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Recently, the technology node shrunk below 7 nm and beyond; cobalt (Co) and its low resistivity, superior adhesion property, and excellent electro-migration performance pledge to transform the integrated circuits' landscape in several areas, especially in interconnects and logic contacts. The present work proposes a weakly alkaline polishing slurry for Co interconnects, mainly consisting of colloidal silica, hydrogen peroxide, glycine, and 1,2,4-triazole at pH 8.1. The feature of tunable high material removal rate (greater than 1000–2000 Å/min) and fitting removal selectivity (~ 160) between Co and oxide dielectric could be realized by a moderately variable concentration of glycine complexing agent. Moreover, several analytical techniques, including electrochemical analysis, X-ray photoelectron spectroscopy survey, and adsorption isotherm characterization, were used to understand the interaction mechanism during Co material removal process. The results reveal that 1,2,4-triazole could adsorb on the Co oxide layers via physisorption, achieving an inhibition effect to avoid Co excessive corrosion. Furthermore, the oxidization of hydrogen peroxide, the complexation of glycine zwitterions, and the abrasive mechanical action are critical to maintaining the appropriate material removal rate. Based on the results with research-level wafers, the optimized Co bulk slurry was ultimately applied to the production-level of Co and oxide dielectric wafers. The residual particle, haze condition, and surface profile after polishing have been researched simultaneously. [ABSTRACT FROM AUTHOR]

Cobalt (Co) has been applied as one of the most promising candidates of barrier metals for copper (Cu) interconnects. The present work describes the static etching and chemical mechanical polishing process of Cu and Co, which were conducted by potassium persulfate (K2S2O8) as an oxidizer at various pH values. It was found that compared with the conventional oxidizer hydrogen peroxide (H2O2)-based slurries, the K2S2O8-based slurries exhibited a relatively high Co removal rate, as well as the diminished particulate contamination and excellent post-etching morphology. A slurry consisting of 3 vol% colloidal silica, 10 mM K2S2O8, and 5 mM benzotriazole (BTA) produced a Co removal rate of ~ 127 Å/min at pH 10, along with a removal rate selectivity of ~ 1 between Cu and Co films. Based on the data of X-ray photoelectron spectroscopy, scanning electron microscopy, and nano-scratch depth tests, the interplaying mechanisms of chemical and mechanical on Cu and Co removal rates in K2S2O8-based slurries were investigated. [ABSTRACT FROM AUTHOR]

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]

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]

Although there are substantial studies on chemical mechanical polishing (CMP) processes of ruthenium (Ru) as a barrier layer in periodate-based slurries, little is known about the passivation mechanism of inhibitors and the galvanic corrosion mechanism of Cu. In this study, the synergetic effect of benzotriazole (BTA) and potassium molybdate (K 2 MoO 4 ) on the polishing performance of Ru and Cu in KIO 4 -based slurry was investigated. The galvanic corrosion of Cu in a Cu–Ru coupled system was studied from a completely different perspective. X-ray photoelectron spectroscopy combined with other measurements was used to reveal the synergetic passivation mechanism of BTA and K 2 MoO 4 . The results show that the galvanic corrosion of Cu is strongly mitigated in the presence of both BTA and K 2 MoO 4 . Based on the data, it was regarded that the adsorbed MoO 4 2− not only modified the surface structure of Ru and Cu, but also supported the adsorption of BTA passivation film. Also, it was found that insoluble salts were deposited into the gaps of the passivation film, which improved the compactness of the molybdate-BTA film. The CMP tests showed that the selectivity of the material removal rate of Cu to Ru can be evidently improved in the presence of BTA and K 2 MoO 4 . The increase of oxidizer content and the reduction of polishing down force could help to further decrease the MRR selectivity between Cu and Ru. [ABSTRACT FROM AUTHOR]

Copper chemical mechanical polishing/planarization (CMP) is subject to mechanical actions by abrasive wear coupled with simultaneous chemical effects via slurries at the wafer/pad interface. Therefore, it is necessary to investigate slurry chemical effects on the contact interface. The chemical roles of friction as functions of slurry pH during copper CMP process were studied. The wettability and particle size of the slurry had non-dominant influence on the friction force of the polishing interface. According to OCP measurements, XPS and Raman analysis, chemical reactions occurring on the polishing interface led to varying the tribology behavior during CMP process. The formation of Cu-BTA complex under acidic conditions increased the coefficients of friction (COF), while chemical dissolution under alkaline conditions resulted in lower COF. The results provide more understanding of tribological principles and further optimization of the CMP process. [ABSTRACT FROM AUTHOR]

• Surface doping of CeO 2 as CMP abrasives was done using La, Nd and Yb. • O vacancy formation energy and Ce3+ content was calculated by DFT and XPS. • Ce3+ content of CeO 2 is largely improved after doping. • Doped CeO 2 as CMP abrasive improves the polishing rate of SiO 2 and surface quality. Ce3+ in CeO 2 , rather than Ce4+, is believed to provide assistance to the breaking up of Si O bond during chemical mechanical polishing (CMP) of silica. In the paper, lanthanide metals (La, Nd and Yb) doped CeO 2 nanoparticles were synthesized by modified incipient impregnation method in order to improve the content of Ce3+ in CeO 2 as polishing. X-ray photoelectron spectroscopy (XPS) experiments and density function theory (DFT) calculation demonstrate this approach could achieve surface doping of CeO 2 nanoparticles, and facilitates the formation of oxygen vacancy and Ce3+ content. CMP experiments show that the polishing rate and the surface quality of silica wafer are obviously improved by using the doped CeO 2 as abrasive particles. Especially for Nd/CeO 2 , content of Ce3+ increases from 0.146 to 0.235, the polishing rate of silica is accelerated by 29.6% in alkaline slurries, and a better surface quality (Sa = 9.6 Å) is obtained. [ABSTRACT FROM AUTHOR]