Method and apparatus for electrodeposition of group iib-via compound layers

Abstract

Methods and apparatus are described for electrodeposition of Group IIB-VIA materials out of electrolytes comprising Group IIB and Group VIA species onto surfaces of workpieces. In one embodiment a method of electrodeposition is described wherein the control of the process is achieved by measuring an initial value of the electrodeposition current at the beginning of the process and adding Group VIA species into the electrolyte to keep the electrodeposition current substantially constant, such a within +/−10% of the initial value throughout the deposition period. In another embodiment an apparatus comprising multiple deposition chambers are described, each deposition chamber containing an anode and a workpiece, and wherein two thirds of the deposition chambers within the apparatus contain anodes comprising a substantially pure Group VIA element in their composition, and the rest of the deposition chambers contain anodes free from any Group VIA element in their composition.

1 . An apparatus for electrodeposition of a Group IIB-VIA compound layer onto multiple workpieces during a deposition period, from an electrolyte comprising Group VIA species, the apparatus comprising;
 a tank,   multiple deposition chambers, each containing an anode and at least one of the workpieces and configured to be connected to the tank so that the electrolyte can be circulated at a predetermined electrolyte flow rate by a at least one pump between the multiple deposition chambers and the tank, wherein   two thirds of the multiple deposition chambers each contains an anode comprising a substantially pure Group VIA element in its composition, and one third of the multiple deposition chambers each contains an anode without any Group VIA element in its composition.   
     
     
         2 . The apparatus in  claim 1  wherein the predetermined electrolyte flow rate is adjusted such that a volume of the electrolyte in each deposition chamber is exchanged at least 10 times during the deposition period. 
     
     
         3 . The apparatus in  claim 1  wherein the Group VIA element is Te and the Group IIB-VIA compound layer is a CdTe layer. 
     
     
         4 . The apparatus in  claim 1  further comprising porous dividers placed between the anode and the workpiece within the two thirds of the multiple deposition chambers to form a first compartment around the anode and a second compartment around the workpiece. 
     
     
         5 . The apparatus in  claim 4  further comprising a first feed line and a second feed line that are configured to regulate the electrolyte flow coming from the at least one pump and entering the first compartment and the second compartment, respectively. 
     
     
         6 . The apparatus in  claim 5  wherein the first feed line and the second feed line are configured such that the electrolyte flow entering the first compartment is larger than the electrolyte flow entering the second compartment. 
     
     
         7 . A method of electrodepositing a Group IIB-VIA compound layer on a workpiece surface immersed in an electrolyte comprising dissolved Group IIB ionic species and dissolved Group VIA ionic species, the method comprising,
 immersing an anode into the electrolyte,   applying a negative voltage to the workpiece surface with respect to the anode,   measuring a value of a deposition current passing through the anode and the workpiece surface, and   periodically adding a source of Group VIA ionic species into the electrolyte to keep the value of the deposition current substantially constant.   
     
     
         8 . The method of  claim 7  wherein the Group IIB-VIA compound layer is CdTe and the source of Group VIA ionic species comprises tellurium oxide. 
     
     
         9 . The method of  claim 8  wherein the source is liquid comprising tellurium oxide particles.