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Single-sided lapping is crucial in sapphire wafering processes for improving flatness and achieving the target wafer thickness using loose abrasives. In single-sided lapping process, the Material removal rate (MRR) is a key factor for reducing process time and cost. However, the MRR is limited when using loose abrasives because abrasives mostly act by rolling and sliding. Many researchers have studied fixed abrasives to increase the MRR, but the MRR decreases with time. To solve this problem, the self-dressing effect was studied with various pressures, velocities, cutting fluids and wafers. The MRR decreased due to the wear of abrasives, and the pressure and velocity have little effect on the self-dressing. Lapping experiments were done using cutting fluid with a lapped wafer and sawed wafer. The MRR, plate roughness and thickness were measured to study the wear of the abrasive and the self-dressing effect. The cutting fluid delayed the wear of the abrasives and thus improved the decrease in MRR, but it had little effect on the self-dressing effect, like in the case when water was used. When using cutting fluid and a sawed wafer, the MRR was high and did not decrease. A concentrated load on the plate caused by shape error and saw marks on the sawed wafer could produce the self-dressing effect. We verified that a sawed wafer could produce the self-dressing effect on even a worn plate. [ABSTRACT FROM AUTHOR]

Multi-wire sawing with diamond wire is used to slice hard and brittle materials such as sapphire, silicon carbide, or silicon into thin wafers. Compared to traditional slicing methods, multi-wire sawing with diamond wire has many advantages, including reduced kerf loss, efficient machining, and improved form accuracy. However, the process is associated with several unexpected problems, including considerable kerf loss and inefficient cutting during the initial cutting step. Thus, materials cannot be constantly removed due to the instability of the cutting performance of the diamond wire. These phenomena are defined as the break-in characteristics of diamond wire. This paper focused on the break-in characteristics of diamond wire and the effects of these characteristics on the cutting performance. In an experiment, a single-wire sawing machine equipped with a monitoring system was used to analyze the horizontal and vertical cutting forces which arose during the cutting process. The cutting performance was evaluated by means of cutting profile measurements. The wires used were analyzed by the newly developed vision measurement system and through scanning electron microscope (SEM) imagery. On the basis of results, it was found that the break-in characteristics of diamond wire are strongly correlated with the wear behaviors of the diamond wire. [ABSTRACT FROM AUTHOR]

Diamond abrasive-coated wire is a tool for the precise multi-wire sawing of mono-crystal ingots to manufacture substrates. This tool is used to cut hard materials such as silicon carbide, gallium nitride, sapphire and silicon. The cutting performance of diamond wires strongly influences the accuracy of substrates in terms of roughness, total thickness variation and BOW. Nonetheless, changes in cutting performance as a result of gradual wear through repeated contact complicate the optimization of diamond wire use. A characterization method is proposed for the cutting performance and lifetime of a diamond wire based on mathematical modeling and experimental results. The theoretical model predicts that cutting accelerates with the application of a strong feed force and small abrasives due to an increase in indentation depth for each abrasive. Experimental results showed that a wire with a low concentration exhibited an increased material removal rate. However, the lifetime of the wire displayed an opposite trend; that of a diamond wire can be classified into two regimes. The first one is an increased loss of abrasives as a result of rapid wear attributed to a low concentration; the second regime is caused by a drop in actual contact pressure due to the enlarged contact area between the workpiece and the bonding material enveloping the abrasives. [ABSTRACT FROM AUTHOR]

Abstract: Up to now, the conditioning model with an oscillating conditioner wheel has not been studied. In this paper, kinematic analysis of the conditioning process and mathematical modeling of pad wear while the conditioner wheel oscillates is studied and the results show how the various parameters of the conditioning process influence the pad shape. The conditioning of the polishing pad is one of the most important processes associated with the CMP (Chemical Mechanical Polishing). As the wafer is polished, the surface of the pad can be deteriorated with a reduced polishing rate and reduced planarity due to wear and glazing of the pad. Thus, the polishing pad needs to be conditioned to maintain its effectiveness. In general, the conditioning process is used to regenerate the pad surface by breaking the glazed area of the pad and increase the MRR (Material Removal Rate) and give us longer pad life. However, as the conditioning process continues, the pad shape becomes more and more concave over the whole pad while the conditioner wheel oscillates (Y.Y. Zhou, E.C. Davis, Mat. Sci. Eng. B. 68 (1999), 91–98). It has been shown that the concavity of the polishing pad increases with conditioning time – longer conditioning induces a higher incidence of concavity of the polishing pad. Therefore, the conditioning process is related to the WIWNU (Within Wafer Non-Uniformity). Through this conditioning model, thickness variation of the polishing pad can be predicted. [Copyright &y& Elsevier]

Abstract: Heat is an indispensable factor in understanding the removal rate and WIWNU (within wafer non-uniformity) in CMP (chemical mechanical polishing). The principal heat generation mechanism results from the two-body abrasion mode. Experiments are implemented using the on-machine temperature measuring system with an IR digital camera. This paper investigates the primary process parameters affecting heat generation and temperature distribution on pad surfaces. Meanwhile, the change of temperature affects the characteristics of both slurry and pads. The change in the pH value of the slurry due to the alteration of temperature affects the surface state of the abrasive particles and therefore the agglomeration of abrasives happens above a certain temperature. Moreover, the temperature changes the first and second elastic moduli of the pads and their real contact area, which is closely related to the removal rate and WIWNU. [Copyright &y& Elsevier]

Chemical mechanical polishing (CMP) is the process of planarization which was achieved by both chemical reaction and mechanical force. The polishing consists of moving wafer to be polished against the polyurethane pad, carrying slurry between wafer and polyurethane pad. There have been, however, some problems including dishing, erosion, high cost of consumables, environmental problems and scratches due to diamonds dropped out of conditioner. In particular, the slurry used in CMP not only increases the cost of consumables, but also interferes with the environmentally benign semiconductor manufacturing. This paper introduces the encapsulated abrasive pad to achieve the environmentally benign CMP and self-conditioning mechanism of pad. The self-conditioning just means that additive conditioning process on pad is not necessary between polishing wafers. Hydrophilic polymers were used to develop the encapsulated abrasive pad. When these polymers keep in contact with water, they have soluble and swelling characteristics. The removal rate of the encapsulated abrasive pad showed higher than that of general CMP process using slurry and polyurethane pad. The self-conditioning of pad was verified through experiment, which showed the possibility of environmentally benign process only using de-ionized water in interlayer dielectric CMP. [Copyright &y& Elsevier]

Abstract: Micropatterned thin films when planarized using chemical mechanical polishing (CMP) accompany several inherent problems, especially dishing defects. The deteriorations in surface planarity limit the accuracy and flexibility of next fabrication steps, thus accounting for a major portion of yield losses in the mass production of microelectronic components. A hybrid polysilicon (poly-Si) planarization using a protective dioxide (SiO2) film and two slurries having diametrically opposite poly-Si-to-SiO2 selectivity is developed to suppress dishing defects in the CMP of patterned poly-Si films. A 30nm-thick protective SiO2 film is deposited on a patterned poly-Si film to protect recessed areas on the uneven poly-Si film; the SiO2-protected poly-Si film is planarized with the first slurry having low material selectivity to selectively remove the protective SiO2 film placed on protruding areas while effectively remaining it located on recessed areas; the primarily planarized poly-Si film is polished again with the second slurry having high material selectivity to minimize the amount of dishing defects. For diverse poly-Si layers having different pattern widths of 5–90μm, the dishing amount is measured less than 23.1nm after the hybrid poly-Si planarization, and noticeably the dishing amount is insensitive to the pattern width. This shows that our hybrid poly-Si planarization can improve the planarity of each poly-Si film in the fabrication of multi-level (or three-dimensional (3D)) microdevices. The dependence of the material removal rate of poly-Si films on critical slurry parameters such as slurry pH and abrasive concentration is also intensively discussed. [Copyright &y& Elsevier]

Abstract: Ceria-based high selectivity slurry (HSS), which shows high polishing selectivity of silicon oxide to silicon nitride, was applied to the shallow trench isolation (STI) chemical mechanical planarization (CMP) process for giga-bit scale memory fabrication. While the wafer-to-wafer non-uniformity (WTWNU) and within-wafer non-uniformity (WIWNU) are superior to conventional silica-based slurry, the level of slurry induced scratches is too high for the ceria-based slurry to be used in present CMP processes. By optimizing the CMP process and filtering method, however, the number and depth of these scratches were reduced considerably to the level where the yield of gate oxide was sufficient to meet the requirement of manufacturing. In this paper, the authors discussed the possible causes of scratches when using ceria-based slurry and how these scratches affect to lower the breakdown yield of gate oxides. In addition, the authors investigated the relationship between within wafer non-uniformity and cell threshold voltage (V t) variation and probe test 1 (PT1) yield variation. [Copyright &y& Elsevier]

An ultrahigh power output from a triboelectric nanogenerator (TENG) with a serrated electrode in a low‐frequency contact‐separation mode which is able to directly drive high voltage‐operating devices without the need for an external power supply is demonstrated. When a serrated electrode‐based TENG (SE‐TENG) is driven, the microstructurally serrated electrode creates a spark discharge in the gap between the serrated electrode and a wire, resulting in tremendously boosted triboelectric power output. Based on the spark discharge phenomenon, a boost adaptor is designed to secondarily boost the triboelectric power output performance, and consequently an ultrahigh triboelectric output voltage of 5 kV and current density of 2 A m−2 are achieved. The boost adaptor concept can be applied to any typical TENG for achieving higher power‐generating performance. Finally, two high voltage applications, a Crookes tube and plasma generation, are demonstrated using the SE‐TENG and boost adaptor without any external power supply equipment. The ultrahigh power‐generating SE‐TENG based on the spark discharge phenomenon occurring in the unique electrode structure has considerable potential to operate high voltage applications directly in harsh environments where electricity cannot be supplied. [ABSTRACT FROM AUTHOR]

Abstract: Since copper (Cu) electrochemical mechanical planarization (ECMP) process is both a mechanical and electrochemical process, a polymeric pad must have mechanical integrity and chemical resistance to survive the rigors of polishing. Mechanically, a polishing pad should have acceptable levels of hardness and modulus, and good abrasion resistance to endure the Cu ECMP process. Chemically, a polishing pad should be able to survive the aggressive electrolyte chemistries, which include either highly alkaline, or high acidic electrolyte. Therefore, the characteristics of the polishing pad have been measured and evaluated. Although the material removal rate (MRR) is proportional to the current density of the Cu ECMP process, the planarization and uniformity in the wafer level are poor. To improve planarization of the wafer level, the effect of the abrasive is evaluated, with respect to the planarization and uniformity of the wafer and the abrasive properties of the electrolyte. In this study, the concentration of the abrasive (silica; SiO2) in the electrolyte with H3PO4 6wt%, H2O2 0.5wt%, and BTA 0.5wt%, glycine 0.5wt% and citric ammonium 5wt% should be above 10vol%. [ABSTRACT FROM AUTHOR]

Abstract: ECMD (electrochemical mechanical deposition) process consists of a traditional ECP (electrochemical plating) mechanism and a mechanical component. That is, this technique involves both electrochemical plating and mechanical sweeping of the material surface by the polishing pad. The mechanism of the ECMD process may be achieved through two mechanisms. The first mechanism may be the electrochemical plating on the surface where mechanical sweeping of polishing pad does not reach, and the second mechanism may be that the plating rate in the area that is mechanically swept may be reduced by the polishing pad. In this study, the effects of the mechanical component were investigated through various polishing pad types and hole ratios. In comparison to various polishing pad types using the manufactured the ECMD system, the plating rate and WIWNU (within wafer non-uniformity) using the experimental non-pore polishing pad were better than those of the experiments using other polishing pads. [Copyright &y& Elsevier]

Abstract: High roughness and a greater number of defects were created by lithium niobate (LN; LiNbO3) processes such as traditional grinding and mechanical polishing (MP), should be decreased for manufacturing LN device. Therefore, an alternative process for gaining defect-free and smooth surface is needed. Chemical mechanical planarization (CMP) is suitable method in the LN process because it uses a combination approach consisting of chemical and mechanical effects. First of all, we investigated the LN CMP process using commercial slurry by changing various process conditions such as down pressure and relative velocity. However, the LN CMP process time using commercial slurry was long to gain a smooth surface because of lower material removal rate (MRR). So, to improve the material removal rate (MRR), the effects of additives such as oxidizer (hydrogen peroxide; H2O2) and complexing agent (citric acid; C6H8O7) in a potassium hydroxide (KOH) based slurry, were investigated. The manufactured slurry consisting of H2O2–citric acid in the KOH based slurry shows that the MRR of the H2O2 at 2wt% and the citric acid at 0.06M was higher than the MRR for other conditions. [Copyright &y& Elsevier]

Abstract: The pad roughness plays a key role in material removal in oxide chemical mechanical polishing (CMP) process. Its variation also has an effect on within wafer non-uniformity. The R pk among roughness parameters, which is related to pad wear characteristics, was investigated to find the correlation between spatial roughness distribution of a polishing pad, and material removal profile in CMP, using two different types of slurries. The removal rate of ceria-based slurry for STI CMP was higher in the wafer center than that of the silica-based slurry. This is because the pad roughness distribution in a convex shape is formed across the pad radius in the contact area between pad and wafer instead of the degradation of pad roughness during CMP. Also, there is an increase of R pk results in the increase of average friction force by comparison with the decrease of friction force in CMP using silica-based slurry. This result may be expected as the effect of the chemical tooth of ceria abrasive and slurry accumulation in the wafer center causes a roughening of the pad surface just as sandpaper. [Copyright &y& Elsevier]