Fabrication of silicon molds for polymer optics

Abstract

A silicon mold used for structuring polymer microcavities for optical applications is fabricated, using a combination of DRIE (deep reactive ion etching) and anisotropic chemical wet etching with KOH + IPA. For polymer optical microcavities, low surface roughness and vertical sidewalls are often needed. This is achieved by aligning the mold precisely to the [110] direction of a silicon (100) wafer and etching very close to the (110) surfaces using a DRIE Bosch process. The surface roughness of the sidewalls is then removed with a short etch in KOH + IPA. To achieve this, the parameters for DRIE and KOH + IPA etch have been optimized. To reduce stiction between the silicon mold and the polymers used for molding, the mold is coated with a teflon-like material using the DRIE system. Released polymer microstructures characterized with AFM and SEM are also presented.

Fabrication of one-dimensional photonic crystals by photoelectrochemical etching of silicon

“…As was shown previously [18], such addi tives make it possible to smooth silicon surfaces formed by different crystallographic planes. Nilsson et al [21] managed to reduce the roughness of vertical walls formed by (110) planes in structures obtained by the method of dry reactive ion etching (DRIE), from 70 to 30 nm, using treatment of structure's walls in an aqueous solution containing 3M of KOH and 2M of isopropyl alcohol.…”

Effect of low temperature and concentration KOH etching on high aspect ratio silicon structures

“…In the literature, recent studies have already been performed to smooth DRIE sidewalls and remove the scalloping but the alkaline solutions used were high KOH concentration at high temperature [11]. Recently, Shikida et al have studied a high concentration (50% wt.)…”

Single Molecular Detection via Micro-Scale Polymeric Opto-Electro-Mechanical Systems

“…This simplified expression is acquired by substituting the deflection dependant non-linear spring constant [86] for the pull-in displacement [87]. From this equation, the width and length of flexures can be determined for specific resonance frequencies and maximum displacements.…”

“…These scalloped surfaces were not desirable since there was light scattering on the replicated PDMS surface from the mold. Anisotropic potassium hydroxide (KOH) and isopropyl alcohol (IPA) wet etching [87] and oxidation/wet-etching [99] have been shown to make smooth surfaces of etched sidewalls. This isotropic wet etching method was used here since the curved surfaces of the planar microlenses that did not follow the crystal orientation.…”

“…In the grinding step, the lens-to-lens distance was determined by the back substrate thickness. Substrate thickness as thin as 100 µm have been reported in the literature [87]. The distance between the lenses can ranged from 100 µm to 525 µm.…”