A HIGH-VACUUM SYSTEM FOR LASER-INDUCED DEPOSITION OF TUNGSTEN

A new high vacuum system for laser induced chemical vapor deposition of tungsten on silicon is presented in this paper. In this apparatus, tungsten depositions have been performed in the 0.5-15 mbar pressure range at substrate temperatures up to 400-degrees-C. The base pressure of the system is 10(-8) mbar after baking. Samples can be transferred via a sample loading system to maintain a low concentration of impurities. 193 nm UV photons are supplied by an ArF excimer laser (0-50 Hz, 160 mJ). A nitrogen window purge prevents tungsten deposition on the laser entrance and exit windows. Reaction product analysis can be performed with a quadrupole mass spectrometer which has been installed in a separate, differentially pumped, vacuum chamber close to the sample and the laser beam. Tungsten films have been analyzed with Rutherford backscattering spectrometry and scanning electron microscopy. Sheet resistivities less than twice the bulk value have been obtained with this setup.