Photoresist Microstructures Research Articles

Fabrication of Arrays of Microlenses with Controlled Profiles Using Gray-Scale Microlens Projection Photolithography

This paper demonstrates the use of microlens projection lithography using gray-scale masks to fabricate arrays of microstructures in photoresist. In microlens projection lithography, an array of microlenses (diameter d = 1−1000 μm) reduces a common, centimeter-scale pattern in an illuminated mask to a corresponding pattern of micrometer-scale images in its image plane. The pattern of intensity projected by the array of microlenses depends on the shape and gray-level distribution of the pattern on the illuminated mask and on the shape and pattern of the lenses. The distribution of intensity in the microimages could be adjusted using gray-scale masks. After the recording of this intensity distribution in layers of photoresist and developing, the developed resist showed arrays of 3D microstructures over areas larger than 10 cm2. We used these arrays of 3D microstructures as masters and cast transparent elastomer onto them to generate complementary replicas. For a specific microlens array and a fixed light so...

Microellipsometer with radial symmetry.

We report on a novel microellipsometer that uses a spatially filtered high-numerical-aperture (NA) lens for large-angle ellipsometric illumination and high spatial resolution. A radially symmetric ellipsometric signal is achieved with two half-wave plates to produce a pure polarization rotation and a birefringent cube as a radial analyzer. This radial symmetry offers a better signal-to-noise ratio compared with other microellipsometer techniques. Ellipsometric measurement with a spatial resolution of 0.5 microm is performed with a He-Ne (632.8-nm) laser source and an objective lens with an NA of 0.8. Experimental data on SiO2 samples with different thicknesses are in good agreement with spectroscopic ellipsometer results. We acquired ellipsometric images of photoresist microstructure through scanning the sample. Surface profiles of the photoresist microstructure are derived from the ellipsometric data and compared with the results from a stylus profiler.