Thermal stability of monolayer WS₂ in BEOL conditions

Abstract

Monolayer tungsten disulfide (WS2) 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 WS2 in BEOL fabrication conditions should be studied. In this work, the thermal stability of monolayer single-crystal WS2 at typical BEOL conditions is investigated; namely (i) heating temperature of 300 °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 WS2 are performed via scanning electron microscopy (SEM), Raman spectroscopy, photoluminescence (PL) and X-ray photoelectron spectroscopy (XPS). It is found that monolayer single-crystal WS2 is intrinsically stable at these temperature and pressures, even after 20 hours of thermal treatment. The thermal stability of WS2 is also preserved after exposure to low-current electron beam (12 pA) or low-fluence laser (0.9 mJ/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 WS2 in device fabrication flows without compromising the material quality.

Heteroatomic stitching of broken WS2 monolayer with enhanced surface potential

“…Generally, the E′ peak in WS 2 merges with the 2LA(M) peak and together, they construct a high-intensity single peak. 32 In the case of the WS 2 region, E′ was found at ∼349.36 cm −1 and A 1 ′ at ∼417.99 cm −1 , which are close to the literature values reported by S. Pak and co-workers. 33 For the MoS 2 edge region, E′ was found at ∼383.02 cm −1 and A 1 ′ at ∼408.02 cm −1 .…”

Molecularly Hybridized Conduction in DPP‐Based Donor–Acceptor Copolymers toward High‐Performance Iono‐Electronics

“…Typically, the semiconducting channels must undergo baking steps at the BEOL, which temperatures as high as 300 °C. [ 61 ] Currently, no polymer system has been shown to sustain such conditions, posing a challenge for integrating organic‐based synaptic devices in advanced circuits. The bottleneck stems from the fact that to enable ion insertion, polar and bulky sidechains are employed.…”

Unexpected Electron Transport Suppression in a Heterostructured Graphene–MoS2Multiple Field-Effect Transistor Architecture

“…0.85). Laser power was ∼1mW and the typical acquisition time was 4 s. 62 Transport measurements were performed in a vacuum chamber using source-measure units K4200 and K2614B and a Femto DDPCA-300 current preamplifier.…”