Wafer-Scale Integration of Monolayer MoS₂ via Residue-Free Support Layer Etching and Angular Strain Suppression

Abstract

A crack-free and residue-free transfer technique for large-area, atomically-thin 2D transition metal dichalcogenides (TMDCs) such as MoS2 and WS2 is critical for their integration into next-generation electronic devices, either as channel materials replacing silicon or as back-end-of-line (BEOL) components in 3D-integrated nano-systems on CMOS platforms. However, cracks are frequently observed during the debonding of TMDCs from their growth substrates, and polymer or metal residues are often left behind after the removal of adhesive support layers via wet etching. These issues stem from excessive angular strain accumulated during debonding and the incomplete removal of support layers due to their low solubility. In this study, we developed a novel debonding strategy along with an optimized etching protocol to address these challenges. Characterization using Raman spectroscopy, photoluminescence (PL), X-ray photoelectron spectroscopy (XPS), atomic force microscopy (AFM), and optical microscopy (OM) confirmed that the optimized process enables clean, crack-free, and morphologically intact MoS₂ films. The success of the crack-free and residual-free transfer is attributed to two key factors: (1) the suppression of mechanical bending during debonding, which eliminates bending-induced crack formation; and (2) the precise control of etchant concentration, reaction duration, and post-etch rinsing steps, which ensures the complete removal of the support layer without damaging the MoS2 film. Using commercially available fab tools such as wafer bonders and debonders, we successfully demonstrated the clean transfer of a 2-inch monolayer MoS2 film with a high transfer yield of 95 %, highlighting the practical applicability of this process for scalable device fabrication.