Fishing – trapping – and vermin destroying
Patent
1993-08-03
1995-10-03
Jackson, Jerome
Fishing, trapping, and vermin destroying
437 33, 437164, H01L 21265
Patent
active
054551854
DESCRIPTION:
BRIEF SUMMARY
BACKGROUND OF THE INVENTION
To increase the packing density in integrated circuits, so-called oxide edge-bounded bipolar transistors are being used more and more. Described as oxide edge-bounded bipolar transistor is a bipolar transistor whose emitter and base are bounded by an oxide edge at least on one side. The bipolar transistors have lower capacitances.
For the production, the oxide edge is produced on a substrate. After forming the base by ion implantation, a doped polysilicon layer, from which the emitter is produced by outdiffusion, is produced on the surface of the substrate and the oxide edge. Before the polysilicon layer is deposited, the surface of the substrate has to be pretreated, for example, by an HF dip. This process results in thinning of the base at the oxide edge. In the case of very shallow emitter-base profiles, in particular, this results in reduced emitter-collector yields and emitter-collector breakdown voltages in the finished bipolar transistor.
Since bipolar transistors which are not oxide edge-bounded have hitherto generally been used in bipolar technology, no solution to this problem is to be found in the prior art. Known bipolar transistors, such as are described, for example, in European reference EP-A-0 170 250, have an active transistor zone which is defined by the geometry of the base connection disposed at the surface of the substrate. An inactive base which surrounds both the active base and the emitter in an annular manner is formed in the substrate by outdiffusion from the base connection region. The problem of a reduced emitter-collector breakdown voltage does not therefore occur in these bipolar transistors.
SUMMARY OF THE INVENTION
The invention is based on the problem of providing a bipolar transistor structure having a base-emitter structure which is bounded by an insulating zone and which has increased emitter-collector breakdown voltage and improved emitter-collector yield, and also of providing a process for producing it.
In general terms the present invention is a bipolar transistor structure having the following features. The emitter, base and collector are disposed in a vertical sequence in a semiconductor epitaxial layer deposited on a semiconductor substrate in such a way that the emitter adjoins the surface of the semiconductor epitaxial layer. An emitter connection at least partially spanning the emitter is disposed on the surface of the semiconductor epitaxial layer. The emitter and the base, which have an active base, an inactive base and a base edge region, are bounded, at least on one side, by a common insulating zone. The base has a dopant profile parallel to the surface of the semiconductor substrate which is such that, at that edge of the base which is adjacent to the insulating zone, the base edge region is disposed which is more heavily doped than the rest of the base and which adjoins only the emitter, the emitter connection and the collector in addition to the insulating zone and the rest of the base.
The semiconductor substrate and the semiconductor epitaxial layer are monocrystalline silicon and the insulating zone contains SiO.sub.2.
The bipolar transistor of the present invention also has the following features. The insulating zone contains at least a first component and a second component. The first component projects in height above the level of the surface of the semiconductor epitaxial layer in the region of the emitter and has an edge which faces the emitter and the base and which does not extend parallel to the surface of the semiconductor substrate and which converges on the surface of the semiconductor substrate. The second component is disposed as edge covering (spacer) at the edge of the first component above the base edge region and is a doped insulating material, with the result that it is suitable as a diffusion source for the formation of the base edge region.
The second component of the insulating structure is borosilicate glass.
A process of the present invention for producing the bipolar transistor structure having e
REFERENCES:
patent: 4263066 (1981-04-01), Kolmann
patent: 5289024 (1994-02-01), Ganschow
"A Self-Aligned Poly-Emitter Bipolar Transistor," Sep. 1991, Research Disclosure, #329.
IBM Technical Disclosure Bulletin, vol. 29, No. 5, Oct. 1986.
"Punch-Through Guard Ring For Butted Transistor Emitters", pp. 2184-2185.
IBM Technical Disclosure Bulletin, vol. 27, No. 8, Jan. 1985, pp. 4931-4933.
Bowers Courtney A.
Jackson Jerome
Siemens Aktiengesellschaft
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