Research On Fabrication Of Artificial Microstructure Photoelectric Functional Materials By Nanoimprint Lithography

Nanoimprint lithography (NIL) was first proposed in mid-1990s by Stephen Chou. With the advantages of high resolution, high production and low cost, NIL has attracted much attention of researchers. In this paper, the author focused on mold fabrication, process realization and applications of NIL in artificial microstructures fabrication.Mold of micro-area in different depth was fabricated by focused ion beam, which laid a foundation for preparation of artificial microstructures. And the author also fabricated large-area ordered porous alumina template by anodic oxidation after discussing the influence of some conventional parameters, and the porous pattern could be transferred through flexible hybrid mold.The author demonstrated the excellent performance of silicon-metal hybrid structure as antireflective layer for silicon wafer by simulation. To fabricate the hybrid structure, one must use alignment which can add complex operation and equipment cost in conventional NIL. The author designed a process to fabricate silicon-metal hybrid structure by NIL without alignment. Hot embossing NIL was first used to obtain different level resist structure with mold in different depth fabricated by FIB, and then transferred the structure to silicon by inductively coupled plasma etching. And the structure was then coated with NIL resist layer and it was flatted then. The high silicon exposed was etched to surface and other areas were still protected by resist. Metal was deposited by E-beam evaporation and then lifted off to get the final Si-Metal structure.In this paper, the author introduced the advantages of light emitting diodes (LEDs) with patterned sapphire substrates (PSS) and designed a process flow for PSS fabrication. UV-curable NIL was used to realize the first pattern transfer from mold to UV-resist. Inductively coupled plasma etching was used to complete the second pattern transfer from resist to silicon oxide wet etching mask layer. And finally, we applied wet etching method with hot sulfuric acid and phosphoric acid to achieve the third pattern transfer from silica to the sapphire substrate. In this way, the author fabricated PSS with periodic holes (d=1μm, p=3μm, h=450nm) successfully. And the author compared the photo luminescence spectrum of LEDs grown on PSS and plane substrate. Compared with LED grown on plane substrate, the photoluminescence intensity of LED grown on PSS was29.2%and25.8%enhanced at peak position and integration respectively.