Chemical Mechanical Polishing Behavior Research Articles

Polymer coated γ-aminopropyltriethoxysilane-modified α-alumina non-spherical nanocomposite abrasives and their chemical mechanical polishing behavior on glass-ceramic substrate

Polymer coated γ-aminopropyltriethoxysilane-modified α-alumina non-spherical nanocomposite abrasives and their chemical mechanical polishing behavior on glass-ceramic substrate

Synthesis, characterization of CeO2@ZIF-8 composite abrasives and their chemical mechanical polishing behavior on glass substrate

As a kind of abrasive, cerium oxide (CeO2) abrasive provides the most key support for glass planarization, whose material removal rate (MRR) is related to the concentration of Ce3+ in the CeO2 surface. Herein, a series of composite abrasives named zeolite imidazolium cerium oxide (CeO2@ZIF-8) were prepared to increase the concentration of Ce3+ by growing different amounts of zeolitic imidazolate framework (ZIF-8) material on the cerium oxide particles, and their polishing properties on glass substrates were evaluated. When the content of ZIF-8 in the CeO2@ZIF-8 composite abrasive is 1.95 wt%, the MRR using this abrasive can reach up to 22.2 μm/h, which is 28% higher than that of pure ceria abrasive, while a lower average surface roughness (Sa, arithmetic mean height) of 1.23 nm can be obtained. The X-ray photoelectron spectroscopy results revealed an increase in the concentration of Ce3+ ions in the CeO2@ZIF-8 composite abrasive surface. The contact angle tests indicated that the slurries containing CeO2@ZIF-8 abrasives had superior wettability on glass substrate. Therefore, under the synergy of the two aspects, the chemical reaction process between CeO2@ZIF-8 composite abrasives and the glass substrate is remarkably promoted, resulting in outstanding polishing performance. We believe this work adds valuable insights regarding glass CMP by using CeO2@ZIF-8 as abrasives.

Synthesis, Characterization of Ceo2@Zif-8 Composite Abrasives and Their Chemical Mechanical Polishing Behavior on Glass Substrate

Synthesis, Characterization of Ceo2@Zif-8 Composite Abrasives and Their Chemical Mechanical Polishing Behavior on Glass Substrate

Insights into the atomistic behavior in diamond chemical mechanical polishing with [rad]OH environment using ReaxFF molecular dynamics simulation

Diamond has been utilized for various applications such as ultra-precision cutting tools and power semiconductor devices. Chemical mechanical polishing (CMP) is an effective processing method for the planarization of diamond, but the removal mechanism of the carbon atoms in diamond CMP is still under debate. Here, the atomic mechanism of removal in diamond CMP with OH environment was investigated using the molecular dynamics (MD) simulation method of reactive force field (ReaxFF). The simulation results show that with chemical action alone, the substrate surface adsorbs O, H or OH to form C–O, C–H, C–OH, etc., but no carbon atoms are removed from the diamond substrate. However, when the mechanical sliding is added, some carbon atoms are removed in form of CO or CO2, and the other carbon atoms are removed by the attachment to abrasive. The formation of C–C bonds between the diamond substrate and the abrasive or the formation of C–O bonds is a prerequisite for subsequent sliding removal. This work contributes to understanding the removal mechanism of diamond CMP at the atomic level.

CMP behavior of alumina/metatitanic acid core–shell abrasives on sapphire substrates

The abrasive is one of the important influencing factors during the chemical mechanical polishing (CMP) process. Although α-alumina is one of the most commonly used sapphire polishing abrasives due to its high hardness, it often results in surface damage. To receive lower surface roughness and high material removal rate, a common approach is to modify the surface of alumina. In this work, a series of alumina/metatitanic acid composite abrasives with core–shell structure were synthesized. The CMP performances of the pure alumina and alumina/metatitanic acid core–shell abrasives on sapphire substrates were investigated after polishing under the same conditions. Experimental results indicate that the alumina/metatitanic acid core–shell abrasives can not only improve the surface quality, but also further enhance the material removal rate. Furthermore, through the X-ray photoelectron spectroscopy test, this study investigated the chemical effect mechanism of the alumina/metatitanic acid core–shell abrasives in sapphire CMP. The results show that solid-state chemical reactions occur between metatitanic acid shell and sapphire surface during CMP process. We also investigated the mechanical friction mechanism through abrasive wear and adhesive wear.

Preparation of Ce-doped colloidal SiO2 composite abrasives and their chemical mechanical polishing behavior on sapphire substrates

Chemical mechanical polishing (CMP) has become a widely accepted global planarization technology. Abrasive is one of key elements during CMP process. In order to enhance removal rate and improve surface quality of sapphire substrate, a series of novel Ce-doped colloidal SiO2 composite abrasives were prepared by chemical co-precipitation method. The CMP performances of the Ce-doped colloidal SiO2 composite abrasives on sapphire substrate were investigated by using UNIPOL-1502 polishing equipment. The analyses on the surface of polished sapphire substrate indicate that slurries containing the Ce-doped colloidal SiO2 composite abrasives exhibit lower surface roughness, higher material removal rate than that of pure colloidal SiO2 abrasive under the same testing conditions. Furthermore, the acting mechanism of the Ce-doped colloidal silica in sapphire CMP was investigated. X-ray photoelectron spectroscopy analysis shows that solid-state chemical reactions between Ce-doped silica abrasives and sapphire surface occur during CMP process, which can promote the chemical effect in CMP and lead to the improvement of material removing rate.

Potassium Permanganate-Based Slurry to Reduce the Galvanic Corrosion of the Cu/Ru/TiN Barrier Liner Stack during CMP in the BEOL Interconnects

Chemical mechanical polishing (CMP) behavior of Cu/Ru/TiN barrier liner stack was investigated with a slurry comprising of silica abrasives, potassium permanganate (KMnO4), guanidine carbonate (GC) and benzotriazole (BTA) in the alkaline region. The corrosion and polishing behavior of the Cu, Ru and TiN films in the solution consisting of the above additives were characterized by open circuit potential and potentiodynamic measurements, polishing rates, dissolution rates and contact angle measurements. A slurry comprising of 10 mM KMnO4, 1 wt% GC and 5 wt% Silica at pH 10 has shown adequate polish rates as well as low individual film corrosion. However, 1 mM BTA was needed to maintain the ΔECORR of both the Cu/Ru and Ru/TiN couples at <20 mV essential to inhibit any galvanic corrosion while still maintaining low corrosion rates for Cu, Ru and TiN films. The removal rate ratio of Ru:Cu with the optimized slurry was ∼0.8, minimizing the possibility of dishing.

Silica abrasives containing solid cores and mesoporous shells: Synthesis, characterization and polishing behavior for SiO2 film

Oxide porous microspheres as novel abrasives have potential application in efficient and non-damage chemical mechanical polishing (CMP) due to their uniform mechanical and/or absorption properties. In this work, solid silica (sSiO2) cores were coated with mesoporous silica (mSiO2) shells via a modified Stöber method using vinyltrimethoxysilane as silica source and cetyltrimethylammonium bromide as structure directing agent. The obtained allotropic silica (sSiO2/mSiO2) samples were characterized by Fourier transform infrared spectroscopy, thermogravimetric analyzer, transmission electron microscopy, field emission scanning electronic microscopy and N2 adsorption–desorption. The effects of the thickness of mSiO2 shell on the CMP behavior for silicon dioxide films were evaluated by atomic force microscopy. The CMP results indicated that the as-prepared sSiO2/mSiO2 abrasives presented a much higher material removal rate, lower surface roughness as well as lower topographical variations than those of traditional solid silica abrasives. Furthermore, the material removal rate and surface roughness increased with the increase of the thickness of mSiO2 shell. The enhanced polishing performance might be contributed to the improvement of the physical and/or chemical environments in the local contacting region between abrasives and wafers. According to the indentation-based mechanism, these oxide-CMP results were rationalized from both chemical corrosion and mechanical abrasion actions. This work constructed a relationship between polishing behavior and microstructure of novel allotropic silica abrasives.

Preparation of La-doped colloidal SiO2 composite abrasives and their chemical mechanical polishing behavior on sapphire substrates

Chemical mechanical polishing (CMP) has become a widely accepted global planarization technology. Abrasive is one of the key elements in CMP process. In order to enhance removal rate and improve surface quality of sapphire substrate, a series of novel La-doped colloidal SiO2 composite abrasives were prepared by seed-induced growth method. The CMP performance of the La-doped colloidal SiO2 composite abrasives on sapphire substrate were investigated using UNIPOL-1502 polishing equipment. The analyses on the surface of polished sapphire substrate indicate that slurries containing the La-doped colloidal SiO2 composite abrasives achieve lower surface roughness, higher material removal rate than that of pure colloidal SiO2 abrasive under the same testing conditions. Furthermore, the acting mechanism of the La-doped colloidal silica in sapphire CMP was investigated. X-ray photoelectron spectroscopy analysis shows that solid-state chemical reactions between La-doped colloidal SiO2 abrasive and sapphire surface occur during CMP process, which can promote the chemical effect in CMP and lead to the improvement of material removal rate.

Material Removal Mechanism of Ti0.4Sb2Te3 Film during Chemical Mechanical Polishing in Acidic Permanganate-Based Slurry

In this work, the chemical mechanical polishing (CMP) behavior of KMnO4 on Ti0.4Sb2Te3 (TST) film has been studied. The material remove rate (RR) of TST film increases from 80 nm/min to 234 nm/min when the concentration of KMnO4 changes from 50 ppm to 300 ppm, which is much faster than 60 nm/min of the 0.1 wt% H2O2-based slurry. The etched surface morphologies of TST films are observed by scan electron microscope (SEM). To further investigate the chemical behavior of KMnO4, linear polarization scanning (LP) is combined with electrochemical impedance spectroscopy (EIS). Finally, the X-ray photoelectron spectroscopy was also utilized to analyze the chemical reaction mechanism of KMnO4 and TST film surface.

Preparation of Cu-doped colloidal SiO2 abrasives and their chemical mechanical polishing behavior on sapphire substrates

Cu-doped colloidal SiO2 composite abrasives were synthesized by seed-induced growth method. Time of flight secondary ion mass spectroscopy and scanning electron microscopy analyses show that element copper has been doped into colloidal SiO2, and the prepared Cu-doped colloidal SiO2 composite abrasives are all ideal spherical and have good dispersibility. Chemical mechanical polishing (CMP) performances of Cu-doped colloidal SiO2 composite abrasives on sapphire substrates were investigated using UNIPOL-1502 CMP equipment. Experimental results show that, the surface of sapphire polished by Cu-doped colloidal SiO2 composite abrasive exhibit lower surface roughness (Ra) and higher material removal rate (MRR) than that of pure colloidal SiO2 abrasive under the same testing conditions. Furthermore, the acting mechanism of Cu-doped colloidal SiO2 composite abrasive in sapphire CMP was analyzed by X-ray photoelectron spectroscopy, and analytical results show that element Cu in composite abrasives can react with sapphire substrates to form dialuminium copper tetraoxide (Al2CuO4) during CMP, which promotes the chemical effect in CMP and leads to the improvement of MRR.

Core/shell composites with polystyrene cores and meso-silica shells as abrasives for improved chemical mechanical polishing behavior

The core/shell-structured organic/inorganic composite abrasive has an important potential application in damage-free chemical mechanical polishing (CMP) due to its non-rigid mechanical property. In this work, the PS/ M SiO2 composites, containing polystyrene (PS) sphere (211 ± 4 nm) cores and mesoporous silica shells (31 ± 3 nm in thickness) were synthesized through directed surface sol–gel process of tetraethylorthosilicate on the polymer cores in the presence of the cetyltrimethylammonium bromide surfactant. For comparison, the conventional core/shell PS/ N SiO2 composites with non-porous silica shells were also prepared via a modified Stober procedure that involved the hydrolysis of TEOS under acidic condition. The physical properties of the samples were examined by small-angle X-ray diffraction, fourier transform infrared spectroscopy, thermogravimetric analysis, transmission electron microscopy, field emission scanning electron microscopy, and nitrogen adsorption–desorption. As novel abrasives, the core/shell-structured PS/ M SiO2 composites were introduced into the CMP process for silicon oxide films. The oxide-CMP performance among conventional solid silica particles, PS/ N SiO2 composites, and novel PS/ M SiO2 composites was explored by atomic force microscopy. Polishing results indicated that the substrate revealed a comparable root-mean-square surface roughness (0.25 ± 0.03 and 0.22 ± 0.02 nm, respectively) after CMP with PS/ N SiO2 and PS/ M SiO2 abrasives under the same polishing conditions. However, the material removal rate of the PS/ M SiO2 composites (123 ± 15 nm/min) was about three times larger than that of the PS/ N SiO2 composites (47 ± 13 nm/min). The reduced surface roughness and improved removal rate might be due to the optimization of the physical and/or chemical environments in the local contacting region between abrasives and substrates. The as-synthesized core/shell PS/ M SiO2 composites with mesoporous shells are expected to exhibit an important potential application in efficient and damage-free CMP.

Preparation of Fe-doped colloidal SiO(2) abrasives and their chemical mechanical polishing behavior on sapphire substrates.

Abrasives are one of key influencing factors on surface quality during chemical mechanical polishing (CMP). Silica sol, a widely used abrasive in CMP slurries for sapphire substrates, often causes lower material removal rate (MRRs). In the present paper, Fe-doped colloidal SiO2 composite abrasives were prepared by a seed-induced growth method in order to improve the MRR of sapphire substrates. The CMP performance of Fe-doped colloidal SiO2 abrasives on sapphire substrates was investigated using UNIPOL-1502 CMP equipment. Experimental results indicate that the Fe-doped colloidal SiO2 composite abrasives exhibit lower surface roughness and higher MRR than pure colloidal SiO2 abrasives for sapphire substrates under the same testing conditions. Furthermore, the acting mechanism of Fe-doped colloidal SiO2 composite abrasives in sapphire CMP was analyzed by x-ray photoelectron spectroscopy. Analytical results show that the Fe in the composite abrasives can react with the sapphire substrates to form aluminum ferrite (AlFeO3) during CMP, which promotes the chemical effect in CMP and leads to improvement of MRR.

Polymethylmethacrylate (PMMA)/CeO2 hybrid particles for enhanced chemical mechanical polishing performance

The organic/inorganic hybrid particles with polymethylmethacrylate (PMMA) spheres (350–360nm) as inner cores, and ceria nanoparticles (5–10nm) as outer shells were synthesized via electrostatic interaction. Chemical mechanical polishing (CMP) tests for silica films showed that the hybrid particles exhibited lower surface roughness, fewer scratches as well as lower topographical variations than those of solid ceria particles and (PMMA+CeO2) mixed particles. The improved CMP behavior might be attributed to the synergetic effect of the PMMA cores and the ceria shells. Furthermore, we discussed the material removal mechanism of hybrids in CMP process based on the proposal that the core/shell composite abrasives might be considered as micro-fixed abrasive pads.

A mixed elastohydrodynamic lubrication model for simulation of chemical mechanical polishing with double-layer structure of polishing pad

Mixed elastohydrodynamic lubrication (EHL) model has been used to study slurry flow and contact pressure distribution in the chemical mechanical polishing (CMP) process. However, in various mixed EHL simulation frameworks, only a single-layer polishing pad is considered. Consequently, the double-layer polishing pad, which is widely used in semiconductor industry, cannot be designed and optimized from the tribology perspective with the assistance of theoretical simulation. In this paper, multi-layered elastic theory (MLET), which is frequently used to calculate flexible pavement response to truck loading, is introduced into the mixed EHL model. Pad deformation calculated by the MLET has a similar accuracy to that by the 3D finite element method, but its computational cost is much lower. It is very important for accurate and efficient simulation of the tribological behavior and material removal rate (MRR) in CMP. Based on the new simulation method, advantages of a different double-layer structure of polishing pad are discussed. It is found that the upper-hard lower-soft pad has better performance for improving the uniformity of MRR when the wafer surface is uneven, but the boundary exclusion region is bigger than single-layer pad and upper-soft lower-hard pad. The upper-soft lower-hard pad has advantage to reducing the edge exclusion, but the effect is not remarkable when the thickness of the upper layer is not extremely thinner than the lower layer.

Preparation of porous alumina-g-polystyrene sulfonic acid abrasive and its chemical mechanical polishing behavior on hard disk substrate

Porous alumina-g-polystyrene sulfonic acid (Al2O3-g-PSS) was prepared by surface activation, graft polymerization and sulfonation, successively. Fourier transform infrared spectroscopy (FTIR), time of flight-secondary ion massspectroscopy (TOF-SIMS), scanning electron microscopy (SEM), and transmission electron microscope (TEM) analyses showed that the polystyrene sulfonic acid had grafted to the surface of porous alumina, and the prepared porous Al2O3-g-PSS abrasive had porous structure and good dispersibility. The chemical mechanical polishing (CMP) performances of the porous Al2O3-g-PSS abrasive on hard disk substrates were investigated. The results showed that, the surface of hard disk polished by the porous Al2O3-g-PSS abrasive had lower topographical variations and surface roughness (Ra) than those polished by pure porous alumina and solid alumina abrasives.

A mixed elastohydrodynamic lubrication model with layered elastic theory for simulation of chemical mechanical polishing

Mixed elastohydrodynamic lubrication (mixed EHL) model has been successfully used to study phenomena in chemical mechanical polishing (CMP) process. However, in various mixed EHL simulation frameworks, a polishing pad's deformation cannot correctly be described by adopted models for pad deformation such as elastic half-space model and Winkler elastic foundation model. Thus, a more accurate model for pad deformation is needed, since this is the prerequisite for an accurate prediction of contact pressure and material removal rate, which is critical for improvement of polishing quality. In this paper, a layered elastic theory, which is frequently used to calculate flexible pavement response to truck loading, is introduced into the mixed EHL model. It is found that this theory has a similar accuracy to the traditional 3D finite element method for calculating the pad deformation. However, its computational cost is much lower, which is especially important for accurate and efficient simulation of mechanical behavior and material removal rate (MRR) in CMP. In order to highlight benefits of the proposed theory, simulations are carried out based on three different pad deformation models with the mixed EHL model. The pad deformation behavior is found to have a significant influence on the final simulation results, especially the MRR prediction. By comparing the different simulation models, the proposed layer elastic theory is found to be an optimal model for describing the polishing pad deformation behavior in CMP and can provide accurate simulation results on contact pressure distribution and the material removal rate.

Preparation of porous alumina/ceria composite abrasive and its chemical mechanical polishing behavior

A porous alumina/ceria composite abrasive is synthesized by the hydrothermal synthesis method with transmission electron microscope images showing that it has wormhole-like pores. The chemical mechanical polishing performance of the synthesized abrasive on hard disk substrates was then investigated and the results showed that, compared with pure porous alumina and solid alumina, the porous alumina/ceria composite abrasive has a higher material removal rate because of the presence of the active polishing element cerium. Also, the surfaces polished by the porous alumina abrasives had much fewer topographical variations and a lower surface roughness than those polished by solid alumina abrasive.

Effects of (002) β-Ta barrier on copper chemical mechanical polishing behavior

This study proposes that the corrosion resistance of copper film correlates well with underlying barrier's orientation. To test the hypothesis, we performed X-ray diffraction, conducted copper removal rate experiments after chemical mechanical polishing, and tested static potentiodynamic polarization. The results all show that copper deposited on strongly (002) oriented β-Ta barrier layer demonstrated better chemical resistance against surface reaction with the slurry for strong copper (111) orientation. The findings were consistent with the result of the chronoamperometric test at 0.3V in which the more passive film formed on the composite film with (002) β-Ta underlying barrier.

Synthesis of Monodispersed CeO&lt;sub&gt;2&lt;/sub&gt; Nanoparticles Induced by Microwave Irradiation in Alcohol/Water Mixed Solvent and their Application in CMP

CeO2nanoparticles were synthesized by homogeneous precipitation in mixed solvent of alcohol and deionized water under microwave radiation using Ce(NO3)3•6H2O and HMT as starting materials. The structure and morphology of the products were characterized by X-ray diffraction (XRD), transmission electron microscopy (TEM), selected-area electron diffraction (SAED), and BET-N2. The oxide chemical mechanical polishing (CMP) behavior of the as-papered CeO2abrasives was investigated by atomic force microscope (AFM). The results indicated that the obtained CeO2particles were monodispersed with an average diameter of ca. 10 nm. There was a quite good consistency in the particle sizes from TEM and BET analyses. Polishing tests showed that the as-prepared ceria abrasives exhibited a good oxide CMP performance, which might attribute to the uniform size and shape of the as-prepared CeO2particles. In addition, the polishing pressure had an obvious influence on the surface topography, profilogram and roughness.