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Method for Accurate Plating Control In Pulsed Power Supply Applications

IP.com Disclosure Number: IPCOM000013884D
Original Publication Date: 2000-Dec-01
Included in the Prior Art Database: 2003-Jun-18
Document File: 1 page(s) / 38K

Publishing Venue

IBM

Abstract

Many commercial plating power supplies are set up for asynchronous sampling. When running in pulse plating mode, this asynchronous method is not accurately reporting the true current that is being applied to the wafer, substrate, or other plated object. This is especially true when using long pulse widths for alloy plating. Even supplies with control sampling algorithms that are synchronized to the leading edge of the pulse do not always handle long pulse widths well.

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Method for Accurate Plating Control In Pulsed Power Supply Applications

    Many commercial plating power supplies are set up for asynchronous sampling. When running in pulse plating mode, this asynchronous method is not accurately reporting the true current that is being applied to the wafer, substrate, or other plated object. This is especially true when using long pulse widths for alloy plating. Even supplies with control sampling algorithms that are synchronized to the leading edge of the pulse do not always handle long pulse widths well.

    Since the power supply controller knows the value of the pulse width that is being used for each plating operation, it would be a matter of calculation by the controller to set the sampling point to the mid-point of the pulse width. This mid-point would be more of a true measure of the total coulombs being applied to the plated object, than that which can be obtained from any other calculated method. With longer pulse widths, this is even more critical. Many of the existing power supply designs have a sampling algorithm which is asynchronous, which can be seen in the current fluctuations being reported. If the averaging function in the algorithm is sufficiently long, this fluctuation cannot be seen in the reporting function, but can be seen by comparing an external coulomb meter with what is being reported. Even synchronous supplies can have sampling problems with long pulse widths, as most use a fixed sampling time triggered from the leading edge of the pulse. With only one sample point during long pulse widths, inaccurate re...