A Material Removal Rate Model for Tungsten Chemical Mechanical Planarization

Abstract

In this work, a new material removal rate (MRR) model for tungsten chemical mechanical planarization (CMP) is proposed to provide some fundamental insights of slurry components and contact behavior on the removal mechanism. The synergistic effect of mechanical abrasion and chemical reactions on MRR is systematically investigated through using concepts of the steady-state equilibrium, chemical growth kinetics and contact mechanics in W CMP process. A closed-form equation of MRR is formulated to capture the influence of the slurry chemistry and operating parameters on the surface removal mechanism. Then the tungsten CMP model is simplified and verified through comparing the simulated results of removal rates with experimental data. It is found that the MRR has complicated variation behaviors depending on the specific model parameters. The consistency of the simulation results and experiments indicates that the present model can be adopted to capture the influences of chemicals, mechanical abrasion and pad properties on the polishing rate and assist in optimizing the surface uniformity of tungsten wafers.

Surface Forces in Chemical Mechanical Planarization and Semiconductor Wafer Cleaning Systems

“…Thick layers of oxide are used in new vertical integration schemes (etching into the Si wafer, rather than building layers) -these are characterized by a large step height (microns) that needs to be planarized. High oxide rate slurries are used and their removal rate is increased by surface active additives [10][11].…”

Assessing the wear degradation of tungsten in acidic solutions using a lubricated tribocorrosion model

“…[9][10][11][12] It has been proposed that the CMP mechanism of tungsten is the cyclic process including tungsten oxide film formation (passivation), the removal of the passive film (depassivation) by abrasives followed by corrosion of tungsten by the oxidizers, and passive film regeneration (repassivation). [9][10][11][12][13][14] This is a typical tribocorrosion process where the material loss has been found to be the interactive result of mechanical wear and electrochemical corrosion. 13,14 The tribocorrosion mechanism of the commonly used passive metals (e.g.…”

“…As a consequence, the CMP of tungsten plugs becomes a critical factor influencing the planarity of the whole layer in the integrated circuit. 9–12 It has been proposed that the CMP mechanism of tungsten is the cyclic process including tungsten oxide film formation (passivation), the removal of the passive film (depassivation) by abrasives followed by corrosion of tungsten by the oxidizers, and passive film regeneration (repassivation). 9–14 This is a typical tribocorrosion process where the material loss has been found to be the interactive result of mechanical wear and electrochemical corrosion.…”

Profile control processes based on contact types in silicon wafer DSP manufacturing management

“…Micro cutting mechanics was used to investigate the behaviour of the abrasive particles. 12,13 A model based on chemical growth kinetics and contact mechanics was proposed by Xu et al 14 which can be used to capture the influence of slurry chemistry and the process parameters on the MRR. The influence of pad bulk deformation and pad asperity deformation were included in the material removal model proposed by Yang et al 15 which shows a higher accuracy on the prediction of global planarization.…”