A new plasma aided solid-source implantation method for ultra-shallow p/sup +//n junction fabrication

Summary form only given. Ultra-shallow (less than 100 nm) p/sup +//n junctions have been fabricated for the application of sub-micron CMOS source/drain formation using a new plasma-aided solid-source implantation method. In this method, a very thin film (/spl sim/0.7 nm thick) of boron is first sputter deposited on the surface of the silicon wafer from a solid-form boron target. The wafer is then immersed in Ar plasma and biased with a series of negative voltage pulses (-3 kV, 20 /spl mu/s) in a plasma source ion implantation (PSII) chamber. The argon ions are extracted from the plasma sheath and are accelerated so that they bombard the wafer surface. This drives boron into the Si substrate by means of ion beam mixing. This results in a very shallow boron-doped layer. Dopant activation and damage removal are achieved via short-cycle RTA. The boron profiles are measured by SIMS. Recent results show that a 0.7-nm thick boron layer implanted with 3-keV argon at a dose of 4/spl times/10/sup 15/ cm/sup -2/ and annealed at 950/spl deg/C for 10 seconds show a peak boron concentration of 3/spl times/10/sup 20/ cm/sup -3/ and the concentration is more than two orders of magnitude lower at a depth of 20 nm. This process produces extremely shallow p/sup +//n junctions with a comparably low-cost solid-form boron target, while avoiding the hazards and costs of handling highly toxic and reactive gases traditionally used for junction fabrication. In addition, by using argon instead of a chemically reactive plasma, it prevents the erosion of the substrate surface materials by reactive ion etching.