Diode Laser Induced Chemical Vapor Deposition of WSIx from WF6 and SiH4

We have developed a compact and inexpensive laser direct writing system, based on the 796 nm radiation of a 1 W diode laser array for the deposition of tungsten silicides. The laser power incident on TiN substrates varies between 50 and 550 mW. Lines are deposited from a gas mixture of WF6 and SiH4, whose total pressure is kept below 15 Torr to avoid uncontrolled reactions. Experiments are performed in a static reactor with WF6/SiH4 ratios varying from 0.2 to 10. Lines written at speeds ranging from 2 to 100 μm/s have typical thicknesses and widths varying from 30 to 1000 μm and from 4 to 15 μm respectively. Auger Electron Spectroscopy (AES) shows that no fluorine is incorporated in the WSix film, within the limit of detection. Moreover, no oxygen, carbon or nitrogen are detected in the bulk, although some surface contamination is present. From AES measurements, the W/Si ratio is estimated to be between 1.1 and 1.4 for a reactive gas mixture of WF6: SiH4 (1: 3).