Re-distribution of Cu contamination in advanced high-speed CMOS and its influence on device characteristics

Cu contamination will be a crucial concern in advanced high-speed CMOS fabrication using Cu wiring. We evaluated the Cu gettering efficiency of Si wafers quantitatively by counting the Cu atoms that diffused from the backside to the front side of wafers through direct observation using TXRF (total reflection X-ray fluorescence). From this evaluation, we estimated the Cu gettering efficiency of the boron-doped Si layer and the Cu contamination redistribution behavior within a CMOS device. We found that even when the Cu contamination exists only on the Si wafer backside, about half of the Cu atoms diffuse to and segregate at the front surface during annealing. They are also found to segregate in the high concentration (>10/sup 17//cm/sup 3/) boron-doped layers which are used as components of a CMOS structure, such as the p-type well and the source/drain. These segregated Cu atoms will drastically degrade the CMOS device characteristics. The obtained results indicate that Si wafers with high gettering ability and Cu contamination control are indispensable for highly reliable CMOS devices.