A review of monitoring for nanoimprinting

Purpose: This article provides an overview of the monitoring technique for nanoimprint. Optical and electrical monitoring approaches that have the potential for detecting and monitoring mold deformation and cavity filling in nanoimprint will be reviewed. The major part is devoted to the review of an in-situ mold filling monitoring system based on capacitance measurement for nanoimprinting operations. Design/methodology/approach: In carrying out the capacitive monitoring method, a broad range of areas including tuning the imprint process, designing a reliable capacitive sensor, finding out the right materials and a suitable surface micromachining process for sensing electrodes, and data analysis have been covered. In addition, to measure the continuous variations in capacitance, a series of imprinting experiments have been performed isothermally, and the capacitance values have also been measured at various imprinting stages. Findings: The final stage of mold filling near the end, which is of particular interest, can be monitored and the experimental results have demonstrated that the capacitance measurements indeed provide the in-situ information that can tell the mold filling status during nanoimprinting. Research limitations/implications: The use of neural networks to model the functional relationship between the capacitance value and the rising height of mold filling is recommended as another potential area for future research to realize the ultimate objective of providing online real-time mold filling information for imprinting process control. Practical implications: Throughout the study, the authors conclude the proposed capacitance measurement technique is a promising approach for monitoring mold filling in nanoimprinting process, and the practical application of the conducted research is feassible with certain improvement of the robustness of the monitoring technique in harsh environment of higher imprinting temperature. Originality/value: The reviewed monitoring methods are based on the authors’ approved and pending patents [22,32,33]. They are considered pioneering works for the research community of nanoimprint techniques and as the basis of making nanoimprint process automated.