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The fabrication of InGaAs n-channels in CMOS devices requires an intervening buffer layer of GaAs or InP between a Si substrate and the InGaAs channel layer, which has to be planarized to enable the growth of a channel that is free of defects due to uneven surface topography. This report discusses the material removal rates (RRs) and AsH 3 evolution observed during chemical mechanical polishing (CMP) of GaAs using aq. solutions of hydrogen peroxide (H 2 O 2 ) and silica slurries containing H 2 O 2 . GaAs RRs were negligible with deionized water or with silica slurries alone. They were relatively high in aq. solutions of H 2 O 2 alone and showed a strong pH-dependence, with significantly higher RRs in the alkaline region. The addition of silica particles to aq. H 2 O 2 did not increase the GaAs RRs significantly. The evolution of arsenic trihydride (AsH 3 ) during the dissolution of GaAs in aq. H 2 O 2 solution was similarly higher in the basic pH range than in neutral pH or in the acidic pH range. However, no AsH 3 was measured during polishing, evidently because of the relatively high water solubility of AsH 3 . In this report, GaAs removal rates and AsH 3 formation are analyzed using data from contact angle measurements, X-Ray photoelectron spectroscopy (XPS), and X-Ray fluorescence (XRF) spectroscopy. Reaction pathways leading to material removal are proposed.The quest for faster devices in the microelectronic industry has renewed interest in III-V materials such as InP, GaAs, and InGaAs as n-channel candidates because of their high electron mobility. 1,2 During the fabrication of n-channels in CMOS devices, chemical mechanical polishing (CMP) of these materials is required to achieve a smooth and planar surface to enable further processing. There are several environmental health and safety (EHS) issues associated with polishing and wet processing of these III-V materials. 2-5 The EHS concerns for As containing materials include the evolution of toxic arsenic trihydride (AsH 3 ) gas, and the handling of arsenic contaminated slurry waste and used consumables (e.g., polishing pads). For InP, the major concern has been the generation of toxic phosphine gas during polishing. 3,4 In this work, the focus is on the chemical mechanical polishing of GaAs and evolution of AsH 3 .There are several reports on the CMP of GaAs using slurries that contain oxidizers such as hydrogen peroxide (H 2 O 2 ), sodium hypochlorite (NaOCl), and dibromine (Br 2 ). 6-9 McGhee et al. 6 proposed a three step mechanism for GaAs removal in an aqueous solution containing H 2 O 2 and ammonia. An oxohydroxyl layer, consisting of sparingly soluble oxohydroxides of Ga and As, was first formed on the surface. These oxohydroxides were converted to soluble species upon complexation with aq. NH 3 . The soluble species were then removed from the surface by mechanical wiping. In Br 2 -MeOH solutions, they proposed that an adsorbed Br layer was formed on the GaAs surface. The adsorption of bromine was followed by a redox reaction, which continued as lo...

During the chemical mechanical polishing (CMP) of an indium phosphide buffer layer for the fabrication of InGaAs n-channels in CMOS devices, there is interest in controlled removal of In and P atoms from the surface and avoidance of the generation of toxic phosphine (PH 3 ) gas. We report InP removal rates and phosphine generation during InP CMP in hydrogen peroxide based silica particle dispersions in the presence and absence of three different multifunctional chelating carboxylic acids, namely oxalic acid, tartaric acid, and citric acid. The presence of these acids in the polishing slurry resulted in highly smooth surfaces (about 0.1 nm RMS surface roughness) with good InP removal rates (about 400 nm min −1 ) and very low phosphine generation (<15 ppb). The optimized slurry compositions are reported herein. We use chemical dissolution measurements, attenuated total reflectance Fourier transform infrared spectroscopy (ATR-FTIR), X-ray photoelectron spectroscopy (XPS), and zeta potential measurements to discuss the InP removal rate and phosphine generation data and to propose InP removal and phosphine generation mechanisms. Thermodynamic calculations of the Gibbs free energy of reaction are used to validate the proposed reactions.