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Doping of Solids From the Vapor Phase

IP.com Disclosure Number: IPCOM000075272D
Original Publication Date: 1971-Aug-01
Included in the Prior Art Database: 2005-Feb-24
Document File: 3 page(s) / 33K

Publishing Venue

IBM

Related People

Phipps, PB: AUTHOR

Abstract

Using diffusion of arsenic As into silicon Si as an example, this doping technique can be understood by reference to the diagram.

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Doping of Solids From the Vapor Phase

Using diffusion of arsenic As into silicon Si as an example, this doping technique can be understood by reference to the diagram.

The apparatus consists of a vertical tube with a sealed lower end in a furnace, a middle section equipped with a condenser and an upper end sealed by demountable joints and connected to a regulated supply of inert gas, e.g., He, N(2), A, whose pressure can be regulated and measured. The As boils at temperature T(3) to provide an As atmosphere around the silicon wafers held at a measured T(1), the rising As vapor constantly pushes the inert gas out of the vicinity of the silicon. The As vapor condenses at temperature T(2) either to stick or to fall back to the source. Thus, the gas above the condenser is all inert gas and that below the condenser is all arsenic. Since the tube is open, the two pressures are essentially equal.

The As pressure is fixed by the inert gas He, N(2), A, whose pressure can be regulated and measured. When we want a high As pressure, we set a high-inert gas pressure, and the As condenses at a relatively high temperature. T need not be well regulated. If we try to put too much power into the As it boils faster-- cooling the As--the condenser has to carry away more heat, but the pressure is fixed equal to that above the condenser.

By these means, the silicon introduced into the lower part of the apparatus can be maintained in a constant pressure of As at a constant and measured T(1).

The technique can...