Thermal stability of monolayer $W{S}_2$ in BEOL conditions

Abstract

Monolayer tungsten disulfide ($W{S}_2$) has recently attracted large interest as a promising material for advanced electronic and optoelectronic devices such as photodetectors, modulators, and sensors. Since these devices can be integrated in a silicon (Si) chip via back-end-of-line (BEOL) processes, the stability of monolayer $W{S}_2$ in BEOL fabrication conditions should be studied. In this work, the thermal stability of monolayer single-crystal $W{S}_2$ at typical BEOL conditions is investigated; namely (i) heating temperature of $300$ ${}^{\circ }C$, (ii) pressures in the medium- ($10^{-3}$ mbar) and high- ($10^{-8}$ mbar) vacuum range; (iii) heating times from $30$ minutes to $20$ hours. Structural, optical and chemical analyses of $W{S}_2$ are performed via scanning electron microscopy (SEM), Raman spectroscopy, photoluminescence (PL) and X-ray photoelectron spectroscopy (XPS). It is found that monolayer single-crystal $W{S}_2$ is intrinsically stable at these temperature and pressures, even after $20$ hours of thermal treatment. The thermal stability of $W{S}_2$ is also preserved after exposure to low-current electron beam ($12$ pA) or low-fluence laser ($0.9$ $mJ/\mu m^2$), while higher laser fluencies cause photo-activated degradation upon thermal treatment. These results are instrumental to define fabrication and in-line monitoring procedures that allow the integration of $W{S}_2$ in device fabrication flows without compromising the material quality.

21 pages, 5 figures

References in corpus (9)

• Integrated Circuits Based on Bilayer MoS2 Transistors
• Electrical Transport Properties of Single-Layer WS2
• Improved Contacts to MoS2 Transistors by Ultra-High Vacuum Metal Deposition
• Mono- and Bilayer WS2 Light-Emitting Transistors
• Interlayer Exciton Optoelectronics in a 2D Heterostructure p-n Junction
• Spin Hall effect and Weak Antilocalization in Graphene/Transition Metal Dichalcogenide Heterostructures
• Oxidation of Monolayer WS${}_2$ in Ambient is a Photoinduced Process
• High contrast imaging and thickness determination of graphene with in-column secondary electron microscopy
• Excitonic Complexes and Emerging Interlayer Electron-Phonon Coupling in BN Encapsulated Monolayer Semiconductor Alloy: WS0.6Se1.4