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Method of Making Devices With Different Base Widths

IP.com Disclosure Number: IPCOM000047820D
Original Publication Date: 1983-Dec-01
Included in the Prior Art Database: 2005-Feb-08
Document File: 1 page(s) / 11K

Publishing Venue

IBM

Related People

Anantha, NG: AUTHOR [+3]

Abstract

Selective E-beam irradiation of base-area silicon is used to provide different etching rates for making transistors of different base widths on the same chip. Transistors which are desired to have the larger base widths are screened against E-beam irradiation by appropriate masking. Only those areas corresponding to the bases of transistors which are desired to have narrower base widths are left exposed. The exposed areas are subjected to E-beam irradiation, the dosage being determined by the base width desired. After exposure, the silicon overlying the base junctions is etched away by reactive ion etching at rates determined by the E-beam dosage.

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Method of Making Devices With Different Base Widths

Selective E-beam irradiation of base-area silicon is used to provide different etching rates for making transistors of different base widths on the same chip. Transistors which are desired to have the larger base widths are screened against E-beam irradiation by appropriate masking. Only those areas corresponding to the bases of transistors which are desired to have narrower base widths are left exposed. The exposed areas are subjected to E-beam irradiation, the dosage being determined by the base width desired. After exposure, the silicon overlying the base junctions is etched away by reactive ion etching at rates determined by the E-beam dosage. By selectively varying the E- beam dosage in the exposed base areas, different amounts of silicon are removed during a single reactive ion etching step whereby different base widths can be achieved simultaneously. Emitter diffusion is made into all base areas, after the above-mentioned masking is removed, to complete the different base- width transistor structures. If it is desired to avoid the use of any masking, a higher E-beam dose can be used in all base areas, followed by additional doses in those areas where narrower base widths are wanted.

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