Method for purifying polycrystalline silicon

Abstract

Polysilicon fragments are purified to remove metal contaminates by contacting the fragments with a purifying liquid at a flow rate >100 mm/sec. Effective removal without abrasion is accomplished.

1 .- 9 . (canceled) 
     
     
         10 . A method for purifying polysilicon fragments in an etching tank, comprising impinging a purifying liquid in at least one of the process steps onto the surface of the surface of the polysilicon fragments from more than two different directions at a flow velocity of greater than 100 mm/sec. 
     
     
         11 . The method of  claim 10 , wherein the purifying liquid impinges on the surface of the polysilicon fragments by non-directional, diffuse injection of the purifying liquid by means of nozzles. 
     
     
         12 . The method of  claim 10 , wherein the purifying liquid impinges on the surface of the polysilicon fragments via one or more moved nozzle rings in the etching tank. 
     
     
         13 . The method of  claim 10 , wherein the purifying liquid is caused to assume a rotational movement by virtue of the arrangement of the nozzles in the etching tank. 
     
     
         14 . The method of  claim 10 , wherein the polysilicon fragments rotate in a horizontal or vertical direction in a holding device within the purifying liquid. 
     
     
         15 . The method of  claim 10 , wherein the purifying liquid is caused to effect a flow by additional, non-directional injection of air by means of nozzles. 
     
     
         16 . The method of  claim 10 , wherein the flow velocities and flow directions are produced by the use of ultrasound. 
     
     
         17 . The method of  claim 10 , wherein the silicon fragments are additionally moved in a lifting/lowering movement in the etching tank. 
     
     
         18 . The method of  claim 17 , wherein the silicon fragments are wholly or partly removed from the purifying solution during the lifting/lowering movements.