Radio-frequency sputtering system with rotary target for fabricating solar cells

Abstract

One embodiment of the present invention provides a sputtering system for large-scale fabrication of solar cells. The sputtering system includes a reaction chamber, a rotary target situated inside the reaction chamber which is capable of rotating about a longitudinal axis, and an RF power source coupled to at least one end of the rotary target to enable RF sputtering. The length of the rotary target is between 0.5 and 5 meters.

What is claimed is: 
     
         1 . A sputtering system for large-scale fabrication of solar cells, comprising:
 a reaction chamber;   a rotary target positioned inside the reaction chamber, wherein the rotary target is configured to rotate about a longitudinal axis;   an RF power source coupled to at least one end of the rotary target to enable RF sputtering, wherein a length of the rotary target is between 0.5 and 5 meters; and   a capacitance tuner coupled to one end of the rotary target, wherein a capacitance of the capacitance tuner is configured to be tuned periodically.   
     
     
         2 . The sputtering system of  claim 1 , further comprising a power splitter coupled to the RF power source, wherein the RF splitter is configured to:
 split output of the RF power source into two portions; and   feed each of the two portions to one end of the rotary target.   
     
     
         3 . The sputtering system of  claim 2 , wherein the power splitter is configured to split the output of the RF source 50-50. 
     
     
         4 . The sputtering system of  claim 1 , further comprising a plurality of magnets configured to generate a static magnetic field between the rotary target and a carrier that carries a plurality of solar cells. 
     
     
         5 . The sputtering system of  claim 4 , wherein the plurality of magnets are arranged in such a way that magnetic field is stronger at a location corresponding to an edge of the rotary target, thereby facilitating the magnetic field to have a higher strength at the edge of the rotary target. 
     
     
         6 . The sputtering system of  claim 1 , wherein the RF power source has an RF frequency of at least 13 MHz. 
     
     
         7 . The sputtering system of  claim 1 , wherein the capacitance is tuned over a predetermined capacitance range. 
     
     
         8 . The sputtering system of  claim 7 , wherein the predetermined capacitance range is between 0.5 nF and 50 nF. 
     
     
         9 . The sputtering system of  claim 1 , further comprising a coaxial cable configured to couple the capacitance tuner with one end of the rotary target. 
     
     
         10 . The sputtering system of  claim 1 , wherein the rotary target includes one or more layers of ceramic materials, and wherein the ceramic materials include one or more of: a transparent conducting oxide (TCO) material and a dielectric material. 
     
     
         11 . A sputter deposition method for large-scale fabrication of photovoltaic structures, comprising:
 placing a plurality of photovoltaic structures on a carrier within a reaction chamber;   continuously rotating a rotary target about a longitudinal axis;   applying an RF power to at least one end of the rotary target to enable RF sputtering of target material onto surfaces of the solar cells, wherein a length of the rotary target is between 0.5 and 5 meters; and   periodically tuning a capacitance tuner coupled to one end of the rotary target.   
     
     
         12 . The method of  claim 11 , further comprising:
 splitting the RF power into two portions; and   feeding each of the two portions to one end of the rotary target.   
     
     
         13 . The method of  claim 12 , wherein splitting the RF power into two portions involves splitting the RF power into two equal portions. 
     
     
         14 . The method of  claim 11 , further comprising placing a plurality of magnets inside the rotary target to generate a static magnetic field between the rotary target and a carrier that carries a plurality of solar cells. 
     
     
         15 . The method of  claim 14 , wherein placing the plurality of magnets involves arranging the magnets in such a way that magnetic field is stronger at a location corresponding to an edge of the rotary target, thereby facilitating the magnetic field to have a higher strength at the edge of the rotary target. 
     
     
         16 . The method of  claim 11 , wherein the RF power has an RF frequency of at least 13 MHz. 
     
     
         17 . The method of  claim 11 , wherein periodically tuning the capacitance tuner involves tuning a capacitance of the capacitance tuner over a predetermined capacitance range. 
     
     
         18 . The method of  claim 17 , wherein the predetermined capacitance range is between 0.5 nF and 50 nF. 
     
     
         19 . The method of  claim 11 , further comprising inserting a coaxial cable between the capacitance tuner and one end of the rotary target. 
     
     
         20 . The method of  claim 11 , wherein the rotary target includes one or more layers of ceramic materials, and wherein the ceramic materials include one or more of: a transparent conducting oxide (TCO) material and a dielectric material.