Inductively coupled rf plasma source with magnetic confinement and faraday shielding

Abstract

Disclosed is an inductively coupled RF plasma source that provides both magnetic confinement to reduce plasma losses and Faraday shielding to suppress parasitic capacitive components. The inductively coupled RF plasma system comprises an RF power source, plasma chamber, an array of permanent magnets, and an antenna array. The plasma chamber is comprised of walls and a dielectric window having an inner and outer surface wherein the inner surface forms a wall of the plasma chamber. The array of parallel conductive permanent magnets is electrically interconnected and embedded within the dielectric window walls proximate to the inner surface and coupled to ground on one end. The permanent magnet array elements are alternately magnetized toward and away from plasma in the plasma chamber to form a multi-cusp magnetic field. The antenna array may be comprised of parallel tubes through which an RF current is circulated. The antenna array is oriented perpendicular to the permanent magnet array.

1 . An inductively coupled RF plasma system that provides both magnetic confinement and Faraday shielding, the inductively coupled RF plasma system comprising:
 an RF power source for generating an RF current;   a plasma chamber operative to be filled with a working gas that can be used to create a plasma;   a dielectric window having an inner and outer surface wherein the inner surface forms a wall of the plasma chamber;   a permanent cusp magnet array comprised of parallel elements that are electrically interconnected and coupled to ground on one end that is embedded within the dielectric window in a magnetic cusp geometry that is proximate to the inner surface; and   an antenna array coupled with the RF power source and comprised of parallel elongated tubes through which an RF current is circulated, wherein the antenna array is oriented perpendicular to the permanent cusp magnet array.   
     
     
         2 . The inductively coupled RF plasma system of  claim 1  wherein the permanent cusp magnet array elements are alternately magnetized toward and away from the plasma in the plasma chamber to form a multi-cusp magnetic field. 
     
     
         3 . The inductively coupled RF plasma system of  claim 1  wherein the permanent cusp magnet array elements are comprised of permanent magnets comprised of magnetic alloys containing aluminum, nickel and cobalt (Al—Ni—Co), samarium cobalt (Sm—Co), or neodymium, iron, and boron (Nd—Fe—B). 
     
     
         4 . The inductively coupled RF plasma system of  claim 1  wherein the antenna array is in thermal contact with the outer surface of the dielectric window. 
     
     
         5 . The inductively coupled RF plasma system of  claim 1  wherein the dielectric window is further comprised of:
 a first dielectric layer including a plurality of parallel grooves adapted to receive the elements of the permanent cusp magnet array; and 
 a second thinner dielectric layer that is bonded to the first layer thereby separating the permanent cusp magnet array from the plasma. 
 
     
     
         6 . The inductively coupled RF plasma system of  claim 1  wherein the dielectric material comprising the dielectric window is comprised of one of alumina, aluminum nitride, quartz, or sapphire. 
     
     
         7 . The inductively coupled RF plasma system of  claim 1  wherein the magnetic cusp geometry has a small pitch. 
     
     
         8 . An inductively coupled RF plasma system that provides both magnetic confinement and Faraday shielding, the inductively coupled RF plasma system comprising:
 an RF power source for generating an RF current;   a plasma chamber operative to be filled with a working gas that can be used to create a plasma;   a dielectric window having an inner and outer surface wherein the inner surface forms a wall of the plasma chamber;   a permanent cusp magnet array comprised of parallel elements that are electrically interconnected and coupled to ground on one end that is embedded within the dielectric window in a magnetic cusp geometry that is proximate to the inner surface; and   an antenna coupled with the RF power source and comprised of an elongated tube through which the RF current is circulated, wherein the antenna is oriented perpendicular to the permanent cusp magnet array.   
     
     
         9 . The inductively coupled RF plasma system of  claim 8  wherein the permanent cusp magnet array elements are alternately magnetized toward and away from the plasma in the plasma chamber to form a multi-cusp magnetic field. 
     
     
         10 . The inductively coupled RF plasma system of  claim 8  wherein the permanent cusp magnet array elements are comprised of permanent magnets comprised of magnetic alloys containing aluminum, nickel and cobalt (Al—Ni—Co), samarium cobalt (Sm—Co), or neodymium, iron, and boron (Nd—Fe—B). 
     
     
         11 . The inductively coupled RF plasma system of  claim 8  wherein the antenna is in thermal contact with the outer surface of the dielectric window. 
     
     
         12 . The inductively coupled RF plasma system of  claim 8  wherein the dielectric window is further comprised of:
 a first dielectric layer including a plurality of parallel grooves adapted to receive the elements of the permanent cusp magnet array; and 
 a second thinner dielectric layer that is bonded to the first layer thereby separating the permanent cusp magnet array from the plasma. 
 
     
     
         13 . The inductively coupled RF plasma system of  claim 8  wherein the magnetic cusp geometry has a small pitch. 
     
     
         14 . The inductively coupled RF plasma system of  claim 8  wherein the dielectric material comprising the dielectric window is comprised of one of alumina, aluminum nitride, quartz, or sapphire. 
     
     
         15 . A method of providing magnetic confinement and Faraday shielding to an inductively coupled RF plasma source, the method comprising:
 providing an RF power source for generating an RF current;   providing a plasma chamber operative to be filled with a working gas that can be used to create a plasma;   providing a dielectric window having an inner and outer surface wherein the inner surface forms a wall of the plasma chamber;   embedding an electrically conductive permanent cusp magnet array comprised of parallel elements within the dielectric window proximate to the inner surface of the dielectric window;   coupling the permanent cusp magnet array to ground on one end;   alternately magnetizing the elements of the permanent cusp magnet array toward and away from the plasma in the plasma chamber to form a multi-cusp magnetic field; and   coupling an antenna array with the RF power source, the antenna array comprised of parallel elongated tubes external to the dielectric window such that the antenna array is oriented perpendicular to the permanent cusp magnet array.   
     
     
         16 . The method of  claim 15  further comprising:
 circulating the RF current through the antenna array to induce an electric and magnetic field within the plasma chamber. 
 
     
     
         17 . The method of  claim 15  further comprising:
 placing the antenna array in thermal contact with the outer surface of the dielectric window. 
 
     
     
         18 . The method of  claim 15  wherein the permanent cusp magnet array elements are comprised of a magnetic alloy containing aluminum, nickel and cobalt (Al—Ni—Co), samarium cobalt (Sm—Co), or neodymium, iron, and boron (Nd—Fe—B) or any other rare earth magnetic alloys. 
     
     
         19 . The method of  claim 15  wherein the dielectric material comprising the dielectric window is comprised of one of alumina, aluminum nitride, quartz, or sapphire.