A Cahn-Hilliard Modeling of Metal Oxide Thin Films for Advanced CMP Applications

Abstract

Chemical mechanical planarization (CMP) process enables topographic selectivity through formation of a protective oxide thin film on the recessed locations of the deposited metal layer, while a continuous chemical oxidation reaction is followed by mechanical abrasion takes place on the protruding locations. This paper demonstrates a new approach to CMP process optimization in terms of analyzing the nano-scale surface topography of the protective metal oxide films and modeling their growth through a Cahn-Hilliard equation (CHE) approach as an alternative to classical nucleation theory. It is observed that the material removal rate mechanisms and the consequent planarization performance depend on the nature of nucleation of the metal oxide films, which is a function of the oxidizer concentration of the CMP slurry.

A Fundamental Approach to Electrochemical Analyses on Chemically Modified Thin Films for Barrier CMP Optimization

“…This can be attributed to the variability in the corrosion and passivation behavior of the WO 3 aligning with our earlier studies. 20 Titanium MRR values, on the other hand, showed an increase with the increasing H 2 O 2 in the formulated slurries. This can be explained by the faster rate of passive film formation for Ti as represented in Figure 5.…”

“…Based on our earlier studies, we have demonstrated that the oxidation of W is driven by the nucleation and growth mechanisms controlled by the Oswald ripening on the surface. 20 Furthermore, the surface oxide structures and the roughness correlate to the CMP removal rate and defectivity performance. 17 The passive film formation was confirmed by the X-Ray Reflectivity measurements and the Pilling-Bedworth ratio calculations.…”

“…The abrasive particles provide the mechanical action in between the polishing pad and the wafer sample, and their frequency of interacting with the wafer surface determines the time to grow the chemically modified layer. 20 Since a 1/1/1 selectivity was obtained at 0.2M oxidizer concentration at 3wt% slurry solids loading, the slurry solids concentrations were varied at 5, 10 and 15 wt% at the optimal oxidizer concentration of 0.2 M. Figure 9 shows the MRR values of W, Ti, and TiN as a function of slurry solids loading. Furthermore, Table III summarizes the obtained removal rates and the calculated selectivity values.…”

Metal Oxide Thin Film Characterization for New Generation Chemical Mechanical Planarization Development

“…It is well known that the metallic films tend to form a metal oxide layer, which is known to be a protective oxide film for the W CMP [5]. The oxidation reaction on the metal surface results in the metal oxide film formation through nucleation and growth for which the Oswald ripening (reverse diffusion) moderates the film formation [2]. We have demonstrated in earlier work that this mechanism results in the formation of oxide peaks that tend to change the surface roughness as a function of the oxidizer concentration [3].…”

“…Furthermore, a new modeling approach was introduced to CMP process optimization by means of topographic evaluation of the metal oxide thin films. Cahn Hilliard Equation (CHE) was utilized as an alternative to classical nucleation theory in terms of analyzing the topographic nature of the protective metal oxide nano films and modeling their growth, which was observed to affect the CMP performance [2]. It was concluded that the material removal rate mechanisms and the consequent planarization performance depend on the nature of nucleation of the metal oxide films, which is tailored by the oxidizer concentration.…”