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Minimizing Autodoping from a Substrate During the Deposition of a Silicon Epitaxial Layer

IP.com Disclosure Number: IPCOM000078942D
Original Publication Date: 1973-Apr-01
Included in the Prior Art Database: 2005-Feb-26
Document File: 1 page(s) / 12K

Publishing Venue

IBM

Related People

Bratter, RL: AUTHOR [+6]

Abstract

In conventional practice in integrated circuit fabrication, a buried subcollector region is formed at the surface of a semiconductor, e.g. silicon, supporting substrate prior to the deposition of the epitaxial layer. Autodoping has been a persistent problem to the deposition of this epitaxial layer, particularly, when such a buried region is utilized. Autodoping may be broken into two distinct categories: 1) that caused by outdiffusion from the buried region into the epitaxial layer, and 2) that caused by vaporization. Outdiffusion is strictly a solid-state phenomenon and does not significantly complicate the problem of autodoping.

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Minimizing Autodoping from a Substrate During the Deposition of a Silicon Epitaxial Layer

In conventional practice in integrated circuit fabrication, a buried subcollector region is formed at the surface of a semiconductor, e.g. silicon, supporting substrate prior to the deposition of the epitaxial layer. Autodoping has been a persistent problem to the deposition of this epitaxial layer, particularly, when such a buried region is utilized. Autodoping may be broken into two distinct categories: 1) that caused by outdiffusion from the buried region into the epitaxial layer, and 2) that caused by vaporization. Outdiffusion is strictly a solid-state phenomenon and does not significantly complicate the problem of autodoping. However, vaporized impurities, particularly from the buried region, enter into the gaseous phase of the epitaxial layer being deposited and become reincorporated into the epitaxial layer, at points very far from the epitaxial substrate interface.

It has been found that autodoping caused by vaporization from buried regions may be minimized, if immediately after the formation of the buried region by a conventional diffusion step, and with the silicon dioxide diffusion mask still intact, the substrate is baked at a high temperature in the order of 1100 degrees C for from ten to twenty minutes in an inert atmosphere.

In accordance with another aspect of this method, the baking may be carried out at low pressures in the order of 35 Torr in a hydrogen a...