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IN-SITU CONTROL AND END POINT DETECTION FOR PLATING CATHODES

IP.com Disclosure Number: IPCOM000013795D
Original Publication Date: 2000-Aug-01
Included in the Prior Art Database: 2003-Jun-18

Publishing Venue

IBM

Abstract

Current plating systems determine when the proper thickness of plating film has been obtained by using time as the variable, given a constant current power supply. This has necessitated using a very precise power supply to supply the constant currents to the substrate and thiefs. A low cost method to achieve the same results could be attained by using a less precise power supply to provide the constant currents and monitoring the current delivered. With the proper circuitry, the current could be integrated (for example by measuring the current and accumulating it over time) thus providing the total charge (Q) that is being supplied to the substrate or thief. If the supply had drifted slightly high, the total charge would have been delivered in a shorter period of time and thus, if time control was used, the substrate would be plated thick. However, using Q control, the proper thickness of plating can be directly determined and the plating process stopped, providing an accurate and automated end point for plating. The key advantage of this method is allowing improved plating thickness control with low cost components. The precision of the constant current source power supply drives up the cost dramatically as the precision is improved. A typical multi-channel power supply to plate a wafer is about $40k $80k. This approach allows a low precision supply to be used (about $15k) and allows the time of the process to be truncated if the current source was high or extended if the current source was low, based on the proper delivery of the total charge (Q). 1