Microlense

During the fabrication process the surface of the semiconductor is etched and metal contacts are deposited. These features can represent a topographical challenge to subsequent metal wiring levels. For this reason it is important that the dielectric film used tends to smooth out such discontinuities as metal and etched edges (150,217). Additional appHcations for spin-on dielectrics include forming integrated microlenses for optoelectronics (218). 

Techniques for fabricating low-cost optical components such as graded index lenses, microlenses, couplers, splitters, and polarizers are needed to support optical fiber technology. Traditionally, amorphous inorganic materials have been nsed, bnt there are tremendons... 

Chia. T.. J.K. Wesl. and I..L. Hench "Fabrication of Microlenses by Laser Pcnsihcalion on Gel-Silica Glasses." in Chemical Processing of Adsanied Materials (L.L. Hench and J.K. West, Edilois). John Wiley Sons. Inc.. New York. NY. 1992. 

Arrayed microlenses are widely used in a variety of applications that involve miniaturized optical components.172 For example, they can be found at the heart of optical communication systems, facsimile machines, laser printers, and many other kinds of digital information storage or processing devices. In all these applications, the arrayed microlenses simply serve as diode laser correctors, fiber-optic couplers or connectors, and optical scanners. In a set of recent publications, Whitesides and coworkers have also demonstrated that arrayed microlenses could be used as a new platform for photolithography, through which submicrometer-sized structures could be conveniently fabricated as patterned arrays by reducing mm to cm scale features on a photomask.157... 

FIGURE 8.14. (A) A schematic illustration of the setup used to project an F-shaped object onto the focal plane through an array of microlenses. (B, C) images formed at the focal plane of an array of mushroom-shaped (B) and hemispherical (C) microlenses. The microlenses used in all of these demonstrations were fabricated by templating 5.7- tm polystyrene beads against 2D arrays of cylindrical holes that were 5 pm in height and diameter. 

An array of 10- i,m microlenses was fabricated from the adhesion of an aminated silicasol on a poly[methyl(phenyl)silane-co-methyl(3,3,3-tri-fluoropropyl)silane] (CF3PMPS) film patterned by UV light irradiation.132 By soaking the UV-patterned polysilane film into the sol-gel solution, a convex xerogel layer adhered only to the UV-exposed poly silane, which was cured to form a glass that functioned as a condensing lens. 

The reduction of sample size calls for an improvement of detection sensitivity. Optical detection methods have been most commonly applied in most cases. However, fluorescence detection will still gain more importance due to the higher sensitivity of this technique. An interesting approach is the combination of reaction vessels and testing cells. One solution is the incorporation of microlenses below the wells which allow a detection on-site . Highly sensitive methods may be also obtained by the use of miniaturized electrochemical detection systems. 

Reduction photolithography using an array of microlenses (40 pm dia.) was demonstrated. This method achieved a lateral size reduction of 103, and generated a feature size down to 2 pm over a large area (2x2 cm2) [363]. Reduction can also be achieved using 35-mm him photography (8x) or microfiche (25x) [185],... 

An array of circular or elliptical microlenses made of photoresist was constructed on a chip, as shown in Figure 7.7. The microlenses were fabricated on both the bottom glass plate (for focusing the excitation beam), and on the top glass plate (for collecting the emission). In addition, an array of entrance apertures was formed around the focusing microlenses to limit the excitation beam another array of exit apertures was formed around the collecting microlenses to block off... 

Llobera, A., Wilke, R., Biittgenbach, S., Poly(dimethylsiloxane) hollow Abbe prism with microlenses for detection based on absorption and refractive index shift. Labchip 2004, 4, 24-27. 

Biehl et al. demonstrated a method to fabricate microlenses from hybrid organic-inorganic materials on glass using drop-on-demand inkjet printing with 50 /xm nozzles driven by piezoelectric... 

In a somewhat similar fashion, Ishii et alP- have demonstrated inkjet fabrication of polymeric microlenses for optical chip packaging. UV curable epoxy resin is deposited onto optical devices by inkjet printing. When the droplets hit the surface, they form into partial spheres due to their surface tension, and are UV-cured to form the microlens with diameters from 20 to 40 tm with /-numbers of 1.0 to 11.0. Their uniformity in a microlens array was measured to be within 1% in diameter and 3 tm in pitch (total count of 36 lenses). They have also demonstrated hybrid integration of inkjetted microlenses with a wire-bonded vertical-cavity-surface-emitting laser (VCSEL) with coupling efficiencies of 4 dB higher than without the microlens. 

Another report by Cox and Guan discloses collimating microlenses that are printed directly on the end of optical fibers using... 

Risen and Wang developed a method and compositions for producing microlenses and optical filters. According to their method, carboxylated silicone or polysilicone precursor composition is applied to the surface of a substrate to form a precursor droplet, which is thermally oxidized to form a microlens. The substrates utilized were silica, silicates, borosilicate glasses, and silicones. The precursors, which are present in concentrated solutions, are viscous fluids which are used to form microdroplet precursors. A solvent such as ethanol or acetone is added to the precursors to modify and control their flow and surface tension properties, to facihtate the formation of spherical shape of the precursor on substrates. The precursor droplet volume is 4-600 picoliters and forms a droplet of 20 to 1000 micrometers in diameter. 

Cox WR, Guan C. (2001) inkjet printing of gradient-index microlenses, US patent application 2001048968. 

Risen WM Jr, Wang YZ. (2001) Method and compositions for producing microlenses and optical filters, US6294217. 

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