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High Purity Crystal Growing Technique

IP.com Disclosure Number: IPCOM000040986D
Original Publication Date: 1987-Apr-01
Included in the Prior Art Database: 2005-Feb-02
Document File: 1 page(s) / 12K

Publishing Venue

IBM

Related People

Koch, RH: AUTHOR [+2]

Abstract

A technique is described whereby ultra high purity single crystals, as used in the growing of semiconductors, are obtained by controlling the melt portion of the process through the use of controlled high amperage direct current through the crystal. This high current provides an electromigration mass flux of solute away from the crystal, thereby reducing the consistency of the composition so as to produce high quality pure crystals.

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High Purity Crystal Growing Technique

A technique is described whereby ultra high purity single crystals, as used in the growing of semiconductors, are obtained by controlling the melt portion of the process through the use of controlled high amperage direct current through the crystal. This high current provides an electromigration mass flux of solute away from the crystal, thereby reducing the consistency of the composition so as to produce high quality pure crystals.

During the process of growing single crystals, the melt portion of the process produces a concentration of impurities, in front of the advancing interface, that is higher than the solid and higher than the average composition of the melt. This is considered to be caused by the rejection of the solute upon the phase change during the transition from liquid to solid and is illustrated in Fig. 1, showing the eutectic phase of the transition. The portion to the left of the dotted line represents the composition of the solid while the portion to the right of the dotted line represents the composition of the liquid. Position 10 indicates that the composition of the impurities to be less than that of the liquid. As a result, the impurities accumulate in front of the interface, raising the equilibrium of the melt and solid compositions. Although convection and stirring will reduce this effect, it will not eliminate all the impurities.

By introducing a controlled high amperage direct current through the cr...