Trilayer Nanoimprint And Its Applications In Template Duplication And Silicon Nanowire Sensor Fabrication

Due to its low cost,high efficiency and high resolution,the nanoimprint technology, as one of the most promising next generation photolithography techniques has been intensively studied recently.The silicon nanowire(SiNW) sensor has been widely used in gas detection, chemical and biological sensing due to its perfect semiconductor process compatibility and biological compatibility.While the conventional fabrication of SiNW always involves electron beam lithography(EBL) which is expensive with low efficiency.In this work we studied the fabrication of nanowire gas sensor using novel nanoimprint technology,which has not only high potential for application,but also has great scientific value in nanodevice investigation,such as size effect.In this thesis,we developed a novel SU-8/SiO₂/PMMA trilayer nanoimprint process to transfer nanosize patterns.This process possesses advantages of low imprint temperature,good reliability,dimensional controllability and low cost.After optimizing the process parameters,we successfully duplicated the nanoimprint template by this process.The duplicated template which shows sub-10nm dimensional loss include different period gratings(1um,500nm,300nm) and the chiral structure.We further applied this technique to fabricate the SiNW sensors with two different linewidth(75nm,135nm).The fabricated devices were used to detect 250ppm NO₂ and NH₃ gas.The sensitivity of the nanowire devices,especially the 75nm device,show more than 15 times large enhancement comparing to the thin film device which has no any nanostructure.Some of the experimental result has been well explained by the computer simulation.Finally,SiNW sensors with decreased width and perfect surface state has been fabricated by nanoimprint and wet etching.Besides, a seria research about soft template has been done.