Polymer-based membrane mirrors for micro-optical sensors

Friese, C.; Wissmann, Markus; Zappe, Hans

doi:10.1109/icsens.2003.1279022

Cited by 6 publications

(3 citation statements)

References 3 publications

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“…Freestanding mechanical structures such as cantilevers or membranes with thickness below 10 μm have been fabricated [21][22][23]. Lithographic resolution is improved as the film thickness is reduced.…”

Section: Introductionmentioning

confidence: 99%

Processing of thin SU-8 films

Keller¹,

Blagoi

Lillemose

et al. 2008

J. Micromech. Microeng.

150

132

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This paper summarizes the results of the process optimization for SU-8 films with thicknesses 5 μm. The influence of soft-bake conditions, exposure dose and post-exposure-bake parameters on residual film stress, structural stability and lithographic resolution was investigated. Conventionally, the SU-8 is soft-baked after spin coating to remove the solvent. After the exposure, a post-exposure bake at a high temperature T PEB 90 • C is required to cross-link the resist. However, for thin SU-8 films this often results in cracking or delamination due to residual film stress. The approach of the process optimization is to keep a considerable amount of the solvent in the SU-8 before exposure to facilitate photo-acid diffusion and to increase the mobility of the monomers. The experiments demonstrate that a replacement of the soft-bake by a short solvent evaporation time at ambient temperature allows cross-linking of the thin SU-8 films even at a low T PEB = 50 • C. Fourier-transform infrared spectroscopy is used to confirm the increased cross-linking density. The low thermal stress due to the reduced T PEB and the improved structural stability result in crack-free structures and solve the issue of delamination. The knowledge of the influence of different processing parameters on the responses allows the design of optimized processes for thin SU-8 films depending on the specific application.

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Section: Introductionmentioning

confidence: 99%

Processing of thin SU-8 films

Keller¹,

Blagoi

Lillemose

et al. 2008

J. Micromech. Microeng.

150

132

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show abstract

“…Membranes typically used in MEMS (for example SiN) don't allow for such deformation and the only material flexible enough is a polymer. Although several techniques for the polymer membranes fabrication are possible (for example [11]) we tried to find the simplest one. As a result we developed the following process illustrated on the Fig.…”

Section: Fabrication Technologymentioning

confidence: 99%

Concave diffraction gratings fabricated with planar lithography

Grabarnik

Emadi

et al. 2008

Micro-Optics 2008

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This paper reports on the development and validation of a new technology for the fabrication of variable line-spacing non-planar diffraction gratings to be used in compact spectrometers. The technique is based on the standard lithographic process commonly used for pattern transfer onto a flat substrate. The essence of the technology presented here is the lithographic fabrication of a planar grating structure on top of a flexible membrane on a glass or silicon wafer and the subsequent deformation of the membrane using a master shape. For the validation of the proposed technology we fabricated several reflection concave diffraction gratings with the f-numbers varying from 2 to 3.8 and a diameter in the 4 -7 mm range. A glass wafer with circular holes was laminated by dry-film resist to form the membranes. Subsequently, standard planar lithography was applied to the top part of the membranes for realizing grating structures. Finally the membranes were deformed using plano-convex lenses in such a way that precise lens alignment is not required. A permanent non-planar structure remains after curing. The imaging properties of the fabricated gratings were tested in a three-component spectrograph setup in which the cleaved tip of an optical fiber served as an input slit and a CCD camera was used as a detector. This simple spectrograph demonstrated subnanometer spectral resolution in the 580 -720 nm range.

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“…In an effort to increase the total optical power range and deflection of MEMS focusing mirrors, our group and others have explored the use of polymer materials to reduce intrinsic stress of the membrane layer [1,9,29,30,48,49]. Previously, we reported a simple single silicon wafer process that utilizes the polymer SU-8 2002 as the membrane layer [1].…”

Section: Introductionmentioning

confidence: 99%

Four-zone varifocus mirrors with adaptive control of primary and higher-order spherical aberration

et al. 2016

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Electrostatically actuated deformable mirrors with four concentric annular electrodes can exert independent control over defocus as well as primary, secondary, and tertiary spherical aberration. In this paper we use both numerical modeling and physical measurements to characterize recently developed deformable mirrors with respect to the amount of spherical aberration each can impart, and the dependence of that aberration control on the amount of defocus the mirror is providing. We find that a four-zone, 4 mm diameter mirror can generate surface shapes with arbitrary primary, secondary, and tertiary spherical aberration over ranges of ±0.4, ±0.2, and ±0.15 μm, respectively, referred to a non-normalized Zernike polynomial basis. We demonstrate the utility of this mirror for aberration-compensated focusing of a high NA optical system.

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Polymer-based membrane mirrors for micro-optical sensors

Cited by 6 publications

References 3 publications

Processing of thin SU-8 films

Processing of thin SU-8 films

Concave diffraction gratings fabricated with planar lithography

Four-zone varifocus mirrors with adaptive control of primary and higher-order spherical aberration

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