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Solution-based processes have received considerable attention in the fabrication of electronics and sensors owing to their merits of being low-cost, vacuum-free, and simple in equipment. However, the current solution-based processes either lack patterning capability or have low resolution (tens of micrometers) and low pattern fidelity in terms of line edge roughness (LER, several micrometers). Here, we present a surface energy-directed assembly (SEDA) process to fabricate metal oxide patterns with up to 2 orders of magnitude improvement in resolution (800 nm) and LER (16 nm). Experiment results show that high pattern fidelity can be achieved only at low relative humidities of below 30%. The reason for this phenomenon lies in negligible water condensation on the solution droplet. Employing the SEDA process, all-solution-processed metal oxide thin film transistors (TFTs) are fabricated by using indium oxide as channel layers, indium tin oxide as source/drain electrodes and gate electrodes, and aluminum oxide as gate dielectrics. TFT-based logic gate circuits, including NOT, NOR, NAND, and AND are fabricated as well, demonstrating the applicability of the SEDA process in fabricating large area functional electronics.

Eddy-current sensor systems have been employed to determine the real-time thickness distribution of metal films and the thickness at endpoint detection in metal chemical mechanical polishing (CMP) processes, to achieve global planarization and avoid overpolishing or underpolishing. However, the large lift-off distance of 3.5 mm between the sensor coil and metal film gradually decreases with continuous wear of the polishing pad, which has a strong negative impact on the sensitivity and accuracy of the thickness measurement. In this study, a double-coil eddy-current sensor system, with novel characteristic ratio detection capability, is proposed for metal film thickness measurement and compared with a traditional amplitude-based method. The linear relationship between the characteristic ratio and metal film thickness that is immune to lift-off distance is demonstrated both theoretically and experimentally. The experimental results show that the proposed method performs better than the amplitude-based method, reducing the effect of lift-off distance variation and obtaining an excellent linear measurement range from 24 to 2095 nm. The measurement accuracy is as high as 2.1 nm with an excitation frequency of 1.39 MHz and a large lift-off distance of 3.5 mm. The relative measurement error is less than 1.2% and the endpoint thickness ranges from 100 to 180 nm in the Cu-CMP process, when the lift-off distance varies from 3.6 to 3.3 mm.

Abstract: The synthesis of CeO2nanoparticles for CeO2based slurry gains continuous emphasis on improving its performance in the chemical mechanical polishing of dielectric materials. Urea was selected to dominate the growth and morphology during the calcination process. Thermogravimetry experiments were used to analyze the the decomposition behavior. Particle morphology and size were analyzed. Crystalline phase information and surface valence were used to compare the differences in surface physical and chemical properties of ceria by different synthesis process. The CeO2nanoparticles synthesized with urea were dispersed in water as slurry. The particle sizes of CeO2were measured by dynamic light scattering. The Zeta potential of CeO2dispersion were measured to show dispersing performance. The CeO2nanoparticles synthesized with urea condensation show good monodisperse properties. The material removal rate of silicon oxide and surface quality after chemical mechanical polishing were selected to evaluate the chemical mechanical polishing performance. The CeO2nanoparticles synthesized with urea condensation not only yielded better surface quality results than the commercial slurry but also showed a 153% (pH = 4) and 100% (pH = 10) increase in the material removal rate of silicon oxide compared to commercial.

Cobalt (Co) with its low resistivity, excellent resistance to electro-migration with co-deposition property and void-free seamless fill ability, pledges to transform the landscape of integrated circuits in many areas, especially in logic contacts and interconnects. Chemical mechanical polishing (CMP), which utilizes the synergistic action of chemical corrosion and mechanical wear, has been recognized as the exclusive manufacturing approach to achieve global and local planarization of wafer surfaces. In this work, we proposed an innovative hydrogen peroxide (HP) polishing slurry, applying phthalic acid as the complexing agent and oleic acid as the corrosion inhibitor at pH 10. From the results of appropriate material removal/static etching rates as well as the smooth surface morphologies, phthalic acid and oleic acid are identified to be qualified in HP-based slurries for heterogeneous materials of Co interconnects. Moreover, the mechanisms of complexation and inhibition have been revealed by electrochemical analysis and X-ray photoelectron spectroscopy tests. It can be concluded that with the addition of complexing agent phthalic acid in HP-based slurries, the transformation of oxidization from low-valence compounds to high-valence was partially replaced by stronger complexing action, making the removal mechanism be attributed to the combined oxidization and complexation. When oleic acid is introduced, it could react with Co oxides to form a polymer protection layer adsorbing on Co films, achieving an inhibition effect to avoid Co excessive corrosion. Meanwhile, the oxidization of HP as well as the complexation of phthalic acid, combined with the protection of oleic acid play critical roles to maintain the appropriate removal rates and selection ratios.

The adhesion force between slurry particles and the wafer surface has a significant effect on the material removal and ultra-smooth surface formation during the chemical mechanical polishing/planarization (CMP) process. Based on zeta potentials measurements, we calculate the value of adhesion force, which cannot be ignored compared with the Hertz contact force for small sized abrasive particles at low polishing pressures. More over, the impacts of slurry (particle size and pH value) and wafer surface roughness on the adhesion force are evaluated. Theoretical analyses manifest that the adhesion force mainly originates from the van der Waals force and electrical double-layer force, which increases with the increase of the particle size and slurry pH, while decreases with the increase of the wafer surface roughness. The relationships between the adhesion force and scratch depth indicate that scratching would be avoided while enhancing the adhesion force during CMP. These findings would provide some inspirations to understand the CMP technology in depth, and they are also beneficial to engineering super-smooth and super-lubricant surfaces with nano-scaled roughness.

Ru as a novel barrier/liner material for Cu interconnects, has gained application in the sub-10 nm technology node. In this paper, methods to polish patterned wafer with Ru/Ta/TaN tri-layers as liner/barrier have been proposed. Effects of pattern geometry and CMP variables (such as polishing down pressure and oxidant content) on polishing uniformity were fully investigated. Apart from this, interfacial defects after barrier polishing were comprehensive characterized by atomic force microscopy and transmission electron microscopy methods. Results show that hydrogen peroxide (H2O2) is effective in the mutual material removal of Cu/Ru/Ta/TaN/BD1 heterogeneous materials. Good surface quality could be obtained by using proper CMP process, with Cu dishing of 604.1 A for the 100/100 um array.

Cobalt (Co) and its low resistivity, superior adhesion property, and void-free seamless fill ability, pledge to transform the landscape of integrated circuits in many areas, especially in interconnects and logic contacts. Chemical mechanical polishing (CMP), which can realize local and global planarization, has been recognized as one of the indispensable manufacturing approaches for the fabrication of multilevel metal interconnection structures. The present work introduces diethanolamine (DEA) into our alkaline glycine-based slurries for Co CMP process. The action mechanism of DEA on Co CMP process in glycine-based slurries at pH 8.1 has been clearly revealed by various approaches, including polishing and static etching experiments, X-ray photoelectron spectroscopy survey, electrochemical analysis, as well as adsorption isotherm calculation. At low concentrations, DEA could be able to accelerate the polishing process via its auxiliary complexing effect, obtaining higher removal rates and larger corrosion current densities. Some pitting corrosion could appear on Co surfaces due to the production of Co-glycine complex as well as the auxiliary complexing process, making rougher surface qualities. On the other hand, when the DEA concentration increased to a certain level, it could play a role of corrosion inhibitor, protecting Co surfaces by forming a stable passive layer and moderating material removal rates, removal selectivity, and surface roughness.

Galvanic corrosion of Cu is a critical issue during the chemical mechanical polishing (CMP) process of barrier layer, especially when KIO4 is used as the oxidant in the polishing slurry. This paper focuses on the investigation of galvanic corrosion inhibitors (BTA and 1, 2, 4-triazole) for Cu/Ru couple in the KIO4-based solutions. The galvanic corrosion current of Cu was directly measured, and the corrosion inhibition efficiencies (CIE) were calculated. Results show that both BTA and 1, 2, 4-triazole are effective galvanic corrosion inhibitors of Cu. The CIE of 5 mM BTA and 2 mM 1, 2, 4-triazole is up to 69.4 and 59.7, respectively. On this basis, the corrosion inhibition mechanism was proposed. BTA forms a complete and tight three-dimensional multilayer structure on Cu when the concentration is over 0.5 mM. With regard to 1, 2, 4-triazole, the protective film on Cu is two-dimensional, and excessive dosage of 1, 2, 4-triazole will reduce the stability of the surface film, as well as the corrosion inhibition efficiency of Cu.

Cleaning processes draw considerable attention in integrated circuit manufacturing because of the rapid development of technology nodes. Bare silicon wafer cleaning after chemical mechanical polishing (CMP) is one of the most difficult processes used to meet the extremely strict industrial requirements. Herein, the silicon wafer cleaning mechanism is studied in detail. The effects of megasonic and brush cleaning on nanoparticle removal are both analysed through experiments and simulations. The experimental results show that chemical concentration, megasonic vibration power, and brush clamp gap all significantly affect the cleaning performance, and that excessive megasonic power reduces the cleaning performance because more defects are introduced. A model of megasonic nozzle trajectory is also proposed, and optimized parameters, especially the relative velocity between the wafer rotation and nozzle movement, are critical to removing nanoparticles effectively. Furthermore, analysis of combining megasonic and brush cleaning shows that including megasonic cleaning improves the wafer cleaning performance by several orders of magnitude. Based on the optimized cleaning conditions, an ultraclean wafer surface is achieved after CMP.

Chemical mechanical polishing (CMP) of GaN(0001) with a H2O2-SiO2-based slurry is investigated in this paper. The result shows that an atomically flat surface with a roughness of 0.065 nm is obtained after polishing. Compared with a SiO2-based slurry, the H2O2-SiO2-based slurry can realize a higher material removal rate (MRR) and a better surface quality with less scratches. The pH value mainly affects the mean particle size of SiO2 and the chemical environment of the corrosion reaction with H2O2, resulting in different MRRs. An off-site auxiliary polishing method is employed along with the H2O2-SiO2-based polishing system using ultraviolet light to shine the outlet of slurry in order to catalyze the production of substance for oxidation, and it is proved to be efficient by improving the MRR to 103 nm/h. Physical and mathematic removal models are proposed to describe the removal mechanism of GaN CMP.

A finite element analysis (FEA) model is developed for the chemical-mechanical polishing (CMP) process on the basis of a 12-in five-zone polishing head. The proposed FEA model shows that the contact stress non-uniformity is less dependent on the material property of the membrane and the geometry of the retaining ring. The larger the elastic modulus of the pad, the larger contact stress non-uniformity of the wafer. The applied loads on retaining ring and zone of the polishing head significantly affect the contact stress distribution. The stress adjustment ability of a zone depends on its position. In particular, the inner-side zone has a high stress adjustment ability, whereas the outer-side zone has a low stress adjustment ability. The predicted results by the model are shown to be consistent with the experimental data. Analysis results have revealed some insights regarding the performance of the multi-zone CMP.

In this paper, an in-situ interfacial fluid pressure measurement system had been developed for 12'' CMP equipment. Using this system, the interfacial fluid behavior is studied during the polishing process of 12-inch silicon wafer. The effects of the basic polishing variables, including the slurry injection position, the down force, the rotational speed, and the slurry flow rate, on the fluid pressure are investigated systematically. The results suggest that all of these polishing variables have obvious effects on the fluid pressure: the slurry injection position with suitable center distance between the pad and angular distance to the wafer leading edge is good for uniform slurry dispersion and the fluid pressure building; the increasing down force can increase the ratio of the positive pressure and the average fluid pressure significantly; the fluid pressure increases with the rotational speed till a critical speed and then decreases; the fluid pressure increases with the slurry flow rate slightly, the slurry injection position with larger center distance has lower critical speed and has greater dependence on the slurry flow rate due to the lower slurry utilization efficiency caused by larger centrifugal spraying effect.

In the research of Web content-based image retrieval, how to reduce more of the image dimensions without losing the main features of the image is highlighted. Many features of dimensional reduction schemes are determined by the breaking of higher dimensional general covariance associated with the selection of a particular subset of coordinates. This paper starts with analysis of commonly used methods for the dimension reduction of Web images, followed by a new algorithm for nonlinear dimensionality reduction based on the HSV image features. The approach obtains intrinsic dimension estimation by similarity calculation of two images. Finally, some improvements were made on the Parallel Genetic Algorithm (APGA) by use of the image similarity function as the self-adaptive judgment function to improve the genetic operators, thus achieving a Web image dimensionality reduction and similarity retrieval. Experimental results illustrate the validity of the algorithm.

Propagation characteristics of fundamental and higher-order modes are determined in coupled slotlines with three suspended mounting schemes (pedestal, groove, inverse pedestal) for wideband applications of microwave and millimeter-wave integrated circuits. The analysis is based on a novel enhanced spectral domain approach (ESDA) that combines essentially the conventional spectral domain technique with the power conservation theorem. Numerical results, considering also the influence of finite conductor thickness, are presented for propagation constants and characteristic impedance of the fundamental modes. Effects of different suspended mounting schemes on cutoff frequencies of first higher-order even and odd modes are discussed in detail. Field profiles of the fundamental modes in coupled slotlines with and without pedestals are shown. The inherent mechanism of mode transition is explained with respect to different pedestal sizes, indicating that the monomode bandwidth can be extended by appropriately choosing the dimension of pedestal in coupled slotlines.<>

An enhanced spectral domain approach (SDA) is developed for analysis of complex quasi-planar transmission lines. The method is based on a combination of the spectral domain formulation and power conservation theorem. The relationship between electric and magnetic fields is established inside dielectric layers by using the conventional SDA while the characteristic equation related to interface conditions is derived through the power conservation theorem. Maintaining the inherent advantages of the SDA, this technique is able to easily handle more complex quasi-planar structures. Generalized power formulation is also presented to calculate characteristic impedance. Convergence behavior is discussed considering the nature of power conservation. Various finlines with finite thickness of conductors are analyzed to demonstrate its applications.<>

A novel class of leaky-mode cylindrical dielectric resonators including mounting holder and radial-step has been recently proposed as a feed structure for omnidirectional antennas that are suitable for wireless communication systems. In this work, a spectral-domain modeling is developed and used for analysis of these composite cylindrical dielectric resonators considering single and double radiating slots. The dielectric resonators are bounded between two parallel conducting plates so that leaky-wave propagation takes place under some electrical and geometrical conditions. Results and discussion are focused on the properties of low-order leaky TM-modes. Influences of various structural parameters on resonant frequency and quality factor of leaky dielectric resonators are presented in detail. A set of experiments are made to verify the proposed theoretical approach.

Ru as a novel barrier/liner material for Cu interconnects, has gained application in the sub-10 nm technology node. In this paper, methods to polish patterned wafer with Ru/Ta/TaN tri-layers as liner/barrier have been proposed. Effects of pattern geometry and CMP variables (such as polishing down pressure and oxidant content) on polishing uniformity were fully investigated. Apart from this, interfacial defects after barrier polishing were comprehensive characterized by atomic force microscopy and transmission electron microscopy methods. Results show that hydrogen peroxide (H2O2) is effective in the mutual material removal of Cu/Ru/Ta/TaN/BD1 heterogeneous materials. Good surface quality could be obtained by using proper CMP process, with Cu dishing of 604.1 Å for the 100/100 μm array.

The adhesion force between slurry particles and the wafer surface has a significant effect on the material removal and ultra-smooth surface formation during the chemical mechanical polishing/planarization (CMP) process. Based on zeta potentials measurements, we calculate the value of adhesion force, which cannot be ignored compared with the Hertz contact force for small sized abrasive particles at low polishing pressures. More over, the impacts of slurry (particle size and pH value) and wafer surface roughness on the adhesion force are evaluated. Theoretical analyses manifest that the adhesion force mainly originates from the van der Waals force and electrical double-layer force, which increases with the increase of the particle size and slurry pH, while decreases with the increase of the wafer surface roughness. The relationships between the adhesion force and scratch depth indicate that scratching would be avoided while enhancing the adhesion force during CMP. These findings would provide some inspirations to understand the CMP technology in depth, and they are also beneficial to engineering super-smooth and super-lubricant surfaces with nano-scaled roughness.

Galvanic corrosion of Cu is a critical issue during the chemical mechanical polishing (CMP) process of barrier layer, especially when KIO4is used as the oxidant in the polishing slurry. This paper focuses on the investigation of galvanic corrosion inhibitors (BTA and 1, 2, 4-triazole) for Cu/Ru couple in the KIO4-based solutions. The galvanic corrosion current of Cu was directly measured, and the corrosion inhibition efficiencies (CIE) were calculated. Results show that both BTA and 1, 2, 4-triazole are effective galvanic corrosion inhibitors of Cu. The CIEof 5 mM BTA and 2 mM 1, 2, 4-triazole is up to 69.4 and 59.7, respectively. On this basis, the corrosion inhibition mechanism was proposed. BTA forms a complete and tight three-dimensional multilayer structure on Cu when the concentration is over 0.5 mM. With regard to 1, 2, 4-triazole, the protective film on Cu is two-dimensional, and excessive dosage of 1, 2, 4-triazole will reduce the stability of the surface film, as well as the corrosion inhibition efficiency of Cu.

Chemical mechanical polishing (CMP) of GaN(0001) with a H2O2-SiO2-based slurry is investigated in this paper. The result shows that an atomically flat surface with a roughness of 0.065 nm is obtained after polishing. Compared with a SiO2-based slurry, the H2O2-SiO2-based slurry can realize a higher material removal rate (MRR) and a better surface quality with less scratches. The pH value mainly affects the mean particle size of SiO2and the chemical environment of the corrosion reaction with H2O2, resulting in different MRRs. An off-site auxiliary polishing method is employed along with the H2O2-SiO2-based polishing system using ultraviolet light to shine the outlet of slurry in order to catalyze the production of substance for oxidation, and it is proved to be efficient by improving the MRR to 103 nm/h. Physical and mathematic removal models are proposed to describe the removal mechanism of GaN CMP.

Based on a rigorous analysis of finite element and curve fitting techniques, a set of accurate closed-form formulas are presented for the even and odd mode characteristic impedances of the coupled-lines made of two sliced coaxial cables. Compared with the rigorous solutions of the impedances, the values from the general expressions give an accuracy of >1% for a wide-range of cut depths and are suitable for all coupled lines with cables whose outer-inner conductor diameter ratio is between 1.4 and 10. These formulas can be applied to industrial applications of coupled lines.

In this paper, an in-situ interfacial fluid pressure measurement system had been developed for 12″ CMP equipment. Using this system, the interfacial fluid behavior is studied during the polishing process of 12-inch silicon wafer. The effects of the basic polishing variables, including the slurry injection position, the down force, the rotational speed, and the slurry flow rate, on the fluid pressure are investigated systematically. The results suggest that all of these polishing variables have obvious effects on the fluid pressure: the slurry injection position with suitable center distance between the pad and angular distance to the wafer leading edge is good for uniform slurry dispersion and the fluid pressure building; the increasing down force can increase the ratio of the positive pressure and the average fluid pressure significantly; the fluid pressure increases with the rotational speed till a critical speed and then decreases; the fluid pressure increases with the slurry flow rate slightly, the slurry injection position with larger center distance has lower critical speed and has greater dependence on the slurry flow rate due to the lower slurry utilization efficiency caused by larger centrifugal spraying effect.