Fabrication of submicrometer MOSFET's using gas immersion laser doping (GILD)

The fabrication of MOSFET's with submicrometer gate lengths using Gas Immersion Laser Doping (GILD) to dope the source-drain and gate regions of n-channel devices is described. The GILD step relies on a melt/regrowth process, initiated by a pulsed excimer laser (XeCl, λ = 308 nm), to drive in a dopant species adsorbed on the clean silicon surface. High dopant concentrations (1 × 10¹⁹to 2 × 10²¹cm^-3) and shallow junctions (600-1000 Å) make this process ideally suited for source-drain formation in submicrometer structures. In this work the transistors are fabricated using an otherwise conventional NMOS process. The resultant devices have similar source-drain Rsheetvalues and lower poly Rsheetwhen compared to devices fabricated using a conventional implanted source-drain and diffused polysilicon gate. Short-channel devices (L_{poly} = 0.9µm) exhibit excellent I-V characteristics and little change in Vt.