Polishing Time Research Articles

Modeling and experimenting of disc hydrodynamic polishing process for ultra-smooth surfaces

The machining of ultra-smooth surfaces has always been a significant research topic in the fields of optics fabrication. In this paper, disc hydrodynamic polishing (DHDP) process with a novel polishing tool is proposed to produce ultra-smooth surface with sub-nanometer scale surface roughness (Ra < 1 nm) and undamaged sub-surface. In order to explore the principle of the ultra-smooth surface generation in the DHDP process, the material removal mechanism and evolution mechanism of micro-morphology of polished surface were firstly studied by preliminary experiments. Then, theoretical material removal and surface simulation modeling are established on the basis of computational fluid dynamics (CFD), fractal theory for rough surfaces, particle contact mechanics, and erosion mechanisms in DHDP. Finally, a series of polishing experiments was performed on fused quartz glass to verify the theoretical model, which could be applied to predict surface topography and guide the ultra-smooth surface polishing process. The results indicated that the peak-to-valley (PV) value and waviness of the workpiece were reduced in the nanometer level under the erosion action of abrasive particles. Moreover, the surface roughness Ra and PV values decreased with the increase of rotation speed and polishing time. The analysis of power spectral density (PSD) results illustrates that high rotation speed of tool and polishing time (less than 60 min) can reduce the high-spatial-frequency errors distinctly, and the longer polishing time (above 60 min) can also influence on the mid-spatial-frequency errors.

Chemical Mechanical Polishing of GaSb Wafers for Significantly Improved Surface Quality

Gallium antimonide (GaSb) is considered an ideal substrate for heterostructure growth via molecular beam epitaxy. A significant aspect that inhibits the widespread application of infrared plane-array detector growth on GaSb is the starting substrate surface quality. In this study, the chemical mechanical polishing of GaSb wafers is investigated by considering the effects of the polishing pad, polishing solution, polishing time and pH buffer on their surface morphology and roughness. The surface morphology and root mean square (RMS) roughness of the free-standing wafers are characterized using a white light interferometer, a laser interferometer and an atomic force microscope. X-ray tomography is employed to measure the surface crystalline quality and strain defects of the samples subjected to the polishing treatments. The results show that with the optimum polishing condition, the polished GaSb wafers demonstrate high-quality surfaces without haze, scratches or strain defect regions. The peak to valley value is 5.0 μm and the RMS roughness can be controlled at less than 0.13 nm. A buffer layer grown on the GaSb surface with molecular beam epitaxy is examined via atomic force microscopy and high-resolution X-ray diffraction, which show a low RMS roughness of 0.159 nm, a well-controlled two-dimensional growth mode and a full width half maximum of the Bragg diffraction peak of 14.2”, indicating high-quality GaSb wafers. Thus, this work provides useful guidelines for achieving GaSb wafers with high-quality surfaces that show significant promise for substrate applications.

Study on the Electrorheological Ultra-Precision Polishing Process with an Annular Integrated Electrode.

Electrorheological (ER) polishing, as a new ultra-precision super-effect polishing method, provides little damage to the workpiece surface and is suitable for polishing all kinds of small and complex curved surface workpieces. In this paper, an ER polishing tool with an annular integrated electrode is developed. The orthogonal experiments are carried out on the six influencing factors of ER polishing which include the applied voltage, the abrasive particle size, the abrasive concentration, the polishing gap, the polishing time and the tool spindle speed. The influence order of these six factors on the ER polishing is obtained. On this basis, the effect of a single process parameter of ER polishing on surface roughness is studied experimentally.

Effects of Electrochemical Mechanical Polishing on the Polishing Efficiency and Quality of Co with H2O2 and BTA under Alkaline Conditions

With the development of technology nodes below 5 nm, cobalt has attracted extensive attention as an interconnection metal to replace Cu in the next generation of interconnection technology. Here, the appropriate concentrations of colloidal silica, H2O2, and BTA in the polishing solution were determined by static electrochemical measurement and electrochemical mechanical polishing technique. The results showed that the dynamic material removal rate of cobalt could be greatly improved after the addition of the selected solution. X-ray photoelectron spectroscopy was used to explore the reaction process and material generation in the polishing process. Co(Ⅱ)-BTA complex was found to be generated in the reaction process and adsorbed on the surface of cobalt, and it could be removed under a small mechanical force. Finally, the surface roughness of Co under different polishing time was measured by atomic force microscopy. The roughness of cobalt surface was Ra 1.35 nm polished for 10 min, and Ra was 0.418 nm after polishing for 120 min.

Study on electrochemical polishing of TC4 alloy

Using an environmentally friendly acid-alcohol system solution for electrochemical polishing of 3D printed titanium alloy, a typical U-I polarization curve was obtained, and explained the mechanism of electrochemical polishing. In this paper, the influence of electrochemical polishing factors (electrolyte temperature, polishing distance, and polishing time) on the surface roughness of Ti-6Al-4V (TC4) was studied, and optimized the process parameters to obtain a surface roughness of 0.3 μm (1 mm × 1 mm). Electrochemical polishing can reach the level of mechanical grinding and polishing, meeting the requirements for subsequent assembly and use.

Electrochemical Polishing of Extruded and Laser Powder-Bed-Fused Inconel 718

ABSTRACT Electro-chemical polishing (ECP) was utilized to produce sub-micron surface finish on Inconel 718 parts manufactured by Laser Powder-Bed-Fusion (L-PBF) and extrusion methods. The L-PBF parts had very rough surfaces due to semi-welded powder particles, surface defects, and difference layer steps that were generally not found on surfaces of extruded and machined components. This study compared the results of electro-polishing of these differently manufactured parts under the same conditions. Titanium electrode was used with an acid-based electrolyte to polish both the specimens at different combinations of pulsed current density, duty cycle, and polishing time. Digital 3D optical profiler was used to assess the surface finish, while optical and scanning electron microscopy was utilized to observe the microstructure of polished specimens. At optimal condition, the ECP successfully reduced the surface of L-PBF part from 17 µm to 0.25 µm; further polishing did not improve the surface finish due to different removal rates of micro-leveled pores, cracks, nonconductive phases, and carbide particles in 3D-printed Inconel 718. The microstructure of extruded materials was uniform and free of processing defects, therefore can be polished consistently to 0.20 µm. Over-polishing of extruded material could improve its surface finish, but not for the L-PBF material due to defects and the surrounding micro-strain.

Investigating dry electro-chemical polishing of titanium structures

Abstract With the introduction of novel automated polishing methods, more attention has recently been paid to postprocessing methods of metallic implants. One such method is the polishing process known as DryLyte®. The most significant difference to previous electropolishing methods is the use of solid organic polymer particles activated with sulfonic acid acting as the electrolyte. The solid particle electrolyte raises new question in terms of polishing results for small features as well as overall polishing quality of metallic surfaces. The aim of this study was to determine the quality of the polishing process for titanium rods with different initial surface roughness and with tapped holes in three different orientations (0°, 45°, 90°) by subjecting them to the DryLyte® polishing process for 30 min. In addition, the influence of the process parameters voltage and the anodic time T2 during the treatment on the resulting surface quality and the polishing efficiency was determined. In conclusion, the dry electrochemical finishing process has shown great smoothing capabilities for titanium even with small, tapped holes. The Ra values were lowered significantly throughout all titanium samples after 30 min polishing time.

Influence of parameters on the surface roughness of the CO2 laser polished fused silica glass

The laser polishing method has the advantages of high efficiency and no impurity doping. In this paper, the CO2 laser is used to polish the fused silica glasses. The optimized parameters of the CO2 laser are obtained by adjusting scanning speed, duty ratio, frequency, and defocus amount. The polishing times, track pitch and circumference, and initial roughness of the silica samples are studied. The process parameters have a different influence on the roughness of the polished samples. The results show that lower surface roughness can be obtained in line polishing when the power density is close to the evaporation threshold. The surface roughness of the silica sample is reduced by a low heat with multiple polishing. The lower the initial roughness of silica sample, the lower the surface’s roughness is after polished. The lowest surface roughness Ra = 0.22 µm is obtained, and the process parameters are selected: scanning speed 100 mm/s, frequency 15 kHz, duty ratio 50%, defocus +6 mm, track pitch 0.01 mm, unidirectional scan path length 40 mm width 36 mm. When the process parameters are the same and the roughness of multiple line polishing is the same as the roughness of area polishing, the relationship between the ratio of channel width and the number of polishing times in line polishing is equal to the track pitch during area polishing. The influence of track circumference on the roughness can be negligible.

Sliding behaviour and surface quality after static air polishing of conventional and modern bracket materials : In vitro analysis.

As part of orthodontic treatment, air polishing is routinely used for professional tooth cleaning. Thus, we investigated the effects of static powder polishing on sliding behaviour and surface quality of three different bracket materials (polymer, ceramic, metal), including a3D-printed bracket. Two bracket types of each material group were polished with an air-polishing device using sodium bicarbonate. Exposure times were set at 10, 20, and 60 s; the application distance was 5 mm. The force loss due to sliding resistance was tested with an orthodontic measurement and simulation system (OMSS) using a0.016 inch × 0.022 inch stainless steel archwire. Untreated brackets served as control. Polishing effects and slot precision were evaluated using an optical digital and scanning electron microscope. Sliding behaviour and slot precision differed significantly between and within the groups. Prior to polishing, polymer brackets showed the least force loss, ceramic brackets the highest. With progressive polishing time, the resistance increased significantly with titanium brackets (26 to 37%) and decreased significantly with steel brackets (36 to 25%). Polymer brackets showed the smallest changes in force loss with respect to polishing duration. Slot precision showed the largest differences between material groups and was primarily manufacturer-dependent with hardly any changes due to the polishing time. Powder polishing can positively or negatively affect the sliding properties of the bracket-archwire complex but is more dependent on the bracket-archwire material combination (i.e., manufacture-dependent slot precision). For titanium brackets, resistance only increased after 60 s of polishing. For ceramic brackets, effective reduction was observed after 10 s of polishing. Polymer brackets, including the 3D-printed brackets, showed better sliding properties than ceramic or metal brackets even after polishing for 60 s. Removal of plaque and dental calculus should lead to anoticeable improvement of the sliding properties and outweighs structural defects that may develop.

Investigation on anti-skid performance of asphalt mixture composed of calcined bauxite and limestone aggregate

In order to effectively improve the anti-skid performance of asphalt pavement, 88# calcined bauxite was introduced as a kind of high anti-skid aggregate, and the principle of differential polish was applied. With the self-developed three-wheel polishing device (TWPD), dynamic friction coefficient tester (DFT), accelerated stone polishing tester and AMES road laser texture scanner, the polishing performance and distribution maps of mean profile depth (MPD) of limestone and 88# calcined bauxite were obtained. The anti-skid performance of asphalt mixture blended with high and low polished stone value (PSV) aggregates was investigated. Before and after polishing, the MPD and estimated texture depth (ETD) of asphalt mixture blended with different proportions of 88# calcined bauxite were analyzed. The results show that the PSV of 88# calcined bauxite is significantly better than that of limestone. Based on different polished times, the relationship model between dynamic friction coefficient (DF) and vehicle speed was established. The model can reflect the relationship between friction coefficient, polishing times and vehicle speed well. Meanwhile, the reasonable proportion of 88# calcined bauxite is 25%∼ 50% mass of the mineral aggregate in asphalt mixture. The surface of asphalt mixture appeared obviously differential polishing effect, and the anti-skid performance of asphalt pavement was significantly improved. The obtained MPD and ETD values and the distribution maps of MPD were used to demonstrate the proposed optimal scheme. The research results provide new ideas for improving durability and anti-skid performance for asphalt pavement.

Generic model of time-variant tool influence function and dwell-time algorithm for deterministic polishing

In computer-controlled optical surfacing (CCOS) techniques, the tool influence function (TIF) is generally assumed to be time-invariant; thus, two-dimensional convolution can be employed to compute the dwell time. However, the material removal rate is time-variant in some CCOS processes. This time-variant material removal rate makes it difficult to accurately model the TIF and leads to impracticality of the two-dimensional convolution algorithm. We herein establish a novel modelling framework of the TIF considering the time-variant material removal rate in CCOS based on a partial differential equation. An updated dwell-time algorithm is also proposed to address the inverse problem of freeform surface generation by using the established TIF. The proposed modelling technique is well demonstrated in magnetically driven internal finishing and abrasive jet machining. The results demonstrate that the model can precisely predict the polished profile against the polishing time, and the novel dwell-time algorithm outperforms the conventional convolution algorithm in terms of efficiency and accuracy. The modelling framework enables localised freeform surface generation and corrective polishing on internal surfaces. The proposed TIF model and dwell-time algorithm may be extended to other CCOS techniques to achieve better figuring accuracy, such as bonnet polishing, ion beam figuring, and plasma jet machining.

Technological study of polishing animated by a vibratory movement for BK7 glass

The miniaturization of lenses has recently been in high demand in new fields such as medicine and industry. In this paper, a new polishing technique is presented. It is based on the magnetostrictive principle, where the polishing tool is driven by a vibratory motion that generates a frequency. We present an experimental study between the parameters influencing the vibratory polishing process, namely: vibration frequency, polishing time, type of polisher and final state of the optical surface. Different vibrations were examined by roughness and transmission obtained. The results showed that using a frequency of 4.62 KHz with a polisher type Lp66, the surface finish (roughness) and transmission are better (Ra = 4.27 nm, Rq = 5.47 nm and T = 98%) during a one-hour polishing operation with a low material removal rate MRR, a surface profile that tends to be more regular and a shape of about 3.02 µm PV.

High precision fabrication of aluminum optics by optimizing an Ar+ ion beam figuring strategy for polishing the contamination layer.

Benefiting from high specific stiffness and high reflectance, aluminum optics with a complex surface profile are widely used in aerospace optical systems which have strict requirements for volume of the systems. Contact figuring polishing process provides highly deterministic technology for the fabrication of high precision aluminum optics. However, due to the high chemical activity of aluminum, the inevitable contamination layer will generate on the surface and bring difficulties for the subsequent processes, which greatly limit the fabrication precision. Ion beam figuring (IBF) is an effectively technology that can remove the contamination layer and improve surface quality. But, the surface profile may deteriorate during IBF. In this study, through experimental method, the nonuniformity of the contamination layer is found to be the inducer for deterioration and deviation of surface profile during IBF. The mapping between the characteristics of contamination layer and dwell time of contact polishing is studied. The thickness of the contamination layer will firstly increase with dwell time and stabilize to 120 nm when the dwell time exceeds a specific value. The variation of the IBF removal function with removal depth is also revealed through experimental and theoretical methods. Due to the dynamic variation of the composition in the contamination layer during IBF, the removal function increases with the removal depth and stabilizes when the depth exceeds 60 nm (the contamination layer is fully removed). Consequently, we propose two processing strategies to improve the aluminum optics fabrication process. Comparative experiments are performed on two off-axis aspherical surfaces. The results indicate that the surface profile can be stably maintained and improved during IBF processing based on the proposed strategies. Our research will significantly improve the fabrication precision of aluminum optics and promote the application of aluminum optics to the visible and even ultraviolet band.

Electropolishing of Inconel 718 manufactured by laser powder bed fusion: Effect of heat treatment on hardness, 3D surface topography and material ratio curve

In the present study, the laser powder bed fusion (LPBF) technique was used to produce Inconel 718 parts as a fabrication route. The LPBF processed samples microstructure, and surface characteristics were analyzed in both the as-printed and heat-treated conditions. The surface irregularities in the as-printed Inconel 718 was minimized using the pulsed electropolishing technique. The weld bead along the build direction and laser scan path to the build direction was observed. The electropolished results showed that increasing the current density and polishing time decreases the areal surface roughness of the as-printed sample (~64%) and heat-treated sample (~54%). The material ratio curve shows an increase in current density and electropolishing time; the surface topography becomes more uniform and lesser surface undulations for the as-printed samples and less uniform in the case of heat-treated samples. It was attributed to the interplay between microstructural constituent phases and electropolishing process parameters. The material ratio curve serves as an effective method to assess and qualify the surface characteristics of the electropolished LPBF processed samples. Furthermore, the 2D line profilogram and 3D surface topography benefit better understanding the surface finish quality characteristics of electropolished LPBF processed samples.

Effect of chemical composition of calcined bauxite aggregates on mechanical and physical properties for high friction surface course

This paper attempts to show the impact of chemical components on the mechanical and physical performance of calcined bauxite, especially the long-term skid resistance. Firstly, the mechanical and physical properties of five types of calcined bauxites including, the polished stone value (PSV), crush value, Los Angeles Abrasion value (LAA), adhesion property, bulk density and water absorption were tested. The X-ray fluorescence (XRF) and X-ray diffraction (XRD) were applied to examine the chemical and mineral components of aggregate. The Pearson correlation coefficient and Pearson correlation coefficient matrix by Statistic Package for Social Science (SPSS) were utilized to study the relationship between chemical components and mechanical, physical properties of calcined bauxite. Then, the long-term skid resistance of calcined bauxite aggregate was carried out in the laboratory by accelerated polish machine and British Pendulum Tester. The polishing mechanism and the influence of chemical components on the skid resistance of calcined bauxite aggregates were gained by linear regression methods. The asymptotic model was adopted to fit the relationship between British pendulum number (BPN) and polish times. The results indicate that the chemical compositions of calcined bauxite aggregate including Al2O3 and SiO2 along with indicator SiO2/Al2O3 show significant impact on the mechanical and physical properties of calcined bauxites. The final value of PSV (PSVf) is significantly correlated with average grain size (D), corundum, mullite and Aggregate Hardness Parameter (AHP) of calcined bauxite. The asymptotic model can describe the decay process of polish of calcined bauxite with polish time. The PSVn can be expressed with PSVf and SiO2/Al2O3 by linear equation. In addition, the incorporation of calcined bauxite improves MPD (Mean Profile Depth) and BPN of limestone asphalt mixture. This provides a new and interesting way for selecting suitable aggregate used in the pavement surface layer.

Study on Pitch Performance Deterioration in Chemical Mechanical Polishing of Fused Silica

Fused silica (FS) has been widely applied in astronomical telescopes, laser systems, and optical communication. The excellent fabrication of a fused silica surface requires high efficiency and high smoothness. Here, based on the ceria slurry and the pitch lap, the study of chemical mechanical polishing (CMP) of FS surface was carried out. The variations of the polishing removal rate (RR) and polished surface roughness Rq of FS with the polishing time were investigated. Meanwhile, the variations of the pitch performance during the CMP process were analyzed. Compared with the original pitch, the Rq of the used pitch presented an obvious decrement and the thickness of the used pitch was reduced. Scanning electronic microscopy was used to observe the morphologic change of the pitch. Attenuated total reflection-Fourier transform infrared spectroscopy was used to evaluate the chemical change of the pitch. The surface roughness Rq of the pitch was characterized. The viscoelastic characteristics of the pitch were investigated by dynamic shear rheometer tests. The relative mechanism of the pitch performance deterioration was discussed.

Investigations of the Pad Trajectory Effect on the Asymmetric Profile and Arc-Shaped Scratches in Chemical Mechanical Polishing

Research was conducted on the trajectories formed by fixed positions on the pad and how these trajectories affect the asymmetric profile and arc-shaped scratches in chemical mechanical polishing (CMP). Also investigated was whether the local glazing of the pad surface affects the asymmetric profile using the Si3N4 film and ceria slurry, whether the end point detection (EPD) window on the pad could cause a very fine asymmetry profile according to the process conditions using the poly-Si film and silica-based slurry, and the arc-shaped scratches generated in W and Cu CMP were compared with the calculated trajectories. Based on these studies, it was confirmed that the With-In-Wafer (WiW) asymmetry profile can appear and the WiW range can be rapidly changed up to 500% depending on the polish time and the speed of platen and wafer carrier head. It can further be deduced that the repetitive arc-shaped macro scratching phenomenon is caused by a fixed scratch source on the pad. To solve this problem, we suggest the prevention of abrasive aggregation and optimization of in situ conditioning. By comparing the repetitive scratch shape and the calculated trajectory, it was possible to judge the scratches that occurred.

Decortication induced changes in the physico-chemical, anti-nutrient, and functional properties of sorghum

The milling characteristics, physico-chemical properties, nutrient, and functional characteristics of sorghum were evaluated following field-level abrasive decortication to ascertain the impact of polishing parameters. Both grain moisture content and polishing time were found to significantly influence the degree of polish, endosperm yield, percentage broken, grain hardness, and thousand-grain weight. Both the proximate composition and mineral content of the flour decreased owing to decortication, indicating their dominant presence in the bran fractions. A more significant reduction in tannins was observed as compared to phytates meaning that phytates might be more localized in the inner layers, and tannins are majorly concentrated in the outer grain portions. Whole grain flour possessed better water and oil absorption capacities and lower bulk density value compared to polished fractions. There was also an increase in L* (lightness) and decrease in a* (red to green) and b* (yellow to blue) values in the polished flour samples indicating that decortication results in an overall improvement of the color of refined fractions. Results of PCA suggested a significant correlation between certain components namely fibre contents and tannin, ash content and mineral contents, and fibre and water absorption capacity, signifying that they co-vary with respect to one another. The cluster analysis suggested the importance of selected variables and their impact on the responses, as a clear demarcation was seen in the samples obtained from raw and polished grains.

Evaluating Polishability of Zirconia Impregnated PMMA Nanocomposite for Denture Base Application

Artificial biomaterials are being developed for use in denture base with symmetrical properties to restore the aesthetics and functionalities. The rough surface of denture base resin promotes the adhesion of microorganisms and plaque accumulation. This study aimed to explore the consequences of polishing times on the surface roughness of high-impact (HI) heat-polymerized PMMA denture base acrylic resin reinforced with zirconia nanoparticles (nanocomposite). Thirty specimens (25 ± 0.50 mm in diameter and 2 ± 0.10 mm thickness) were fabricated from HI PMMA by adding zirconia nanoparticles at different concentrations of (0 wt.%, 1.5 wt.%, 3 wt.%, 5 wt.%, 7 wt.%, and 10 wt.%). Specimens were divided into six groups (n = 5) and surface roughness (Ra) was measured before and after polishing with a standard protocol for one and two minutes. The addition of zirconia in PMMA at low concentrations (1.5 wt.%, 3 wt.%, and 5 wt.%) did not negatively affect the surface finish of the denture base composites following conventional polishing and remained below the clinically acceptable limit (0.2 µm). After one minute of polishing, only the 10 wt.% zirconia (0.17 ± 0.03 µm) demonstrated a substantial rise in median surface roughness, in comparison with the control group (0.11 ± 0.01 µm). It is concluded that the group containing 3 wt.% (0.10 ± 0.01 µm) of zirconia is the optimum concentration to obtain the best symmetrical surface finish after two minutes of polishing.

Computational Modeling of CMP Pads: Analyzing the Pad Geometry’s Impact on Planarization Efficiency

The pad choice has a dominant effect in polish behavior during a shallow trench isolation (STI) process. That pad must be chosen in connection with the pattern to be polished, as a pattern may consist of features that span various scales. An ideal pad will result in high planarization efficiencies across all feature sizes, in a low within-die range (strong uniformity across the die), and in low within-wafer ranges (strong uniformity across the wafer). Computational simulations make it possible to test various candidate pad designs, in search of an optimal pad design. We present our CMP modeling framework and use it to evaluate the planarization efficiency of a feature array, and the within-die range of a particular pattern, for pads with varying segment widths.The contact wear model simulates the contact between an oxide die and the polymeric polishing pad. We predict the contact pressure distribution by representing three modes of pad deformation: surface deformations due to local indentations, bulk pad segment downward displacements due to net pressures on the segments, and bulk pad rotations due to effective moments. We calculate the bulk deformations uses finite element simulations (details provided in [1]). We calculate the deformation due to local indentations using Nogi and Kato’s approach [2]. We then use the predicted pressure distribution, along with Preston’s equation, to incrementally remove oxide on the die.As discussed in [1], the pad’s surface texture has a dominant effect in contact wear simulations. Whereas [1] used theoretically generated pad surfaces, here, we use experimentally measured, used pad surfaces. Figure 1(a) shows the measured pad scan (left: the 95 mm x 77 mm overview of the concentric ring pad; right: a cross-section through the pad scan).Our experiment uses a 1.35 mm concentric ring pad, where the segments have an elastic modulus of 790 MPa and the subpad has an elastic modulus of 55 MPa. Note that for this particular pad, since the elastic modulus of the segment material is only one order of magnitude greater than the elastic modulus of the subpad, the effects of local surface indentations dominate over any bulk segment downward displacements or rotations.Modelling results (shown in Figure 1b) indicate that simulations for this pad track the experiments well. The lines represent the simulation, and the error bars represent experimental measurements (95% confidence intervals of the mean). Simulations track the experiments reasonably well. Simulations lie within the error bars for all 4 of the trench measurements, and they lie within the error bars for 3 of the 4 active measurements. Further work aims to improve this agreement.The simulations show the evolution of the die’s topography throughout the polish. Figure 1c shows the simulated die topography after 0, 25, 50, and 75 s of polish. Simulations do indeed show oxide planarization, as the within-die range decreases as the polish time increases.We use these contact simulations to evaluate neighborhood effects. For the 200 micron checkerboard array, we change the pattern density of the features directly to the right. Figure 1d shows that as the pattern density of the right neighbor increases, the material removal rate of the features being evaluated decreases. Of particular note is that the length scale over which these neighborhood effects acts is about 4 mm.We also use this model to predict the polish behavior when using different pad designs. Here, we focus on the pad ring width’s impact on the polish properties. We simulate polishes with four different ring widths: 0.35 mm, 0.45 mm, 0.70 mm, and 1.35 mm. Simulations indicate that pads with a larger ring width result in a larger planarization efficiency, compared to the smaller ring width pads. Figure 1e shows a plot of the predicted planarization efficiency versus step height for a 200 µm checkerboard array using a specific pad design. As the pad ring width is increased, simulations predict higher planarization efficiencies, as expected. Further, simulations show that pads with a larger ring width result in a smaller within-die range. Figure 1f shows a plot of the simulated within-die range versus pad ring width. The within-die range is calculated at the instance when the average active oxide thickness across the die is 100 Å. The plot shows that pad designs with a larger ring width result in a smaller within-die range, as expected.Looking forward, our die-scale model can be used to optimize pad designs and die layouts.