Boron diffusion from a spin-on source during rapid thermal processing

Abstract

Proximity rapid (3 min) thermal diffusion has been investigated as a technique for fabricating shallow p-type junctions in submicron metal oxide semiconductor field effect transistors. A layer of spin-on dopant, deposited on a silicon wafer, was used as a dopant source for boron. Sheet resistance measurements, secondary ion mass spectrometry and Fourier transform infrared spectroscopy were used to evaluate the spin-on dopant and rapid thermal diffusion efficiency. Spin-on dopant post-spin baking process was optimised to avoid organic contamination during rapid thermal diffusion. Oxygen content in the rapid thermal diffusion ambient was essential to ensure successful deglazing of the doped oxide and spin-on dopant layers. The oxygen content also affected the doping efficiency of the product and source wafers. For process times less than 2 min, the doping level in the source wafer is less than in the product wafer. For process times greater than or equal to 3 min however, the doping efficiency for both wafers is the same.