Diode Laser Induced Chemical Vapor Deposition of WSI x from WF 6 and SiH 4
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DIODE LASER INDUCED CHEMICAL VAPOR DEPOSITION OF WSIx FROM WF 6 AND SiH 4
P. DESJARDINS, R. IZQUIERDO and M. MEUNIER
Groupe des Couches Minces and D6partement de G6nie Physique, Ecole Polytechnique de Montr6al, P.O. Box 6079, Station A, Montr6al, Qu6bec, H3C 3A7 CANADA ABSTRACT
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 WF 6 and Sill4, whose total pressure is kept below 15 Torr to avoid uncontrolled reactions. Experiments are performed in a static reactor with WF6/SiH 4 ratios varying from 0.2 to 10. Lines written at speeds ranging from 2 to 100 Igm/s have typical thicknesses and widths varying from 30 to 1000 nm and from 4 to 15 g±m 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 : SilH4 (1 : 3). INTRODUCTION
Laser induced deposition of refractory metals and silicides is particularly interesting for applications in microsurgery and custom design [1-4] of circuits. Tungsten has been deposited from WF6 using excimer [5-7], C02 [8,9] and ion (Ar÷, Kr-) [1-4,10-16] lasers. In general, these laser processing systems are large and expensive. Problems related to maintenance and reliability have limited the introduction of such systems in a manufacturing environment. In contrast, semiconductor lasers are easy to operate, require no maintenance and are competitively priced. As the output characteristics, power and wavelength, of diode lasers have improved in the last few years, they are able to play an important role in industrial application of laser processing. The potential use of diode lasers for material processing and device fabrication was first reported by Arjavalingam et al. [17]. They used a 200 mW GaAIAs diode laser array, emitting at 820 nm, to deposit gold from organometallic precursors. We report here the development of 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 and tungsten silicides, from a mixture of WF6, SilH4 and H2. Mat. Res. Soc. Symp. Proc. Vol. 236. @1992 Materials Research Society
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Since many of the materials used in microelectronics do not strongly absorb this wavelength [18], the substrate has to be carefully chosen to obtain a temperature rise sufficient to induce the WF6 reduction reaction. We have chosen, titanium nitride (TiN) for its optical and thermal properties. Moreover, TiN is an excellent barrier layer [19] and is also used as an adhesion layer for W metallization on SiO 2 [20, 21]. Even on such an absorbing substrate, the availabl
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