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![Figure 2.1. Mechanics of particle/glass contact (from Cook [2.7])](profile/Jianfeng-Luo/publication/252085636/figure/fig3/AS:638069275385869@1529138978832/Mechanics-of-particle-glass-contact-from-Cook-27_Q320.jpg)
![Figure 2.2. Wafer-pad contact model of Yu et. al [2.20]](profile/Jianfeng-Luo/publication/252085636/figure/fig4/AS:638069279555585@1529138979138/Wafer-pad-contact-model-of-Yu-et-al-220_Q320.jpg)
![Figure 2.3. The five-step surface kinetics model [2.31]](profile/Jianfeng-Luo/publication/252085636/figure/fig5/AS:638069279559680@1529138979215/The-five-step-surface-kinetics-model-231_Q320.jpg)
Chemical mechanical planarization/polishing (CMP) has obtained broad applications in sub-micron integrated circuit (IC) fabrication in recent years. These applications include inter-layer dielectrics planarization, copper damascene process and shallow trench isolation. However, the broad applications of CMP are often limited by a general lack of un...
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Citations
... Based on this theory, a density step height (DSH) topography prediction model is proposed to determine the influence of the layout pattern density and step height on the pressure distribution. References [8,9] added the influence of the line width and line space information on the CMP topography based on the DSH model. In [10], the linear relationship between step height and MRR was modified to an exponential relationship to improve the accuracy of topography prediction. ...
As a planarization technique, chemical mechanical polishing (CMP) continues to suffer from pattern effects that result in large variations in material thickness, which can influence circuit performance and yield. Therefore, tools for predicting post-CMP chip morphology based on the layout-dependent effect (LDE) have become increasingly critical and widely utilized for design verification and manufacturing development. In order to characterize the impact of patterns on polishing, such models often require the extraction of graphic parameters. However, existing extraction algorithms provide a limited description of the interaction effect between layout patterns. To address this problem, we calculate the average density as a density correction and innovatively use a one-dimensional line contact deformation profile as a weighting function. To verify our hypothesis, the density correction method is applied to a density step-height-based high-K metal gate-CMP prediction model. The surface prediction results before and after optimization are compared with the silicon data. The results show a reduction in mean squared error (MSE) of 40.1% and 35.2% in oxide and Al height predictions, respectively, compared with the preoptimization results, confirming that the optimization method can improve the prediction accuracy of the model.
... The CMP provides a critical support for achieving good surface finish at various levels of IC fabrication. It is also important to have defect free and smooth surface finish for the semiconductor wafers for either utilizing directly for device fabrication or after growing epitaxial heterostructures therein [46][47][48][49][50]. CMP is also required for polishing of copper damascene patterns, low k dielectrics etc. [51]. ...
The semiconductor industry is the backbone of exponentially growing digitization. Countries from the east and the west both are investing significantly to accelerate this growth. Chemical mechanical planarization (CMP) is one of the crucial technologies for expediting this growth. In 1986, IBM first developed CMP for the polishing of oxide layers. In 1988, it was deployed for the polishing of tungsten. Very soon, the CMP process became popular among the academic researchers and industries due to its global as well as local surface planarization capacity. As the number of active components in a wafer is increasing significantly, the feature size is decreasing for developing high performance integrated circuit (IC) chips. Along with the reducing feature sizes, multiple levels are being implemented. These additional levels necessitate multilevel interconnection. To accommodate all these features, CMP has become an inevitable process for both the semiconductor and solar cell wafer manufacturing industries. The CMP provides a critical support for achieving good surface finish at various levels of IC fabrication. Furthermore, the CMP is also used for the surface polishing of a wide range of materials including sapphire wafers, titanium based biomedical implants, aluminium, copper, YAG crystals, zirconium ceramics, cobalt, molybdenum etc. After its development, ample studies have been carried out for further improvement of CMP processes. However, the intricacy of the process parameters for different wafer & pad materials and slurry composition makes it difficult to indiscriminately apply to any wafer or alloys. Most of the studies have been discretely carried out either on a specific wafer material or based on controlled investigations of certain parameters. In this review paper, CMP has been analysed holistically based on its nanoscale tribological aspects. Several studies have been discussed for the relevant parameters at nano and microscale level including morphology, type, and size of abrasive particles, as well as the arrangement of polishing pad asperities and their conditioning to explore the nanotribological characteristics of CMP. Subsequently, atomic force microscopy (AFM) based studies on CMP have been discussed to correlate it with macroscale CMP. As our mother nature is facing environmental crisis world-wide, research communities should develop environment friendly processes for production. In this regard, the scientists are developing environment friendly CMP process to mitigate the burden of environment. At the same time, researchers can save a mammoth quantity of laboratory resources by carrying out the nanoscale studies of CMP using molecular dynamics simulation approach. In this review, both the green CMP and molecular dynamics studies related to CMP have been discussed. Moreover, the readers can grasp the challenges, difficulties, and achievements of CMP from the nanotribological point of view. Finally, the review presents some insights that can be implemented for further improvements of CMP process.
... In 1991, IBM successfully applied CMP technology to the production of 64 Mb DRAM to meet the global planarization requirement with feature sizes below 0.35 μm. CMP is the only surface finishing technology that can effectively provide global planarization, which plays an important role in the ultraprecision surface finishing of integrated circuits such as semiconductor chips, computer hard disk, etc. Subsequently, many universities and companies began to research CMP technology [164][165][166][167][168]. ...
With the extensive application of optical parts in many high-tech fields such as high-power laser, space optics, and aerospace, the requirements for the surface quality of optical parts are also increasing, which requires not only high surface qualities but also low defects including low subsurface damage and strict wavefront errors. As an essential link in the precision and ultraprecision optical manufacturing, various surface polishing methods and techniques have always attracted researchers’ continuous study and exploration. Considering the development of optical part surface polishing technology in recent years, this study analyzes the principle and development process of typical processing methods represented by each kind of polishing technology, expounds the specific research progress of optical part surface polishing technology, including the iterative renewal of traditional technologies and the research development of new technologies, and gives examples for typical applications. Finally, the development trend of optical part surface polishing technology is prospected, which provides a reference for follow-up intensive research in optical manufacturing.
... Since a slurry with low dispersity forms a significant amount of agglomerated large particles, it is considerably affected by mechanical abrasion and the surface of the polished wafer becomes rough. Based on the fully plastic deformation and the abrasive indentation assumption, the indentation depth (∆) of the spherical abrasives into the wafer can be derived as follows 78 where x is the diameter of the abrasives and H w is the hardness of the wafer. F is the force applied on a single abrasive, which can be calculated as follows. ...
The effects of photo-oxidative degradation of polyacids at various concentrations and with different durations of ultraviolet (UV) irradiation on the photo-reduction of ceria nanoparticles were investigated. The effect of UV-treated ceria on the performance of chemical mechanical polishing (CMP) for the dielectric layer was also evaluated. When the polyacids were exposed to UV light, they underwent photo-oxidation with consumption of the dissolved oxygen in slurry. UV-treated ceria particles formed oxygen vacancies by absorbing photon energy, resulting in increased Ce ³⁺ ions concentration on the surface, and when the oxygen level of the solution was lowered by the photo-oxidation of polymers, the formation of Ce ³⁺ ions was promoted from 14.2 to 36.5%. Furthermore, chain scissions of polymers occurred during the oxidation process, and polyacids with lower molecular weights were found to be effective in ceria particle dispersion in terms of the decrease in the mean diameter and size distribution maintaining under 0.1 of polydispersity index. With increasing polyacid concentration and UV irradiation time, the Ce ³⁺ concentration and the dispersity of ceria both increased due to the photo-oxidative degradation of the polymer; this enhanced the CMP performance in terms of 87% improved material removal rate and 48% lowered wafer surface roughness.
... The hydrodynamic force primarily depends on the workpiece/lap interfacial conditions, which can be characterized as being in contact, hydroplaning, or mixed mode [17][18][19]. Contact mode occurs when the relative velocity of the workpiece and lap is low and/or the pressure applied onto the workpiece is high. In contact mode, the hydrodynamic force is very small and the polishing force is mostly carried by the lap asperities through abrasive particles [20,21]. ...
Full-aperture polishing is one of the most important processes in fabricating large flat optical elements. Control of the elements’ surface figure to a high precision in a determined manner has been a major challenge in this process. This study focuses on the converging mechanism and deterministic control of the surface figure in the full-aperture polishing process. A novel balance equation for material removal is proposed to correlate the primary aspects of the polishing condition to the surface figure. The removal balance equation reveals that the final surface figure is determined by the spatial distributions of three factors, including the relative velocity, polishing pressure, and removal coefficient. The dependence of these factors’ distribution on the polishing condition is detailed in theory and experiments, and systematic methods to deterministically control these factors’ distribution are proposed. This study is a significant attempt to reveal the converging mechanism of the surface figure and develop a deterministic full-aperture polishing process.
... 1) The shape of abrasive particles is spherical, with a constant diameter equal to the average particle size. 2) Due to the relatively high polishing pressure and super elasticity of the polyurethane polishing pad, it is assumed that effective abrasive particles within contact area are totally embedded onto the polishing pad and only two-body abrasion is considered [39]. ...
... The polyurethane polishing pad used is a porous material, there are many hollow pores on the pad surface (these hollows will not generate material removal in any case, details can be found in Ref. [25]), and these hollow areas needs to be considered in the modeling, i.e., the overall area taken by the hollow pores, A h , needs to be subtracted from the nominal polishing contact area, A norm . The Greenwood-Williamson (G-W) model [42], which describes the contact relationship between rough polishing pad and smooth workpiece, is used in the present study, and an areal ratio ε, i.e., ratio of the effective contact area over nominal polishing contact area is defined, which is expressed as [39]: ...
... where, R as is the average radius of the pad asperity; D as is the number of the asperities per unit area. Ẽ is expressed as [39]: ...
... Ponton et Rawlings [19,20] ont recensé les différents modèles existantà l'époque en fonction du type de fissures : Palmqvist (P), half-penny ou Médiane (M) (Fig. 3). [17,18]. Fig. 2. Principle of glass ground and polishing by free or bound abrasive grains [17,18]. ...
... [17,18]. Fig. 2. Principle of glass ground and polishing by free or bound abrasive grains [17,18]. Souvent les fissures sont de type P pour les faibles charges appliquées (charges relatives en fonction de la ténacité du matériau) et deviennent du type M quand les charges augmentent. ...
... Optic/pad interfacial conditions can be characterized as two typical modes, i.e., contact and hydroplaning141516. Contact mode occurs when the relative velocity of the optic and pad is low and/or the pressure applied to the optic is high. ...
... Vibrations from the CMP process result from a dynamic interplay among mechanisms taking place at three different scales, namely wafer-pad asperity [42], [43], [48], bulk pad structure [49], [50], and machine kinematics. Much of the literature has focused on deriving analytical models of the CMP process at pad asperity and bulk scales [42]- [45], [47]- [53]. ...
... The Greenwood-Williamson (GW) approach [63] is used to compute the real contact area and pressure in wafer-pad asperity models by Luo et al. [42], [48], [52], Qin et al. [54], and Borucki [53]. The model by Borucki [53] is used in this work, since it provides a closed-form solution for obtaining the mean-separation distance between wafer and pad. ...
We present a deterministic process-machine interaction (PMI) model that can associate different complex time-frequency patterns, including nonlinear dynamic behaviors that manifest in vibration signals measured during a chemical mechanical planarization (CMP) process for polishing blanket copper wafer surfaces to near-optical finish $({rm R}_{{rm a}}sim 5~{rm nm})$ to specific process mechanisms. The model captures the effects of the nonuniform structural properties of the polishing pad, pad asperities, and machine kinematics on CMP dynamics using a deterministic 2$^{circ}$ of freedom nonlinear differential equation. The model was validated using a Buehler (Automet 250) bench top CMP machine instrumented with a wireless (XBee IEEE 802.15.4 RF module) multi-sensor unit that includes a MEMS 3-axis accelerometer (Analog Devices ADXL 335). Extensive experiments suggest that the deterministic PMI model can capture such significant signal patterns as aperiodicity, broadband frequency spectra, and other prominent manifestations of process nonlinearity. Remarkably, the deterministic PMI model was able to explain not just the physical sources of various time-frequency patterns observed in the measured vibration signals, but also, their variations with process conditions. The features extracted from experimental vibration data, such as power spectral density over the 115–120 Hz band, and nonlinear recurrence measures were statistically significant estimators $({rm R}^{{rm 2}}sim 75%)$ of process parameter settings. The model together with sparse experimental data was able to estimate process drifts resulting from pad wear with high fidelity $({rm R}^{{rm 2}}sim 85%)$. The signal features identi- ied using the PMI model can lead to effective real-time in-situ monitoring of wear and anomalies in the CMP process.
... A physical model capable of elucidating the multi-faceted aspects of CMP process dynamics can be used to define features that can track the process, as opposed to the mere signal variations. Existing physical models, however are largely focused on the wafer-pad asperity level mechanics, and explain the material removal regimes dominant at such a scale, such as hydrodynamic, mixed, and direct contact modes [42]–[47]. These models overlook the interaction among mechanics active at different scales, such as bulk pad structure, and machine kinematics. ...
... Vibrations from the CMP process result from a dynamic interplay among mechanisms taking place at three different scales, namely wafer-pad asperity [42], [43], [48], bulk pad structure [49], [50], and machine kinematics. Much of the literature has focused on deriving analytical models of the CMP process at pad asperity and bulk scales [42]–[45], [47]–[53]. For example, Luo et al. [42] and Wang et al. [43] proposed models incorporating pad asperity effects for predicting material removal rate (MRR) in CMP. ...
