Process and plant for the production of a gaseous mixture containing a carrier gas, an oxidizing gas and a silane

Abstract

The invention relates to a process for the production of a final gaseous mixture containing a carrier gas, an oxidizing gas and a silane, with a predetermined content of each of the three gaseous components, comprising the preparation of a primary gaseous mixture containing a neutral gas and the said silane, the silane content of the primary gaseous mixture being below the self-ignition limit of that particular silane in air, and the preparation of a mixture between the primary gaseous mixture and a stream of the said carrier gas and, if appropriate, of [sic] a stream of the said oxidizing gas, in proportions which make it possible to obtain the required final mixture, the mixing being carried out under dynamic conditions.

What is claimed is:  
     
         1 . Process for the production of a final gaseous mixture containing a carrier gas, an oxidizing gas and a silane, with a predetermined content of each of the three gaseous components, comprising the implementation of the following stages: 
 a) a primary gaseous mixture ( 14 ,  1 / 2 ) containing a second neutral gas and the said silane is prepared, the silane content in the primary gaseous mixture being below the self-ignition limit of that particular silane in air;    b) a first gas stream, containing the said carrier gas, with a controlled residual content of the said oxidizing gas, is available;    c) the required final mixture is prepared according to one or other of the following two procedures, as a function of the residual content of oxidizing gas in the said gas stream containing the said carrier gas: 
 P1: the said first gas stream ( 4 ) is mixed ( 15 ) with a second stream of the said primary gaseous mixture and with a third stream of the oxidizing gas ( 3 ), in proportions which make it possible to obtain the required final mixture, the addition of the oxidizing gas stream being carried out under dynamic conditions;  
 P2: the said first gas stream is mixed with a second stream of the said primary gaseous mixture, in proportions which make it possible to obtain the required final mixture, the addition of the primary mixture stream being carried out under dynamic conditions.  
   
     
     
         2 . Process according to    claim 1   , characterized in that the mixing according to the procedure P1 is carried out in two stages: 
 i) an intermediate mixture between the said first gas stream ( 4 ) and the said primary gaseous mixture second stream is prepared; and    ii) the said third stream of the oxidizing gas ( 3 ) is added to the intermediate mixture in proportions which make it possible to obtain the required final mixture.    
     
     
         3 . Process according to    claim 1    or    2   , characterized in that the final mixture thus formed is homogenized due to the fact that the pipe ( 16 ) in which the said first gas stream moves adopts, downstream of the points ( 22 ,  23 ) for addition of the said primary mixture second stream and of the said third stream of the oxidizing gas, in the case of the procedure P1, or downstream of the point for addition of the said primary gaseous mixture second stream, in the case of the procedure P2, a coil shape.  
     
     
         4 . Process according to one of    claims 1    to    3   , characterized in that the silane used is monosilane SiH 4 .  
     
     
         5 . Process according to one of the preceding claims, characterized in that the said first gas stream is a nitrogen stream of cryogenic origin and in that the procedure P1 is then applied.  
     
     
         6 . Process according to one of    claims 1    to    4   , characterized in that the said first gas stream is an impure nitrogen stream obtained by separation from air by permeation or adsorption, containing a residual oxygen content, and in that the procedure P2 is then applied.  
     
     
         7 . Process according to    claim 6   , characterized in that the residual oxygen content in the said first gas stream is between 0.1% and 12% by volume.  
     
     
         8 . Process according to one of    claims 1    to    4   , characterized in that the said first gas stream is a dry air stream and in that the procedure P2 is then applied.  
     
     
         9 . Process according to one of    claims 1    to    4   , characterized in that the said oxidizing gas is oxygen or a gas containing oxygen.  
     
     
         10 . Process according to one of    claims 1    to    4   , characterized in that the said oxidizing gas is nitrous oxide.  
     
     
         11 . Process according to one of the preceding claims, characterized in that the said carrier gas is a neutral gas.  
     
     
         12 . Process according to one of    claims 1    to    4   , characterized in that the said carrier gas is a mixture of a neutral gas and of a reducing gas.  
     
     
         13 . Process according to    claim 11   , characterized in that the said neutral carrier gas and the said second neutral gas are identical.  
     
     
         14 . Process according to one of the preceding claims, characterized in that the final gaseous mixture thus formed is directed to at least one user point where a surface treatment operation is performed on polymer films by deposition of a silicon-based layer, under dielectric-barrier electrical discharge.  
     
     
         15 . Process according to one of the preceding claims, characterized in that, in the case where the procedure P1 is applied, the gas velocity in the pipe in which the said first gas stream moves is greater than the gas velocity in the pipe in which the said oxidizing gas third stream moves and in that, in the case where the procedure P2 is applied, the gas velocity in the pipe in which the said first gas stream moves is greater than the gas velocity in the pipe in which the said primary mixture second stream moves.  
     
     
         16 . Process according to    claim 15   , characterized in that, in the case where the procedure P1 is applied, the ratio X of the gas velocity in the pipe in which the said first gas stream moves to the gas velocity in the pipe in which the said oxidizing gas third stream moves is between 1 and 300.  
     
     
         17 . Process according to    claim 15   , characterized in that, in the case where the procedure P2 is applied, the ratio X of the gas velocity in the pipe in which the said first gas stream moves to the gas velocity in the pipe in which the said primary mixture second stream moves is between 1 and 300.  
     
     
         18 . Plant for the production of a final gaseous mixture containing a carrier gas, an oxidizing gas and a silane, with a predetermined content of each of the three gaseous components, comprising: 
 a gas source, containing the said carrier gas, with a controlled residual content of the said oxidizing gas;    a source of a primary gaseous mixture ( 14 ,  1 / 2 ) containing a second neutral gas and the said silane, the silane content in the primary gaseous mixture being below the self-ignition limit of that particular silane in air;    if appropriate, a source of the said oxidizing gas ( 3 ), depending on the residual content of oxidizing gas in the said gas source containing the said carrier gas;    a mixing region ( 15 ) capable of producing the required final mixture;    characterized in that the said mixing region contains a first pipe ( 16 ) capable of making a first stream of the said gas containing the said carrier gas move and a second pipe ( 18 ) capable of making a primary gaseous mixture second stream move and, if appropriate, a third pipe ( 17 ) capable of making a third stream of the said oxidizing gas move, the second and third pipes emerging at their downstream part in the first pipe, and in that the dimensions of the pipes are arranged in such a way that the gas velocity in the first pipe can be greater than the gas velocity in at least one of the other pipes.    
     
     
         19 . Plant according to    claim 18   , characterized in that the dimensions of the pipes are arranged in such a way that the ratio X of the gas velocity in the first pipe to the gas velocity in the third pipe is between 1 and 300.  
     
     
         20 . Plant according to    claim 18   , characterized in that the dimensions of the pipes are arranged in such a way that the ratio X of the gas velocity in the first pipe to the gas velocity in the second pipe is between 1 and 300.  
     
     
         21 . Plant according to one of    claims 18    to    20   , characterized in that the said first pipe ( 16 ) adopts, downstream of the points ( 22 ,  23 ) for connection of the second and third pipes to the first pipe, a coil shape.  
     
     
         22 . Plant according to one of    claims 18    to    21   , characterized in that the said primary gaseous mixture source is composed of bottles of second neutral gas/silane preprepared mixture.  
     
     
         23 . Plant according to one of    claims 18    to    21   , characterized in that it comprises a pure silane source ( 2 ) and a second neutral gas source ( 1 ) and in that the said primary gaseous mixture source is obtained by mixing between the silane originating from the said pure silane source and the neutral gas originating from the said second neutral gas source ( 1 ).  
     
     
         24 . Plant according to    claim 23   , characterized in that the said primary gaseous mixture source is composed of a buffer tank ( 8 ).  
     
     
         25 . Plant according to one of    claims 18    to    24   , characterized in that the said silane is monosilane.  
     
     
         26 . Plant according to one of    claims 18    to    25   , characterized in that the said oxidizing gas source is oxygen or air or nitrous oxide.  
     
     
         27 . Plant according to one of    claims 18    to    26   , characterized in that the said gas source containing the said carrier gas is nitrogen of cryogenic origin.  
     
     
         28 . Plant according to one of    claims 18    to    26   , characterized in that the said gas source containing the said carrier gas is impure nitrogen obtained by separation from air by permeation or adsorption, the residual oxygen content of which is between 0.1 and 12% by volume.  
     
     
         29 . Plant according to one of    claims 18    to    26   , characterized in that the said gas source containing the said carrier gas is dry air.  
     
     
         30 . Gaseous mixture containing a carrier gas, an oxidizing gas and a silane, with a predetermined content of each of the three gaseous components, such as obtained by the process according to any one of    claims 1    to    17   .