Hexagonal microlens array modeling and fabrication using a thermal reflow process

Lin, Che-Ping; Yang, Hsiharng; Chao, Ching‐Kong

doi:10.1088/0960-1317/13/5/333

Cited by 113 publications

(61 citation statements)

References 12 publications

(16 reference statements)

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“…Reflow of the photoresist takes place at temperatures beyond the glass transition temperature, at which the resist becomes soft and starts flowing on the substrate due to surface tension [7]. This approach for reflow is referred to as thermal reflow.…”

Section: Thermal Reflowmentioning

confidence: 99%

Vertically tapered layers for optical applications fabricated using resist reflow

Emadi¹,

Grabarnik

et al. 2009

J. Micromech. Microeng.

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This paper reports on the IC-compatible fabrication of vertically tapered optical layers for use in linear variable optical filters (LVOF). The taper angle is fully defined by a mask design. Only one masked lithography step is required for defining strips in a photoresist with trenches etched therein of a density varying along the length of the strip. In a subsequent reflow, this patterned photoresist is planarized, resulting in a strip with a local thickness defined by the initial layer thickness and the trench density at that position before reflow. Hence a taper can be flexibly programmed by the mask design to be from 0.001• to 0.1 • , which enables the simultaneous fabrication of tapered layers of different taper angles. The 3D pattern of resist structures is subsequently transferred into Si or SiO 2 by appropriate etching. Complete LVOF fabrication involves CMOS-compatible deposition of a lower dielectric mirror using a stack of dielectrics on the wafer, tapered layer formation and deposition of the top dielectric mirror. Design principle, processing and simulation results plus experimental validation of the technique on the profile in the resist and after transfer of the taper into Si and SiO 2 are presented.

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Section: Thermal Reflowmentioning

confidence: 99%

Vertically tapered layers for optical applications fabricated using resist reflow

Emadi¹,

Grabarnik

et al. 2009

J. Micromech. Microeng.

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“…A variety of methods, which can be divided into moldless or mold-assisted techniques, have been reported for fabricating microlenses and microlens arrays. Concerning moldless techniques, grayscale photolithography [1], thermal reflow [2], laser micromachining [3][4][5], inkjet printing [6], microcontact printing [7], and self-assembly [8,9] have been proposed to fabricate various polymeric, glass, silicon, and ceramic microlens arrays. However, many of these methods require sophisticated machinery, such as photo-or electron-beam lithography systems and lasers, thus, greatly limiting the high-throughput and low-cost aspects of the production of such microlenses.…”

Section: Introductionmentioning

confidence: 99%

Biconvex Polymer Microlenses with Tunable Imaging Properties Designed by Janus Droplet Microfluidics

2015

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This work presents a technique for fabricating biconvex polymer microlenses using microfluidics, and then evaluates their tunable optical properties. A glass microfluidic channel was employed to rapidly mass-produce nanoliter-sized biphasic Janus droplets, which consist of a biconvex segment of a photocurable monomer and a concave-convex segment of a non-curable silicone oil that contained a surfactant. Subsequent photopolymerization produces polymeric biconvex spherical microlenses with templated dual curvatures. By changing the flow-rate ratios of the photocurable and non-curable droplet phases in the microfluidic channel, the radii of curvature of the two lens surfaces and the thicknesses of the resultant microlenses can be varied. The resulting biconvex microlenses with different shapes were used in image projection experiments. Different magnification properties were observed, and were consistent with the properties estimated quantitatively from the geometrical parameters of the lenses.

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“…There are several methods for fabricating MLAs, such as ink-jet printing [14], lithographic patterning methods using an electron beam [15], a proton beam [16] or an ion beam [17], and thermal reflow methods [18][19][20][21][22][23]. In thermal reflow methods, photoresist (PR) cylinder structures made by photolithography are melted by thermal energy above the glass transition temperature of the PR.…”

Section: Introductionmentioning

confidence: 99%

Design and Fabrication of Multi-Focusing Microlens Array with Different Numerical Apertures by using Thermal Reflow Method

Park¹,

Lee²,

Park³

et al. 2014

Journal of the Optical Society of Korea

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We present design and fabrication of a multi-focusing microlens array (MLA) using a thermal reflow method. To obtain multi-focusing properties with different numerical apertures at the elemental lens of the MLA, double-cylinder photoresist (PR) structures with different diameters were made within the guiding pattern with both photolithographic and partial developing processes. Due to the base PR layer supporting the thermal reflow process and the guiding structure, the thermally reflowed PR structure had different radii of curvatures with lens shapes that could be precisely modeled by the initial volume of the double-cylinder PR structures. Using the PR template, the hexagonally packed multi-focusing MLA was made via the replica molding method, which showed four different focal lengths of 0.9 mm, 1.1 mm, 1.6 mm, and 2.5 mm, and four different numerical apertures of 0.1799, 0.2783, 0.3973, and 0.4775.

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Hexagonal microlens array modeling and fabrication using a thermal reflow process

Cited by 113 publications

References 12 publications

Vertically tapered layers for optical applications fabricated using resist reflow

Vertically tapered layers for optical applications fabricated using resist reflow

Biconvex Polymer Microlenses with Tunable Imaging Properties Designed by Janus Droplet Microfluidics

Design and Fabrication of Multi-Focusing Microlens Array with Different Numerical Apertures by using Thermal Reflow Method

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