A 2-step diffusion method was proposed for leveling the depth profiles of Pt-induced traps. The Pt was first diffused at high temperatures in a N ambient, and was then re-diffused at a lower temperature. The results showed that this method caused the trap concentration near to the surface of a wafer to decrease, while that deep within the wafer increased. Therefore, the depth profile of the trap concentration could be evened out throughout the entire wafer.

B.Deng, C.Shu, H.Kuwano: Semiconductor Science and Technology, 1996, 11[4], 535-7