A new plasma aided solid-source implantation method forultra-shallow p⁺ junction fabrication

摘要

Summary form only given. Ultra-shallow (less than 100 nm) p⁺ junctions have been fabricated for the application ofsub-micron CMOS source/drain formation using a new plasma-aidedsolid-source implantation method. In this method, a very thin film (~0.7nm thick) of boron is first sputter deposited on the surface of thesilicon wafer from a solid-form boron target. The wafer is then immersedin Ar plasma and biased with a series of negative voltage pulses (-3 kV,20 μs) in a plasma source ion implantation (PSII) chamber. The argonions are extracted from the plasma sheath and are accelerated so thatthey bombard the wafer surface. This drives boron into the Si substrateby means of ion beam mixing. This results in a very shallow boron-dopedlayer. Dopant activation and damage removal are achieved via short-cycleRTA. The boron profiles are measured by SIMS. Recent results show that a0.7-nm thick boron layer implanted with 3-keV argon at a dose of4×10¹⁵ cm^-2 and annealed at 950° C for 10seconds show a peak boron concentration of 3×10²⁰ cm^-3 and the concentration is more than two orders of magnitudelower at a depth of 20 nm. This process produces extremely shallowp⁺ junctions with a comparably low-cost solid-form borontarget, while avoiding the hazards and costs of handling highly toxicand reactive gases traditionally used for junction fabrication. Inaddition, by using argon instead of a chemically reactive plasma, itprevents the erosion of the substrate surface materials by reactive ionetching