Plasma processing apparatus and method

Abstract

To improve processing uniformity by improving a working characteristic in an edge exclusion region. Provided is a plasma processing apparatus for processing a sample by generating plasma in a vacuum vessel to which a processing gas is supplied and that is exhausted to a predetermined pressure and by applying a radio frequency bias to a sample placed in the vacuum vessel, wherein a conductive radio frequency ring to which a radio frequency bias power is applied is arranged in a stepped part formed outside a convex part of the sample stage on which the wafer is mounted, and a dielectric cover ring is provided in the stepped part, covering the radio frequency ring, the cover ring substantially blocks penetration of the radio frequency power to the plasma from the radio frequency ring, and the radio frequency ring top surface is set higher than a wafer top surface.

What is claimed is: 
     
         1 . A plasma processing apparatus that generates plasma in a processing chamber that is supplied with a processing gas and is exhausted to reduce its pressure to a predetermined pressure and processes a sample placed on a sample stage by applying a radio frequency bias to the sample stage provided in the processing chamber,
 wherein a conductor ring to which the radio frequency bias is applied is provided outside an outer periphery of the sample on the sample stage to which the radio frequency bias is applied,   the conductor ring is covered with a dielectric cover that makes a plasma ion sheath formed above it have substantially a plasma ion sheath potential produced only by plasma generation, and   the height of an equipotential surface of a lowermost part in the plasma ion sheath above the conductor ring is set higher than a top surface of the sample placed on the sample stage.   
     
     
         2 . A plasma processing apparatus that has a processing chamber that is arranged in a vacuum vessel and whose interior is decompressed, a sample stage that is arranged in this processing chamber and holds a wafer to be processed mounted on its top surface, and an electrode that is arranged in the sample stage and to which a radio frequency bias power is applied by being connected with a radio frequency power generator, and processes the wafer by using plasma formed in the processing chamber while applying the radio frequency bias power thereto, the plasma processing apparatus
 comprising:   a ring-shaped part made of a conductor that is arranged in a step part arranged to encircle the wafer on an outer peripheral side of a plane holding the wafer on the sample stage and to which the radio frequency bias power applied to the electrode in the sample stage is applied; and   a cover comprised of a dielectric material that covers a top surface and an inner peripheral side of the ring-shaped part and is arranged in the stepped part;   wherein the radio frequency bias power applied to the ring-shaped part is not coupled to the plasma, and a top surface of the ring-shaped part is set higher than a top surface of the wafer.   
     
     
         3 . The plasma processing apparatus according to  claim 2 ,
 wherein the top surface of the ring-shaped part is set higher than the wafer top surface, being raised by a range of 5.0 mm or less.   
     
     
         4 . The plasma processing apparatus according to  claim 2 ,
 wherein an inner peripheral edge of the ring-shaped part is larger than an outer peripheral edge of the wafer by a range of 1.0 to 10 mm.   
     
     
         5 . The plasma processing apparatus according to  claims 2 ,
 wherein the thickness of the dielectric material of the cover above the top surface of the ring-shaped part is in a range of 1.0 mm to 5.0 mm.   
     
     
         6 . A plasma processing method for processing a sample placed on a sample stage, comprising:
 generating plasma in a processing chamber to which a processing gas is supplied and that is exhausted to decrease its pressure to a predetermined pressure; and at the same time applying a radio frequency bias to the sample stage provided in the processing chamber,   wherein a plasma ion sheath formed outside the sample outer periphery on the sample stage to which the radio frequency bias is applied is controlled to substantially have the plasma ion sheath potential produced only by the plasma generation, and   the height of the equipotential surface in the lowermost part in the plasma ion sheath outside the sample outer periphery is set higher than a top surface of the sample to effect the processing of the sample.   
     
     
         7 . A plasma processing method, comprising:
 placing and holding a wafer to be processed on a top surface of a sample stage placed in a processing chamber whose interior is decompressed;   forming plasma in the processing chamber; and   processing the wafer while applying a radio frequency bias power to an electrode placed in the sample stage from a radio frequency power generator,   wherein the sample stage has a ring-shaped part placed in a stepped part arranged encircling the wafer on an outer periphery side of a plane holding the wafer and made of a conductor to which the radio frequency bias power applied to an electrode in the sample stage is applied, and a cover comprised of a dielectric that covers a top surface and an inner periphery side of the ring-shaped part and is arranged in the stepped part,   the top surface of the ring-shaped part is set higher than a top surface of the wafer, and   the radio frequency bias power applied to the ring-shaped part is uncoupled to the plasma.   
     
     
         8 . The plasma processing method according to  claim 7 ,
 wherein the top surface of the ring-shaped part is set higher than the wafer top surface, being raised by a range of 5.0 mm or less.   
     
     
         9 . The plasma processing method according to  claim 7 ,
 wherein an inner peripheral edge of the ring-shaped part is in a range of 1.0 to 10 mm, inclusive.   
     
     
         10 . The plasma processing method according to  claims 7 ,
 wherein the thickness of the dielectric material of the cover above the top surface of the ring-shaped part is in a range of 1.0 to 5.0 mm.   
     
     
         11 . A plasma processing method for processing a wafer,
 comprising:   generating plasma in a vacuum vessel to which a processing gas is supplied and that is exhausted to reduce its pressure to a predetermined pressure; and at the same time applying a radio frequency bias to a sample stage on which a sample is mounted in the vacuum vessel and a conductor ring provided encircling the sample outside a sample mounting plane of the sample stage   wherein the conductor ring is covered with a dielectric cover,   an electric potential of the plasma ion sheath formed above the conductor ring by application of the radio frequency bias is controlled to be substantially an electric potential by plasma generation,   the thickness of the plasma ion sheath is thinned, and   the height of the equipotential surface of the plasma ion sheath is set higher than the height of the equipotential surface of a processing surface of the sample to effect the processing of the sample.