Characteristics of Pulsed Plasma Doping (P2LAD) Sources for Ultra-Shallow Junction Formation

Summary form only given. Ultra-shallow junctions (USJ) are required for fabrication of sub-0.1 mum transistors in semiconductor integrated circuits. The most straightforward fabrication method is to extend the beam-line ion implantation technology to ultra-low energies (100s eV to a few kV). Due to space charge induced divergence, low energy beams are restricted to low currents resulting in lower throughputs. Several alternative techniques have been proposed for fabricating USJ. The most promising candidates are plasma implantation methods which include pulsed plasma doping (P²LAD) and plasma ion immersion implantation (PIII). P²LAD is an attractive, simple and low cost alternative to beam line technologies, P²LAD is capable of delivering high dose rates at ultra-low energies (0.02-20 kV) using conventional plasma processing technologies. For sufficiently low pressures, the ions are implanted into the wafer with energies largely determined by the pulse voltage and the ion charge. In this talk, results from a computational investigation of P ²LAD will be discussed. The investigation was preformed using a modified version of the hybrid plasma equipment model to address such quasi-DC pulsed biases. An inductively coupled plasma (ICP) is used to generate ions in pressures of 10s mtorr. A quasi-DC pulsed bias is applied to the substrate to accelerate ions. Typical bias pulse lengths range between 5 and 50 mus and bias voltages are up to 20 kV. Results will be presented for Ar/NF₃ (a surrogate for Ar/BF₃ ) and BF₃ gas mixtures. The consequences of pulse width, wafer bias voltage waveform, ICP power and pressure on discharge characteristics and ion energy distributions (IEDs) to the substrate will be discussed. The shape of the bias waveform has important consequences on the IEDs not only because of the transit times of the ions but also due to instabilities that can be launched into the plasma