Silicon wafer tower with inclined support teeth

Abstract

A silicon tower for removably supporting a plurality of silicon wafers during thermal processing. A tower includes plural silicon legs secured on their ends to two bases. A plurality of slots are cut in the legs allowing slidable insertion of the wafers and support for them. Preferably, the teeth incline upwardly at 1-3° and have horizontal support areas polished on their ends. Preferably, the legs are machined from virgin polysilicon formed by chemical vapor deposition from silane. The bases may be either virgin poly or monocrystalline silicon and be either integral or composed of multiple parts. Virgin polysilicon is preferably annealed to above 1025° C. before machining. Silicon parts may be joined by applying a spin-on glass between the parts and annealing the assembly.

1 . A wafer support tower for supporting wafers in parallel in spaced relationship along a vertical axis, comprising: 
 two silicon bases;    a plurality of silicon legs joined at opposite ends to said two bases; and    a plurality of teeth cut into said legs at an upwardly sloping angle of between 1° and 3° with respect to said vertical axis to support said wafers on upper sides of distal ends thereof.    
     
     
         2 . The tower of  claim 1 , wherein said silicon legs comprise virgin polysilicon.  
     
     
         3 . The tower of  claim 2 , wherein said virgin polysilicon has been annealed.  
     
     
         4 . The tower of  claim 1 , wherein support surfaces extending perpendicularly to said axis are formed in said distal ends to support said wafers.  
     
     
         5 . The tower of  claim 4 , wherein said support surfaces are polished.  
     
     
         6 . The tower of  claim 4 , wherein said support surfaces support said wafers at places located at between 69% and 72% of a radius of said wafers.  
     
     
         7 . The tower of  claim 4 , wherein said teeth have a generally wedge shape with said support surfaces being formed in a narrower side of said wedge shape.  
     
     
         8 . The tower of  claim 1 , wherein said teeth have a generally wedge shape with said distal ends being located in a narrower side of said wedge shape.  
     
     
         9 . The tower of  claim 1 , wherein said plurality of legs consists of either three or four of said legs.  
     
     
         10 . A method of fabricating a silicon support tower, comprising the steps of: 
 in each of a plurality of silicon legs extending along a first axis, cutting a plurality of parallel slots to form teeth therebetween inclined at an angle of between 1° and  3 ° to a first side of said teeth with respect to a perpendicular to said first axis; and    joining opposite ends of said plurality of silicon legs to respective ones of two silicon bases to allow said teeth to support a plurality of wafers on said first sides thereof.    
     
     
         11 . The method of  claim 10 , wherein said silicon legs comprise virgin polysilicon.  
     
     
         12 . The method of  claim 10 , wherein said legs are annealed prior to said cutting step.  
     
     
         13 . The method of  claim 10 , further comprising forming support surfaces extending perpendicularly to said first axis on said first sides of said teeth at distal ends thereof.