Surface modified quartz glass crucible and its modification process

Abstract

A surface modified quartz glass crucible and a process for modifying the crucible includes a layer of a metal oxide on the whole or a part of the inside and/or outside of the crucible, and baking it. At least an inside surface of the crucible is coated with a said metal oxide of magnesium, calcium, strontium or barium. The coated layer of the crucible does not abrade easily and provides a high dislocation free ratio of silicon single crystals pulled by using the crucible.

What is claimed is:  
     
         1 . A quartz glass crucible comprising a layer of a metal oxide, wherein said layer is baked on at least a portion of an inside and/or outside surface of said crucible.  
     
     
         2 . The quartz glass crucible according to  claim 1 , wherein the layer of a metal oxide is baked on at least a portion of the inside surface of the crucible.  
     
     
         3 . The quartz glass crucible according to  claim 1 , wherein the metal oxide is an oxide of magnesium, calcium, strontium, or barium.  
     
     
         4 . The quartz glass crucible according to  claim 1 , wherein the amount of the metal oxide on the surface of the crucible is from 1×10 −9  to 1×10 −6  mol/cm 2 .  
     
     
         5 . The quartz glass crucible according to  claim 1 , wherein the metal oxide is baked on the surface of the crucible at a temperature of from 400 to 1,200° C.  
     
     
         6 . The quartz glass crucible according to  claim 1 , wherein the metal oxide is baked on the surface of the crucible at a temperature of from 600° C. to 1,200° C.  
     
     
         7 . The quartz glass crucible according to  claim 1 , wherein the metal oxide is baked onto the surface of the crucible for from 10 to 120 minutes.  
     
     
         8 . A surface modification process for a quartz glass crucible, said process comprising, 
 coating a coating liquid comprising a metal salt on at least a portion of an inside and/or an outside surface of said crucible,    drying said coated liquid, and    baking said dried coated liquid at a higher temperature than a thermal decomposition temperature of said metal salt to bake a coated layer of a metal oxide on said surface of said crucible.    
     
     
         9 . The process of  claim 8 , wherein the metal salt is one or more organic acid salts of magnesium, calcium, strontium, or barium.  
     
     
         10 . The process of  claim 8 , wherein the organic acid salt is a carboxylate.  
     
     
         11 . The process of  claim 10 , wherein the carboxylate has the formula C n H 2n+1 COO, where n is an integer of 3 to 7.  
     
     
         12 . The process of  claim 11 , wherein the carboxylate is derived from n-butyric acid, α-methyl butyric acid, iso-valeric acid, 2-ethyl butyric acid, 2,2-dimethyl butyric acid, 3,3-dimethyl butyric acid, 2,3-dimethyl butyric acid, 3-methyl pentanoic acid, 1,4-methyl pentanoic acid, 2-ethyl pentanoic acid, 3-ethyl pentanoic acid, 2,2-dimethyl pentanoic acid, 3,3-dimethyl pentanoic acid, 2,3-dimethyl pentanoic acid, 2-ethyl hexanoic acid, or 3-ethyl hexanoic acid.  
     
     
         13 . The process of  claim 8 , wherein the coating liquid comprises from 0.01 to 15 weight % of metal based on the amount of the metal oxide.  
     
     
         14 . The process of  claim 8 , wherein the dried coating liquid is baked on ata temperature of from 400 to 1200° C., for 10 to 120 minutes.  
     
     
         15 . The process of  claim 8 , wherein the coating liquid comprises from 0.5 to 10 wt. % of metal based on the amount of the metal oxide.  
     
     
         16 . The process of  claim 8 , wherein the coating liquid comprises an organic solvent selected from the group consisting of an ester, an alcohol, a ketone, a hydrocarbon and mixtures thereof.  
     
     
         17 . The process of  claim 16 , wherein the solvent is toluene.  
     
     
         18 . A quartz glass crucible obtained by the process of  claim 8.