Mechanisms of Thin Film Ti And Co Silicide Phase Formation on Deep-Sub-Micron Geometries and Their Implications and Applications To 0.18 °m CMOS and Beyond

Abstract

AbstractWe studied the kinetics of the high resistivity to low resistivity phase transformation for Ti and Co silicides on deep-sub-micron geometries. Fundamental differences between the growth characteristics for Co and Ti result in different scaling behavior. While the the TiSi2 C54 phase grows by a random nucleation and growth process from the polymorphic TiSi2 C49 phase, CoSi 2 grows by a diffusion limited process from CoSi. A strong linewidth and C49 grain size dependence for the TiSi2 C49 to C54 transformation can be related to low nucleation density. A Johnson-Mehl-Avrami analysis was performed for the TiSi2 C49 to C54 transformation obtaining the distribution of Avrami exponents and transformation times for individual 0.26 μm lines, showing that all lines transformed with similar one-dimensional growth characteristics. We found a strong dependence of the half-transformation times on film thickness and linewidth. While activation energies depend strongly on film thickness, ranging from 4.2 to 5 eV for films 64 to 28 nm thick, they are insensitive to linewidth indicating a different nature for the effect of linewidth and thickness. We also found a reduction of agglomeration temperatures with decreasing linewidth or film thickness resulting on a narrower process window for deep-submicron devices. A small linewidth dependence was measured for CoSi to CoSi2 transformation rates, with activation energies of 2 to 2.2 eV for 0.27 μm and wider lines. Both Co and Ti selfaligned silicide processes were implemented successfully into a 0.18 μm technology.