Pad Wear Research Articles

Wear of Polishing Pad and Pattern Optimization of Fixed Abrasive Pad

The polishing pad plays a significant role in the Chemical Mechanical Polishing (CMP) process and its wear influences the surface accuracy of the polished wafer. A new polishing pad wear model is introduced and the law of pad wear along the pad radius is discussed, thus a new FAP with optimized pattern is designed and prepared in order. The flatness of the wafer lapped with a uniform pattern pad and that with an optimized pattern was compared. Results show that the PV value of the latter is lower that of the former.

Treatment of particulates and metals from highway stormwater runoff using zeolite filtration

Highways are stormwater-intensive land uses, since they are impervious and have high pollutant mass emissions from vehicular activity. Vehicle emissions include pollutants such as heavy metals, oil and grease, particulates from sources such as fuels, brake pad wear, tire wear, and litter. The presence of heavy metals in highway stormwater runoff is of concern, as they are very toxic due to enhanced bioavailability, and have the potential not to degrade in the environment. Therefore, this research was carried out to understand the characteristics of metal pollutants in stormwater runoff from highways in Korea and to treat that runoff using zeolite filtration. The filtration facility was constructed on Korea Highway number 251 (Gaeryong I/C). The facility was operated during storms with durations of 0.3–4.8 h, and the influent treatment rate was varied from 3.60 to 17.34 m3/day. The first flush phenomenon for metal pollutants was observed in all of the storm events. The average removal efficiency was determ...

Experimental Analysis of Pad Wear Response Effect on Removal Rate Variations in Tungsten Chemical Mechanical Polishing

We investigated the effects of the pad surface response during polishing and conditioning on the removal rate variation in a tungsten chemical mechanical polishing (CMP) process. We examined the coefficient of friction (COF) to identify the tribology of the pad conditioning. The variation in the removal rate was dependent on the COF during conditioning. We also evaluated the effects of diamond edge degradation of the pad conditioner disk on its cutting ability from the viewpoint of mechanical wear. The results showed that the decline in pad wear rate was caused by a decrease in the cutting ability as the diamond sharp edges rounded off, while the diamond contact area with the pad surface depended little on the diamond abrasive degradation. Furthermore, we demonstrated the usefulness of measuring the height ratio of the asperity called “top surface area (TSA) ratio” as an appropriate topographical parameter to study the dependence of COF during conditioning on the decay of the removal rate. We present a clear correlation between the pad wear rate degradation and the TSA ratio after CMP to elucidate an increase in the conditioning COF related to truncation of the asperity tip by wear and plastic deformation.

CMP pad wear and polish-rate decay modeled by asperity population balance with fluid effect

An important task in chemical–mechanical polishing (CMP) is to determine when the pad should be changed or reconditioned. A model which can predict the pad asperity probability distribution function (PDF) during polishing and conditioning is valuable for this purpose. Previous work has been done without incorporating fluid mechanics into the model in L.J. Borucki, J. Eng. Math. 43 (2002) 105–114, but that will overestimate the pad wear because the fluid reduces the load applied on the individual asperities. This work models the wear of pad asperities and polish-rate decay in CMP by coupling the population balance model with fluid mechanics. Modeling results with and without fluid effect are compared. Polish-rate model results are compared with experimental data in D. Stein et al., J. Electron. Mater. 25 (10) (1996) 1623–1627, and the results agree with experimental results for both cases by using different wear rate coefficients to fit experimental data. A lesser wear rate coefficient must be used to fit Stein’s data for the fluid case compared to the case without fluid. The wear rate of the pad is calculated from the rate of change of the pad–wafer separation distance during polishing because only asperities above this distance will be in contact and worn down and that portion will be piled up at the pad–wafer separation distance on the PDF curve of the pad asperities. The PDF evolution model results with fluid show much less pad wear compared to the case without fluid. Also if fluid is neglected, pad–wafer separation distance will continue to drop until it is zero, while for the fluid case, it will eventually reach a dynamic steady-state with no pad wear indicating that the load is entirely supported by the fluid. Accurate predicting the interface gap (pad wear) is critical for controlling both mechanical and chemical removal rate and within wafer non-uniformity (WIWNU). These results show that fluid is an important factor which needs to be included into the model in predicting the interface gap and surface profile evolution of the pad during polishing and conditioning.

Modeling of Polishing Pad Wear in Chemical Mechanical Polishing

The polishing pad’s wear influences the surface accuracy of the polished wafer. A new polishing pad wear model is established using the idea of Finite Element Analysis (FEA) and the effect of polishing parameters on the wear of polishing pad is discussed.

Distribution of polishing times for a wafer with different patterned polishing pads during CMP and CCMP

During chemical-mechanical polishing (CMP), the polishing pad is placed under a wafer and it completely covers the wafer. Compensating CMP (CCMP) decreases the polishing pad wear and enhances end-point detection (EDP). In CCMP, a polishing pad is placed above the wafer and does not completely cover the wafer. Regardless of CMP or CCMP, there are grooved patterns on the polishing pads. However, on the difference in polishing situations as affected by the polishing pads with different grooved patterns during polishing of wafer, theoretically there was no past reference with related studies. This study analyzes the effects of various pattern designs–concentric circles, grids, spirals and waves–on polishing pads. A numerical analytical model constructed in this study is utilized to analyze and compare the distribution of polishing times, also the polishing pads with different patterns during CMP or CCMP analytic results can function as a qualitative reference for the planarization of processing and a reference for selecting an appropriate pattern design for polishing pads. The analytic method adopts CAD-designed patterns and shapes, which are converted into a binary matrix by image processing. The various profiles and patterns of polishing pads, as well as different polishing paths, are also considered. Problems such as deformation caused by turning the pattern, ineffective polishing and the transformation of shape pixels to a physical length are corrected.

Investigation on Surface Hardening of Polyurethane Pads During Chemical Mechanical Polishing (CMP)

Temperature control to stabilize the microscale contact surface between the pad and wafer, especially to prevent pad surface degradation, plays an important role in chemical mechanical polishing (CMP) processing of sub- 50-nm devices. In this work, we investigated the phenomenon of pad surface hardening for various process temperatures and developed an effective method to minimize changes of the mechanical properties of the pad surface using diamond conditioner. The pad hardening characteristics were measured based on the force–distance (F-D) curve obtained by atomic force microscopy (AFM), and thermogravimetric analysis (TGA). F-D curve data showed that the increase of the elastic modulus with pad usage time at high process temperature was ~1.5 times higher than at low process temperature. Also, TGA of a used polishing pad revealed a link between the endothermic peak intensity at 600°C and pad surface hardening. To prevent surface glazing or hardening throughout the lifetime of a pad at high process temperature, the optimum diamond size was investigated. Pad wear was investigated for various diamond conditioners with diamond grit size ranging from 100 μm to 270 μm. The results of pad surface analysis using scanning electron microscopy (SEM) and three-dimensional optical profiling showed that the 210 μm grit size was best for removing deformed layers, with the pad surface remaining consistent during the lifetime of the pad as verified by TGA and the F-D curve. The results of pad surface analysis are important for the design of conditioners that can produce pads with stable dynamic mechanical properties and prolonged lifetime at high process temperature.

Analyses of Diamond Disk Substrate Wear and Diamond Microwear in Copper Chemical Mechanical Planarization Process

Diamond disk substrate wear and diamond microwear in the copper chemical mechanical planarization process were investigated in this study. Three types of disks (D1, D2, and D3) made by three different manufacturers were analyzed. For each type of disk, 24 h static etch tests were performed with Fujimi PL-7103 and Cabot Microelectronics Corporation iCue 600Y75 slurries at 25 and . Scanning electron microscopy (SEM) analysis showed that there was no appreciable microwear on the diamond after the static etch tests for all three types of disks. Disks D1 and D3 showed no appreciable corrosion on the diamond disk substrate for both slurries at both temperatures. In comparison, disk D2 showed apparent surface corrosion using the Fujimi PL-7103 slurry at 25 and and the Cabot Microelectronics Corporation iCue 600Y75 slurry at . Inductively coupled plasma-mass spectroscopy (ICPMS) analysis was performed before and after the static etch tests to investigate metal concentration increases in the slurry due to diamond disk substrate corrosion. The ICPMS analysis was consistent with the SEM images, showing a significant Ni concentration increase in the slurry for disk D2 with the Fujimi PL-7103 slurry at 25 and and the Cabot Microelectronics Corporation iCue 600Y75 slurry at . In addition to the above static etch tests, 24 h wear tests were performed on each type of diamond disks with Fujimi PL-7103 and Cabot Microelectronics Corporation iCue 600Y75 slurries at two different platen temperatures (25 and ). SEM analysis was performed on selected aggressive and inactive diamonds as well as on the surrounding disk substrate before and after the wear tests. SEM images showed that there was microwear on the cutting edges of the aggressive diamonds for disks D1 and D3 with both slurries at 25 and . For disk D2, there was microwear on the cutting edges of the aggressive diamond with the Fujimi PL-7103 slurry at and with the Cabot Microelectronics Corporation iCue 600Y75 slurry at 25 and , and the aggressive diamond broke off from the disk substrate with the Fujimi PL-7103 slurry at . The SEM images also showed that there was no microwear on the inactive diamond for all three types of disks with both slurries at 25 and , confirming that the inactive diamonds did not participate in regenerating pad asperities during conditioning. The pad thickness profile was measured after the wear tests, and the effect of platen temperature on pad wear rate was investigated.

Assessment of methods for collecting fallout brake pad wear debris for environmental analysis

Three methods for collecting or generating fallout brake pad wear debris for environmental analysis were assessed: collection from wheels or hubs of automobiles (natural), generation from an inexpensive sanding process (sanded), and collection of fallout debris from dynamometer tests using the Los Angeles City Traffic protocol (LACT). Brake wear debris was collected from four automobiles with semimetalic brake pads and analyzed for physicochemical properties. For automobiles where all three types of debris were collected, bulk copper mass fractions ranged from 22–23% in sanded particles and 24–27% in LACTparticles, but were reduced to 1–6% in natural debris. The smaller copper mass fraction in natural debris was attributed to contamination with road dust, which was found to comprise 37–97% of the natural particles. The ratio of surface to bulk copper mass fraction was up to five times larger for natural than LACT debris, suggesting that copper may leach into stormwater faster and to a greater extent for natural particles. While the LACT method appears best for collecting only fallout particles, significant differences in copper distributions in the natural and LACT debris suggests that metal distribution in LACT debris may not be representative of fallout particles generated under actual driving conditions, where airborne road dust may play a role. Although dynamometer tests have been the preferred method for generating debris for assessment of metal dissolution from brake particles, data from this study indicate that such samples may result in biased estimates of metal leaching.

Design, Characteristics and Performance of Diamond Pad Conditioners

AbstractA wide range of diamond pad conditioner (disk) designs have been characterized and key performance metrics have been collected. Relationships between design characteristics including diamond size and shape, spatial density, and tip height distribution and polishing pad wear rates and pad surface textures have been established for a variety of pads.Estimation of the depth-of-penetration of working diamonds, from used disk analyses, allows meaningful topographic assessments of alternative conditioner designs and predictions of relative performance. An example of an improved conditioner that illustrates this design methodology is given.Conditioner aggressiveness and its decay in various slurries have been measured to assess disk lifetime in Chemical Mechanical Planarization (CMP) processes environments. Key factors affecting disk lifetime are discussed and an improved-lifetime conditioner for use in aggressive slurries will be reviewed.

Slurry-Induced Pad Wear Rate in Chemical Mechanical Planarization

In this study, the extent of the pad wear rate during the shallow trench isolation chemical mechanical planarization process was investigated for several combinations of the type of abrasive particles (i.e., colloidal and fumed silica), abrasive content, and abrasive concentration. Results showed a relation between pad wear rate and abrasive concentration for both fumed and colloidal slurries. Results indicated that the pad wear rate using the colloidal silica slurry was higher by approximately 42 and 6% at 3 and 25 wt % silica, respectively. Under the same abrasive content, pad wear rate for fumed slurry was 23% higher compared to colloidal slurry.

Optimization of Double-Sided Polishing Conditions to Achieve High Flatness: Consideration of Relative Motion Direction

Silicon (Si) wafers are the most commonly used substrates of semiconductor devices. The device design rule is miniaturization, and the device chip size is being increased to improve device integration, requiring that Si wafers be manufactured with higher flatness and larger diameters. The polishing used as a finishing process of Si wafers, however, has a serious problem; it is very difficult to set the appropriate conditions for polishing the Si wafer while wearing the polishing pad stably to high flatness. In our previous work, a method of optimizing polishing conditions based on kinematical analysis was proposed to achieve high flatness of the wafer and pad. The method, however, did not consider the effect of the relative motion direction between the wafer and the pads as an important factor in polishing behaviors. Therefore, in this study, an optimization method considering the relative motion direction is newly developed, and a series of double-sided polishings of silicon wafers shows that the wafer flatness calculated by the method corresponds well with that in the polishing experiments. Furthermore, to make the distribution of pad wear more uniform, the optimization of polishing conditions, including the wafer carrier specifications, is conducted, and the feasibility is clarified.

Airborne wear particles from passenger car disc brakes: A comparison of measurements from field tests, a disc brake assembly test stand, and a pin-on-disc machine

Most modern passenger cars have disc brakes on the front wheels. Unlike drum brakes, disc brakes are not sealed off from the ambient air. During braking, both the rotor and the pads wear, and this wear process generates particles that may become airborne. In field tests it is difficult to distinguish these particles from others in the environment. It is thus preferable to conduct tests using laboratory test stands where the cleanness of the surrounding air can be controlled. However, the validity of results from these test stands should be verified by comparison with field tests. This article presents a comparison of the number and volume distributions of airborne wear particles as measured online in field tests, in a disc brake assembly test stand, and in a pin-on-disc machine. In all cases, grey cast iron rotors and low metallic pads were tested. A promising correlation between the three different test methods is shown. The number- and volume-weighted mean particle diameter for all test methods is about 0.4 and 2-3 μm, respectively.

Advances in SAGD Drilling in Western Canada Using Innovative Bit Technology

Abstract Western Canada's massive oil sands are being exploited at deeper levels by steam-assisted gravity drainage (SAGD). Carefully geosteered parallel pairs of large diameter horizontal wellbores are drilled for concurrent steam injection into the upper well and oil production from the lower. The bitumen cemented sands of the McMurray Formation have challenged both operational and engineering personnel responsible for drilling these difficult wells. Bits of all designs have required custom features to combat the highly abrasive sands with sloughing and hole cleaning problems, while delivering an optimally steered well path through tight reservoir tolerances. A cross-functional team of operator engineers and drilling personnel, together with field engineers, bit designers and office personnel from the bit manufacturer, joined together to analyze the challenges and fast track fit-for-purpose solutions for all SAGD projects in Alberta. Steel tooth roller cone bits require extensive extra thick layers of hard facing to resist tooth wear. Sand washing through the cones causes high levels of erosion which is hindered by extensive hard facing. The gauge areas of the bits are rotated and/or slid through a cuttings bed of coarse abrasive sand particles, resulting in rounded gauge (RG) and shirttail damage (SD), which again require tungsten carbide and hard facing wear pads and shirttail protection. Elastomer or metal-faced seals have been enhanced to prevent sand encroachment on the bearings during motor drilling. Polycrystalline Diamond Compact (PDC) bits were also faced with significant erosional problems drilling horizontally, which have required special wear pads and updrill features to ensure hole gauge, steer ability and the ability to back ream through the cuttings bed. Depth-of-cut (DOC) features for build rates of 9 degrees per 30 m, ensure steer ability when linked to wear-resistant cutters, especially when placed on the gauge. Spiral gauge features work like an auger to clean sand away from the bit, while customized gauge lengths ensure a match between bit and motor for optimized steerability. Collectively, these PDC and steel tooth bits have become the enabling technology for drilling and completing SAGD wells, especially now that bits can be re-run on future wells, further reducing cost per metre. Introduction Steam-assisted gravity drainage (SAGD) is the most popular enhanced oil recovery technology being adopted by Canadian heavy oil producers. It is very effective in mobilizing bitumen and achieving high recovery from thick, high permeability reservoirs (low gravity <10 °API). An estimated 174 billion barrels of oil in the Athabasca, Cold Lake and Peace River deposits are potentially recoverable with the present technology(1–3). However, with technological improvements, Canada oil sands reserves could be close to 315 billion barrels. The biggest deposit is the Athabasca, which is thicker and shallower; the Cold Lake deposit is thinner and deeper. Surface mining is only feasible for recovering 10% of the oil sands deposits between 70 and 75 m of surface. SAGD is the current method of choice to access resources too deep to mine and will recover the potential 90% of the remaining oil sands deposits with cyclic steam stimulation (CSS).

Sex differences in the use of absorbent (incontinence) pads in independently living elderly people: do men receive less care?

To examine the use and satisfaction of absorbent (incontinence) pads in independently living men and women aged 60 and above with urinary incontinence (UI). The subjects participated in a large-scale study about the prevalence of UI. All the independently living patients in nine family practices aged 60 or above with uncomplicated UI, who were willing to participate in the study were interviewed at home. In total, 56 men and 314 women were interviewed. Fifteen per cent of the men and 87% of the women with UI used pads. All men and nine out of 10 women used different kinds of absorbent pads, and half of the men and women used pads specifically made for UI. Only half of the men and two-third of the women felt satisfied with the pads. The reasons for not being satisfied were: leakage, irritation and discomfort. The use of pads, the use at daytime and the type of pads were correlated to the severity of incontinence. Only one out of nine men with UI uses pads in contrast with four out of five women. Only half of them wear pads specifically made for UI. Men are less satisfied about the pads compared with women.

A Matching Game for CMP Pads and Conditioners

The relationship between a pad and a conditioner may be the most critical among all "consumables" in a CMP process. The effect of a pad conditioner on pad can be both short-term (instant) and long-term (stability). This paper compares the instantaneous effect of different conditioners on removal rate of oxide, tungsten, and copper CMP. The impact of conditioners in removal profile in copper polishing and rate stability (long-term) in oxide polishing are also presented. The pad wear rate by conditioners of different aggressiveness on Epic® D100 vs. conventional hard pad is compared and the benefits and risks of adopting a more aggressive conditioning on Epic® D100 pad vs. a less aggressive conditioning on conventional pad is discussed.

Study of Conditioner Abrasives in Chemical Mechanical Planarization

AbstractChemical Mechanical Planarization (CMP) has emerged as the central technology for polishing wafers in the semiconductor manufacturing industry to make integrated multi-level devices. Both chemical and mechanical processes work simultaneously to achieve local and global planarization. Although extensive research has been carried out to understand the various factors affecting the CMP process, many aspects remain unaddressed. One such aspect of CMP is the role of abrasives in the process of conditioning. Abrasives play an important role during conditioning to regenerate the clogged polishing pads. This research is focused on the study of abrasives in the process of conditioning with a focus on the size of abrasives. With diamond being widely used as an abrasive for conditioning the polishing pad, five different sizes of diamonds ranging from 0.25μm to 100μm were selected to condition the commercially available IC 1000 polishing pad. Properties like pad roughness and pad wear were measured to understand the effect of the abrasive size on the pad morphology and pad topography. In-situ ‘coefficient of friction’ was also monitored on the CETR bench top tester. The final impact was seen in the form of surface defects on the polished copper wafers using optical microscopy.

Watershed Modeling of Copper Runoff to San Francisco Bay from Brake Pad Wear Debris

This watershed modeling effort was conducted as part of a larger study by the Brake Pad Partnership (BPP) that examines the potential impact of copper from brake pad wear debris (BPWD) released to the environment in the San Francisco Bay (SF) Region. The watershed model provides runoff loads to a Bay modeling effort to assess resulting concentrations in SF Bay. The U.S. EPA's Hydrological Simulation Program-FORTRAN (HSPF) model was set up for each of the 22 BPP modeled sub-watersheds that drain to the SF Bay. HSPF model runs were performed for each sub-watershed for the entire time period of water year 1981 through water year 2005. Model results were processed for flow, sediment, and copper loads; and annual and mean annual loads were tabulated. Uncertainty in both non-brake and brake release estimates was assessed by representing alternative scenarios of source loadings. Three cases of copper release scenarios were modeled -- with high, low, and median releases. Each of these three scenarios was modeled with and without releases from brake pads in order to determine the relative contribution of copper from brake pads in runoff to the Bay. The total anthropogenic contribution from brake pad wear debris towards total loads of copper to the Bay for the median estimate case varies from 15% to 57%. As expected, the brake pad contribution is much lower for the rural sub-watersheds than for the heavily urbanized subwatersheds, reflecting alternative human activity and traffic levels. Additional scenario runs were performed to assess the impacts of copper lost through the normal buildup/washoff attenuation algorithms and the time period for copper loads to return to background levels if all sources were eliminated. Scenario runs also considered impacts of climate changes such as wet and dry periods, and the relative impacts on loadings.

브레이크 스퀼 해석에서 패드 마모의 영향에 관한 연구

This paper studies the effect of pad at initial stage and wear during braking on the dynamic contact pressure distribution. Wear is influenced by variable factor (contact pressure, sliding speed, radius, temperature) during dynamic braking and variation in contact pressure distribution. Many researchers have conducted complex eigenvalue analysis considering wear characteristic with Lim and Ashby wear map. The conventional analysis method is assumed the pad has smooth and flat surfaces. The purpose of this paper is to validate that wear rate induced by braking is considered for the precise squeal prediction. After obtaining pad wear from experiment, it is incorporated with FE model of brake system. Finally, the comparisons in fugitive nature of squeal will be carried out between the complex eigenvalue analysis and noise dynamometer experiment.

The Role of Membranous Urethral Afferent Autonomic Innervation in the Continence Mechanism After Nerve Sparing Radical Prostatectomy: A Clinical and Prospective Study

We evaluated the somatic and autonomic innervation of the pelvic floor and rhabdosphincter before and after nerve sparing radical retropubic prostatectomy using neurophysiological tests and correlated findings with clinical parameters and urinary continence. From February 2003 to October 2005, 46 patients with prostate cancer were enrolled in a controlled, prospective study. Patients were evaluated before and 6 months after nerve sparing radical retropubic prostatectomy using the UCLA-PCI urinary function domain and neurophysiological tests, including somatosensory evoked potential, and the pudendo-urethral, pudendo-anal and urethro-anal reflexes. Clinical parameters and urinary continence were correlated with afferent and efferent innervation of the membranous urethra and pelvic floor. We used strict criteria to define urinary continence as complete dryness with no leakage at all, not requiring any pads or diapers and with a UCLA-PCI score of 500. Patients with a sporadic drop of leakage, requiring up to 1 pad daily, were defined as having occasional urinary leakage. Two patients were excluded from study due to urethral stricture postoperatively. We evaluated 44 patients within 6 months after surgery. The pudendo-anal and pudendo-urethral reflexes were unchanged postoperatively (p = 0.93 and 0.09, respectively), demonstrating that afferent and efferent pudendal innervation to this pelvic region was not affected by the surgery. Autonomic afferent denervation of the membranous urethral mucosa was found in 34 patients (77.3%), as demonstrated by a postoperative increase in the urethro-anal reflex sensory threshold and urethro-anal reflex latency (p <0.001 and 0.0007, respectively). Six of the 44 patients used pads. One patient with more severe leakage required 3 pads daily and 23 showed urinary leakage, including 5 who needed 1 pad per day and 18 who did not wear pads. Afferent autonomic denervation at the membranous urethral mucosa was found in 91.7% of patients with urinary leakage. Of 10 patients with preserved urethro-anal reflex latency 80% were continent. Sensory and motor pudendal innervation to this specific pelvic region did not change after nerve sparing radical retropubic prostatectomy. Significant autonomic afferent denervation of the membranous urethral mucosa was present in most patients postoperatively. Impaired membranous urethral sensitivity seemed to be associated with urinary incontinence, particularly in patients with occasional urinary leakage. Damage to the afferent autonomic innervation may have a role in the continence mechanism after nerve sparing radical retropubic prostatectomy.