C - Chemistry – Metallurgy – 30 – B
Patent
C - Chemistry, Metallurgy
30
B
148/1.2
C30B 15/30 (2006.01) C30B 15/00 (2006.01)
Patent
CA 1182385
METHOD FOR CONTROLLING THE OXYGEN LEVEL OF SILICON RODS PULLED ACCORDING TO THE CZOCHRALSKI TECHNIQUE Abstract The present invention relates to an improved method for pulling semiconductor monocrystalline rods, in parti- cular silicon rods, according to the Czochralski tech- nique. The average oxygen concentration profile (02) is first determined for a given pulling equipment as a function of the length (L) of the rods pulled at a con- stant crucible rotation speed, that is, (02) = f(L). The improvement consists in pulling the rods at a crucible rotation speed VRC which varies as a function of L accord- ing to a predetermined profile to ensure an oxygen concen- tration profile which is about constant along the rod. In practice, under normal. conditions, it is sufficient to ensure at any moment that: grad VRC = k grad f(L) where k is a positive proportionality factor depending on the operating conditions. For example, if the oxygen concentration profile (02) at a constant rotation speed (Ro) represents a curve in bell form, the desired pro- file of the crucible rotation speed VRC will have in- verse form of the bell curve. The oxygen concentration profile of the rod thus obtained will be virtually linear. This method is mainly used to manufacture semiconductor wafers whose oxygen level will match the specification of the different production lines.
377160
Combronde Jacques
Felix Jean-Claude
International Business Machines Corporation
Rosen Arnold
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