Eluding Metal Contamination in CMOS Front-End Fabrication by Nanocrystal Formation Process

A technique to form metal nanocrystals on silicon or thin SiO2 film by Rapid Thermal Annealing (RTA) of thin metal film is developed and integrated into standard CMOS processing to make EEPROM devices and improve metal-semiconductor contact resistance. I-V and C-V measurements are carried out on MOSFETs and MOS capacitors containing Au, Ag, Pt, and Si nanocrystals as floating gate for universal mobility and minority carrier lifetime extraction. Mobility around 300 cm2/V-sec and minority carrier lifetime within 0.02 ∼ 0.1 μsec are observed for all cases including the control samples that do not go through the metal nanocrystal formation process, which suggests that the substrate is virtually free from metal contamination. Using this technique, thicker metal film can potentially be achieved as well by stitching thin metal layers on top of the nanocrystals.