Method and apparatus for the solution deposition of oxide

Abstract

A metal and oxygen material such as a transparent electrically conductive oxide material is electro deposited onto a substrate in a solution deposition process. Process parameters are controlled so as to result in the deposition of a high quality layer of material which is suitable for use in a back reflector structure of a high efficiency photovoltaic device The deposition may be carried out in conjunction with a masking member which operates to restrict the deposition of the metal and oxygen material to specific portions of the substrate. In particular instances the deposition may be implemented in a continuous, roll-to-roll process. Further disclosed are semiconductor devices and components of semiconductor devices made by the present process, as well as apparatus for carrying out the process.

1 . A method for the electro deposition of a layer of a metal and oxygen material on a substrate, said method comprising the steps of:
 providing a substrate;   providing deposition apparatus including: a tank; a volume of electrolyte material disposed in said tank; an electrode station disposed in said tank, said electrode station including at least one electrode which is in contact with said electrolyte material, said at least one electrode at least partially comprised of a metal; a substrate support for spacedly retaining at least a portion of the substrate from the at least one electrode; and a power supply in electrical communication with said electrode station;   retaining said substrate in operative communication with the support so that at least a portion of the substrate is in a spaced apart relationship with said at least one electrode and so that electrolyte material is disposed therebetween;   establishing electrical communication between said power supply, said at least one electrode, said electrolyte material and said substrate so that the power supply, when energized, will establish a flow of electrical current between the at least one electrode, the electrolyte material and the substrate, which current flow electro deposits a material which includes said metal and oxygen on the substrate;   operating the power supply at a first level so as to establish a flow of electrical current, of a first magnitude, between said substrate, the electrolyte and at least one portion of said at least one electrode so as to deposit said metal and oxygen material on said substrate at a first deposition rate;   continuing to operate said power supply at said first level so as to deposit a first layer of said metal and oxygen material onto said substrate at said first deposition rate, said first layer having a first thickness; and thereafter,   operating said power supply at a second level so as to establish a flow of electrical current of a second magnitude between said substrate, said electrolyte material and at least one portion of said at least one electrode so as to deposit a layer of said metal and oxygen material at a second deposition rate which is less than said first deposition rate, and   continuing to operate said power supply at said second level so as to deposit a second layer of said metal and oxygen material having a second thickness onto the first layer of said metal and oxygen material having said first thickness.   
     
     
         2 . The method of  claim 1 , including the further step of periodically interrupting the flow of electrical current during the time that said first layer of metal and oxygen material and/or said second layer of said metal and oxygen material is being deposited. 
     
     
         3 . The method of  claim 1 , including the step of inputting ultrasonic energy to said electrolyte material during or following the deposition of at least a portion of said first or second layers of metal and oxygen material. 
     
     
         4 . The method of  claim 1 , including the further step of bubbling a gas through said electrolyte material during at least a portion of the deposition of the metal and oxygen material. 
     
     
         5 . The method of  claim 1 , wherein said substrate is maintained in a partiphobic orientation while at least one of said first and second layers of metal and oxygen material is being deposited thereupon. 
     
     
         6 . The method of  claim 1 , wherein said metal is zinc and said metal and oxygen material is a zinc and oxygen material. 
     
     
         7 . The method of  claim 6 , wherein said electrolyte material comprises an aqueous solution of Zn(NO 3 ) 2 . 
     
     
         8 . The method of  claim 7 , wherein the concentration of Zn(NO 3 ) 2  is approximately 0.03 M. 
     
     
         9 . The method of  claim 7 , wherein said electrolyte material further includes a boron containing species. 
     
     
         10 . The method of  claim 7 , wherein said electrolyte material further includes a member selected from the group consisting of: EDTA, sucrose, a dicarboxylic acid, and combinations thereof. 
     
     
         11 . The method of  claim 1 , wherein said electrolyte material is maintained at a temperature of at least 50° C. 
     
     
         12 . The method of  claim 1 , wherein said zinc and oxygen material comprises ZnO. 
     
     
         13 . The method of  claim 6 , wherein said zinc and oxygen material comprises a member selected from the group consisting of: ZnO; clusters of ZnO; Zn  2+  ions; Zn (OH) 2  and combinations thereof. 
     
     
         14 . The method of  claim 1 , wherein said electrode station includes at least a first electrode and a second electrode; and wherein, said power supply is operated at said first level so as to establish said flow of electrical current of said first level between said substrate, said electrode material and said first electrode, and said power supply is operated at said second level so as to establish said flow of electrical current of said second level between said substrate, said electrode material and at said second electrode. 
     
     
         15 . The method of  claim 1 , wherein the substrate comprises an elongated web, and wherein said deposition apparatus includes a web transport system, which is operative in combination with the substrate support to continuously advance the substrate through the tank while said metal and oxygen material is being deposited thereupon. 
     
     
         16 . The method of  claim 1 , wherein said substrate is metallic. 
     
     
         17 . The method of  claim 1 , wherein said substrate comprises a metal selected from the group consisting of steel, stainless steel, silver, aluminum, nickel, gold, chromium and combinations thereof. 
     
     
         18 . The method of  claim 1 , wherein said substrate comprises a metallic member having a layer of ZnO electro deposited upon at least a portion thereof. 
     
     
         19 . The method of  claim 1 , including the further steps of:
 affixing a masking member onto a portion of the substrate prior to the deposition of any of said metal and oxygen material thereunto, and   removing said masking member from said substrate after said metal and oxygen material has been deposited thereunto; whereby said masking member prevents the deposition of said metal and oxygen material onto masked portions of said substrate.   
     
     
         20 . The method of  claim 19 , wherein said substrate is ferrous and said masking member is magnetically affixable thereto. 
     
     
         21 . In a method for the electroplating of a layer of a metal and oxygen material onto a substrate wherein said substrate is disposed in an electrolyte in a spaced apart relationship with an electrode, and wherein a power supply is operative, when energized, to establish a flow of electrical current through said electrode, said electrolyte, and said substrate so as to deposit a layer of said metal and oxygen material on said substrate, characterized in that:
 energizing said power supply at a first level during the time that a first portion of said metal and oxygen material is electroplated onto said substrate so that said first portion is deposited at a first deposition rate and thereafter energizing said power supply at a second level during the time that a second portion of said layer is electroplated atop said first portion wherein said second level of power is selected so that the deposition rate of said second portion is less than the deposition rate of said first portion.