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Optimum Preprocessing Heat Treatment for Lifetime Improvement

IP.com Disclosure Number: IPCOM000088641D
Original Publication Date: 1977-Jul-01
Included in the Prior Art Database: 2005-Mar-04
Document File: 1 page(s) / 12K

Publishing Venue

IBM

Related People

Hu, SM: AUTHOR

Abstract

A wafer heat treatment followed by a withdrawal from the furnace produces clusters of point defects, vacancies and/or interstitial defects by condensing these point defects formed at high temperatures. These point defect clusters then serve as nucleation centers for oxygen precipitation in a second heat treatment step. This phenomenon is analogous to the case in which a sequential oxidation process produces abundance of oxidation stacking faults.

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Optimum Preprocessing Heat Treatment for Lifetime Improvement

A wafer heat treatment followed by a withdrawal from the furnace produces clusters of point defects, vacancies and/or interstitial defects by condensing these point defects formed at high temperatures. These point defect clusters then serve as nucleation centers for oxygen precipitation in a second heat treatment step. This phenomenon is analogous to the case in which a sequential oxidation process produces abundance of oxidation stacking faults.

An optimum sequence of heat treatment prior to any thermal processing normally to be carried out improves device yields. The process is as follows:

Cleaned silicon wafers are heat-treated at a temperature of between 950- 1050 degrees C in dry oxygen for a period of not less than one hour. The wafers are removed from the furnace and allowed to cool for about 30 minutes or more. The wafers are again placed into the furnace at the same temperature as above in an inert atmosphere for not less than 8 hours, preferably more than 24 hours. The first heat treatment of not less than one hour serves to introduce nucleation centers for the precipitation process of oxygen in silicon in the second heat treatment, and also allows sufficient depletion of oxygen from the wafer surface so that precipitation of oxygen in the subsequent heat treatment will not occur up to the wafer surface which is normally the active region of wafers.

Alternatively, the initial oxidation step m...