On-line characterisation of metallic micro contamination for ULSI microelectronics

The metallic micro contamination is a challenge for the “scientific fabrication” needed for 0.18 μm ULSI technology; its control has to be rapid and on-line. We show that it can be done by non-intrusive recombination lifetime measurements. Surface Photo Voltage (SPV), Microwave Photo Conductive Decay, Elymat and the recently introduced Surface Charge Analyses with lifetime extension (SCA-SPV) are tested. We compare these different and somewhat complementary techniques in the case of iron micro contamination. We show that the Elymat technique which is a simple one in its principle must be driven by a very sophisticated three dimensional analysis for correct interpretation of the results. Applying such an analysis we show, that for the range of ULSI grade silicon wafers the characteristics of iron micro contamination can be deduced with high precision down to concentrations below 10¹¹ cm^-3 (topography of contamination, chemical type of contamination, lifetime, energy levels). The practical consequences of our results for a fast and cost effective contamination monitoring in a ULSI production line are discussed