Forming a Fresnel Zone Lens: Effects of Photoresist on Digital-micromirror-device Maskless Lithography with Grayscale Exposure

Huang, Yi‐Hsiang; Jeng, Jeng-Ywan

doi:10.3807/josk.2012.16.2.127

Cited by 7 publications

(4 citation statements)

References 24 publications

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“…The ability of GSL to fabricate arbitrary 3D structures makes it a noteworthy technique, suitable for several applications. MEMS devices [2][3][4][5][6], microfluidic devices with variable dimensions channels [7], mold creation for nanoimprint 2 techniques [11], non-binary topography of many photonic devices and more [8][9][10] make GSL a suitable fabrication technique. Microlenses [12][13][14] , circular Dammann gratings [15], multispectral filters arrays [16] and spectrometer chips [17] have been fabricated using GSL.…”

Section: Introductionmentioning

confidence: 99%

“…Yi-Hsiang Huang et al used a digital micromirror device to create a mask pattern. The design was consisted of just 3 grayscale levels [3] .Loomis et al [25] and LeCompte et al [26] approached the linearization of the photoresist behavior against exposure dose but their approach is slightly more complicated. Kaste et al analyzed the behavior of PR and its relation to developer concentration, soft baking and development duration and energy dosage but the resulting patterned PR has high surface roughness and it was a single continuous slope [27].…”

Section: Introductionmentioning

confidence: 99%

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Optimization of Grayscale Lithography for the Fabrication of Flat Diffractive Infrared Lenses on Silicon Wafers

Bouchouri,

Akram,

Øhlckers

et al. 2024

Preprint

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Grayscale Lithography (GSL) is an alternative approach to the standard Binary Lithography in MEMSfabrication, enabling the fabrication of complicated arbitrary 3D structures on the wafer, without the need for multiple masks and exposure steps. Despite its advantages, GSL’s effectiveness is highly dependent on controlled lab conditions, equipment consistency, and finely-tuned photoresist exposure and etching processes. This works presents a thorough investigation of the challenges of GSL for Silicon (Si) wafers and presents a detailed approach on how to minimize the fabrication inaccuracies, aiming to replicate the intended design as closely as possible. Utilizing a maskless laser writer, all aspects of the GSL as analyzed, from photoresist (PR) exposure parameters to Si etching conditions. A practical application of GSL is demonstrated in the fabricationof 4 μm deep Silicon Fresnel Lenses for Long Wave Infrared imaging (8-12 μm). The surface topography of a Fresnel lens is a good case to apply GSL as it has varying shapes and size features that need to be preserved.. The final fabricated lens profiles show good match with the initial design and demonstrate successful etching of coarse and fine features and demonstrating images taken with an LWIR camera.

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Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Optimization of Grayscale Lithography for the Fabrication of Flat Diffractive Infrared Lenses on Silicon Wafers

Bouchouri,

Akram,

Øhlckers

et al. 2024

Preprint

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“…The pattern transfer process is achieved through a single shot deep silicon etching step which translates into an improvement in manufacturing yield by more than 40%. Furthermore, Si:SiO 2 etch selectivity is more than an order of magnitude higher compared to Si:PR etch selectivities [25][26][27][28][29][30]49 , thus enabling us to create really tall (up to 500 μm), high aspect ratio (~ 10-15) structure the likes of which will be immensely useful in applications that rely on mesoscale features. The process described employs full-dose exposure and thus circumvents all the challenges and difficulties associated with partial dose gray exposure.…”

mentioning

confidence: 99%

A Novel Hardmask-to-Substrate Pattern Transfer Method for Creating 3D, Multi-level, Hierarchical, High aspect-ratio Structures for Applications in Microfluidics and Cooling Technologies

Hazra

Zhang

et al. 2022

Preprint

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This letter solves a major hurdle that mars photolithography-based fabrication of micro-mesoscale structures in silicon. Conventional photolithography is usually performed on smooth, flat wafer surfaces to lay a 2D design and subsequently etch it to create single-level features. It is, however, unable to process non-flat surfaces (already etched wafers) to create more than one level to give rise to multi-level, 3D, hierarchical structures in the substrate. In this study, we have described a novel cleanroom-based process flow that allows for easy creation of such multi-level, hierarchical structures in a substrate. This is achieved by introducing an ultra-thin sacrificial silicon dioxide hardmask layer on the substrate, which is first 3D patterned via multiple rounds of lithography. Then, this 3D pattern is scaled vertically by a factor of 200 – 300 and transferred to the substrate underneath via a single shot deep etching step. The proposed method is also easily characterizable. Using features of different topographies and dimensions, the etch rates and selectivities were quantified, these characterization information were later used while fabricating specific target structure. Furthermore, this study comprehensively compares the novel pattern transfer technique to already existing methods of creating multi-level structures, like grayscale lithography, chip stacking and double-sided etching. The proposed process was found to be cheaper, faster, and easier to standardize compared to other methods – this makes the overall process more reliable and repeatable. We hope it will encourage more research into hybrid structures that hold the key to dramatic performance improvements in several micro-mesoscale devices.

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“…However, the use of a photomask is expensive and increases turnaround time. Maskless lithography involves the use of a digital micromirror device (DMD) as a virtual mask in place of a physical mask; this alternative method requires only binary data for the modulation of the light [10][11][12][13][14][15][16].…”

Section: Introductionmentioning

confidence: 99%

Optical Proximity Corrections for Digital Micromirror Device-based Maskless Lithography

Hur¹,

Seo²

2012

Journal of the Optical Society of Korea

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We propose optical proximity corrections (OPCs) for digital micromirror device (DMD)-based maskless lithography. A pattern writing scheme is analyzed and a theoretical model for obtaining the dose distribution profile and resulting structure is derived. By using simulation based on this model we were able to reduce the edge placement error (EPE) between the design width and the critical dimension (CD) of a fabricated photoresist, which enables improvement of the CD. Moreover, by experiments carried out with the parameter derived from the writing scheme, we minimized the corner-rounding effect by controlling light transmission to the corners of a feature by modulating a DMD.

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Forming a Fresnel Zone Lens: Effects of Photoresist on Digital-micromirror-device Maskless Lithography with Grayscale Exposure

Cited by 7 publications

References 24 publications

Optimization of Grayscale Lithography for the Fabrication of Flat Diffractive Infrared Lenses on Silicon Wafers

Optimization of Grayscale Lithography for the Fabrication of Flat Diffractive Infrared Lenses on Silicon Wafers

A Novel Hardmask-to-Substrate Pattern Transfer Method for Creating 3D, Multi-level, Hierarchical, High aspect-ratio Structures for Applications in Microfluidics and Cooling Technologies

Optical Proximity Corrections for Digital Micromirror Device-based Maskless Lithography

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