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Cobalt (Co) with its low resistivity, superior adhesion property, and void-free seamless fill ability, pledges to transform the landscape of integrated circuits in many areas, especially in interconnects and logic contacts. The present work describes the selection and optimization process of the complexing agent and inhibitor in chemical mechanical polishing barrier slurries relevant for heterogeneous materials of Co interconnects. An alkaline colloidal silica based slurry has been proposed, consisting of 0.5 wt% hydrogen peroxide, 5 mM dipotassium ethylenediaminetetraacetic acid (EDTA-2K), 13 mM potassium oleate (PO) and producing a Co removal rate of 45.6 Å/min, along with an appropriate removal rate selectivity between oxide dielectric, barrier layer and Co, which reaches above ∼ 2:1:1. Furthermore, synergetic effects of the oxidizer, complexing agent EDTA-2K and inhibitor PO on the Co CMP process have been investigated systematically by several analytical techniques, including electrochemical analysis, X-ray photoelectron spectroscopy survey, and adsorption isotherm characterization. The role of EDTA-2K affecting SERs and MRRs embodies in its strong complexing ability by dissociating to full deprotonated EDTA ion and then reacting with Co to produce very stable chelate Co(Ⅱ)EDTA. Moreover, the effect of inhibitor PO has a critical point. With the addition of PO at a low concentration, an effective passivation layer could be formed on Co surfaces spontaneously via chemisorption, protecting Co from severe pitting corrosion. While in case of PO at high concentration, Co(Ⅱ)PO ligand will be generated, reducing the stability of the original PO-Co passive layer and providing paths for complexing agent EDTA-2K to produce Co(Ⅱ)EDTA chelate. [ABSTRACT FROM AUTHOR]

Effects of catalyst concentration and ultraviolet intensity on chemical mechanical polishing (CMP) of GaN were deeply investigated in this paper. Working as an ideal homogeneous substrate material in LED industry, GaN ought to be equipped with a smooth and flat surface. Taking the strong chemical stability of GaN into account, photocatalytic oxidation technology was adopted in GaN CMP process to realize efficient removal. It was found that, because of the improved reaction rate of photocatalytic oxidation, GaN material removal rate (MRR) increases by a certain extent with catalyst concentration increasing. Cross single line analysis on the surface after polishing by Phase Shift MicroXAM-3D was carried out to prove the better removal effect with higher catalyst concentration. Ultraviolet intensity field in H 2 O 2 -SiO 2 -based polishing system was established and simulated, revealing the variation trend of ultraviolet intensity around the outlet of the slurry. It could be concluded that, owing to the higher planarization efficiency and lower energy damage, the UV lamp of 125 W is the most appropriate lamp in this system. Based on the analysis, defects removal model of this work was proposed to describe the effects of higher catalyst concentration and higher power of UV lamp. [ABSTRACT FROM AUTHOR]

GaN is so hard and so chemically inert that it is difficult to obtain a high material removal rate (MRR) in the chemical mechanical polishing (CMP) process. This paper discusses the application of photocatalytic oxidation technology in GaN planarization. Three N-type semiconductor particles (TiO 2 , SnO 2 , and Fe 2 O 3 ) are used as catalysts and added to the H 2 O 2 –SiO 2 -based slurry. By optical excitation, highly reactive photoinduced holes are produced on the surface of the particles, which can oxidize OH − and H 2 O absorbed on the surface of the catalysts; therefore, more OH* will be generated. As a result, GaN MRRs in an H 2 O 2 –SiO 2 -based polishing system combined with catalysts are improved significantly, especially when using TiO 2 , the MRR of which is 122 nm/h. The X-ray photoelectron spectroscopy (XPS) analysis shows the variation trend of chemical composition on the GaN surface after polishing, revealing the planarization process. Besides, the effect of pH on photocatalytic oxidation combined with TiO 2 is analyzed deeply. Furthermore, the physical model of GaN CMP combined with photocatalytic oxidation technology is proposed to describe the removal mechanism of GaN. [ABSTRACT FROM AUTHOR]

When the feature size of integrated circuit continues to shrink below 14 nm, ruthenium (Ru) has become one of the most promising candidates for the application of novel barrier layer. To reveal the material removal mechanism of Ru during chemical mechanical polishing (CMP), surface characteristics of Ru in KIO 4 -based slurry were investigated. The corrosion behavior of ruthenium was measured by the surface chemistry and morphology analysis. Then the mechanical properties of the passivated/corroded surface were evaluated by AES and tribocorrosion experiments. CMP experiments were carried out to make clear the effects of surface property during polishing. It was found that the Ru surface chemistry and mechanical properties vary obviously as a function of slurry pH. In neutral slurries, the Ru surface is covered with RuO 2 ·2H 2 O/RuO 3 inhomogeneous passivation films, with the highest material removal rate obtained during the CMP process. It could be concluded that the material removal mechanism largely depends on the slurry pH values. In near neutral slurries, Ru is passivated with thick and heterogeneous oxides film, which proves the easiest to be mechanically removed during polishing. The weak alkaline slurry is preferred in order to achieve desirable polishing rate as well as avoid the formation of toxic RuO 4 . [ABSTRACT FROM AUTHOR]

Abstract: In this paper, the contact stress distribution on the wafer surface in multi-zone CMP is investigated using finite-element analysis based on a 12-in. and four-zone CMP model. Afterwards, a 12-in. and four-zone polishing head with the same size as the numerical model is developed and CMP experiments are carried out to verify the above numerical calculations. The results show that both the contact stress on the wafer surface and the material removal rate of the wafer can be adjusted by varying the applied load at the zones and the retaining ring in multi-zone CMP, the multi-zone MRR model appears to agree well with the experimental data, and the non-uniformity material removal rate of the wafer can be improved in multi-zone CMP. It is expected that this investigation can give some direct assistance to the 12-in. wafer fab. [Copyright &y& Elsevier]

This paper focuses on the study of micro-galvanic corrosion of the Cu/Ru couple in KIO 4 solution. Practical nobility across the Cu/Ru interface was evaluated by Volta potential mapping, and the morphological changes were monitored by in-situ atomic force microscopy measurements during exposure in a KIO 4 solution. Chemical composition of precipitated corrosion product was analyzed by Confocal Raman spectroscopy immediately after the exposure. The results show that Cu is the anode of the Cu/Ru couple, and accelerated dissolution of Cu preferentially occurs near the Cu/Ru interface. However, subsequent formation of insoluble Cu(IO 3 ) 2 ·nH 2 O leads to precipitation, which impedes further Cu corrosion. [ABSTRACT FROM AUTHOR]

In the ultra large-scale integration process, as chemical mechanical polishing (CMP) is developing to higher precision, nano level planarity and sub-nano level roughness of wafer surfaces become key problems to be overcome. In this work, a theoretical model for local and total material removal was proposed based on the particle sliding trajectories and chemical-mechanical synergy, and the material removal distribution on wafer surface were analyzed. Furthermore, the chemical-mechanical mechanism was studied and synergy maps constructed. It is found that the passivation-wear and additive-synergistic effects dominate the material removal during CMP. This study establishes a correlation mechanism between the nano material removal and global uniformity of wafer surfaces, which provides theoretical and experimental framework for optimizing the slurry and the process parameters. [ABSTRACT FROM AUTHOR]

In this study, a specially designed carrier with a one-zone pneumatic loading system that uses a thick copper disk as the workpiece was developed. Comparative studies of the fluid pressure and workpiece orientation between the disk and wafer carriers during chemical mechanical polishing were conducted. The results reveal that the copper disk leans down toward the leading edge and produces a negative-dominated (approximately 70%) fluid pressure, which differs from the multi-zone carrier but agrees with other studies in which the fluid pressure is measured from the disk side. Different balancing statuses and wedged gaps are formed in these two structures. [ABSTRACT FROM AUTHOR]

Abstract: A novel in-situ wafer bending/orientation measurement system, cooperated with our previous developed fluid pressure mapping system, was developed for 12-inch chemical mechanical polishing (CMP) equipment. Wafer bending and wafer orientation are studied for copper wafer sliding against the IC1000 pad. The results reveal a micron level wafer bending, and a slight wafer pitch angle of 10−5 degree. Both the wafer pitch angle and interfacial fluid pressure increase with the speed till a critical speed and then decrease. The convergent-dominated wedged gap caused by the convexly bended, trailing edge pitched wafer gives a reasonable explanation to the positive-dominated fluid pressure. [Copyright &y& Elsevier]

Using atomic force microscopy and scanning electron microscopy, the mechanical removal mechanism of silicon with different exposure surfaces of cerium oxide (CeO 2) is studied. It is discovered that the main type of mechanical wear between Si and CeO 2 is adhesive wear. The silicon removal rate relationship is RR 1 1 RR means removal rate of silicon by CeO 2. (CeO 2 (111))> RR(CeO 2 (100))> RR(CeO 2 (110)). Additionally, the relationship of the friction force remains constant: F 2 2 F means friction force between silicon and CeO 2. (CeO 2 (111)) > F(CeO 2 (110)) > F(CeO 2 (100)). This is consistent with the ceria wear rate relationship of WR 3 3 WR means wear rate of CeO 2. (CeO 2 (111)) > WR(CeO 2 (110)) > WR(CeO 2 (100)). This paper provides a deeper insight into the mechanical material removal mechanism during chemical mechanical polishing processes; thus, providing a reference for CeO 2 particle orientation control. Image 1 • Si mechanical removal mechanism was studied using different exposure surfaces of CeO 2. • Adhesive wear is the main wear type between Si and CeO 2. • The friction relationship between Si and CeO 2 remains constant. • CeO 2 (111) is found to have the strongest Si removal capacity. • CeO 2 (110) has the weakest Si removal capacity, related to its highest surface energy. [ABSTRACT FROM AUTHOR]

Fault diagnosis with transfer learning has achieved great attention. However, existing methods mostly focused on single-source-single-target sceneries. In some cases, there may exist multiple source domains. Therefore, a reinforcement ensemble deep transfer learning network (REDTLN) is proposed for fault diagnosis with multi-source domains. Firstly, various new kernel maximum mean discrepancies (kMMDs) are used to construct multiple deep transfer learning networks (DTLNs) for single-source-single-target domain adaptation. The differences of kernel functions and source domains can help the DTLNs learn diverse transferable features. Secondly, a new unified metric is designed based on kMMD and diversity measures for unsupervised ensemble learning. Finally, using the unified metric as the reward, a reinforcement learning method is firstly explored to generate an effective combination rule for multi-domain-multi-model reinforcement ensemble. The proposed method is verified with experiment datasets, and the results empirically show its effectiveness and superiority compared with other methods. [ABSTRACT FROM AUTHOR]