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Gettering by Oxygen Precipitation

IP.com Disclosure Number: IPCOM000088246D
Original Publication Date: 1977-May-01
Included in the Prior Art Database: 2005-Mar-04
Document File: 2 page(s) / 34K

Publishing Venue

IBM

Related People

Hu, SM: AUTHOR [+3]

Abstract

The precipitation of oxygen which is present in silicon semiconductors forms gettering sites for impurities with a consequent improvement in the electrical properties of devices fonmed in the semiconductor. Heating to promote such precipitation at temperatures of about 1,000 degrees C for 4 to 6 hours or more in a dry oxygen or preferably inert atmosphere also causes oxygen diffusion from the semiconductor surface so that a defect-free surface layer is formed.

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Gettering by Oxygen Precipitation

The precipitation of oxygen which is present in silicon semiconductors forms gettering sites for impurities with a consequent improvement in the electrical properties of devices fonmed in the semiconductor. Heating to promote such precipitation at temperatures of about 1,000 degrees C for 4 to 6 hours or more in a dry oxygen or preferably inert atmosphere also causes oxygen diffusion from the semiconductor surface so that a defect-free surface layer is formed.

The maximum yield benefits are obtained by the selection of proper oxygen levels and/or total heating times for specific device processes. For field-effect transistor (FET) devices, short total heating times during processing will require either higher initial oxygen content or a preheating treatment of varying times to assure oxygen precipitation. For bipolar devices premature precipitation may be harmful so that oxygen content and total heating times are selected to produce precipitation late in the cycle but prior to emitter formation.

For example, the figure illustrates the relationship between thermal treatment (Dt) and amounts of precipitation for various initial oxygen concentrations (line
A). These data represent the thermal treatment resulting in a decrease in dissolved oxygen to a level of 1/e of the initial concentration, expressed in terms of oxygen diffusion lengths Dt. Complete precipitation (95%) is represented by line B. The onset of precipitation occurs clo...