Pre-coated silicon fixtures used in a high temperature process

Abstract

A silicon-based wafer support tower particularly useful for batch-mode thermal chemical vapor deposition and other high-temperature processes, especially reflow of silicate glass at above 1200° C. The surfaces of the silicon tower are bead blasted to introduce sub-surface damage, which produces pits and cracks in the surface, which anchor subsequently deposited layer of, for example, silicon nitride, thereby inhibiting peeling of the nitride film. Wafer support portions of the tower are preferably composed of virgin polysilicon. The invention can be applied to other silicon parts in a deposition or other substrate processing reactor, such as tubular sleeves and reactor walls. Tubular silicon members are advantageously formed by extrusion from a silicon melt or by fixing together silicon staves in a barrel shape. The tower parts are preferably pre-coated with silicon nitride or polysilicon prior to chemical vapor deposition of these materials, or with silicon nitride prior to reflow of silica.

1 . A method of heat treating a silicon wafer, comprising the steps of: 
 providing a silicon support fixture having support surfaces for supporting at least one silicon wafer and being pre-coated with a layer of silicon nitride;    placing at least one silicon wafer onto said support surfaces of said fixture; and    heating said at one silicon wafer supported on said fixture to a temperature of at least 1320° C.    
     
     
         2 . The method of  claim 1 , wherein said temperature is at least 1350° C.  
     
     
         3 . The method of  claim 1 , wherein said layer of silicon nitride has a thickness of between 0.1 and 10 μm.  
     
     
         4 . The method of  claim 1 , where said support fixture is configured to support a plurality of wafers on respective teeth formed in and extending from at least three silicon legs.  
     
     
         5 . A method of uniformizing a silicate layer on a substrate, comprising the steps of: 
 providing a silicon support tower having support surfaces for supporting a plurality of substrates, said tower being pre-coated with a layer of silicon nitride;    placing a plurality of substrates onto support surfaces of said tower, said substrates having a silicate layer coated thereon; and    heating said substrates supported on said tower to an annealing temperature sufficient to reflow said silicate layer.    
     
     
         6 . The method of  claim 5 , wherein said annealing temperature is at least 1200° C.  
     
     
         7 . The method of  claim 6 , wherein said annealing temperature is at least 1350° C.  
     
     
         8 . The method of  claim 5 , wherein said silicate layer is coated by flame hydrolysis.  
     
     
         9 . The method of  claim 5 , wherein said silicon nitride layer is pre-coated by chemical vapor deposition.  
     
     
         10 . The method of  claim 5 , wherein said silicon nitride layer has a thickness of between 0.1 and 10 μm.  
     
     
         11 . The method of  claim 5 , wherein said tower has legs including said supporting surfaces formed of virgin polysilicon.  
     
     
         12 . The method of  claim 5 , further comprising surface treating of at least some other portions than said support surfaces of said tower.  
     
     
         13 . A tower for supporting a plurality of substrates during processing, comprising: 
 two silicon bases; and    at least three virgin polysilicon legs attached to said bases and having respective support surfaces for supporting a plurality of substrates and pre-coated with a layer of a material selected from the group consisting of silicon nitride and polysilicon.    
     
     
         14 . The tower of  claim 13 , wherein said material comprises silicon nitride.  
     
     
         15 . The tower of  claim 13 , wherein said material comprises polysilicon.  
     
     
         16 . The tower of  claim 13 , wherein said there are four of said legs and said support surfaces are disposed at between 68% and 72% of a radius of a circular substrate.  
     
     
         17 . The tower of  claim 13 , wherein said support surfaces are formed in teeth extending at angles of 86° to 89° from longitudinal axes of said legs.  
     
     
         18 . The tower of  claim 13 , wherein said legs are surface treated to introduce subsurface damage prior to being pre-coated with said layer.  
     
     
         19 . The tower of  claim 13 , wherein said a layer has a thickness of between 0.1 and 10 μm.  
     
     
         20 . A method of forming a silicon tube, comprising: fixing together a plurality of at least twenty of silicon staves all extending parallel to a central axis.  
     
     
         21 . The method of  claim 20 , wherein said fixing process includes welding.  
     
     
         22 . The method of  claim 20 , wherein said fixing process includes applying a silica based spin-on glass to interfaces between said staves.  
     
     
         23 . The method of  claim 20 , wherein said staves have grooves and tongues fittable in said grooves and extending parallel to said central axis.  
     
     
         24 . The method of  claim 20 , wherein said staves are arranged in a circular pattern about said central axis.  
     
     
         25 . The method of  claim 20 , wherein staves comprise virgin polysilicon.  
     
     
         26 . The method of  claim 20 , wherein said staves have trapezoidal shapes.  
     
     
         27 . The method of  claim 20 , further comprising circularizing an interior surfaces of said staves fixed together.  
     
     
         28 . A silicon tube, comprising a plurality of at least twenty of silicon staves fixed together in a closed pattern with an interior bore and extending parallel to a central axis.  
     
     
         29 . The silicon tube of  claim 28 , wherein said staves are composed of virgin polysilicon.  
     
     
         30 . The silicon tube of  claim 28 , wherein said staves are welded together.