PCD dresser for dressing CMP polyurethane pads

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.

A new thermally stable diamond cutter has proven effective in drilling medium to hard limestone and moderately abrasive sand. This new type of diamond is called "Ballas" which is a synthetic polycrystalline diamond. Ballas can be thought of as a more refined, or pure, polycrystalline diamond compact cutter which is free of foreign material within or attached to the diamond mass. The Ballas cutter is thermally stable up to 1200 degrees C compared to a conventional polycrystalline diamond compact which is only thermally stable up to 750 degrees C. This additional temperature resistance allows the use of self sharpening polycrystalline diamond to be used in harder, more abrasive formations which cannot be cut with the present diamond compact material. The use of the Ballas material has shown significant rate of penetration advantage in drilling the carbonate formations of East Texas and the depleted sands of So. Louisiana. Along with the success, present bit designs have experienced some problems drilling some of the clean plastic shales common on the Gulf Coast.

A major effort has been made to evaluate the commercial application of bits fitted with STRATAPAX Drill Blanks for drilling oil wells. Over 40 field runs have been made with such Diamond Cutter bits and a significant potential economic application of the new material is indicated. Further development work will be required to improve bit design and manufacture as well as the wear and engineering characteristics of the diamond cutters. Introduction Surface-set diamond bits usually contain natural diamonds. The available, as-manufactured, Synthetic diamonds are too small to be used economically in these bits for oilfield drilling. A technique has, however, been developed by the General Electric Company to bind small synthetic diamonds together with a diamond-to-diamond bond on top of a tungsten-carbide substrate. As a result, a relatively large diamond cutter could be produced. The technique was initiated in the manufacture of diamond compacts for machining and dressing purposes. The product was named "COMPAX Industrial Diamond Blank". product was named "COMPAX Industrial Diamond Blank". With the success of this application, these diamond blanks were introduced into the drilling-bit industry. Recently a similar product, named STRATAPAX Drill Blank, was offered particularly for rock-drilling purposes. Mainly during the past few years several companies began to develop bits suitable for fitting with these diamond blanks for use in oil-well drilling. This paper reviews the results of a major effort obtained from over forty field runs with such bits, fitted with either COMPAX or STRATAPAX blanks. Such bits will be referred to as Diamond Cutter bits. In addition, some general information on STRATAPAX Drill Blanks is discussed and results of a number of laboratory experiments are presented. Though a competitive product - SYNDITE is now also available, it has not been product - SYNDITE is now also available, it has not been included in the field tests reported here. WHAT IS A 'STRATAPAX DRILL BLANK'? Examples of a STRATAPAX Drill Blank are shown in Fig. 1. Each blank is made up of a thin diamond layer (minimum thickness 0.5 mm or 0.020 in), firmly bonded to a tungsten-carbide substrate. This layer is obtained by subjecting a mixture of small high-quality synthetic blocky diamond particles and a small amount of catalyst to very high pressures and temperatures. Because of the catalyst selected the diamond layer has only an effective operating-temperature limit of about 700 degrees C, beyond which level the bond between the individual diamond crystals loses its strength. This temperature limitation has proved to be a significant handicap in the development of the processes for attaching the STRATAPAX Drill Blanks to the processes for attaching the STRATAPAX Drill Blanks to the bit, because conventional diamond bit manufacturing methods use temperatures over 900 degrees C. This temperature limitation could also affect the wear of the cutting edge of the bit in actual operation. The diamond layer features a polycrystalline structure without cleavage planes. This is only matched in nature by carbonado diamonds, which have only been used to a limited extent in drilling bits because of their short supply and high cost. The cost of STRATAPAX Drill Blanks is also high, but unlike the carbonado diamonds, the supply of diamond blanks is virtually unlimited. The diamond blank exhibits the following important advantages over the types of natural diamonds generally used in bits for oilfield application:–a generally sharper cutting edge–higher-quality diamond crystals–a polycrystalline and crack-free structure. These advantages only apply if the temperature limit for the diamond layer is not exceeded. Since this limit may be exceeded during the drilling operations, there is clearly a need for further improvement of the STRATAPAX Drill Blanks. The diamond layer is firmly bonded to a tungsten-carbide substrate, which is about 2.7 mm thick.

Grinding performance of an aluminium-bonded diamond wheel on ceramics and glass: J. Sugishita, N. Kawabata, K. Kumamoto, Precision Engineering, 13(3), pp. 184–188. (Jul 1991)

The objective of this work is to study the performance of the Nd:YAG laser to cut thick free standing CVD diamond films. The high flexibility of this type of laser, given by the possibility to guide the laser beam by means of an optical fibre represents a great advantage in order to automate the cutting process in the production lines. Laser cutting technology is imperative to shape non-conductive CVD diamond parts for electronic, optical and mechanical applications, namely heat sinks, infrared transparent windows and small tips to braze onto machining tool holders. Concerning diamond tool production, the rapid cutting method by laser here proposed provides an advantage to CVD diamond when compared to conventional polycrystalline diamond (PCD) blanks that are cut by the Electro-Discharge Machining (EDM), a time-consuming and very expensive technique due to the electrodes cost.Free-standing diamond films were grown on silicon wafers by microwave plasma chemical vapour deposition (MPCVD) method in a ASTeX PDS 18 unit. The diamond growth parameters were: microwave power 4.35kW; total pressure 110Torr; H2 flow 400s.c.c.m.; CH4 flow 30s.c.c.m; deposition time 70h. The final film thickness was approximately 500μm. The diamond plates were then released by chemical dissolution of the Si substrate in a nitric/hydrofluoric acids mixture. The equipment employed to perform the cutting experiments consisted of a pulsed Nd:YAG laser delivering a maximum average power of 500W at a wavelength of 1064 nm. The laser beam was coupled to an optical fibre of 400μm diameter and 10 m long. The pulsed beam coming out of the fibre was focused onto the surface of the free standing diamond coating by means of a commercial cutting head, having a lens of 80 mm focal length, in which the laser beam was coaxial to the Ar gas jet used as assist gas.In this paper we discuss the results of the work carried out to analyse the influence on cuts quality of laser processing parameters such as: cutting speed 5-20mm/s; pulse width 0.3-1ms; pulse energy 0.8-4.6J; power 80-470W. Scanning electron microscopy was used to look into film cracking events and to appraise the cut width and linearity. Micro-Raman spectroscopy allowed the evaluation of the graphitisation level on the cut surface.The objective of this work is to study the performance of the Nd:YAG laser to cut thick free standing CVD diamond films. The high flexibility of this type of laser, given by the possibility to guide the laser beam by means of an optical fibre represents a great advantage in order to automate the cutting process in the production lines. Laser cutting technology is imperative to shape non-conductive CVD diamond parts for electronic, optical and mechanical applications, namely heat sinks, infrared transparent windows and small tips to braze onto machining tool holders. Concerning diamond tool production, the rapid cutting method by laser here proposed provides an advantage to CVD diamond when compared to conventional polycrystalline diamond (PCD) blanks that are cut by the Electro-Discharge Machining (EDM), a time-consuming and very expensive technique due to the electrodes cost.Free-standing diamond films were grown on silicon wafers by microwave plasma chemical vapour deposition (MPCVD) method in a ASTeX P...

Sintered polycrystalline diamond cubicles were oriented to make CMP pad conditioners. The dressing experiments demonstrated the capability of fast pad cutting and efficient removal of glazed layer that is formed by polishing wafers with slurry on dressed pad.

Absorption and cathodoluminescence spectra have been recorded for single crystals of diamond and polycrystalline films of diamond, grown by microwave-assisted chemical vapor deposition (CVD) using methane and hydrogen. The investigation has been carried out to see to what extent the properties of CVD diamond are similar to those of conventional diamond, and to what extent they are unique. Studies have been made of the as-grown material, which has not been intentionally doped, and also samples that have been subjected to radiation damage and thermal annealing. The single crystals grown using methane concentrations of 0.5 to 1.0% exhibit bright blue “band A” emission and also intense edge emission, similar to the cathodoluminescence spectra of some natural type IIa diamonds. This implies that the crystals are relatively free from structural and chemical defects, a conclusion which is reinforced by the absence of any zero-phonon lines in the absorption spectra of crystals which have been subjected to radiation damage and annealing at 800 °C. Before radiation damage the spectrum does, however, reveal an absorption which increases progressively to higher energies, and which may be associated with sp2-bonded carbon. The Cathodoluminescence spectra after radiation damage indicate that the crystals contain some isolated nitrogen, and the detection of H3 luminescence, following thermal annealing at 800 °C, demonstrates for the first time that these samples contain small concentrations of nitrogen pairs. All of the polycrystalline films, grown using methane concentrations between 0.3 and 1.5%, have an absorption which increases progressively to higher energies, and which again is attributed to sp2-bonded carbon. This absorption is stronger in the films grown using higher methane concentrations. Films grown at a methane concentration of 0.3% also exhibit bright blue cathodoluminescence, although the edge emission is undetectably weak. The use of higher methane concentrations produces films with evidence in the cathodoluminescence spectra of nitrogen + vacancy and nitrogen + interstitial complexes, as well as optical centers unique to CVD diamond. One particular defect produces an emission and absorption line at 1.681 eV. By implanting conventional diamonds with 29Si ions it has been confirmed that this center involves silicon, and it has been shown that the 1.681 eV luminescence is relatively more intense in implanted diamonds which have a high concentration of isolated nitrogen.

Detailed observations were made on two selected GE synthetic diamonds; one was representative of the more perfect specimens, the other of less perfect but more common specimens. Diffraction topography of the more perfect crystal revealed lattice defects interpreted as dislocation bundles radiating from a central region, individual dislocations apparently resolvable locally, and a severely strained surface layer. Dislocations were not resolved in the less perfect specimen. Absorption topography using monochromatic Cu Kα and Cu Kβ radiations showed a nickel-rich surface film on the more perfect specimen, but few internal Ni-rich particles. The less perfect specimen contained many Ni-rich globules 2 to 15 μ in diameter, sheets of submicron-size Ni-impurity occluded under certain crystal edges and some Ni-rich surface film. The face-centered cubic ``satellite'' diffraction pattern of the less perfect specimen showed the presence of large crystallites misoriented up to 6° from the diamond matrix and fine crystallites closely parallel to the matrix. An explanation is put forward for the development of cube faces on synthetic diamonds.

In this research, the effect of adding 2.5, 5.0 and 10 wt% niobium (Nb) as a binding agent was investigated for High Pressure-High Temperature (HPHT) sintering of polycrystalline diamond (PCD). Samples were sintered at 1750 °C and 7.7 GPa. Detailed characterization of the as-sintered materials revealed a uniform dispersion of the Nb additives in the diamond matrix and no interfacial cracking was observed. Higher concentration of binder increased tendency to intergranular failure. The formation of NbC and NbC0.84 phases after sintering was identified, indicating that some of the matrix carbon may have undergone graphitization.

Polycrystalline diamond (PCD) tools are widely used for cutting tools because PCD has no crystal orientation and is an isotropic material, it is low in cost, and it is easily machined by electric discharge machining. PCD is sintered from diamond abrasives with an alloy metal, such as cobalt, and it is difficult to reduce the surface roughness and the edge accuracy compared with single crystal diamond. In this study, high efficiency and high precision machining of the PCD wheel were investigated. In the experiments, PCD wheels were ground with a diamond wheel, and the effects of the grinding direction and the load on the tool preciseness and the scribing performance were examined.

Polycrystalline diamond end mill cutting edge design to improve ductile-mode machining of silicon

A study on micro-hole machining of polycrystalline diamond by micro-electrical discharge machining

The extreme hardness of Polycrystalline Diamond (PCD) makes it an ideal choice for the machining of hard materials as a cutting tool. Due to the high hardness, fabrication of PCD tools relies on conventional abrasive grinding which suffers from low machining efficiency. Electrical discharge machining (EDM) is an advanced machining process and can be utilised to fabricate complicated PCD tools. High temperature of sintering and EDM processes creates residual stress inside PCD and can result in unmatured failure of PCD tools. This paper analyses the distribution of residual stress in PCD after electrical discharge machining process.

Synthetic diamonds made by high-temperature and high-pressure synthesis using an Fe–Co solvent/catalyst leave nanoparticles of the solvent/catalyst within the diamond matrix. These nanoparticles strongly affect the magnetic properties of the diamond. The magnetization versus field was compatible with the response of superparamagnetic particles. The mean size and separation of the inclusions were calculated. The inclusion size was found to be constant to within 10%, whereas the saturation magnetization varied by a factor of 100. A transmission electron microscope image of a single inclusion from a Fe–Co/diamond grit showed a dark, iron-rich core surrounded by a halo of material of intermediate contrast to the lighter diamond matrix. The size of the core is consistent with the magnetization measurements while the halo is of similar size to that determined by small-angle neutron scattering. The compressive strength increased linearly with the inclusion separation.

Micro-channels machining on polycrystalline diamond by nanosecond laser