In situ differential atomic force microscopy (AFM) measurement for ultra-thin Thiol SAM patterns by area-selective deposition technique

Developing novel characterization methods is crucial to enhancing the accuracy and precision of measurements in semiconductor ultrathin films. By combining "bottom-up" and "top-down" patterning techniques, we successfully fabricated five uniform alkyl thiol-derived self-assembled monolayer (SAM) patterns. Employing the innovative in situ differential Atomic Force Microscopy (AFM) Measurement, we analyzed the thickness, morphology, and mechanical properties of the thiol films. This method greatly reduced errors caused by uneven substrates, resulting in more precise measurements compared to large-area measurements. It is shown that as the thiol chain length increased, the variation in SAM film thickness aligned consistently with the thickness of a single Atomic Layer Deposition (ALD) cycle, and the surface roughness of the SAM surface mirrored that of ALD. Consequently, the experiment affirms the effectiveness of the SAM film in simulating ALD, providing validation for the precision and feasibility of the in situ differential results. Furthermore, adhesion measurement results revealed a diminishing passivation effect of SAM as the chain length increased. This suggests that an appropriate SAM could be selected as a passivation material through real-time monitoring of the mechanical properties of the mask surface during the Area-Selective Deposition (ASD) process. Conclusions: In situ differential AFM measurements characterize the surface thickness, morphology and mechanical properties of thiol self-assembled monolayer patterns. [Display omitted]