Transparent pressure barrier for microwave plasma processing

Abstract

This disclosure relates to a reactor including an energy source configured to generate a microwave in a direction of propagation. A reaction chamber is coupled to the energy source. A waveguide disposed in the reactor includes a window positioned at an angle, such as being misaligned, relative to the direction of propagation of the microwave such that an average dielectric constant experienced by the microwave increases over a region where the window occupies a greater fraction of a cross-sectional area of the waveguide. The window includes one or more dielectric materials that have respective dielectric constants that increase along the propagation direction in a first region that is adjacent to a first face of the window, and decrease in a second region that is adjacent to a second face of the window. The dielectric materials have a mass density that varies based on one or more pores formed therein.

What is claimed is: 
     
         1 . A reactor comprising:
 an energy source configured to propagate microwave energy in a direction;   a reaction chamber coupled to the energy source; and   a waveguide including a window positioned at an angle relative to the direction of propagation of the microwave energy such that an average dielectric constant of the microwave energy increases over a region in which the window incrementally occupies additional cross-sectional area of the waveguide.   
     
     
         2 . The reactor of  claim 1 , wherein the reaction chamber is configured to receive the microwave energy through the window. 
     
     
         3 . The reactor of  claim 1 , wherein the window comprises a material configured to influence propagation of the microwave energy. 
     
     
         4 . The reactor of  claim 1 , wherein the window comprises a first face and a second face that is positioned substantially opposite to the first face. 
     
     
         5 . The reactor of  claim 4 , wherein the window comprises one or more dielectric materials contained between the first face and the second face. 
     
     
         6 . The reactor of  claim 5 , wherein the window is disposed within the waveguide, and each dielectric material of the one or more dielectric materials has a dielectric constant configured to:
 increase along the direction of propagation in a first region of the waveguide that is adjacent to the first face of the window; and   decrease along the direction of propagation in a second region of the waveguide that is adjacent to the second face of the window.   
     
     
         7 . The reactor of  claim 5 , wherein the dielectric materials include one or more pores. 
     
     
         8 . The reactor of  claim 7 , wherein the dielectric materials have a mass density that varies based on the one or more pores. 
     
     
         9 . The reactor of  claim 6 , wherein the first region of the waveguide is configured to compress the microwave energy. 
     
     
         10 . The reactor of  claim 6 , wherein the second region of the waveguide is configured to decompress the microwave energy. 
     
     
         11 . The reactor of  claim 6 , wherein the waveguide comprises a third region positioned between the first region and the second region. 
     
     
         12 . The reactor of  claim 11 , wherein the third region comprises the dielectric materials with respective dielectric constants that are configured to remain uniform throughout the third region in the direction of propagation of the microwave. 
     
     
         13 . The reactor of  claim 1 , wherein the window is disposed within a pressure barrier. 
     
     
         14 . The reactor of  claim 13 , wherein the window is substantially shaped as a parallelogram. 
     
     
         15 . The reactor of  claim 14 , wherein the waveguide includes a plurality of bends. 
     
     
         16 . The reactor of  claim 15 , wherein the bends are shaped as one or more of an “E” or an “H,” and wherein the bends include twists. 
     
     
         17 . The reactor of  claim 15 , wherein the bends are configured to influence the direction of the propagation of the microwave energy. 
     
     
         18 . The reactor of  claim 1 , further comprising one or more additional windows. 
     
     
         19 . The reactor of  claim 18 , wherein the one or more additional windows are configured to:
 form at least one protection volume disposed between adjacent windows of the one or more additional windows; and   form at least one protection volume disposed between the one or more additional windows and the window.   
     
     
         20 . The reactor of  claim 1 , wherein the average dielectric constant ranges from 2 to 10.