Silicide Film Formation in the Ta/Ti/Si System by RF Induction Heating
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Silicide Film Formation in the Ta/Ti/Si System by RF Induction Heating J. Pelleg, S. Rosenberg and M. Sinder Materials Engineering Department, Ben Gurion University of the Negev, Beer Sheva, 84105, Israel
ABSTRACT Silicidation of Ta-Ti-Si film on Si (111) and Si (100) substrates was investigated by a new radio frequency (RF) heating in order to evaluate the progress of reaction and establish whether the substrate orientation influence on the rate of reaction prevails. Substrate orientation was observed notwithstanding the high temperatures applied and the very short duration of RF. It was observed that while the reaction on Si (111) goes to completion, on Si (100) substrates under the same conditions intermediate phases remained. A qualitative analysis of the RF treatment of a conductor film on the silicon substrate is presented. It is done for the first time using the mathematical approach of the heat explosion theory. According to the analysis the specimens might experience either heating at constant temperature or by a sudden temperature increase. The relation between the parameters for the heat explosion regime is presented in simple analytical form. Measurable quantities such as sheet resistance and the magnetic field applied determine the stage of the process. The value of the resulting sheet resistance indicates whether the progress of the RF occurred by heating in the slow growth temperature regime or in the heat explosion stage where reactions of a conductor film occur within a fraction of a second. INTRODUCTION Heating of a conductor film on silicon substrate in a radio-frequency (RF) magnetic field perpendicular to the film surface is one of the rapid thermal processing (RTP) that can be used for fabrication in the semiconductor industry for various purposes [1]. Metallic films, silicides, borides or nitrides are good candidates for RF processing since they posses low resistivity. An RF heating can propagate very rapidly and in a self-accelerated mode in a heat explosion manner [2]. The conditions for which the RF treated specimen is in the explosion regime is evaluated. It will be used to investigate silicide formation in the Ta-Ti-Si system. The temperature is a key factor in determining the progress of a silicidation reaction. Very high temperatures are reached within a matter of a few seconds by the use of RF. It was reported that the rate of silicidation is silicon substrate orientation dependent [3-6]. One might expect that the rate for the end phase formation in the silicidation process might be less critical to the influence of substrate orientation than in conventional RTP. Moreover it was often observed that at equivalent temperatures and reaction times the silicide formed is not necessarily the desired end phase of the system. For example in the Ta/Ti/Si system [7] at 1023 K for 250 s, on Si (100) substrate only a few X-ray diffraction (XRD) lines have indicated formation of (Ti,Ta)Si2 while
on Si (111) many more lines were indexed as belonging to the same phase. Similar is the
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