Evaluation of Contamination of Power Semiconductor Device Wafers

Hiroshi Kohno, Rigaku Journal 29(1), 9-14, 2013

Introduction

TXRF spectrometers are widely used as evaluation instruments for measuring contamination in the semiconductor fabrication process. This is mainly because the TXRF technique allows non-destructive analysis for almost all elements (Na~U) in the periodic table.

TXRF spectroscopy is possible due to the property of X-rays as they irradiate a at surface, such as a Si wafer or glass. Each material has a unique critical angle. If the incident angle of the X-rays is above the critical angle, the X-rays penetrate the surface deeply; if the incident angle is smaller than the critical angle, the X-rays are reflected off the surface totally, or what is termed total reflection. In the total reflection condition, any fluorescence X-rays will occur only from contamination on the surface and the surface material will not add background noise to the measurement. The penetration depth of the incident X-rays under the conditions of total reflection is theoretically around 5 nm, and thus TXRF is classified as a surface analysis. Metal contamination evaluation of SiC wafers by TXRF for power device applications is examined in this paper.