Laser-Assisted Low Temperature Deposition of WSi x from WF 6 and SiH 4
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LASER-ASSISTED
LOW TEMPERATURE DEPOSITION OF WSIx FROM WFs AND SIH 4
R. IZQUIERDO, P. DESJARDINS, N. ELYAAGOUBI AND M. MEUNIER
Groupe des Couches Minces and Ddpartement de Gdnie Physique, Ecole Polytechnique de Montreal, Qu6bec, Canada, H3C 3A7.
ABSTRACT
A laser direct writing system has been developed for low temperature deposition of WSix on TiN from a gas mixture of WF 6 and SiH 4 . An Ar+ laser (488 nm, 1.5 W) and a diode laser (796 nm, 1.0 W) are used as photon sources. Lines are written at scan speeds of up to 100 jim/s from a flowing gas mixture of WF 6 and SiH 4 diluted in Ar. Lines 1.5 to 11 jim wide and 20 to 180 nm thick are obtained at a writing speed of 100 jim/s with the Ar+ laser. Lines written using the diode laser are typically 4 to 12 jm wide and 160 to 860 nm thick. W/Si ratio in the deposits, as measured by Auger electron spectroscopy (AES), is between 1.5 and 1.8. Surface analysis of the interaction of this gas mixture with the TiN surface without laser irradiation shows that W, Si and F are adsorbed on the surface when exposed simultaneously to WF 6 and SiH 4 producing an adsorbed layer where W/Si ratio is 1.3 and F/W ratio 1.7. INTRODUCTION
The modification of microelectronics circuits is one of the principal applications of laser direct writing [1,2]. Since these modifications are performed on completed circuits, low temperature processing is necessary in order to prevent heat damage to the underlayer structures.The laser-assisted deposition of W from WF6 and SiH 4 has been reported to proceed at temperatures as low as 175 0C [3]. Even though laser deposition of various metals and metal silicides have been studied in recent years and many potential applications have been demonstrated in research laboratories [4,5], it is difficult to introduce such systems in the manufacturing environment [6]. In general, the lasers used in these processes are large and expensive. Maintenance and reliability are also important issues for industry. For this reason, we developed a reliable, compact and relatively low cost deposition system based on a diode laser. We investigated low temperature laser assisted deposition of WSix from WF6 and SiH 4 and compare the results obtained with this system to those obtained with a conventional direct writing system based on an Ar+ laser. As the deposition from this gas mixture greatly depends on the surface processes [7], we studied the gas surface interaction without laser irradiation by X-ray photoelectron spectroscopy (XPS). LASER DIRECT WRITING SYSTEM AND EXPERIMENTAL PROCEDURE
The laser direct writing system has been presented elsewhere [8]. In this system the laser acts as a heat source to initiate a pyrolitic process. Two types of lasers were used. First, the beam of an Ar+ laser (488 nm, 1.5 W) is focalized on the substrate to a 2 jim circular spot, using a long working distance 25 X, 0.31 NA objective. The lines deposited with this conventional system are compared with those deposited with the newly developed system which uses an AIGaAs diode Mat. Res. So
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