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Browse Prior Art Database

ONE STEP TRANSISTOR FORMATION

IP.com Disclosure Number: IPCOM000005536D
Original Publication Date: 1984-Apr-01
Included in the Prior Art Database: 2001-Oct-12
Document File: 2 page(s) / 80K

Publishing Venue

Motorola

Related People

D.L. Flowers: AUTHOR [+3]

Abstract

One step transistor formation can be accomplished by utilizing a simultaneously present, mixed dopant, n-type and p-type in a liquid source which is spun on the semiconductor wafer, baked, and diffused.

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MOTOROLA Technical Developments Volume4 April 1984

ONE STEP TRANSISTOR FORMATION

by D.L. Flowers, H. Hughes, and D. Tam

ABSTRACT:

   One step transistor formation can be accomplished by utilizing a simultaneously present, mixed dopant, n-type and p-type in a liquid source which is spun on the semiconductor wafer, baked, and diffused.

INTRODUCTION:

   Transistors are routinely made via a two step diffusion process at high temperature, 900°C, wherein a source of one conductivity type, for example, boron, p-type, is diffused into n-type, single crystal silicon to form the base-collector region. Next, an n-type dopant, arsenic, is diffused into the base region to form the emitter base junction thus completing the essential part of npn transistor formation. It was of interest to try to make a transistor in two one step diffusion process utilizing a spin-on dopant film consisting of liquid organ@silica glass, solvents, and a suitably selected mixture of n-type and p-type dopants. Experiments were planned and carried out spinning the suitably formulated, spin-on sources containing different ratios of arsenic to boron on the wafers and diffusing todetermine the flexibility and utility of the process. The process was also applied to a TMOS device structure to determine the effect of the arsenic to boron ratio on the threshold voltage of the TMOS device.

EXPERIMENTAL RESULTS AND DISCUSSION:

   To test the one step diffusion, transistor formation hypothesis, spin-on sources were made with a dry SiO, film concentration of 4.5 x 10" atoms per cubic centimeter of arsenic dopant. The ratio of arsenic to boron in the films was varied from 1:l to l:O.Ol. Diffusion wa...