Slurry Film Thickness Research Articles

초음파 분사 노즐의 분사 범위에 따른 슬러리 막 두께의 변화가 재료제거율에 미치는 영향

Most of the consumables used in the CMP (Chemical Mechanical Planarization) process are discarded because it is difficult to reuse them. Slurry accounts for most of the consumables, so research is being conducted to reduce the amount of slurry used. A previous study explains that when the same amount of slurry is injected, the material removal rate is improved when the slurry is injected wide and thin instead of the tube nozzle, which is the conventional slurry injection method. However, there was no change in the injection method due to the problems of the injection method suggested in previous studies and the lack of follow-up studies. Thus, in this paper, an injection method through an ultrasonic spray nozzle is proposed to improve the problems of the injection method proposed in previous studies. Additionally, it is intended to calculate the slurry film thickness according to the spraying range and to explain the effect of the film thickness on the material removal rate.

Recycling of waste glass powder as paste replacement in green UHPFRC

Featured by a high cement content and a large consumption of quartz sand, ultra-high performance fiber reinforced concrete (UHPFRC) encounters hindrance in the pursuit of carbon neutralization and extensive application. Recycling materials (e.g., waste glass) may lower the performance of UHPFRC when used as cement/aggregate substitution. To conquer this problem, an innovative paste replacement method, i.e., adding waste glass powder (WGP) to substitute an equal volume of paste without altering the paste composition, was employed. An optimum amount of WGP was revealed for remarkably enhancing the workability, compressive strength, bending strength and microstructure of UHPFRC. Meanwhile, cement content was reduced by 18.8% to 365 kg/m3, whilst the strength was remarkably increased to exceed 150 MPa. To explore the mechanism, the wet packing density and slurry film thickness (SFT) of the paste were determined, whereby empirical models were established based on SFT and fiber factor (FF) for workability. Lastly, certain synergistic effects between the combined use of WGP and steel fibers on the properties of green (low carbon) UHPFRC were identified.

Study on the relationship between slurry film thickness and rheology of fillers based on film theory

The key problem of paste filling technology lies in whether paste can meet the requirements of stope structural parameters on cementing strength, pipe transportation and mining methods on filling performance. The separated paste will cause serious wear and even pipe blockage in the pipeline transportation process. If the paste is separated in the stope, the strength of the filling body will be uneven, and accidents such as delamination and stacking will occur. The occurrence of these situations is extremely unfavorable to the filling operation. Just as the material determines the performance, in order to ensure the paste has excellent filling performance, it is necessary to systematically study the internal relationship between paste filling materials and filling performance. Paste is a complex suspension system composed of aggregate, water, cementing materials and additives. Compared with traditional low-concentration classified tailings slurry, it has the characteristics of wide particle size distribution, high solid content, strong chemical action on particle surface, etc. Under the interaction of these factors, paste presents macroscopic characteristics such as plasticity and stability. These macroscopic characteristics are embodied in rheology, that is, rheological characteristics of paste. The research shows that the rheological properties of paste are affected by the gradation, concentration and cementing material of filling material, and the change of gradation of filling material has the most significant effect on the rheological properties of paste. The change of the micro-level composition causes the change of the rheological properties of the paste on the macro level, thus causing the change of the paste filling performance. In the final analysis, the gradation of the traceable filling material is an important factor that determines the paste filling performance.

Roles of packing density and slurry film thickness in synergistic effects of metakaolin and silica fume

Metakaolin (MK) and silica fume (SF) have been added either individually or in combination to improve concrete performance. Recent studies proved that the combined addition of MK and SF offers synergistic effects, but the mechanism behind is still not unclear. Herein, it is postulated that the synergistic effects arise mainly from the successive filling effects of the MK and SF into voids between larger size particles, which increase the wet packing density (WPD). The present work indicated that the slurry formed of the water and ultrafine particles plays an important role. Good correlation of the workability measures to the slurry film thickness (SFT) revealed the governing factor of SFT for the first time. Moreover, the synergistic effects of MK and SF on the compressive and flexural strengths have been studied based on cementing efficiency and synergistic factors. Correlation of the synergistic factor to the WPD revealed that the WPD plays an important role.

Roles of superplasticiser dosage, water film thickness and slurry film thickness in flowability of cementitious paste

Cementitious paste samples proportioned with blended ordinary Portland cement, pulverised-fuel ash and condensed silica fume (CSF), with different water/cementitious materials ratios and varying superplasticiser (SP) dosages, were produced for packing density and flowability measurements. The results showed that increasing the SP dosage significantly increased the packing density and water film thickness (WFT) of the cementitious paste, and increases in SP dosage and WFT contributed to increasing the flowability of the cementitious paste. At the same SP dosage and WFT, cementitious pastes containing CSF tended to have higher flowability. It is postulated that this is because the finest portion of CSF and water flowed together as a slurry that coated the larger sized particles with a certain slurry film thickness (SFT). Regression analysis of the test data revealed a very good correlation of flowability to SP dosage and SFT.

In situ measurement method for film thickness using transparency resin sheet with low refractive index under wet condition on chemical mechanical polishing

We suggest that a transparency resin sheet with low refractive index can be applied to the measurement of a silicon dioxide (SiO2) film on a silicon wafer under wet condition for a film thickness measurement system on chemical mechanical polishing (CMP). By adjusting the refractive indices of the resin sheet and water, stable measurements of the SiO2 film can be expected, irrespective of slurry film thickness fluctuation because it has robustness against the slurry film. This result indicates that the transparency resin sheet with low refractive index is a useful for monitoring system of CMP.

Study on Variable Rotation Polishing Method in Chemical Mechanical Polishing Process

Variable rotation polishing method has been studied to improve performance for the next generation wafer size of 450 mm in Chemical Mechanical Polishing (CMP) technology. This method adds the backward rotation of a polishing platen against the only forward rotation, i.e. the conventional polishing. Polishing slurry could be more efficiently supplied into the center area of the larger wafer due to the backward rotation of the platen. Material removal rate at the condition the backward rotation experimentally became 38% higher in comparison with only forward rotation. In this case, slurry film thickness of the Variable Rotation Polishing (VRP) method was slightly thinner than that of conventional rotation. Next, the asperities of polishing pad surfaces were evaluated by confocal laser scanning microscope. The higher material removal rates would also be achieved by the movement of the asperity bending back and forth direction on the polishing pad surface during the forward and backward rotation of the platen. These observed polishing pad surfaces indicated that the asperity preservation on the polishing pad is one of dominant parameters to improve the material removal rate of wafer surface in CMP process.

Effect of retaining ring slot designs and polishing conditions on slurry flow dynamics at bow wave

The effect of retaining ring slot design and polishing conditions on slurry flow dynamics at the bow wave was investigated. An ultraviolet enhanced fluorescence technique was employed to measure the slurry film thickness at the bow wave for two polyetheretherketone (PEEK) retaining rings with different slot designs. Multiple sliding velocities, slurry flow rates and ring pressures were investigated. Results showed that the retaining ring with the sharp angle slot design (PEEK-1) generated significantly thicker slurry films at the bow wave than PEEK-2 which had a rounded angle slot design. For PEEK-1, film thickness at the bow wave increased with increasing flow rate and ring pressure and decreased with increasing sliding velocity. On the other hand, film thickness at bow wave did not change significantly for the PEEK-2 ring at different polishing conditions indicating an apparent robustness of the PEEK-2 design to various operating conditions. With retaining rings having different designs, and all else being the same, a thinner bow wave was preferred since it was indicative of a ring design that allowed more slurry to flow into the pad-wafer interface. Therefore, the work underscored the importance of optimizing retaining ring slot design and polishing conditions for efficient slurry utilization.

Models of nanoparticles movement, collision, and friction in chemical mechanical polishing (CMP)

Nanoparticles have been widely used in polishing slurry such as chemical mechanical polishing (CMP) process. The movement of nanoparticles in polishing slurry and the interaction between nanoparticles and solid surface are very important to obtain an atomic smooth surface in CMP process. Polishing slurry contains abrasive nanoparticles (with the size range of about 10–100 nm) and chemical reagents. Abrasive nanoparticles and hydrodynamic pressure are considered to cause the polishing effect. Nanoparticles behavior in the slurry with power-law viscosity shows great effect on the wafer surface in polishing process. CMP is now a standard process of integrated circuit manufacturing at nanoscale. Various models can dynamically predict the evolution of surface topography for any time point during CMP. To research, using a combination of individual nanoscale friction measurements for CMP of SiO2, in an analytical model, to sum these effects, and the results scale CMP experiments, can guide the research and validate the model. CMP endpoint measurements, such as those from motor current traces, enable verification of model predictions, relating to friction and wear in CMP and surface topography evolution for different types of CMP processes and patterned chips. In this article, we explore models of the microscopic frictional force based on the surface topography and present both experimental and theoretical studies on the movement of nanoparticles in polishing slurry and collision between nanoparticles, as well as between the particles and solid surfaces in time of process CMP. Experimental results have proved that the nanoparticle size and slurry properties have great effects on the polishing results. The effects of the nanoparticle size and the slurry film thickness are also discussed.

Effect of concentric slanted pad groove patterns on slurry flow during chemical mechanical planarization

The present study presents the effect of applied wafer pressure, slurry flow rate and degree of groove slanting on the overall hydrodynamics of a typical chemical mechanical planarization (CMP) process by quantifying the slurry film thickness in pad-wafer region. This is done via dual emission ultraviolet (UV) enhanced fluorescence measurements, which use fluorescent dyes on the slurry to relate the intensity of the light to the film thickness. Slurry film measurements were taken in-situ at several wafer pressure, slurry flow rate and groove patterns in a 200-mm CMP tool. The film thickness measurements obtained in this study showed a correlation between groove designs and the amount of slurry transported from the grooves to the pad land areas. Also this study corroborates a previously hypothesized slurry flow mechanism generated when the slanted groove pads were used during copper CMP.

Effect of Slurry Application/Injection Methods and Polishing Conditions on Bow Wave Characteristics

In this study, the effect of slurry application/injection methods and polishing conditions on slurry flow dynamics at the retaining ring bow wave was investigated. Two slurry application/injection methods (standard slurry application method and novel slurry injection method) were used. For each method, an ultraviolet enhanced fluorescence system was implemented to measure the slurry film thickness at bow wave for a polyetheretherketone (PEEK) retaining ring at different sliding velocities, slurry flow rates and ring pressures. Results indicated that the novel slurry injection method generated significantly thicker slurry film at the bow wave than that of the standard slurry application method. For both methods, slurry film thickness at the bow wave increased with increasing flow rate and ring pressure while it decreased with increasing sliding velocity.

A Three-Dimensional Hydrodynamic Lubrication Model for Chemical-Mechanical Polishing Considering Pad Roughness

A three-dimensional hydrodynamic lubrication model based on lubrication theory is developed which accounts for pad roughness and slurry flow. The distribution of the slurry film thickness and pressure between the pad and the wafer are predicted using the model. The effects of the pad roughness, the polishing applied load and rotation speed on slurry film thickness and tilt angle are discussed. At last, a CMP experiment is carried out. It is found that the results are proved the three-dimensional model considering pad roughness agrees well with our experimental data. The results improve the previous models so that the CMP process can be better simulated using the model. Furthermore, they are useful in the processing of CMP and the design of the pad roughness.

Numerical and Experimental Research of the Slurry Film in Chemical Mechanical Polishing (CMP)

A three-dimensional hydrodynamic lubrication model for chemical-mechanical polishing is presented based on the Reynolds equation and Reynolds boundary condition. By solving the Reynolds equation, the slurry film pressure distribution has been obtained. The effects of minimum film thickness and the wafer tile angle on the film pressure are analyzed, and the influence of the polishing applied load and rotation speed on slurry film thickness and tilt angle are discussed. At last, by experiment, it is found that the simulation results are similar to experiment results which film thickness is increasing with the increasing of rotation speed, decreasing of the applied load. It is proved that the simulation is reliable.

Effect of Retaining Ring Slot Design on Slurry Film Thickness during CMP

This article studied the effect of retaining ring slot designs on the slurry film thickness within the pad-wafer interface during chemical mechanical planarization (CMP). Two retaining rings, with standard and alternative slot designs, were tested. Slurry film thickness within the pad-wafer interface was measured during polishing using dual emission UV-enhanced fluorescence. Results showed that slurry flow rate, pressure, and pad-wafer rotational rate had impacts on the slurry film thickness. Under the same polishing condition, the ring with the alternative slot design generated, on average, 30% thicker slurry film compared with the ring with the standard slot design.

Design and Evaluation of Pad Grooves for Copper CMP

Variations in the chemical mechanisms of copper chemical-mechanical planarization (CMP) can appear due to the effect of pad grooving on net flow under the wafer, pad, wafer, and slurry temperature, and reactants and polish debris concentration. Furthermore, changes in the mechanical abrasion of the passive film might appear due to the effect of pad grooving on slurry film thickness under the wafer, friction force at the pad–wafer interface, pad compressibility, and pad–wafer contact area. The effective transport of slurry in and out of the pad–wafer interface becomes critical particularly for processes in which by-products are detrimental to polishing rates. By combining logarithmic and spiral grooves, paths are created to introduce fresh slurry into, and spent slurry and debris out of, the pad–wafer interface. The experimentally grooved pads were tested and statistically compared to a commercial pad in terms of removal rate (RR), average coefficient of friction, and average pad leading edge temperature. Also a flat (i.e., not grooved) pad was included in this study to evaluate in general the effect of pad grooves in copper CMP. The results indicate that the pad achieving the highest relative values for RR, coefficient of friction , and is the one that combines a negatively directed logarithmic groove with a positively directed spiral groove. This pad results in a 24% increase in RR and a 28% increase in compared to the concentrically grooved pad. To establish the mechanical and chemical contributions to the process, experimental data were then theoretically evaluated. A three-step model in combination with a previously developed flash heating (FH) temperature model was proposed for copper CMP. In all cases, the model root-mean-square (rms) error fell in the range of 322–, while the experimental repeatability error was in the range of 118–. This model presented an expression to characterize the rate of oxide growth and the addition of a third step to characterize the dissolution rate of copper oxide . The relative values of and (mechanical rate constant) as a function of showed that the process was more limited by film removal through mechanical abrasion, especially at low values of . However, as increased this limitation was reduced and there was a transition to a more balanced process.

Advances in Understanding and Control of CMP Performance: Contact-Hydrodynamics at Wafer, Groove, and Asperity Scale

ABSTRACTExamining CMP at any scale, one finds coupled contact mechanics and fluid mechanics. Increasingly sophisticated experimental and computational techniques have revealed aspects of solid-solid interaction and slurry flow at the wafer and groove scale and, more recently, at the texture scale. Successful prediction of CMP performance hinges on identifying universal physics that span these scales. In this paper we first review results of novel asperity-scale experiments that characterize the pad texture both as a solid topography subject to contact deformation and as an equivalent porous medium for slurry flow. These measures reveal that much of the texture volume is inactive as flow space, a feature confirmed quantitatively by computational modeling of flow across a conditioned CMP pad surface built from 3-D microscopy images. For hydrodynamics, the findings establish active fluid volume per unit area as the property that bridges from asperity scale to wafer scale. We then derive a fundamental basis for CMP removal rate prediction based on contact and hydrodynamics, using a Sommerfeld number defined across the groove and texture length scales. The resulting equation, containing a single unknown proportionality constant, demonstrates that the often used product of downforce and table speed tracks removal rate only when the hydrodynamic state affords adequate pad-wafer contact. Departures from the Preston equation attributed in other models to chemically-limited regimes of CMP are explained in the present treatment as changes in hydrodynamic film thickness and contact area—a fact confirmed by direct measurement. Removal rate predictions are discussed for ILD, STI, and copper processes using both conventional and non-Prestonian slurries, including variations in downforce, table speed, temperature, pad properties, and groove design. Finally, the influence of regional pad-wafer hydrodynamics is illustrated by applying the contact-hydrodynamics equation to grooves specially configured to vary the slurry film thickness from wafer center to edge. Local removal rates are well predicted using locally defined values of the groove-texture Sommerfeld number, confirming the generality of the contact-hydrodynamic description at least from wafer to asperity scale. Findings are further discussed in the context of next-generation pad architectures—not only to achieve more effective pad-wafer contact and slurry delivery, but also to favorably decouple contact and fluid mechanics in CMP pad design.

Nano particles’ behavior in non-Newtonian slurry in mechanical process of CMP

Thin fluid film is thought to be formed between the wafer surface and the pad asperity. Hydrodynamic pressure on the surface asperity is periodically generated when particles are passing through it. Fatigue fracture occurs under the effect of periodic pressure, and the fatigue begins from the top to the bottom of the asperity. The removal rate is calculated based on the energy-balance fracture theory. Particle size and its relative velocity are important parameters that affect the polishing effect. Using the multiphase model and the power–law viscosity model of the slurry, particle’s velocity and its distribution in the slurry are numerically calculated. The results indicate that the slurry film thickness needs to be in the same order of the particle size that the particle can generate effective hydrodynamic pressure to remove the asperity materials.

Effects of Disk Design and Kinematics of Conditioners on Process Hydrodynamics during Copper CMP

This study focuses on determining the effect of conditioner disk design, kinematics, and pressure on the slurry distribution under the wafer as measured by the slurry film thickness between the wafer and the pad during actual polishing. Film thicknesses are measured using dual emission UV-enhanced fluorescence, which for thickness measurement requires the slurry to be tagged with two different fluorescent dyes. Results indicate that the wafer is tilted toward the center of the pad and that the extent of wafer tilt is a strong function of conditioning disk pressure. Increasing the oscillation frequency of the conditioner disk or the rotation rate decreases the slurry film thickness and the film thickness increases with slurry flow rate.

Material removal model for chemical–mechanical polishing considering wafer flexibility and edge effects

This paper describes a two-dimensional, multiscale, material removal model for chemical–mechanical planarization that includes: (i) asperity deformation; (ii) bulk pad deformation; (iii) wafer compliance; (iv) carrier film deformation; (v) slurry flow; (vi) material removal by abrasive particles in the slurry. A finite element method is used to establish the relationship between the contact stress and the deformation of an idealized asperity made of a hyperelastic material. The total local stress due to the multitude of asperities is computed using the Greenwood–Williamson approach. The wafer deformation, bulk pad deformation, and slurry film thickness are then evaluated from the estimated contact stresses and hydrodynamic fluid pressures. The material removal rate on the wafer is computed as a function of position on the wafer. The wafer scale material removal rate results show large changes in rate near the wafer’s edges, as often seen in practice, with very uniform removal across most of the wafer surface. The computational algorithm used to calculate the contact stresses, slurry fluid pressures, material removal rates, and the global force and moment balances is summarized.

Measurements of Slurry Film Thickness and Wafer Drag during CMP

Chemical mechanical planarization (CMP) is a process widely used for the manufacture of silicon integrated circuits. In this work, we measured the thickness of the slurry film between the wafer and the pad during polish while simultaneously measuring the frictional drag. All experiments are performed on a 1:2 scale laboratory tabletop rotary polisher with variable pad speed and wafer downforce control. Dual emission laser-induced fluorescence techniques optically measured the slurry film thickness through a dual-camera imaging system. The resulting data are discussed for wafers polished with a 3.1 wt % abrasive concentration slurry solution on Freudenberg’s FX-9 polishing pads. It was found that the degree of surface curvature of the wafer substrate significantly influences the slurry film thickness and wafer drag, and therefore, the polish. The convex wafer shows the expected behavior of increased downforce reduces the slurry film thickness and increases the coefficient of friction. Further, as the pad speeds up, the slurry thickness increases and the friction decreases. The concave wafer shows no change in slurry film thickness and a decrease in the frictional coefficient with increasing downforce. Both the film thickness and frictional coefficient appear to decrease slightly with increasing pad speed. This difference between the two wafer shapes reflects the different fluid mechanics in each case. © 2004 The Electrochemical Society. All rights reserved.