16 September 1994 CHARM-2: a new tool for characterization of wafer charging in ion- and plasma-based IC processing equipment
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A new, powerful, easy-to-use tool (CHARM-2) for characterizing wafer charging during wafer processing in ion-based and plasma-based IC processing equipment has been developed. The technique uses dedicated, pre-fabricated 6 inch wafers populated with sensors which monitor the driving forces behind charging damage: peak surface-substrate potentials; peak current densities impinging on a wafer; and total integrated UV dose. The CHARM-2 sensors measure these variables in terms of volts, amps/cm2, and photon flux. The measurement technique consists of pre-conditioning the CHARM-2 wafers on a tester, placing them in the process chamber, performing the given process, and testing the wafer again. Wafer maps of surface-substrate potentials, fluxes of ions, electrons, and UV photons, are generated in a matter of minutes, providing the user with a 'fingerprint' of the charging characteristics of the process/equipment. The CHARM-2 wafers are also re-usable, and thus more economical than test wafer techniques which use oxide breakdown or transistor stress characteristics. The ability to empirically characterize the J-V characteristics of charging sources using the CHARM-2 monitor wafers also opens the way for prediction of failure rates of oxides subjected to specific processes, if the oxide Qbd distributions are known.
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Wes A. Lukaszek, Joseph Reedholm, Michael I. Current, Nick Tripsas, "CHARM-2: a new tool for characterization of wafer charging in ion- and plasma-based IC processing equipment", Proc. SPIE 2336, Manufacturing Process Control for Microelectronic Devices and Circuits, (16 September 1994); doi: 10.1117/12.186791; https://doi.org/10.1117/12.186791


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