Chemical micromachining

D. Kendall, A new theory for the anisotropic etching of silicon and some underdeveloped chemical micromachining concepts, J. Vac. Sci. Technol. A8, 3598, 1990. 

Rolf Schuster, Viola Kirchner, Philippe Allongue and Gerhard Erd, Electro-chemical micromachining. Science, 289 (2000), 98-101. 

Chemical micromachining (CMM) involves one or more chemical reactions by which a workpiece substrate is oxidized to produce reaction products, which are carried away Ifom the surface by the medium. In general, oxidation-reduction or complexation-type reactions are involved in CMM. Figure 1.16 shows the basic arrangements of CMM. Although no external current is supplied, anodic and cathodic sites are present on the reactive surface such that the rate of material removal (oxidation) is balanced by the rate of reduction of the etchant species. The metal removal reaction typically... 

Kendall DL (1990) A new theory for the anisotropic etching of silicon and some underdeveloped chemical micromachining concepts. J Vac Sci Technol A 8(4) 3598-3605 Kittisland G et al (1990) A sub-micron particle filter in silicon. Sens Actual A21-3 904-907 Klima O et al (1993) Transport properties of self-supporting porous silicon. J Non-Cryst Solid 164-166 961-964... 

Chemical micromachining is one of the methods of choice for fabrication of microlenses [123]. Silicon and germanium were used as lens materials. For spherical and aspheric geometries solutions for anisotropic etching are used, while nonmonotonous surfaces can be fabricated by combining masks and anisotropic etching. This method was used to fabricate various types of optical concentrators, among them cones and inflected surfaces [107]. 

Goodey A., Lavigne J.J., Savoy S.M., Rodriguez M., Curey T., Tsao A., Simmons G., Wright J., Yoo S.-J., Sohn Anslyn E.V., Shear J.B., Neikirk D.P., McDevitt J.T., Development of multi-analyte sensor arrays composed of chemically derivatized polymeric microspheres localized in micromachined cavities, J. Am. Chem. Soc. 2000b 123 2559-2570. 

The core components of a complete microsystem are the integrated sensing, acting or passive micromechanical devices. In most cases, a naked chip manufactured in bulk or surface micromachining is used for the detection of a physical or chemical quantity or some actuation principle, like the dosage of ink droplets in inkjet printheads. A complete microsystem can consist of a complex set of these devices. 

In parallel with improvements in chemical sensor performance, analytical science has also seen tremendous advances in the development of compact, portable analytical instruments. For example, lab-on-a-chip (LOAC) devices enable complex bench processes (sampling, reagent addition, temperature control, analysis of reaction products) to be incorporated into a compact, device format that can provide reliable analytical information within a controlled internal environment. LOAC devices typically incorporate pumps, valves, micromachined flow manifolds, reagents, sampling system, electronics and data processing, and communications. Clearly, they are much more complex than the simple chemo-sensor described above. In fact, chemosensors can be incorporated into LOAC devices as a selective sensor, which enables the sensor to be contained within the protective internal environment. Figure 5... 

J. Cerdk, A. Cirera, A. Vilk, A. Cornet, and J.R. Morante. Deposition on micromachined silicon substrates of gas sensitive layers obtained by a wet chemical route a CO/CH4 high performance sensor , Thin Solid Films 391 (2001), 265-269. 

Initially, the reactor was to be built using silicon wafers, 92 but more recent efforts have focused on a stainless steel reactor. The reformer, 7.5 x 4.5 x 11.0 cm (371 cm ), houses up to 15 stainless steel plates (0.5 mm thick) with chemically etched microchannels and heating cartridges. Conventional and laser micromachining techniques were used to fabricate the reformer body. The microchannel dimensions are 0.05 x 0.035 x 5.0 cm . The reactor inlet was carefully designed to allow uniform flow conditions. ... 

Figure 11.24 A silicon wafer array, with micromachined pyramidal wells (detail shown right) for holding receptor derivatised beads. Fluid containing the experimental solution is added to the top of the array and flows through the bead matrix, and out of the bottom of the pyramidal wells holding the beads. Analyte binding by the differential receptors anchored to the beads gives a recognition pattern unique to each analyte mixture (reproduced with permission from [34] 2001 American Chemical Society).

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