Deposited charge measurements on silicon wafers after plasma treatment

In plasma processing, especially during the etching process in microelectronics, and as the feature size decreases, charging damage to thin gate oxides can be produced which does not occur when wet chemical processes are used. It is currently believed that such damage occurs when excess charge is deposited on a wafer because of nonuniformities in the plasma parameters across the surface of the wafer. To predict the occurrence of charging damage, unpatterned wafers are exposed to a plasma in which nonuniformity is introduced across the wafer surface. Surface photovoltage (SPV) and contact potential difference (CPD) techniques can be used to determine the regions where excess charge is deposited and thus where the potential for charging damage exists. Wafer maps of these measurements are made to show the difference between uniform and nonuniform charge distributions.