Polyurethane Pad Research Articles

Quantitative analysis of physical and chemical changes in CMP polyurethane pad surfaces

Polishing pads play a key role in chemical–mechanical polishing (CMP), which has been recognized as a critical step to improve the topography of wafers for semiconductor fabrication. In service, chemical and mechanical changes in a polishing pad are expected to have a significant impact on the pad's CMP performance. Scanning electron microscopy (SEM) showed changes in the pore geometry on the CMP pad surface after use. The average height of the roughness between the pores of the polishing pad was measured using white light interferometry (WLI). Attenuated total reflectance Fourier Transform Infrared (ATR/FTIR) method was found to provide a novel opportunity for the nondestructive surface analysis of pad materials. Results of an ATR/IR microscopy study that evaluated the extent of chemical degradation of pad materials both before and after polishing cycle are presented. The infrared results identified that the changes in chemical state of used pad materials, specifically for CO and COC infrared stretching bands, were a surface phenomenon.

回転スピン制御法による鋼球の多段階研磨 発泡ポリウレタンパッドによる研磨

Spin angle controlled ball lapping method developed recently, is to have an excellent performance to lap the ball, in which V-groove lapping plates are separated into two parts and three plates are able to rotate independently. Present paper focuses on polishing characteristics of a steel ball using vesicant polyurethane pad. Experiments are conducted using an aluminum oxide grain ranging from 5.5 to 0.3 μ m in size. It is found that the surface roughness of steel ball polished by vesicant polyurethane pad is smaller than that of the cast iron lap. Experiments show that the grain size degradation is very effective for decreasing the surface roughness of ball. It describes that spin angle θ influence on both of the surface roughness and stock removal of the ball.

Comparison and Evolution of Copper CMP Consumable Technology

AbstractIntensive investigation of copper CMP over the past decade has revealed that consumable technology is of critical importance. There are several reasons for this, but all are ultimately due to the chemical and material properties of copper and associated barrier layers. Moreover, in comparison to conventional dielectric polishing, copper CMP (and, perhaps, metal CMP in general) is of a much more chemical nature. This is a consequence of the fact that metal removal generally requires an oxidation-reduction mechanism while, in contrast, dielectric removal typically requires only simple hydrolysis. As any chemist knows, oxidation-reduction reactions are often notoriously hard to control and easily upset by contaminants. Of course, contaminants can be intentionally added to the chemistry for beneficial purposes in which case they become known as “proprietary additives”.In addition, to the removal chemistry, abrasive and pad technology has also undergone considerable evolution. Indeed, free abrasive, fixed abrasive, and abrasiveless technologies have all been developed. In the case of fixed abrasive polishing, this has required modification of the pads as well, however conventional and abrasiveless polishing can be carried out with conventional polyurethane pads. This picture is further complicated by the various available hardware configurations and the use of multiplaten processes.

Effect of CMP Pad Exposure to Aqueous Media on the Pad Properties. Part 1. Dynamic Mechanical and Modulated DSC Analysis

AbstractSoaking of polyurethane-based CMP pad in oxide slurry, de-ionized water, and pH buffer solution, and its effect on thermal and mechanical properties of the pads was studied using Dynamic Mechanical Analysis and Modulated Differential Scanning Calorimetry. Pad softening due to soaking was established, and softening mechanisms are discussed. Diffusion of the aqueous medias to polyurethane pad was described using Fickian diffusion model.

The bending of an aluminum structural frame with a rubber pad

In this study, research for process design in the bending of a structural frame of AA6061-T6 with a rubber pad was conducted. In this process, the conventional lower die made of metal is replaced with a polyurethane pad, resulting in high flexibility during bending. Vulcanized polyurethane rubber with a shore A hardness of 60 was used for the pad. Experiments on a newly developed bending machine were carried out by controlling the stroke of the roller and the horizontal movement of the roller pad lower die. From this, the relation between the roller path and the geometry of the materials bent was obtained for the process design of producing a roof-rail part of a passenger car, the experimental result being compared with the target profile. For more accurate process design, it is required to control the roller path interactively. Based on experience in developing the prototype bending machine, it is construed that a fully automated bending system with a rubber pad to produce various light-weight components for automotive body frames can be successfully developed.

Effect of Tribological Properties of Undoped and Florine-Doped Silicon Di-Oxide Fims on Chemical Mechanical Planarization Process

AbstractChemical mechanical planarization (CMP) occurs at an atomic level at the slurry/wafer interface and hence slurries and the interaction of the films and polishing pads play a critical role in the successful implementation of this process. Understanding the tribological properties of a dielectric layer in the CMP process is critical for successful evaluation and implementation of the materials. In this paper, we present the effect of tribological properties of undoped and florine doped silicon dioxide films on their CMP process. A micro-CMP tester was used to study the fundamental aspects of CMP process. We have studied the CMP process of oxides on polyurethane pads (IC1000-B4/SubaIV) with colloidal silica slurry at different conditions. The coefficient of friction (COF) and acoustic emission signal was monitored during process. The COF was measured during the process and was found to varies differently for different samples and with down force and platen roatation. The effects of machine's parameters on the polishing performance and correlation of physical phenomena with the process has been discussed.

Polyurethane Pad Degradation and Wear Due to Tungsten and Oxide CMP

ABSTRACTPolyurethane polishing pads are commonly used for chemical-mechanical polishing (CMP) of semiconductor wafers. Structural, chemical, and mechanical property changes of the polishing pads due to CMP are examined. Tungsten and oxide film layers are polished from the wafer surface using the polishing pad and abrasive slurry system. The polishing pad surface is flattened with polishing, and hence, reducing the effective area for slurry transport. The abrasive is used for abrading off the film from the surface. W, Al, I, and K accumulate in the polishing pad after tungsten CMP and Si accumulates after oxide CMP. Material accumulates in the pad pores and grooves. Electron Microprobe X-ray Analysis and Wavelength Dispersive Spectrometry (WDS) were used to examine the changes across the thickness of the pad. Fourier Transform Infrared Spectroscopy (FTIR) was used to determine the changes to the polyurethane isocyanate group. The reduction in the isocyanate group and increase in the hydroxyl group after tungsten CMP indicates that a hydrolysis reaction of the isocyanate to form carboxylic acid occurs.

426 回転スピン制御法によるパッドを利用した鋼球の多段階研磨(OS12 研削・砥粒加工)

426 回転スピン制御法によるパッドを利用した鋼球の多段階研磨(OS12 研削・砥粒加工)

PERFORMANCE CHARACTERIZATION OF CERIUM OXIDE ABRASIVES FOR CHEMICAL-MECHANICAL POLISHING OF GLASS

Investigation of the nature of chemomechanical polishing (CMP) for glass requires an in-depth knowledge of the influences of abrasive physical properties and slurry chemistry. In the present work, eight cerium oxide abrasives were used to polish fused silica on a polyurethane pad. Results from pre-polished surfaces re-polished in aqueous and non-aqueous suspensions and from corrosion testing of solutions recovered from abrasive suspensions were used to discern chemical, chemomechanical, and mechanical equivalents for each abrasive. Performance indices (i.eabrasive quality values) were generated from the equivalents and related to conventional polishing of lapped surfaces. Optimally performing abrasives were found to require a balance of equivalents (i.eset ratio) as dictated by inherent chemical activities, heat treatments, and milling. From solution chemistry testing, particle/workpiece attraction via surface charge was found to increase the chemomechanical effect. The CMP mechanism is concluded to be a chemical reaction at the particle/workpiece interface promoted primarily by mechanical interactions such as abrasion, with both cerium oxide and rare-earth oxyfluoride constituents promoting the reaction.

423 ポリシングによるパッドの減耗評価

423 ポリシングによるパッドの減耗評価

Mechanism for Subambient Interfacial Pressures While Polishing With Liquids

This paper reports the results of a model for predicting the development of subambient pressures during the polishing of flat hard substrates by sliding against a compliant pad in the presence of a slurry (liquid). This work is an extension of our prior experimental work on the polishing of single crystal silicon wafers with polyurethane pads and high pH slurries containing silica particles. Subambient pressures have important implications in the polishing rate and uniformity of silicon and, therefore, in the manufacture of large-scale integrated circuits. The subambient pressure is the result of pad asperity compression at the wafer leading edge followed by elastic reexpansion beneath the wafer due to the nonuniform wafer/pad contact stress. Liquid is expelled from interasperity voids where high leading edge contact stress causes asperities to be compressed. Lower contact stress behind the leading edge causes asperity reexpansion leading to recreation of interasperity voids and subambient liquid pressures. A Poiseuille like in-flow of liquid from the sides of the wafer limits the value of the subambient pressure. Numerical simulations predict subambient pressures as a function of liquid viscosity and relative velocity of the pad and wafer and the pad and wafer mechanics which follow the same trend as the experimental data. [S0742-4787(00)01702-1]

Polishing Parameter Dependencies and Surface Oxidation of Chemical Mechanical Polishing of Al Thin Films

We describe chemical mechanical polishing (CMP) of blanket and patterned aluminum films employing a polyurethane pad and a slurry based on alumina particles as the abrasive and hydrogen peroxide as the oxidizer. The experiments were conducted at pressures from 19 to 47 kPa and at linear velocities from 26 to 48 m/min, and yielded Al removal rates from 80 to 250 nm/min. The oxidant concentration has a weak effect on the removal rate of Al. Polishing selectivities of Al to silicon dioxide as high as 130:1 were obtained with the maximum selectivities being observed at regions of low pressures and low velocities. The Preston equation fails to describe the dependence of the removal rate on pressure and velocity, and a power function is proposed instead. X‐ray photoelectron spectroscopy was used to examine the surface of Al before and immediately after CMP. These experiments provided information on the thickness of the oxidized Al layer. We found that larger removal rates correlated with a smaller Al‐oxide thickness. We conclude from this that Al CMP proceeds by oxidation of the Al and subsequent Al‐oxide removal. © 1999 The Electrochemical Society. All rights reserved.

Interfacial Pressure Measurements at Chemical Mechanical Polishing Interfaces

We have found that the entrainment of a slurry between a silicon surface and a polyurethane pad will cause the generation of subambient pressure at that interface. These pressures cause the silicon to be further impressed into the pad. We have measured these pressures and this paper reports on the pressure distribution maps over an area beneath a 100mm diameter silicon wafer. The pressures are generally not uniform. The leading 2/3 of the wafer has subambient pressures of the order of 50kPa and the trailing 1/3 of the wafer has positive pressures of approximately 10kPa. The reasons for the subambient pressures is related to the dynamics of the compression of pad asperities, the boundary effects of the silicon edge, the rebound of the asperities, and re-infiltration of the slurry.

単結晶Ｓｉレンズの非球面創成研磨に関する研究

Aspherical lenses of single crystal silicon (Si) are used for the scope and the camera of infrared wavelength, because the very large refractive index of the material leads to substantial reflection loss. These aspherical lenses of infrared wavelength materials were manufactured by diamond cutting. But the single crystal silicon is a hard and brittle material, it is difficult to obtain a mirror surface without a micro crack when the lens diameter is large. In this case, aspherical polishing has to be applied after diamond cutting in order to generate an aspherical surface most precisely. In this study, a computer controlled polishing system using a small rotating polisher was developed for precision finishing of a large size of aspherical surface after diamond cutting. The characteristics of this polishing system are, as follows: (1) A disk shape of forming polyurethane pad was used as the polishing tool, and its rotating axis was controlled to be always normal at the machining point of the workpiece surface. (2) The polishing load was applied from the normal direction of the machining point and controlled to be constant. In the aspherical polishing tests, spherical surface of diamond turned single crystal silicon (111) was polished to generate an aspherical shape. As a polishing abrasive, colloidal silica was used. As a result, a form accuracy of about 0.2 μm P-V (±0.1 μm) and a surface roughness of less than 0.02 μm Rmax were obtained.

High-precision sheet-metal workpieces manufactured by flexible-die forming using a visco-plastic pressure-carrying medium

The new technology of sheet-metal flexible-die forming (FDF) using a special visco-plastic pressure-carrying medium (VPCM) has a lot of advantages compared with conventional FDF which uses pressure-carrying media such as liquid, gas, or a rubber or polyurethane pad. The advantages can be illustrated in the manufacturing of three high-precision hemispherical workpieces, these hemispherical workpieces being assembled together and used in a special machine. Because conventional sheet-metal forming technology and conventional FDF technology do not meet the requirements, an exploratory attempt is made to manufacture these hemispherical workpieces by the new FDF using the VPCM. The experimental results show that the workpieces can be manufactured successfully by the new FDF technology, the quality of the products meeting their technological requirements. In this paper, the forming process has been specified and the die structure designed in compliance with the features of the workpieces and the new FDF technology. The experimental results indicate that it is important to control the process parameters. Further, the variation of the drawing force, blank-holding force and VPCM pressure in the medium container with the stroke are given. On the basis of the experimental results, empirical equations for the VPCM pressure in the container are given. Both qualitative and quantitative analysis has been undertaken in respect of the quality of the product.

A new technology of sheet-metal flexible-die forming using a viscoplastic pressure-carrying medium

The conventional pressure-carrying media of sheet-metal forming are solid materials (a rubber or polyurethane pad), liquid (oil and water) and gas (pressured air and expanding air). The various flexible-die forming methods using the above pressure-carrying media have a lot of different characteristics and have promoted the development of sheet metal forming technology. There are, however, a lot of disadvantages in using these pressure-carrying media. In order to explore a new pressure-carrying medium, numerous experiments have been undertaken, as a result of which a new type of pressure-carrying medium called a viscoplastic pressure-carrying medium (VPCM) has been synthesized. In this paper, a new kind of flexible-die forming technology using VPCM has been put forward and used to manufacture many different workpieces. The experimental results have shown that this kind of technology has a lot of advantages, such as a small drawing coefficient, good surface fineness, high dimensional-accuracy, and a simple and a general-service die structure. Moreover, This technology can also be used to manufacture complicated workpieces with a large degree of deformation or substantial local deformation. According to the practical uses of this technology, three sets of die are described also in this paper.

Seat Angles and Support

To the Editor: The article by Shields and Cook (November 1988) comparing the effects of lumbar support and seat angles on buttock pressure was nicely done and appropriately demonstrated those effects. My own investigations into seat design to decrease pressure on the ischial tuberosities have led me to the use of a cushion (usually a high-density polyurethane pad about 14 to 16 in long × 8 to 9 in wide × 1 to 1.5 in high), which is placed across the front part of the seat so that the ischial tuberosities rest just off the posterior aspect of the cushion. This shifts the concentrated pressure from under the ischial tuberosities and distributes it over a broader area under the upper thighs. Skin shear is decreased, and the pelvis is anchored posteriorly in the chair, making the backrest more effective. [ ARTICLE][1] [1]: /lookup/volpage/68/1682?iss=11

Influence of the dimensional characteristics of polyurethane foam on high rate anaerobic digestion of piggery manure

Completely mixed anaerobic reactors containing ca 10 % of their working volume as polyurethane (PUR) foam, can digest heterogenous slurries such as pig manure in a stable way at short hydraulic retention times of the order of 6.0 to 7.5 day. The influence of pore size and pad size of the PUR foam on the process was investigated. The PUR foam with the smallest pore size investigated (i.e. 45 pores per inch) gave the best biogas yield and biogas production rate. Pad size seemed to be of minor importance, having no effect on the performance of the digesters within the range examined (1 to 3.6 cm rib length). Apparently, diffusion of fatty acids into the PUR pads appeared not to be rate limiting under the lab scale reactor conditions examined.

Conditions for Strict Autotrophic Culture of Tobacco Callus

Organic gelling agents such as agar and agarose provide a heterotrophic substrate for growth of illuminated tobacco callus. When green cells are incubated in CO(2)-free air on a medium lacking sucrose but solidified with 1% agar, an increase in relative dry weight is sustained through two passages. Similar results with different inoculum sources, and with three brands of agar and two forms of agarose, suggest this is a general phenomenon. A fully autotrophic culture system was developed employing polyurethane pads to support cells in a liquid medium lacking sucrose. Growth was negligible in two passages in CO(2)-free air, and increased with each added increment in CO(2) concentration.

High rate anaerobic digestion of piggery manure with polyurethane sponges as support material

The use of polyurethane foam sponges to colonize methanogenic associations for the digestion of piggery manure has been investigated. Fermentors containing polyurethane pads as colonization matrix reached a biogas production rate of ca. 2.0 litres per litre reactor per day (30–33°C), hydraulic retention time 7.5 daysl and a biogas yield of 16 litres per litre piggery manure (7–9% TS). Corresponding control fermentors containing no pads reached a gas production rate of 1.3 litres per litre reactor per day and only about 10 litres biogas per litre piggery manure.