Study of pulsed plasma doping by Langmuir probe and ion mass-energy analyzer

Plasma diagnostics in a pulsed plasma doping system, for semiconductor applications, have been carried out. An ion mass and energy analyzer was used to measure the ion species and ion energy distribution in the plasma doping process. Time-resolved Langmuir probe measurements were carried out to determine the plasma parameters. Preliminary results show that BF₂⁺ is the dominant ion species in the BF₃ plasma, and other molecular fragments also exist. The Langmuir probe data in Ar plasma indicate that during a 20 μs long implant pulse the plasma density is in the order of 10⁹∼10¹⁰ cm^-3 and the electron temperature is 0.4-14 eV. Between the pulses, the density decays exponentially at first and then reaches a nonzero value. The existence of electron beams, hot electrons, fast decay of electron temperature, and residual plasma were observed in both Ar and BF₃ plasmas.