KrF excimer laser crystallization of silicon thin films

A KrF excimer laser operating at 249 nm has been employed to crystallize si licon thin films deposited by electron cyclotron resonance plasma-enhanced chemical vapor deposition (ECR PECVD) and by RF magnetron sputtering on Com ing glass and SiO2. All films display a substantial improvement in crystall inity after ELC with the optimum laser fluence for as-deposited ECR films b eing higher than for sputtered films. This is probably related to the prese nce of Si-H-x bonds in the former. A pronounced bimodality in the Raman spe ctra of some amorphous, as-deposited ECR samples has been observed after la ser crystallization where, in addition to the peak at 520 cm(-1), a strong peak at 509 cm(-1) is also present. Such behavior has not been reported pre viously to our knowledge in ELC silicon films. Interestingly, the XRD spect ra of these samples do not exhibit any peaks suggesting the films are compo sed of nano-grain material. The dehydrogenation of ECR films by ELC has bee n demonstrated to be substantial, the hydrogen content typically decreasing from similar to 30 at% in an as-deposited film to similar to 10 at% after a single low fluence laser shot. Raman spectroscopy has shown that the film bonding changes from predominantly Si-H-2 to SI-H after ELC. Electrical re sistivity measurements of phosphorus-doped films show a controllable and re peatable change with laser fluence. The results in this paper show that it is possible to crystallize and controllably change the electrical character istics of ECR PECVD produced silicon thin films by ELC. (C) 2000 Kluwer Aca demic Publishers.