≒qμN|E| ² , and by preventing current concentration, N does not increase, energy consumption P is also small, and the breakdown resistance of the element is improved.

〔Effect of the invention〕

As explained above, the present invention introduces a buried layer of conductivity type opposite to that of the collector in the collector region, thereby forming an energy barrier against the majority of carriers flowing through the collector, thereby reducing current concentration at the center of the base. The energy consumed in this part can be reduced, and as a result, high voltage resistance can be achieved.

[Brief explanation of drawings]

FIG. 1 is a sectional view of one embodiment of the present invention, FIG. 2 is a sectional view of another embodiment of the invention, and FIG. 3 is a sectional view of an example of a conventional vertical high voltage semiconductor device. 1... Emitter, 2... Base, 3... Buried layer for preventing current concentration, 4... Collector low concentration layer, 5,
5a... Collector high concentration layer, 6... Base electrode,
7... Emitter electrode, 8, 8a... Collector electrode, 9... Surface protective film, 10... Center part of base,
11...Resistance (polycrystalline silicon resistance).

Claims (1)

[Claims] 1. A semiconductor device comprising a collector region of a first conductivity type, a base region of a second conductivity type in contact with the collector region, and an emitter region of a first conductivity type in contact with the base region and spaced apart from the collector region, A high breakdown voltage semiconductor device, characterized in that a semiconductor substrate of a first conductivity type serving as a collector is partially provided with a buried layer of a second conductivity type and having a higher concentration than the collector substrate, spaced apart from a base region.