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Bipolar Transistor Structures

IP.com Disclosure Number: IPCOM000082991D
Original Publication Date: 1975-Mar-01
Included in the Prior Art Database: 2005-Feb-28
Document File: 2 page(s) / 50K

Publishing Venue

IBM

Related People

Masters, BJ: AUTHOR [+3]

Abstract

One way to improve bipolar structures, which reduces peripheral emitter defects, is to fill in the emitter's contact hole with SiO(2) during emitter drive-in and then implanting and annealing the base. The thick oxide screen contours the collector junction to form a small pedestal, which in turn slightly increases the base width in the critical emitter's periphery.

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Bipolar Transistor Structures

One way to improve bipolar structures, which reduces peripheral emitter defects, is to fill in the emitter's contact hole with SiO(2) during emitter drive-in and then implanting and annealing the base. The thick oxide screen contours the collector junction to form a small pedestal, which in turn slightly increases the base width in the critical emitter's periphery.

Fig. 1 shows a pedestal type profile, with the oxide thicker than the screening material (preferably Si(3)N(4) and underlayer SiO(2)). Also shown is the emitter contact window 4, base contact window 6, collector contact window 8, base implant mask 10, emitter junction 12, and collect junction 14.

Two advantages to the pedestal type profile besides reducing peripheral emitter defects are: 1) improves the transistor's BVCEO characteristics, and 2) increases the collector base junction's capacitance.

In order to decrease the collectorbase junction's capacitance, a thinner emitter oxide is used, as shown in Fig. 2. The oxide over the emitter is the same thickness or thinner (in stopping power) than the masking material off the emitter.

An additional advantage is that the emitter ion implant deposition is determined by the Si(3)N(4) opening. If the SiO(2) layer is etched back laterally under the Si(3)N(4), there may be emitter base shorts, because metal is touching the exposed junction. However, pedestal type profiling prevents emitter base shorts, because any undercut region i...