Photoresist reflow method of microlens production: modeling and fabrication techniques

O’Neill, Feidhlim T.; Walsh, Christopher R.; Sheridan, John T.

doi:10.1117/12.553316

Cited by 6 publications

(6 citation statements)

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“…When the unexposed photoresist was melted, the photoresist surfaces were pulled into a shape that minimizes the energy of the system due to the surface tension. If gravitational effects are presumed to be negligible, which, for very small lenses, will generally be the case, and assuming ideal conditions, one would expect the shape of these microlenses to be well approximated by a spherical surface [9,10]. In this simulation, we assumed the surface tension is the most important impact element.…”

Section: Research Articlementioning

confidence: 98%

“…It is difficult to achieve large focal length in the millimeter range for microlenses by positive photoresist thermal reflow process [11]. Besides, the profiles formed by this method could be much more complex than the simple surface energy minimization, which resulted in a huge aberration of the microlenses for certain fabrication parameters [9,10,12]. Hsieh et al has presented a method to extend the focal length of reflowed microlens arrays based on two materials.…”

Section: Introductionmentioning

confidence: 98%

“…In recent years, many fabrication methods [4][5][6][7][8] were proposed to create a long focal length microlens or extend the focal length of MLA. The thermal reflow method has been proposed for many years [9,10]. The photoresist reflow method involves melting photoresist structures to fabricate a microlens shaped by the liquid resist's surface tension.…”

Section: Introductionmentioning

confidence: 99%

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Ultralong focal length microlens array fabricated based on SU-8 photoresist

et al. 2015

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In this paper, a novel method to fabricate ultralong focal length microlens arrays has been proposed. The microlens arrays were fabricated based on surface tension when heating temperature is over a glass transition temperature of SU-8 photoresist. An ultralong focal length was achieved by the large radius of curvature of a photoresist surface. Microlenses of widths from 30 to 210 μm were successfully fabricated. The longest focal length was up to 4.4 mm from the microlens of 210 μm width. The formation mechanism was also studied and validated by simulation based on the finite element method.

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Section: Research Articlementioning

confidence: 98%

Section: Introductionmentioning

confidence: 98%

Section: Introductionmentioning

confidence: 99%

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Ultralong focal length microlens array fabricated based on SU-8 photoresist

et al. 2015

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“…In this paper, we address the reflow behavior of thin polymer films, focusing our attention on the accurate detection of surface shape during the course of time. Although a large amount of work was already performed to understand and control resist reflow for lens manufacturing [7], our approach distinguishes itself from existing state of art since dynamics of the contact line (substrate/ resist/atmosphere) does not need to be considered in order to model our system based on a supported thin film. An analytical solution describing the system evolution is proposed in this paper and compared with experiments.…”

Section: Introductionmentioning

confidence: 99%

Reflow of supported sub-100 nm polymer films as a characterization process for NanoImprint lithography

Leveder

Rognin

Landis

et al. 2011

Microelectronic Engineering

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In this paper, we address the reflow behavior of polymer thin films, focusing our effort on the accuracy of surface shape recognition. Although much work was already performed to control resist reflow during lens manufacturing for instance, our approach is significantly different since no contact line (substrate/ polymer/atmosphere) needs to be considered. Here, a linear stability approach is successfully developed to describe the thin film evolution which is also compared with experiments. Polystyrene films, with thickness ranging from few tens of nanometers up to several hundred of nanometers were patterned with NanoImprint lithography technique. Atomic force microscopy measurements were used to characterize smooth or steep shapes, respectively. Mechanical measurements of earlier stages of pattern reflow were directly accessible without any assumption, contrary to the diffraction method usually employed. We show that by controlling the reflow process of any complex surface shape during the course of time, measurements of material parameters such as thin film viscosity, surface tension, or even Hamaker constant can be made possible.

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“…They can be melted and cooled as in thermal reflow or printed using inkjet technology and cured with ultra-violet (UV) irradiation [15,16]. Larger lenses can take on aspheric shapes due to the effects of gravity [17,18]. Application of an electrostatic field gives greater control over the shape of the lens [19].…”

Section: Introductionmentioning

confidence: 99%

Rapid fabrication of miniature lens arrays by four-axis single point diamond machining

McCall¹,

Tkaczyk²

2013

Opt. Express

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A novel method for fabricating lens arrays and other nonrotationally symmetric free-form optics is presented. This is a diamond machining technique using 4 controlled axes of motion -X, Y, Z, and C. As in 3-axis diamond micro-milling, a diamond ball endmill is mounted to the work spindle of a 4-axis ultra-precision computer numerical control (CNC) machine. Unlike 3-axis micro-milling, the C-axis is used to hold the cutting edge of the tool in contact with the lens surface for the entire cut. This allows the feed rates to be doubled compared to the current state of the art of micro-milling while producing an optically smooth surface with very low surface form error and exceptionally low radius error.

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Photoresist reflow method of microlens production: modeling and fabrication techniques

Cited by 6 publications

References 0 publications

Ultralong focal length microlens array fabricated based on SU-8 photoresist

Ultralong focal length microlens array fabricated based on SU-8 photoresist

Reflow of supported sub-100 nm polymer films as a characterization process for NanoImprint lithography

Rapid fabrication of miniature lens arrays by four-axis single point diamond machining

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