On the Parameters of Inductively Coupled and Microwave BF3 Plasmas Used for Plasma Immersion Ion Implantation

Abstract

AbstractSummary: A comparison of inductively coupled plasma (ICP) and microwave plasma sources was carried out under the same discharge conditions, in the same discharge chamber, and using the same diagnostics method. Investigations were fulfilled over a wide range of external discharge parameters (at pressures 0.5–20 mTorr and for powers deposited in the plasma at 400–1 500 W) in boron trifluoride and in argon discharges. A variety of plasma parameters (Te, ne, n+, EEDF) and their radial profiles at a 2 cm distance above a wafer holder were determined by using a single Langmuir probe technique. Analysis of measurements has shown that the charged particle concentrations in the ICP are higher than are obtainable in a microwave discharge, for a deposited power at 1.2 kW the ICP source produced an ion number density of ∼1012 cm−3. The required plasma uniformity can be maintained in ICP over a wider range of external discharge parameters than in microwave plasma. The use of microwave plasma source gives a bi‐Maxwellian type EEDF, whereas the EEDF of ICP is close to the single Maxwellian distribution with an electron temperature higher than the temperature of cold electrons in microwave discharge. BF3 plasma is electronegative, with a degree of electronegativity of ∼0.3–0.5 for both plasma sources.Electron currents as functions of potential applied to a cylindrical Langmuir probe in inductively coupled and microwave BF3 plasmas.magnified imageElectron currents as functions of potential applied to a cylindrical Langmuir probe in inductively coupled and microwave BF3 plasmas.