Analytical Techniques for Trace Elemental Analyses on Wafer Surfaces for Monitoring and Controlling Contamination

Direct measurement of trace elements on wafer surfaces by TXRF is quick and nondestructive. SR-TXRF has similar features to TXRF, but much better detection limits mainly due to the high flux. VPD-TXRF and VPD-SR-TXRF improve the detection capability to various degrees. However, some elements (e.g. Cu) may have recovery problems at certain concentrations. VPD-ICP-MS is a destructive technique because of dissolving native oxide, but it can analyze most of elements in the periodic table and especially well for low Z elements. By using NIST standards for calibration, quantification can be verified relatively easily. All of these techniques can be complementary to each other and provide comprehensive analyses for the semiconductor industry.