Method and device for surface treatment with a plasma at atmospheric pressure

Abstract

This method for surface treatment with a plasma at atmospheric pressure comprises the step of introducing a treatment gas into a treatment reactor ( 16 ), in which a surface ( 14 ) to be treated is placed between two exciting electrodes ( 22, 24 ), and applying a supply voltage to the two electrodes so as to cause the appearance of a discharge ( 12 ) in the treatment gas. The supply voltage is an AC voltage whose amplitude and frequency are adapted in order to maintain at least some of the components of the treatment gas in the excited state, and/or the presence of electrons, between two successive half-cycles of the supply voltage.

1 . Method for creating an electric discharge in an initial gas which is at atmospheric pressure and lies between two exciting electrodes, by applying a supply voltage to the two electrodes, characterized in that the supply voltage is an AC voltage whose amplitude and frequency are adapted in order to maintain at least a portion of the components of the gas in the excited state, and/or the presence of electrons, between two successive half-cycles of the supply voltage.  
     
     
         2 . Method for creating an electric discharge according to  claim 1 , characterized in that the supply voltage lies between about 5 kV and 30 kV, and its frequency lies between about 200 Hz and 35 kHz.  
     
     
         3 . Method for creating an electric discharge according to  claim 2 , characterized in that the frequency of the voltage is less than or equal to 15 kHz.  
     
     
         4 . Method for creating an electric discharge according to one of  claims 1  to  3 , characterized in that the initial gas is introduced into the inter-electrode space with a gas velocity of between 0 m/s and 10 m/s.  
     
     
         5 . Method for creating an electric discharge according to one of  claims 1  to  4 , characterized in that the initial gas includes one or more of the gases in the group formed by nitrogen, argon, silicon precursor gases, oxygen and gases capable of releasing oxygen.  
     
     
         6 . Method for creating an electric discharge according to one of  claims 1  to  5 , characterized in that the thickness of the gas space between the exciting electrodes is between about 0.5 and 5 mm.  
     
     
         7 . Method for creating an electric discharge according to one of the preceding claims, characterized in that at least one of the electrodes is covered with a dielectric or semiconductor material, the thickness of which advantageously lies in the range of from a few tens of microns to 1 cm, and preferably in the range of from 500 microns to 2 mm.  
     
     
         8 . Device for creating an electric discharge in a gas at atmospheric pressure, including two exciting electrodes, at least one of the electrodes being covered with a dielectric or semiconductor material, a source for supplying the inter-electrode space with an initial gas and a voltage supply source which is connected to the exciting electrodes, characterized in that the voltage supply source is capable of delivering an AC voltage whose amplitude and frequency are adapted in order to maintain at least a portion of the components of the gas in the excited state, and/or the presence of electrons, between two successive half-cycles of the voltage.  
     
     
         9 . Device for creating an electric discharge according to  claim 8 , characterized in that the thickness of said dielectric or semiconductor material lies in the range of from a few tens of microns to 1 cm, and preferably in the range of from 500 microns to 2 mm.  
     
     
         10 . Method for surface treatment with a plasma at atmospheric pressure, including the step of introducing a treatment gas into a treatment reactor, in which a surface ( 14 ) to be treated is arranged between two exciting electrodes ( 22 ,  24 ), and applying a supply voltage to the two electrodes so as to cause the appearance of a discharge ( 12 ) in the treatment gas, characterized in that the supply voltage is an AC voltage whose amplitude and frequency are adapted in order to maintain at least a portion of the components of the gas in the excited state, and/or the presence of electrons, in the region in which the discharge is established, between two successive half-cycles of the supply voltage.  
     
     
         11 . Method for surface treatment according to  claim 10 , characterized in that, the surface to be treated being capable of generating species liable to de-excite the excited or unstable species in the gas, the proportion of said species liable to de-excite the gas, in the region in which the discharge is established, is limited by implementing one or more of the following measures: 
 i) the treatment gas includes at least one component capable of interacting with said species liable to cause de-excitation;    j) the power of the discharge is controlled, in order thus to control the rate at which said species liable to cause de-excitation are generated;    k) the rate at which the treatment gas is replenished in the inter-electrode space is controlled.    
     
     
         12 . Method for surface treatment according to one of claims  10  and  11 , characterized in that the supply voltage has an amplitude which lies between about 5 kV and 30 kV, and its frequency lies between about 200 Hz and 35 kHz.  
     
     
         13 . Method for surface treatment according to  claim 12 , characterized in that the frequency of the voltage is less than or equal to 15 kHz.  
     
     
         14 . Method for surface treatment according to one of  claims 10  to  13 , characterized in that the treatment gas is introduced into the inter-electrode space with a gas velocity of between 0 m/s and 10 m/s, with a preferential range of less than or equal to 5 m/s.  
     
     
         15 . Method for surface treatment according to one of  claims 10  to  14 , characterized in that the treatment gas includes one or more of the gases in the group formed by nitrogen, argon, silicon precursor gases, oxygen and gases capable of releasing oxygen.  
     
     
         16 . Method for surface treatment according to one of  claims 10  to  15 , characterized in that the thickness of the inter-electrode gas space is between about 0.5 and 5 mm.  
     
     
         17 . Method for surface treatment according to one of  claims 10  to  16 , characterized in that the aim of the treatment is to deposit a silicon-based material on said surface, and in that the treatment gas includes a carrier gas, a silicon precursor gas, and oxygen or a gas capable of releasing oxygen.  
     
     
         18 . Device for surface treatment with a plasma at atmospheric pressure, comprising a treatment reactor ( 16 ) including two exciting electrodes ( 22 ,  24 ), between which an article ( 14 ) to be treated is arranged, a source for supplying the reactor with a treatment gas and a voltage supply source ( 26 ) which is connected to the exciting electrodes ( 22 ,  24 ), characterized in that the voltage supply source ( 26 ) is capable of delivering to the electrodes a supply voltage which is adapted in order to cause the appearance of a discharge ( 12 ) in the treatment gas and whose amplitude and frequency are capable of maintaining at least some of the components of the treatment gas in the excited state, and/or the presence of electrons, between two successive half-cycles of the supply voltage.  
     
     
         19 . Device for surface treatment with a plasma according to  claim 18 , characterized in that at least one of the electrodes is covered with a dielectric or semiconductor material, the thickness of which advantageously lies in the range of from a few tens of microns to 1 cm, and preferably lies in the range of from 500 microns to 2 mm.  
     
     
         20 . Product with a silicon-based deposit, characterized in that this deposit is obtained in accordance with the method according to claim  17 .