A chemical mechanical planarization model for aluminum gate structures

Self Cite

In this work, a new aluminum gate chemical mechanical planarization (CMP) model for material removal rate (MRR) is proposed in high-k metal gate (HKMG) process. Using the basic principles of steady-state oxidation reaction and mechanical abrasion mechanism, the combinational interaction of chemical and mechanical coupled effects on MRR was systematically described by process parameters, pad properties and concentration of oxidizer, and then balanced to construct an overall polishing rate. Because of the great significance of the slurry pH on MRR in CMP process, the effects of surface forces, including the influences of van der Waals (vdW) and double-layer (DL) forces simultaneously acted between the wafer and the particles were investigated. Meanwhile, the influence of particle sizes, abrasive loadings and zeta potentials of the wafer and particles on MRR was also analyzed. It is found that the attractive vdW forces strengthen the MRR, while the DL forces, calculated to be repulsive, lower the MRR. The magnitude of surface forces increases with a smaller particle size compared with the pad-particle force. When zeta potentials of the wafer and particles are considered as a function of slurry pH, the experimental trends for the MRR with slurry pH, applied pressure and abrasive loading were predicted well by the present model. Therefore, the governing equation of aluminum removal reveals some insights into the HKMG CMP process and can be utilized for optimizing and controlling the polishing rate of aluminum gate structures and performing sensitivity analyses of operating parameters. With the steady shrinkage of the feature size and device geometry of modern integrated circuits (ICs), chemical mechanical planarization (CMP) has become the most important process choice for the surface planarization in the fabrication of advanced multilever ICs in microelectronic industry.1 A variety of materials and structures, including copper damascene metallization, oxides in shallow trench isolation (STI) and inter-level dielectrics (ILD), replacement metal gate for high-k metal gate (HKMG) structures and fin field effect transistor (FinFET) devices are polished with different slurries. [2][3][4] In CMP process, a rotating wafer with different types of design structures is pushed against a rotating polishing pad which is immersed in slurries containing chemicals and abrasive particles. Pattern structures on the wafer surface are first chemically passivated by slurry chemicals and then removed by effects of contact interactions of abrasive particles which are trapped between the pad and the wafer. The contact mechanism of the particles in the slurry provides the opportunity to remove the material from the wafer surface at an acceptable production rate. 5The material removal rate (MRR) which has been studied extensively from both a modeling and experimental standpoint depends sensitively on pattern geometry, process parameters, chemical reactions, pad properties and mechanical abrasion. If the CMP process is not properly controlled...

mentioning

confidence: 99%

mentioning

confidence: 99%

A Material Removal Rate Model for Aluminum Gate Chemical Mechanical Planarization

Chen

2015

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“…In order to capture the collision reaction process between different species and describe the main chemical effects of different components in the polishing stage, the first-order unit chemical reaction has been generally recognized and adopted by previous researchers to construct the chemical kinetics based CMP models of copper, thermal oxide and aluminum materials. 2,5,[11][12][13]23,27,28,[34][35][36][37] The previous investigations could give good descriptions of the dependence of the polishing rate on the concentration of chemicals in the slurry, which had been validated by experimental results of different materials. We think that the first-order unit chemical reaction is an effective and reasonable approximation to be introduced into the present chemical mechanical kinetics modeling process for model assumption and simplicity.…”

Section: Modelingmentioning

confidence: 78%

A Material Removal Rate Model for Tungsten Chemical Mechanical Planarization

Xu¹,

Cao²,

Liu³

2022

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A tungsten removal rate model is proposed in the chemical mechanical planarization (CMP) process to investigate the removal mechanism with consideration of the synergistic effect of chemical reaction and mechanical abrasion. Based on the fundamentals of steady-state chemical reaction and mechanical abrasion, a chemical reaction kinetics CMP model is first built up to relate the removal rate to the chemical reagent and mechanical rate parameters. Then the Greenwood-Williamson contact theory is introduced into the chemical reaction kinetics model to construct a closed-form equation of removal rate, which captures the synergistic coupling effect of chemical and mechanical interactions. Furthermore, the present model is verified by the collected experimental data and utilized to investigate the impact of the design pattern effects on the removal rate. The consistency of the model prediction and the experimental data as well as the removal characteristics of design pattern structures indicate that the new proposed tungsten CMP model can be adopted to elucidate the synergistic effect of chemical and mechanical interactions and perform the sensitivity analysis of the design pattern dependency on removal rate of tungsten films.

“…Meanwhile, the reversible surface reaction is also ignored in the present modeling. 2,6,7,[10][11][12]19 The detailed modeling parameters are gradually considered as the model develops.…”

Section: Modelingmentioning

confidence: 99%

“…3,4,15,20,22,46,47 Meanwhile, the contact mechanics-and chemical kinetics-based removal rate models are also proposed to investigate the synergistic effect of chemical reaction and mechanical abrasion. 2,6,12,27 Fluid hydrodynamics-and chemical reaction kinetics-based CMP models are also put forward to reveal the removal mechanism of CMP systems. 19,21 In waferscale CMP modeling, the contact pressure distribution between the wafer surface and the polishing pad plays an important role in the material removal rate profile and surface uniformity, especially for the wafer edge regions.…”

mentioning

confidence: 99%

A Wafer-Scale Material Removal Rate Model for Chemical Mechanical Planarization

Chen

Liu

et al. 2020

Self Cite

In this work, a new wafer-scale material removal rate (MRR) model is proposed to investigate the underlying removal mechanism of wafer surface in the chemical mechanical planarization (CMP) process. Based on the governing equation of the plate theory, chemical reaction kinetics and wear theory, an analytical CMP model has been constructed to capture the influence of mechanical abrasion and chemical reactions on the removal rate with high efficiency. The effect of the elastic modulus of the pad, platen rotational speed, polishing temperature and reactant concentrations on the removal mechanism is investigated in detail to elucidate the intrinsic removal behavior. It is found that the material removal rate is sensitive to the elastic modulus of pad, temperature distribution, and chelator concentration, more sensitive to the oxidizer concentration, and most sensitive to the platen rotational speed. The magnitude of the removal rate can be adjusted significantly by properly selecting a good configuration of these influencing factors. The model predictions of the MRR profiles are consistent with the published experimental data at different polishing conditions. Therefore, the present CMP model can give insights into the wear mechanism of polishing process and may be utilized as a simulation tool for further optimization of removal rate and surface uniform control.