Patent ID: 7449065
Filing Date: 2008-11-11
Classification: C30B

Abstract:
1. A method for crystal growth of a low-defect, tetrahedrally-bonded, single crystal comprising the steps of: a) providing a crystal seed having a defined vertical central axis with said central axis having a top and said central axis being parallel within 5 degrees to a selected crystal direction, with said crystal seed having several connected major portions substantially cylindrically symmetric about said central axis, and said major portions comprising of (1) a base located at the top of said central axis and having a diameter and opposite lower and upper ends, (2) a tapered portion extending downward from said lower end of said base, said tapered portion having a lower end that is smaller in diameter than said diameter of said base, (3) a columnar portion extending downward from said lower end of said tapered portion, and (4) a tip portion at the lowermost end of said columnar portion; b) providing a growth apparatus with first, second and third chambers respectively defining interlaced region c) providing a holder located inside said third chamber for holding said base of said crystal seed so that said tapered portion of said crystal seed lies between both said first and second passageways and extends completely through said region d) providing means within said first chamber for axial crystal growth of said tip portion of said crystal seed in a manner that maintains the diameter of said tip portion as measured perpendicular to said central axis, to be less than 10 percent of the diameter of said base of said crystal seed; e) providing means within said second chamber for lateral crystal growth of said tapered portion of said crystal seed; and f) providing means for moving said base of said crystal seed along said central axis and in a manner that maintains the location of the growing said tip portion fixed within 1 cm relative to said first growth chamber.