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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
Document File: 1 page(s) / 25K

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.

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IN-SITU CONTROL AND END POINT DETECTION FOR PLATING CATHODES

   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 tru...