Polishing silicon wafers

Abstract

An endless belt for a belt type polishing machine comprises a support fabric and a polymer layer of relatively low hardness. The polymer layer is formed with drainage grooves. The support fabric may comprise a non woven or woven material, or a membrane with oriented reinforcing yarns. A further version comprises a spiral-link fabric supporting a woven or non woven layer carrying the polymer layer. The polymer layer may be a double layer, the upper of which is either harder or softer than the lower layer.

1 . For use in polishing silicon wafers, an endless belt to act as a polishing tool, wherein said belt comprises a woven or non-woven fabric coated with a suitable polymer.  
     
     
         2 . A belt according to  claim 1 , wherein said polymer is polyurethane, having a low Shore-D hardness.  
     
     
         3 . A belt according to  claim 2 , wherein the Shore-D hardness of the polyurethane is in the range 65-75.  
     
     
         4 . A belt according to  claim 1 , wherein said polymer is a thermoset or thermoplastic polymer having a high abrasion resistance.  
     
     
         5 . A belt according to  claim 4 , wherein said polymer is selected from the group comprising: polyamides, silicones, fluropolymers, epoxy resins and thermoplastic polyurethanes.  
     
     
         6 . A belt according to  claim 2 , wherein the coating comprises an upper layer and an intermediate layer, of materials having different hardness.  
     
     
         7 . A belt according to  claim 6 , wherein the upper layer is of a harder material than the intermediate layer.  
     
     
         8 . A belt according to  claim 6 , wherein the upper layer is of a softer material than the intermediate layer.  
     
     
         9 . A belt according to  claim 8 , wherein the upper layer is of a foamed plastic material.  
     
     
         10 . A belt according to  claim 8 , wherein the upper layer comprises a layer of beads of plastic, glass or soluble material.  
     
     
         11 . A belt according to  claim 10 , wherein said beads comprise expanded polystyrene pellets which are dispersed into the upper layer.  
     
     
         12 . A belt according to  claim 6 , wherein abrasive particles or fibres are incorporated in the upper layer.  
     
     
         13 . A belt according to  claim 6 , wherein the surface of the upper layer is provides with a micro-textured coating.  
     
     
         14 . A belt according to  claim 1 , wherein said fabric is woven in endless form and embodies yarns of high tensile strength and low elongation.  
     
     
         15 . A belt according to  claim 6 , wherein said high tensile strength yarns are selected from the group comprising:—meta or para-aramids; polyetherimide; polyimide; polyetherketone; PEEK; gel spun UHMW polyethylene; and polybenzimidazole.  
     
     
         16 . A belt according to  claim 6 , wherein said high tensile strength yarns comprise a mixture or blend of two or more such yarns.  
     
     
         17 . A belt according to  claim 6 , wherein said yarns are of any one of:—glass fibres, carbon or ceramic yarns, basalt fibres, other rock fibres or mixtures of mineral fibres with synthetic polymer yarns.  
     
     
         18 . A belt according to  claim 1 , wherein said fabric is a non woven fabric formed from one or more yarn staples.  
     
     
         19 . A belt according to  claim 18 , wherein said yarn staple comprises one or more groups of fibres selected from the group comprising:—meta or para aramids; polyetherimide; polyimide; polyetherketone; PEEK; gel-spun UHMW polyethylene; polybenzimidazole; glass fibres, carbon fibres, ceramic fibres; basalt fibre; other rock fibres.  
     
     
         20 . A belt according to  claim 1 , wherein said fabric comprises a non woven fabric incorporating additional spaced apart linear yarns extending substantially in a common direction and a polymeric matrix material interconnecting and at least partially encapsulating each said yarn.  
     
     
         21 . A belt according to  claim 20 , wherein said linear yarns are oriented in the running direction of said belt.  
     
     
         22 . A belt according to  claim 20 , wherein said linear yarns are oriented in transversely of said belt.  
     
     
         23 . A belt according to  claim 22 , wherein additional reinforcing yarns are provided extending in the running direction of said belt.  
     
     
         24 . A belt according to  claim 1 , wherein said belt has a relatively high open area.  
     
     
         25 . A belt according to  claim 24 , wherein said belt includes a spiral-link belt.  
     
     
         26 . A belt according to  claim 25 , wherein said spiral-link belt supports a woven or non woven fabric layer which is coated or impregnated with said polymer.  
     
     
         27 . A belt according to  claim 1 , wherein the surface of said belt is formed with grooves extending in the running direction of the belt to remove wet slurry generated in use.  
     
     
         28 . Apparatus for polishing silicon wafers, incorporating an endless belt to act as a polishing tool, wherein said belt is a belt according to  claim 1.