A Coupled Material Removal Model for Chemical Mechanical Polishing Processes

Abstract

Chemical mechanical polishing (CMP) is a process used to obtain planarized surfaces in microelectronic device manufacturing. The planarization is achieved by material removal from the wafer surface by synergistic effect of chemical and mechanical actions. The material removal rate (MRR) in chemical mechanical processes have a linear dependency on applied down pressure. However, some experimental studies have reported nonlinear relationship between MRR and applied pressure. The nonlinearity can be attributed to complex interactions among the wafer, pad, abrasive particles, and chemical agents in the slurry. Therefore, in modelling CMP processes, coupling of both the chemical and mechanical actions is imperative to provide insight into the nonlinear behavior of MRR, because treating the chemical effects only as a mere means of softening the wafer surface fails to explain the nonlinear behavior of MRR in silicon dioxide CMP. Here, we present a model that couples micro-contact mechanics with diffusion of slurry into the wafer and predict MRR in CMP of silicon dioxide. The model is validated with experimental results available in the literature. Moreover, the developed model may be used to explain the nonlinear increase in MRR of silicon dioxide with increasing applied pressure.

Model-Based Optimization of CMP Process Parameters for Uniform Material Removal Selectivity in Cu/Barrier Planarization

“…The developed and validated model couples contact mechanics (mechanical actions) with the diffusion of water into the wafer as chemical effects to calculate MRR in a typical CMP process. 24 Though a detailed explanation of our model is given in our previous work, 24 we provide a brief description here. The model considers only the diffusion of water into the wafer as the sole chemical effect of the slurry and chemical etching of the wafer is negligible.…”

“…It is well established that in a CMP process the MRR is directly proportional to the downforce applied and the slurry solid loading and inversely proportional to the size of abrasive particles. 24 The coupled model takes into account only the number of effective particles. 24 Effective particles are defined as the particles trapped in the contact area between the wafer and pad asperities.…”

“…24 The coupled model takes into account only the number of effective particles. 24 Effective particles are defined as the particles trapped in the contact area between the wafer and pad asperities. These particles remove material from the wafer by indenting into the wafer and sliding along its surface.…”

“…In this study, we use a material removal model, developed in our previous work, 24 to optimize the CMP process parameters such as downforce ( ) F , slurry solid concentration (D s ), and abrasive particle radius(R p ) to obtain the desired material removal selectivity of different materials. The model couples the contact mechanics with the diffusion of water into the wafer to calculate MRR.…”

Surface Morphology Evolution during Chemical Mechanical Polishing Based on Microscale Material Removal Modeling for Monocrystalline Silicon

“…The predicted MRR showed good consistency for different abrasive sizes and ASD standard deviations. Suratwala et al [15][16][17][18] extended Luo's model by applying fitted chemical material removal in a single-abrasive material removal volume. The simulated surface morphology captured salient features such as roughness, surface texture, and power spectral density (PSD).…”