Semiconductor manufacturing chamber with plasma/gas flow control device

Abstract

A method of plasma etching a semiconductor wafer includes: securing the semiconductor wafer to a mounting platform within a process chamber such that an outer edge of the semiconductor wafer is encircled by a sloped annular ring having a plurality of perforation therein, the sloped annular ring having an inner edge at a first end of the sloped annular ring and an outer edge at a second end of the sloped annular ring. Suitably, the first end is opposite the second end and the first end resides in a first plane and the second end resides in a second plane different from the first plane. The method further includes generating a plasma within the process chamber such that the semiconductor wafer is exposed to the plasma and creating a flow of at least one of plasma and gas through the perforations in the sloped annular ring.

What is claimed is: 
     
         1 . A tool for processing a semiconductor wafer, said tool comprising:
 a process chamber;   a mounting platform configured to have the semiconductor wafer selectively secured thereto, said mounting platform being housed in the process chamber;   an inlet port through which a process gas is introduced into the process chamber;   a first electrode that is selectively energized to excite the process gas within the process chamber into a plasma; and   an annular plate having a plurality of perforations therein, said annular plate being housed within the process chamber; wherein:
 the annular plate encircles an outer edge of the semiconductor wafer when the semiconductor wafer is secured to the mounting platform; 
 the annular plate has a first edge at a first end thereof and a second edge at a second end thereof, said first end being opposite the second end; 
 the first end resides in a first plane and the second end resides in a second plane different from the first plane, said first plane being located above the second plane and below or coplanar with the semiconductor wafer when the semiconductor wafer is secured to the mounting platform; and 
 the first edge has a first radius measured from a central axis of the annular plate and the second edge has a second radius measured from the central axis, said second radius being greater than the first radius. 
   
     
     
         2 . The tool of  claim 1 , further comprising:
 a vacuum pump operatively coupled to the process chamber on a side of the annular plate opposite the semiconductor wafer when the semiconductor wafer is secured to the mounting platform.   
     
     
         3 . The tool of  claim 1 , further comprising:
 a second electrode that is selectively energizable, said first electrode and said second electrode being on opposite sides of the annular plate with respect to one another.   
     
     
         4 . The tool of  claim 1 , wherein the annular plate has a surface that extends between the first and second edges thereof, said surface being inclined away from the first plane by an angle in a range of between greater than 0 degrees and less than 90 degrees. 
     
     
         5 . The tool of  claim 1 , wherein the annular plate has a surface that extends between the first and second edges thereof, said surface being inclined away from the first plane by an angle in a range of between greater than about 30 degrees and less than about 60 degrees. 
     
     
         6 . The tool of  claim 1 , wherein a difference between the second radius and the first radius is in a range of between greater than or equal to 0.1 cm and less than or equal to 550 cm. 
     
     
         7 . The tool of  claim 1 , wherein a distance between the first plane and the second plane is greater than or equal to 0.1 cm. 
     
     
         8 . The tool of  claim 1 , wherein:
 the semiconductor wafer has a device side on which semiconductor device structures are formed and a back side opposite the device side, said back side facing the mounting platform when secured thereto; and   when the semiconductor wafer is secured to the mounting platform, the back side is offset from the first plane by a distance.   
     
     
         9 . The tool of  claim 1 , wherein the perforations of the annular plate comprise circular through holes. 
     
     
         10 . The tool of  claim 1 , wherein the perforations of the annular plate comprise radially elongated slits. 
     
     
         11 . The tool of  claim 1 , wherein the perforations of the annular plate have radial symmetry with respect to a vertical axis of the annular plate. 
     
     
         12 . A system for exposing a semiconductor wafer to a plasma, said system comprising:
 a process chamber in which the semiconductor wafer is held while it is exposed to the plasma;   a delivery system that provides a process gas to the process chamber, said process gas being selectively excited into the plasma to which the semiconductor wafer is exposed;   a radio frequency generator that selectively energizes an electrode to selectively excite the process gas within the process chamber; and   a control ring that surrounds a region within the process chamber where the semiconductor wafer is held, said control ring comprising a perforated annular surface extending between a first edge and a second edge; wherein:
 the first edge resides in a first plane and the second edge resides in a second plane different from and not co-planar with the first plane; and 
 the annular surface is inclined between the first and second planes. 
   
     
     
         13 . The system of  claim 12 , further comprising:
 a controller which at least one of regulates and coordinates operation of at least one of the delivery system and the radio frequency generator.   
     
     
         14 . The system of  claim 12 , wherein the control ring has a surface that extends between the first and second edges thereof, said surface being inclined away from the first plane by an angle in a range of between greater than 0 degrees and less than 90 degrees. 
     
     
         15 . The system of  claim 12 , wherein the control ring has a surface that extends between the first and second edges thereof, said surface being inclined away from the first plane by an angle in a range of between greater than about 30 degrees and less than about 60 degrees. 
     
     
         16 . The system of  claim 12 , wherein the perforations of the control ring comprise circular through holes. 
     
     
         17 . The system of  claim 12 , wherein the perforations of the control ring comprise radially elongated slits. 
     
     
         18 . The system of  claim 12 , wherein the perforations of the control ring have radial symmetry with respect to a vertical axis of the control ring. 
     
     
         19 . A plasma etching system comprising:
 a process chamber;   a mounting platform disposed in the process chamber and configured to hold a semiconductor wafer to be etched;   a gas inlet of the process chamber arranged to flow a gaseous etchant into the process chamber;   at least one electrode disposed in the process chamber and configured to excite the gaseous etchant into a plasma; and   an exhaust ring surrounding the mounting platform and having perforations through which the gaseous etchant and/or the plasma pass prior to the gaseous etchant and/or the plasma exiting the process chamber, the exhaust ring having a frustoconical surface inclined at an angle in a range of between greater than about 30 degrees and less than about 60 degrees, the exhaust ring being oriented so that the frustoconical surface inclines outward with increasing distance from the gas inlet.   
     
     
         20 . The plasma etching system of  claim 19 , wherein the perforations of the exhaust ring comprise circular or radially elongated through holes.