Novel Nano-scale Overlay Alignment Method for Room-temperature Imprint Lithography

A novel nano-scale alignment technique based on Moiré signal for room-temperature imprint lithography in the submicron realm is proposed. The Moiré signals generated by a pair of quadruple gratings on two templates respectively are optically projected onto a photodetector array, then the detected Moiré signals are used to estimate the alignment errors in x and y directions. The experiment result indicates that complex differential Moiré signal is sensitive to relative displacement of the pair of marks than each single Moiré signal, and the alignment resolutions obtained in x and y directions are ±20nm(3σ) and ±24nm(3σ). They can meet the requirement of alignment accuracy for submicron imprint lithography.

Imprint Lithography at Room Temperature with Novolak Resin and Its Application

1 Results Imprint lithography[1] has attracted considerable attention from the viewpoint of low cost fabrication,because light exposure systems are not required. Up to now,polymethylmethacrylate (PMMA) films and hard molds were often used in imprint lithography.In this paper,we report on the successful demonstration of imprint lithography using novolak resin (OFPR-800),which is more suitable than PMMA for dry etching,and a soft mold such as a soft polyester sheet,which has a two-dimensional (2D) square ...

Implementation of Autofocus in Alignment System for Layered Imprint Fabrication

Autofocus method based on the analysis of image content information is investigated to reduce the alignment error resulting from mark positioning uncertainty due to defocus in microstructure layered fabrication process based on multilevel imprint lithography. The applicability of several autofocus functions to the alignment mark images is evaluated concerning their uniformity, sharpness near peak, reliability and measure computation efficiency and the most suitable one based on power spectrum in frequency domain (PSFD) is adopted. To solve the problem of too much computation amount needed in PSFD algorithm, the strategy of interested region detection and effective image reconstruction is proposed and the algorithm efficiency is improved. The test results show that the computation time is reduced from 0.316 s to 0.023 s under the same conditions while the other merits of the function are preserved, which indicates that the modified algorithm can meet the mark image autofocusing requirements in response time, accuracy and robustness. The alignment error due to defocus which is about 0.5 μm indicated by experimental results can be reduced or eliminated by the autofocusing implementation.

Self-nucleation of Patterned Polymer Thin Films Defined by Soft Lithography

The nucleation of crystals is often a determining step in the phase transition of materials,but it remains a challenge to control the density and specific location of nuclei simultaneously.Here we fabricated the isolated single crystals of uniform size with controlled number density and spatial distribution by self-nucleation of patterned dendritic crystals.Imprint lithography creates the periodic void space on the surface of poly(ethylene oxide)-b-poly(2-vinyl pyridine)(PEO-b-P2VP)block copolymer thin films and provides spatial redistribution of polymers,leading to the preferential nucleation and subsequent oriented growth of dendrites in the periodic arrays of imprinted lines.The morphology and thermal stability of the patterned crystals can be adjusted by tuning embossing conditions(e.g.,temperature and pressure).Furthermore,in the self-nucleation technique,the annealing temperature and heating rate are used as the feedback parameters to map the number density and spatial distribution of regrown single crystals.Such PEO-b-P2VP crystalline pattern can be used as a versatile template for large-area manufacturing of selective metal patterns for electronic devices and other applications.

Control of visible‑range transmission and refection haze by varying pattern size,shape and depth in fexible metasurfaces

Cost-efective soft imprint lithography technique is used to prepare fexible thin polymeric surfaces containing a periodic arrangement of nanodimples and nanobumps of sub-micron size.Using a single master mold of self-assembled colloidal crystal,metasurfaces with diferent depths and heights of patterns with a fxed pitch are possible,which makes the process inexpensive and simple.These metasurfaces are studied for their difuse and total transmission and refection spectra in the visible range.The transmission haze and refection haze are calculated from the measurements.The surface containing nanobumps of lesser pattern height result in higher values of refection and transmission haze than from surfaces containing nanodimples of much higher depth for the same pitch.The haze is more dependent on the pattern depth or height and less dependent on the pitch of the pattern.Far-feld transmission profles measured in the same wavelength range from the patterned surfaces show that the scattering increases with the increase of the ratio of pattern depth/height to pitch,similar to the haze measurements conducted with a closed integrating sphere.These profles show that the angular spread of scattered light in transmission is within 10°,explaining the reason for the relatively low transmission haze in all the patterned surfaces.Simulation results confrm that the nanobump pattern gives higher transmission haze compared to nanodimple pattern.By controlling the ratio of pattern depth/height to pitch of the features on these surfaces,both an increase in optical haze and a balance between total refection intensity and total transmission intensity can be achieved.