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Furnace Ramping to Reduce Slip Dislocation Generation on Large Semiconductor Wafers

IP.com Disclosure Number: IPCOM000048161D
Original Publication Date: 1981-Dec-01
Included in the Prior Art Database: 2005-Feb-08
Document File: 2 page(s) / 25K

Publishing Venue

IBM

Related People

Barile, CA: AUTHOR [+3]

Abstract

The double polysilicon process requires a masterslice built using high temperature diffusions, anneals and oxidations on a (100) P- type large wafer substrate. Stress in a semiconductor substrate wafer can be induced in several ways. When this stress exceeds a critical value, there is dislocation generation in the wafer. Stress can be generated in the following ways: (1) When a boat containing such wafers is pulled out of a high temperature furnace, stress builds up across the wafers as a result of temperature gradients. This stress is generated whether the wafers are bare or have surface films. (2) For wafers with surface films, additional sources of stress can exist involving silicon dioxide films or silicon nitride films.

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Furnace Ramping to Reduce Slip Dislocation Generation on Large Semiconductor Wafers

The double polysilicon process requires a masterslice built using high temperature diffusions, anneals and oxidations on a (100) P- type large wafer substrate. Stress in a semiconductor substrate wafer can be induced in several ways. When this stress exceeds a critical value, there is dislocation generation in the wafer. Stress can be generated in the following ways: (1) When a boat containing such wafers is pulled out of a

high temperature furnace, stress builds up across the

wafers as a result of temperature gradients. This

stress is generated whether the wafers are bare or

have surface films.

(2) For wafers with surface films, additional sources of

stress can exist involving silicon dioxide films or

silicon nitride films. The most probable source for the

silicon dioxide stress is the difference in thermal

expansion coefficient of silicon and silicon dioxide.

The stresses in the silicon nitride film are intrinsic

and are the result of densification taking place at

the film deposition temperature. Both of these types

of stress are greatly enhanced by stress concentration

that can be produced near the wafer edge by temperature

gradients.

The stress gradients described in (1) and (2) above can be reduced by furnace ramping, that is, the controlled raising or reducing of a temperature of a body. Examples of ramping processes are shown in Fig. 1 for the recessed isolation oxidation a...