Search

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]

In the via-middle process of 3-D integrated circuit manufacturing, through-silicon via (TSV) annealing causes mechanical stress not only to its surrounding structures, including liner and landing pad, but also the contacts nearby. This process may result in a noticeable pop-out in TSVs and/or contacts, thus complicating the subsequent chemical mechanical polishing (CMP). In addition, residual stress may cause delamination or crack. In this paper, we conducted detailed simulations of the residual stress and pop-out mechanisms for TSVs and neighboring contacts. Our primary focus was on the interplay of TSV-induced and contact-induced stresses and their combined impact on pop-out height. In addition, we conducted a sensitivity analysis of key parameters, including distance, plasticity, annealing temperature, and the distribution of neighboring contacts. This paper showed that these parameters notably affect the stress and the pop-out of TSVs and contacts. This in turn is expected to complicate the subsequent CMP steps. Finally, we applied the linear superposition method to predict stress and validated its accuracy by comparing the results with finite element analysis simulation. The results of the comparison demonstrated that the superposition method was accurate. Therefore, it could be used to predict the stress for full-chip design. [ABSTRACT FROM PUBLISHER]

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]