Diamond Pad Conditioners with Oriented Polycrystalline Diamond Cubes

Chemical mechanical polishing (CMP) has become a critical planarization technique in the manufacture of advanced integrated circuit devices. It can effectively remove the topography of thin film on wafer, and achieves the good planarization either in local or global region, and also the polished object will have the excellent surface quality. Recently, new materials and architectures have been introduced in the manufacturing process of IC production, so some consumables still require further study and development, mainly due to the stricter requirements. In this dissertation, the improvement in CMP performance by various pad conditioner designs and fixed nanodiamond pad was investigated experimentally. The main consumables under research, which included the polishing pad and the pad conditioner, in CMP performance were evaluated, and the polishing planarization was also analyzed and improved. The fixed nanodiamond pad was the developed consumable, and through a series of experiments in silicon CMP to obtain the proper pad design and verify the pad’s validity. In the comparison of the performance of the experimental fixed nanodiamond pad, several commercial slurries were adopted. In citing the findings from the experimental results, the value and practicality of this study was discussed. The surface roughness and thickness of the polishing pad influenced the material removal rate directly, and the uniformity of both the surface roughness and thickness of the polishing pad were significant factors of the with-in wafer non-uniformity in CMP process. The compressibility and the friction force could be used to evaluate the polishing pad. Using a corrective conditioning profile, the non-uniformity of material removal rate was significantly improved, and also the service time of the polishing pad was lengthened. The design of pad conditioner was critical as it determined the efficiency of the grooving action. The pad conditioner chose the polycrystalline diamond as its substrate, which could increase the wear resistance. The diamond cutting tips on pad conditioner had the same size, shape, and protrusion height, which was beneficial for the dressing behavior and stability. The effect of various fixed abrasive pad designs on polishing characteristics during silicon wafer polishing was investigated. Due to the different manufacturing method for these fixed nanodiamond pads, the abilities of controlling the nanodiamond particles were different. Consequently, the surface roughness of the polished silicon wafer was remarkably improved by the fixed nanodiamond pad, and result also revealed that the pad hardness was a key factor in keeping the abrasives effective in the pad-wafer interface. In comparison with the performance of slurry process in silicon CMP, although the fixed nanodiamond pad process had a relatively low polishing efficiency that depended simply on the mechanical abrasion. For the same reason, a relatively thick damaged layer was formed in the polished silicon subsurface, as the fixed nanodiamond pad was used. However, it was comparable with the slurry process in terms of surface topography of polished silicon wafer, due to its extremely small and nearly spherical particles.

This paper investigating a revolutionary design of pad conditioners is based on carving a structure out of sintered polycrystalline diamond (PCD) matrix. The PCD dresser is manufactured by wire electro discharge machining to form cutting pyramids of a specific size with a designed shape. The dressing characteristics of pad surface textures are studied by comparison with conventional diamond pad conditioner. Experimental results indicate that the PCD dresser can dress asperities of the pad more uniformly than the conventional diamond dresser due to PCD dresser having identically shaped tip and the same height diamond. In addition, the cutting rate of PCD dresser for IC1000 pad not only is reduced by about 30% and also it can dress pad more effectively than conventional diamond dresser.

Kinik Company pioneered diamond pad conditioners protected by DLC barrier (DiaShield® Coating) back in 1999 (Sung & Lin, US Patent 6,368,198) and there has been no follower since then. Kinik's offered two varieties of DiaShield® Coatings: ultrahard tetrahedral amorphous carbon and superhard hydrogenated DLC. Kink also evaluated Cermet Composite Coating (CCC or C3, patent pending). C3 is unique that the coating composition grades from a metallic (e.g. stainless steel) under layer to a ceramic (e.g. Al2O3 or SiC) exterior. The metallic under layer can form metallurgical bond with metallic matrix on the diamond pad conditioner. The ceramic exterior is both wear and corrosion resistant. The gradational design of C3 coating will assure its strong adherence to the substrate because there is no weak boundary between coating and substrate. By dipping diamond pad conditioners of various designs in acidic solution (e.g. copper cleaning solution) for extended periods of time (e.g. 50 hours) the chemical inertness of various matrix materials are determined with the decreasing ranking as: hydrogenated DLC > C3 coating > tetrahedral amorphous carbon > sintered nichrome > brazed alloy > electroplated nickel.

Polycrystalline diamond (PCD) has excellent properties such as high hardness, high chemical inertness, high wear resistance and a low friction coefficient. Thus, it has been expected to be applied to used in various mechanical parts such as sliding parts. However, diamond is difficult to machine owing to its high hardness and chemical inertness. Therefore, a highly efficient and high-quality machining process is required for PCD. In this study, the authors developed fixed abrasive polishing tools for the mirror-like surface finishing of PCD that contain mechanochemical abrasive grains with diamond grains. As a result of fixed abrasive polishing experiments, it was clarified that a mirror-like surface can be obtained by fixed abrasive polishing using a tool containing SiO2 and diamond abrasives. Moreover, it was found that the removal efficiency can be increased under a high-temperature condition.

The tribological behaviors of silicon nitride (Si3N4) sliding against sintered polycrystalline diamond (PCD) were investigated by varying the relative humidity (RH) in the testing atmosphere. The results indicated that higher RH corresponds to higher wear loss of Si3N4 and the wear loss of PCD almost fell close to zero. Especially in the case of 85% RH, both a maximum wear loss of Si3N4 and a maximum friction coefficient were achieved. In addition, this study revealed insights into the interface chemistry effects on the wear behavior of Si3N4 under humidity. When water molecules were introduced into the testing atmosphere, the hydrolysis reaction occurred on the Si3N4 surface with the formation of the Si‐O‐Si bond across the sliding interface. And then, the hydration reaction dominated the process, during which Si‐OH was formed through the bond fracture of the Si‐O‐Si. The X‐ray photoelectron spectroscopy results showed that the ratios of Si‐OH/Si‐O and Si‐N/Si‐OH+Si‐O bonds increased as the relative RH levels increased. As a consequence, the wear loss of Si3N4 significantly increased. Thus, due to the hydrolysis and hydration reactions, the tribological behaviors of Si3N4 against sintered polycrystalline diamond can be essentially controlled via varying RH levels.

With the current popularity of finish hard turning, the need for improved productivity and tool life is of significant importance to manufacturers. The present work explores the effects of cryogenic coolants in machining hardened materials, from an industrial perspective, with emphasis on productivity and tool life improvement, environmental effects, as well as reliable performance characteristics for brittle tools. Both alumina ceramic (Al2O3) and polycrystalline cubic boron nitride (PCBN) tools show significant tool life improvement in cryomachining of hard ferrous materials, such as 52100 bearing steel and A2 tool steel. Significant productivity gains have also been observed in cryogenic machining of WC-Co rolls with polycrystalline diamond (PCD) tools. The enhanced performance of cryomachining is attributed to more efficient heat removal from the cutting insert, as well as reduction in thermal softening of the cutting tools at higher temperatures.

Freestanding polycrystalline diamond films produced by Microwave Plasma Chemical Vapor Deposition (MWCVD) were investigated for high power and high temperature electronic applications. The diamond films were deposited on polished tungsten substrates using 5000 W to I500 W power, 15.33 kPa pressure, methane-hydrogen-oxygen precursor gas between 0.5% CH/sub 4/ and 95% CH/sub 4/, oxygen/carbon ratio between 0 and 0.33, and temperature from 600/spl deg/C to 900/spl deg/C. The diamond film parted from the substrate as the samples cooled after deposition due to the difference in the thermal expansion coefficients of diamond and tungsten. Cohesive freestanding films of randomly oriented polycrystalline diamond were obtained ranging from 10 /spl mu/m to 150 /spl mu/m thick Either aluminum or tungsten metal contacts were deposited on the diamond to form parallel plate capacitors. Electrical measurements were performed before and after annealing. The dielectric constant and the loss tangent at temperatures from 23/spl deg/C to 300/spl deg/C were determined from capacitance measurements over a 20 Hz to 1 MHz frequency range. The effect of methane concentration, oxygen concentration, deposition temperature and annealing on the frequency and temperature stability of the dielectric properties of CVD diamond capacitors was investigated. Dielectric constants ranging between 8.0 and 4.2 and resistivities between 1/spl times/10/sup 8/ ohm-cm and 5/spl times/10/sup 14/ ohm-cm were obtained for the diamond samples.

Mirror surface finishing of hardened stainless steel using spherical PCD tool

Examination with x-ray photoelectron spectroscopy (XPS) of CF4 plasma etched GaAs(100) wafers unveils a residual surface reaction layer composed of Ga-fluoride and Ga-oxide. Efficient removal of this contamination layer by a brief immersion in a dilute NH4OH wet etch is demonstrated. The formation of a thin native oxide upon exposure to atmosphere of the clean substrate surface cannot be avoided, however. Prospective replacement of this wet etch processing by in situ thermal annealing in hydrogen was investigated. The recorded XPS spectra show almost complete desorption of fluorine after annealing at 200 °C, whereas a temperature of ∼600 °C is required for entire removal of residual surface Ga-oxide. Heat treatment in H2 also compares favorably with vacuum annealing, for which a noticeable reduction of the surface contamination layer was found only after annealing at 600 °C. The cleaning efficiency of hydrogen processing may be attributed to the reactive nature of this ambient.

Introduction:Enlargement of the root canal may potentially affect efficient smear layer (SL) removal. The aim of the present in vitro study was to compare SL removal following canal preparation with two different sizes/tapers by means of scanning electron microscopy (SEM). Methods and Materials: A total of 50 extracted human mandibular premolars were decoronated. The teeth were randomly divided into two experimental groups (n=20) and two negative control groups. In groups 1 and 2 the sizes of master apical file (MAF) were #25 and 40, respectively. Coronal part of the canals were flared with #2 Piezo drills in group 1 and sizes #2 to 6 in group 2. Finally FlexMaster NiTi rotary instruments were used to complete canal preparation (25/0.04 and 35/0.06 in groups 1 and 2, respectively). The irrigation protocol consisted of 10 mL of 17% ethylenediaminetetraacetic acid (EDTA) for 1 min followed by 10 mL of 5.25% NaOCl for 3 min. The patency of dentinal tubules was evaluated under SEM with Hülsmann scores. Data were analyzed with the Kruskal-Wallis and Mann-Whitney U tests. Results:The number of patent dentinal tubules in coronal third of the group 1 was significantly more than group 2 (P<0.001). However, this difference was not significant for the middle and apical segments. There was a significant difference in the number of patent dentinal tubules between coronal, middle and apical thirds (P<0.05). Conclusion:Increasing the canal preparation size did not lead to better cleanliness of the canal walls and more efficient smear layer removal.

In this paper, the removal of the sulfide layer formed on an FV(520)B stainless steel in the simulated environment of air compressor blade service conditions in a reaction kettle by arc plasma was investigated to explore the mechanism and technology of the sulfide layer removed by arc plasma from a blade surface. The sulfide lattice energy is studied by using the Born Haber cycle. Besides, the energy balance of the removal process is calculated. The treated surface morphology of samples was analyzed by scanning electron microscopy and energy dispersive spectrometer. The results indicate that the energy of the arc spot is enough to evaporate the sulfide film. Due to the different electronic work functions, an arc spot is first formed on the sulfide film, and then the voltage signal is segmented during the removal process. The voltage signal in the removal process can remove sulfide without harming the metal matrix. Besides, the increase in current can improve the removal efficiency and the surface roughness of the sample. It can be revealed, by analyzing the surface composition of samples with different currents, that the sulfur content is very low, indicating that it is feasible to remove the sulfide layer by arc spot plasma.

Aim:The aim of the present study was to evaluate the efficiency of different endodontic irrigants in the removal of smear layer through scanning electron microscopic image analysis.Materials and Methods:The present in vitro study was carried out on 45 single-rooted extracted human mandibular premolar teeth with single canal and complete root formation. Teeth were randomly assigned to three groups with 15 teeth in each group. Group I samples were irrigated with 17% ethylenediaminetetraacetic (EDTA) irrigation, Group II with 7% maleic acid irrigation, and Group III with 2% chlorhexidine irrigation. Scanning electron microscope evaluation was done for the assessment of smear layer removal in the coronal, middle, and apical thirds. Comparison of the smear layer removal between the three different groups was done by Kruskal–Wallis test, followed by Mann–Whitney U test for comparing individual groups. A P value less than 0.05 was considered to be statistically significant.Results:Statistically significant difference was seen between the two test groups (17% EDTA vs. 7% maleic acid and 17% EDTA vs. 2% chlorhexidine) in smear layer removal at coronal, middle, and apical thirds of the root canal. The most efficient smear layer removal was seen in Group I with 17% EDTA irrigation compared with other groups (P < 0.05) and the least by 2% chlorhexidine.Conclusion:The present study shows that 17% EDTA efficiently removes the smear layer from root canal walls.

The coalescence of aluminum and aluminum alloy drops in molten salt flux was observed in different salt fluxes as a function of time. Salts based on equimolar NaCl–KCl with addition of other metal chlorides or metal fluorides were used. All salts showed the ability to coalesce metal drops into one drop, but time taken for complete coalescence was different for different salts. Metal drops are covered with oxide film, which hinders their ability to coalesce into one metal drop. Thus, the coalescence ability of any salt depends on the efficiency of oxide removal by the salt. Removal of oxide layer from aluminum surface by equimolar NaCl–KCl and equimolar NaCl–KCl containing 5 mass%NaF was observed by interference microscopy. It was found that the oxide layer was not removed by equimolar NaCl–KCl, while it was removed by equimolar NaCl–KCl containing 5 mass%NaF. Coalescence ability of salt is related to weight loss of metal in salt and interfacial tension between metal and salt.

Unveiling changes of microbial community involved in N and P removal in constructed wetlands with exposing to silver nanoparticles

On-machine tool resharpening process for dry machining of aluminum alloys employing LME phenomenon