AVS 45th International Symposium
    Plasma Science and Technology Division Friday Sessions
       Session PS-FrM

Paper PS-FrM2
Laser Detection of Chlorinated Neutral Etch Products During Cl@sub 2@ / Ar@super +@ Etching of Si(100)

Friday, November 6, 1998, 8:40 am, Room 318/319/320

Session: Plasma-Surface Interactions - II
Presenter: N. Materer, JILA, NIST, and University of Colorado, Boulder
Authors: N. Materer, JILA, NIST, and University of Colorado, Boulder
R.S. Goodman, JILA, NIST, and University of Colorado, Boulder
S.R. Leone, JILA, NIST, and University of Colorado, Boulder
Correspondent: Click to Email
Pulsed laser single-photon ionization time-of-flight mass spectrometry is used to investigate neutral etch products formed during ion enhanced etching of Si(100). Single-photon ionization is accomplished using the ninth harmonic of a Nd:YAG laser at 118 nm to ionize neutral species. This approach eliminates dissociative ionization difficulties found in conventional electron impact ionization. Ions are first ejected from the region in frunt of the wafer by pulse field extraction prior to the laser pulse. The Ar@super +@ ion bombardment energy is varied from 275 to 1000 eV, and the flux of molecular chlorine is varied from 10@super 1@@super 4@ to 10@super 1@@super 5@ molecules per cm@super 2@. Under all conditions examined, SiCl is the major product. Neutral Si atoms are also detected during etching and there is some evidence for SiCl@sub 2@. The Si and SiCl products decay within 20µsec after a 500µsec ion pulse. This fast decay supports a mechanism in which these etch products are formed in a direct collisional process. In addition, the influence of the molecular chlorine flux is examined in detail. The introduction of molecular chlorine is found to first rapidly increase the yield of neutral Si and, at higher fluxes, to slowly decrease the yield. This subsequent decrease is attributed to the generation of an increasingly chlorinated surface. As in the case of Si, the yield of SiCl as a function of molecular chlorine flux increase rapidly at first. However unlike the Si yield, this fast increase is followed by a gradual increase at fluxes higher than 10@super 1@@super 5@ molecules per cm@super 2@. The direct detection of etch products results mechanistic details that can be compared to recent molecular dynamic simulations.