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Process Modification for Improved Bipolar Circuit Performance

IP.com Disclosure Number: IPCOM000048974D
Original Publication Date: 1982-Apr-01
Included in the Prior Art Database: 2005-Feb-09
Document File: 3 page(s) / 80K

Publishing Venue

IBM

Related People

Jambotkar, CG: AUTHOR

Abstract

Modifications in a bipolar process sequence are described which provide for improved performance characteristics of the resulting transistors. The preferred process sequence is as follows: 1. Wafer processing is performed conventionally up to reoxidation after diffusion of collector reach-through. The transistor structure at this stage is shown in Fig. 1A - 1B in two diffenent cross-sections. Fig. 6 shows the mask geometries. Figs. 1A through 5A correspond to the cross-sections at B-B in Fig. 6, while Figs. 1B through 5B correspond to the cross sections at A-A in Fig. 6. In Figs.

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Process Modification for Improved Bipolar Circuit Performance

Modifications in a bipolar process sequence are described which provide for improved performance characteristics of the resulting transistors. The preferred process sequence is as follows: 1. Wafer processing is performed conventionally up to reoxidation after diffusion

of collector reach-through. The transistor structure

at this stage is shown in Fig. 1A - 1B in two diffenent

cross-sections. Fig. 6 shows the mask geometries.

Figs. 1A through 5A correspond to the cross-sections

at B-B in Fig. 6,

while Figs. 1B through 5B correspond to the cross

sections at A-A in Fig. 6. In Figs. 1-5, N+ 4, P+ 6, N- 8,

SiO(2) 10, ROI 12 and N+ 14 represent, respectively, the

conventional

tional subcollector, subisolation, epi, epi reoxidation,

recessed oxide isolation and collector reach-through.

2. Deposit now approximately 800 (see original) Si(3)N(4)

16. Using an "E" mask with the

geometry shown in Fig. 6, form windows in the Si(3)N(4)

16/SiO(2) 10

composite through reactive ion etching (RIE). Diffuse in

boron to form the eventual P base lR (Figs. 2A - 2B).

3. After thermal growth of approximately 800 (see original)

base reoxidation layer SiO(2). 20, deposit approximately

800 (see original) Si(3)N(4) 22 (Fig. 3A - 3B)

4. Using an "F" mask with geometry shown in Fig. 6, form

windows in Si(3)N(4) 22 using RIE, leaving underlying

Si(3)N(4) 16 practically in

place. Next, etch exposed SiO(2) to obtain the

structure illustrated in Figs. 4A - 4B. Either the highly

selective wet BHF etching or selective RIE (using, e.g.,

CHF) may be employed to etch the exposed SiO(2). 5. Using photoresist and the "H*" mask shown in Fig. 6, form windows in Si(3)N(4) 16 through RIE above collector

reach-through (and Schottky

anode/cathode). Misalignment between masks "F"

and "H*" is of no consequence. Retaining the photoresist

mask, wet etch (or RIE) exposed SiO2. 6. Through chemical vapor deposition (CVD), deposit about 500 A SiO and about 300-500

A Si(3)N(4). Using vertically directional RIE, remove

this composite of SiO(2)/Si(3)N(4) everywhere excepting

in the SiO(2) undercut, filling...