Plasma reactor for the treatment of large size substrates

Abstract

A radiofrequency plasma reactor (1) for the treatment of substantially large sized substrates is disclosed, comprising between the electrodes (3, 5) of the plasma reactor a solid or gaseous dielectric layer (11) having a non planar-shaped surface-profile, said profile being defined for compensating a process non uniformity in the reactor or generating a given distribution profile.

1 . A capacitively coupled radiofrequency plasma reactor ( 1 ,  20 ) comprising: 
 at least two electrically conductive electrodes ( 3 ,  5 ) spaced from each other, each electrode having an external surface ( 3   a ,  5   a ),    an internal process space ( 13 ) enclosed between the electrodes ( 3 ,  5 ),    gas providing means ( 7 ) for providing the internal process space ( 13 ) with a reactive gas,    at least one radiofrequency generator ( 9 ) connected to at least one of the electrodes ( 3 ,  5 ), at a connection location ( 9   a ), for generating a plasma discharge in the process space ( 13 ),    means ( 8 ) to evacuate the reactive gas from the reactor,    at least one substrate ( 15 ) defining one limit of the internal process space, to be exposed to the processing action of the plasma discharge, said at least one substrate ( 15 ) extending along a general surface ( 15   a ) and being arranged between the electrodes ( 3 ,  5 ),    characterized in that said plasma reactor ( 1 ,  20 ) further comprises at least one dielectric layer ( 11 ) extending outside the internal process space, as a capacitor electrically in series with said substrate ( 15 ) and the plasma, said dielectric layer ( 11 ) having capacitance per unit surface values which are not uniform along at least one direction of said general surface ( 15   a ), for generating a given distribution profile, especially for compensating a process non uniformity in the reactor.    
     
     
         2 . A capacitively coupled radiofrequency plasma reactor comprising: 
 at least two electrically conductive electrodes ( 3 ,  45 ) spaced from each other, each electrode having an external surface ( 3   a ,  5   a ),    an internal process space ( 13 ) enclosed between the electrodes ( 3 ,  5 ),    gas providing means ( 7 ) for providing the internal process space with a reactive gas,    a radiofrequency generator ( 9 ,  91 ) for geneating a plasma discharge in the process space ( 13 ), said generator connected to at least one of the electrodes ( 3 ,  45 ) at a connection location, preferably centrally arranged on said electrodes,    an additional radiofrequency generator ( 93 ) connected to at least one of the electrodes ( 3 ,  45 ), for increasing the ion bombardment on said substrate,    means ( 8 ) to evacuate the reactive gas from the reactor,    the at least one substrate ( 35 ) defining one limit of the internal process space to be exposed to the processing action of the plasma discharge, said at least one substrate extending along a general surface and being arranged between the electrodes,    characterized in that said plasma reactor ( 1 ,  20 ) further comprises at least one dielectric layer ( 95 ) extending outside the internal process space, as a capacitor electrically in series with said substrate ( 35 ) and the plasma, said dielectric layer ( 11 ) having capacitance per unit surface values which are not uniform along at least one direction of said general surface ( 15   a ), for generating a given distribution profile, especially for compensating a process non uniformity in the reactor.    
     
     
         3 . The reactor of    claim 1    or    claim 2   , characterized in that said dielectric layer has a thickness (e 1 ) along a direction perpendicular to the general surface of the substrate, said thickness being non uniform along said dielectric layer, so that the reactor has said location dependent capacitance per unit surface values.  
     
     
         4 . The reactor according to    claim 3   , characterized in that: 
 the said dielectric layer ( 15 ) is the thickest in front of the location in the process space ( 13 ) which is the farest away from said connection location ( 9   a ) where the radioirequency generator is connected to said at least one electrode,    and said thickness decreases from said process space location as the distance between the process space location and the connection location on the corresponding electrode decreases.    
     
     
         5 . The reactor according to anyone of    claims 1    to    4   , characterized in that said dielectric layer ( 15 ) has at least one non planar-shaped external surface.  
     
     
         6 . The reactor according to anyone of    claims 1    to    5   , characterized in that at least one of said electrodes has a non planar-shaped surface facing the substrate.  
     
     
         7 . The reactor of anyone of    claims 1    to    6   , characterized in that: 
 said one dielectric layer is locally delimited by a surface of one of said electrodes ( 5   a ,  41   b ,  51   b ), and  
 said delimitation surface of said one electrode is curved.  
 
     
     
         8 . The reactor according to anyone of    claims 1    to    7   , characterized in that said dielectric layer comprises at least one of a solid dielectric layer and a gaseous dielectric layer, or a combination of the both mentioned.  
     
     
         9 . The reactor according to anyone of the preceding claims, characterized in that the at least one substrate comprises a plate having a non planar-shaped external surface.  
     
     
         10 . The reactor of anyone of the preceding claims, characterized in that the at least one substrate ( 65 ) has a curved shape.  
     
     
         11 . The reactor according to anyone of the preceding claims, characterized in that spacing members are arranged between said substrate ( 35 ′,  65 ) and one of the electrodes ( 25 ,  45 ), said spacing members having elongations being non uniform.  
     
     
         12 . The reactor according to    claim 11   , characterized in that the spacing members ( 89 ) at the non-substrate-end being surrounded by a space ( 91 ), for at least partially compensating the electromagnetic perturbation induced by the contact between the spacing member and the substrate.  
     
     
         13 . A process for treating at least one substrate ( 15 ,  35 ′,  65 ) in a radiofrequency plasma reactor ( 1 ,  20 ), comprising the steps of : 
 locating the at least one substrate ( 15 ,  65 ) between two electrodes ( 3 ,  5 ), the at least one substrate extending along a general surface ( 15   a ),  
 having a circulation of a reactive gas within the reactor, so that such a gas is present in an internal process space ( 13 ) arranged between the electrodes,  
 having a radiofrequency generator ( 9 ) connected to at least one of the electrodes ( 3 ,  5 ), at a connection location ( 9   a ),  
 having a plasma discharge in at least a zone of the internal process space ( 13 ) in such a way that said substrate is exposed to the processing action of the plasma discharge,  
 characterized in that it further comprises the steps of creating an extra-capacitor electrically in series with said substrate and the plasma, said extra-capacitor having a profile, and  
 defining the profile of the extra-capacitor in such a way that it has location dependent capacitance per unit surface values along at least one direction of the general surface of the substrate, for generating a given distribution profile, especially for compensating a process non uniformity in the reactor.  
 
     
     
         14 . The process according to    claim 13   , characterized in that 
 the radiofrequency discharge is generated at a frequency higher than for example 1 MHz, preferably higher than 19 MHz,    the at least one substrate has a surface larger than 0.5 m 2 ,    and the largest dimension of the substrate surface exposed to the plasma discharge is higher than 0.7 m.    
     
     
         15 . The process of    claim 13    or    claim 14   , characterized in that the step of defining the profile of the extra-capacitor comprises the step of defining such a profile having a non planar-shape along a surface, in such a way that said extra-capacitor is materially defined by at least one dielectric layer having a non uniform thickness along said surface.