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A METHOD TO REDUCE THE RADIAL RESISTIVITY GRADIENT OF (111) AS-GROWN SILICON CRYSTAlLS

IP.com Disclosure Number: IPCOM000006443D
Original Publication Date: 1992-May-01
Included in the Prior Art Database: 2002-Jan-03
Document File: 1 page(s) / 60K

Publishing Venue

Motorola

Related People

Herng-Der Chiou: AUTHOR

Abstract

The radial resistivity gradient (RRG) of (111) crys- tals is about double the RRG values of (100) crystals. The reason is that during (111) crystal growth, the center of the crystal tends to grow laterally and forms (111) facet planes. The rate of dopants incorporated into the solid is much higher in the (111) fast lateral planes than the other crystal planes resulting in the higher dopant in the center of the crystals.

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MOTOROLA INC. Technical Developments Volume 15 May 1992

A METHOD TO REDUCE THE RADIAL RESISTIVITY GRADIENT OF (111) AS-GROWN SILICON CRYSTAlLS

by Herng-Der Chiou

  The radial resistivity gradient (RRG) of (111) crys- tals is about double the RRG values of (100) crystals. The reason is that during (111) crystal growth, the center of the crystal tends to grow laterally and forms (111) facet planes. The rate of dopants incorporated into the solid is much higher in the (111) fast lateral planes than the other crystal planes resulting in the higher dopant in the center of the crystals.

  For both (100) and (111) crystals with a given dopant type, the RRG can be improved by increasing the crys- tal rotation rate relative to the crucible rotation rate. How- ever, there is a limitation on the crystal rotation rate, especially for the large diameter crystals.

  In this new approach we propose to grow (111) crys- tals off orientation about 8" (8' to 10") toward the < llO> direction and get rid of facet growth to improve the radial resistivity gradient. The crystal growth conditions arc similar for growing the on- and the off-orientation crystals.

  This new method imprbves the RRG of (111) wafers significantly. Figure 1 shows the RRG for G50 wafers (Sb-doped) grown by the old process (grew on-orienta- tion): average RRG at R/2 is about 13% and that at 6mm is about 24%. Figure 2 shows the results from this new process which improves the average RRG at R/2 to 2% and the average...