Plasma processing method and apparatus thereof

Abstract

The amount and area of irradiation of excited species to the surface of a workpiece can be increased, the irradiation can be uniformly performed on the whole surface, and the loss of effective excited species is suppressed, so that the treating performance and efficiency can be remarkably improved. A pulse voltage is applied between discharge electrodes which are opposingly positioned, to produce a corona discharge between pointed ends of the discharge electrodes, and the surface of a workpiece is irradiated with excited species including plasma produced by the corona discharge, thereby treating the surface. The discharge electrodes are configured by a central electrode and two peripheral electrodes opposingly placed in a state where the central electrode is interposed between the peripheral electrodes. The pulse voltage is alternately applied by pulse voltage applying means configured with using an even voltage doubler rectifier circuit to the central electrode and two peripheral electrodes of the discharge electrodes. The corona discharge is alternately generated between one of the two peripheral electrodes and the central electrode.

1 . A plasma treating method in which a pulse voltage is applied between discharge electrodes which are opposingly positioned, to produce a corona discharge between pointed ends of said discharge electrodes, and a surface of a workpiece is irradiated with excited species including plasma produced by the corona discharge, thereby treating said surface, wherein 
 the pulse voltage is alternately applied by pulse voltage applying means configured with using an even voltage doubler rectifier circuit to a central electrode and two peripheral electrodes of said discharge electrodes, said discharge electrodes being configured by said central electrode and said two peripheral electrodes opposingly placed in a state where said central electrode is interposed between said peripheral electrodes, and the corona discharge is alternately generated between one of said two peripheral electrodes and said central electrode.    
   
   
       2 . A plasma treating method according to  claim 1 , wherein a rectangular pulse voltage is used as the pulse voltage.  
   
   
       3 . A plasma treating method according to  claim 1 , wherein a pulse voltage configured by plural pulsating waves which are obtained by full-wave rectifying an AC voltage is used as the pulse voltage.  
   
   
       4 . A plasma treating method according to  claim 1 , wherein a magnetic field is formed in vicinities of said pointed ends of said discharge electrodes and in places where charged particles in the plasma exist, and the excited species including plasma are irradiated toward said surface of said workpiece by a pushing force acting on charged particles moving in the magnetic field.  
   
   
       5 . A plasma treating method according to  claim 1 , wherein a reactive gas is introduced between said central electrode and said peripheral electrodes opposing said central electrode at atmospheric pressure or a vicinity of atmospheric pressure, whereby an excitation gas flow including plasma is caused to be irradiated toward said surface of said workpiece.  
   
   
       6 . A plasma treating apparatus in which a pulse voltage is applied between discharge electrodes which are opposingly positioned, to produce a corona discharge between pointed ends of said discharge electrodes, and a surface of a workpiece is irradiated with excited species including plasma produced by the corona discharge, thereby treating said surface, wherein 
 said discharge electrodes are configured by a central electrode and two peripheral electrodes placed to oppose said central electrode, a center terminal of pulse voltage applying means configured with using an even voltage doubler rectifier circuit is connected to said central electrode, side terminals of said pulse voltage applying means are connected to said peripheral electrodes, respectively, and, based on an alternating voltage applied to said central electrode and said peripheral electrodes, the corona discharge is alternately generated between said central electrode and said peripheral electrodes.    
   
   
       7 . A plasma treating apparatus according to  claim 6 , wherein said central electrode is formed into a hammer-like shape, and said peripheral electrodes are placed in a state where said peripheral electrodes oppose tip end portions of arms which are extended in opposing directions.  
   
   
       8 . A plasma treating apparatus according to  claim 6 , wherein said pulse voltage applying means is a rectangular-pulse voltage generating power source.  
   
   
       9 . A plasma treating apparatus according to  claim 6 , wherein said pulse voltage applying means is configured by an AC power source, and a rectifier circuit which generates a pulse voltage formed by plural pulsating waves obtained by full-wave rectifying the AC voltage.  
   
   
       10 . A plasma treating apparatus according to  claim 6 , wherein magnetic field forming means is disposed, said magnetic field forming means forming a magnetic field in vicinities of said pointed ends of said discharge electrodes which are opposingly placed, and in places where charged particles in the plasma exist, to be able to apply a pushing force to a charged particle moving in the magnetic field, the pushing force causing excited species including plasma to be irradiated toward said surface of said workpiece.  
   
   
       11 . A plasma treating apparatus according to  claim 10 , wherein said magnetic field forming means is configured by: a permanent magnet; a pair of magnetic members which are connected to N and S poles of said permanent magnet, and which elongate to vicinities of said pointed ends of said pair of discharge electrodes; and a pair of pole pieces which are continuous to tip ends of said magnetic members, and which form a gap between end faces.  
   
   
       12 . A plasma treating apparatus according to  claim 10 , wherein said magnetic field forming means is configured by: an electromagnet connected to a DC power source; a pair of magnetic members which are connected to N and S poles of said electromagnet, and which elongate to vicinities of said pointed ends of said pair of discharge electrodes; and a pair of pole pieces which are continuous to tip ends of said magnetic members, and which form a gap between end faces.  
   
   
       13 . A plasma treating apparatus according to  claim 6 , wherein means for introducing a reactive gas between said discharge electrodes at atmospheric pressure or a vicinity of atmospheric pressure is disposed, and the reactive gas is introduced via said means, whereby an excitation gas flow including plasma is caused to be irradiated toward said surface of said workpiece.