METHOD FOR RECYCLING SILANE (SiH4)

Abstract

The invention relates to a method for recycling silane that comprises the following consecutive steps: a) injecting a mixture of pure silane/pure hydrogen (SiH4/H2) in a reaction chamber for making silicon-containing thin layers; b) extracting from the mixture the excess of silane not used during step a)/hydrogen (SiH4/H2) via a pump using a supply gas; c) discharging from said pump, at a pressure close to the atmospheric pressure, a mixture containing at least silane (SiH4), hydrogen (H2) and an amount different from zero of said supply gas; d) separating the silane (SiH4) from the hydrogen/supply gas mixture resulting from the mixture from step c), the silane thus obtained containing less than 100 ppm of supply gas, preferably less than 10 ppm of supply gas and more preferably less than 1 ppm of supply gas; characterised in that at least 50%, preferably 70%, and more preferably 80% of the silane (SiH4) from step b) is reused after step d) for a new step a).

1 - 9 . (canceled) 
     
     
         10 . A silane recycling method comprising the following successive steps:
 a) injection of a pure silane/pure hydrogen (SiH 4 /H 2 ) mixture into a reaction chamber in order to fabricate thin films containing silicon;   b) extraction of the pure silane/pure hydrogen mixture unused in step a) by means of a pump employing a feed gas;   c) delivery by said pump at a pressure close to atmospheric pressure of a mixture comprising at least silane (SiH 4 ), hydrogen (H 2 ) and a non-zero amount of said feed gas; and   d) separation of silane (SiH 4 ) from the mixture of step c), said silane obtained comprising less than 100 ppm of the feed gas,   
       wherein at least 50% of silane (SiH 4 ) in the pure silane/pure hydrogen mixture of step b) is reused after step d) for a new step a). 
     
     
         11 . The method of  claim 10 , further comprising a step of:
 e) separation of hydrogen (H 2 ) from a mixture resulting from step d), said hydrogen obtained comprising less than 100 ppm of the feed gas,   
       wherein at least 50% of the hydrogen (H 2 ) in the pure silane/pure hydrogen mixture of step b) is reused after step e) for a new step a). 
     
     
         12 . The method of  claim 10 , wherein said feed gas is nitrogen (N 2 ). 
     
     
         13 . The method of  claim 12 , wherein the mixture of step c) comprises 30% to 90% nitrogen (N 2 ). 
     
     
         14 . The method of  claim 10 , further comprising a compression step between steps c) and d), during which step the pressure of the mixture is increased to between 2 bars and 35 bars. 
     
     
         15 . The method of  claim 10 , wherein step d) is carried out by cryogenic distillation and/or separation. 
     
     
         16 . The method of  claim 10 , wherein the silicon thin-film fabrication in the reaction chamber is carried out in a vacuum. 
     
     
         17 . The method of  claim 10 , further comprising, before injection step a), controlling and adjusting a ratio of a concentration of hydrogen (H 2 ) to a concentration of silane (SiH 4 ) containing the silane obtained in step d). 
     
     
         18 . The method of  claim 10 , further comprising depositing a silicon-containing film employing the silane obtained in step d). 
     
     
         19 . A silane recycling method comprising the following successive steps:
 a) injection of a pure silane/pure hydrogen (SiH 4 /H 2 ) mixture into a reaction chamber in order to fabricate thin films containing silicon;   b) extraction of the pure silane/pure hydrogen mixture unused in step a) by means of a pump employing N 2 ;   c) delivery by said pump at a pressure close to atmospheric pressure of a mixture comprising at least silane (SiH 4 ), hydrogen (H 2 ) and between 30% and 90% N 2 ; and   d) cryogenic separation of silane (SiH 4 ) from the mixture of step c), said silane obtained comprising less than 10 ppm of N 2 ,   
       wherein at least 50% of silane (SiH 4 ) in the pure silane/pure hydrogen mixture of step b) is reused after step d) for a new step a).