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Despite the fact that substantial research has been conducted on the through-silicon via (TSV) formation process during three-dimensional integration, there is still less understanding on the chemical mechanical planarization (CMP) process and post-CMP via dishing control mechanism in TSV fabrication. In this study, we investigated the synergistic effect of mechanical and chemical factors on the CMP performance of TSV, and analyzed the experimental results from different aspects. A high-resolution surface-profile-measuring instrument, combined with Scanning Electron Microscopy (SEM) and other measurements, was used to demonstrate the mechanism of non-uniformity and via dishing, and the experimental results indicate that via dishing and non-uniformity of wafers are strongly mitigated by combining high down force with low down force. Based on numerical analysis, it can be concluded that the solution of the via protrusion issue requires a sufficiently high hydrogen peroxide concentration in order to modify the removal rate selectivity of copper and barrier/oxide. The polishing time should be strictly controlled to prevent oversize dishing or protrusion. Moreover, material removal models for via dishing, based on several factors mentioned above, were established to elucidate the mechanism of via dishing/protrusion formation, and to illustrate the further optimization of the TSV–CMP process. [ABSTRACT FROM AUTHOR]

Highlights: [•] This study aimed to maximize the material removal rate and minimize the within wafer non-uniformity simultaneously. [•] The design of experiment approach was used to optimize the process parameters for CMP of a 12-inch wafer. [•] Confirmation tests indicated that MRR of 6551Å/min and WIWNU of 4.72% can be obtained using the optimum combination. [ABSTRACT FROM AUTHOR]

Highlights: [•] Wafer bending and fluid pressure are measured during 12-inch multi-zone CMP. [•] Multi-zone carrier has zone-loading effect on wafer bending. [•] Zone pressure configuration affects wafer bending and fluid pressure. [•] Convexly-bended wafer generates the largest fluid pressure due to a suitable wedged gap. [•] Higher edge zone pressure contributes to concave bending and lower fluid pressure. [Copyright &y& Elsevier]

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]

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]