Wafer etching

Fabricating waveguides on the surface of a wafer provides ready access to fluidic channels without the need for through-wafer etching as required in a wafer... 

FIGURE 2.21 (a) Wafer-etch geometry, (b) An image of the slurry layer between a patterned wafer and a Fruedenburg FX9 polishing pad. 

Chemical mechanical polishing (CMP) represents a specialized type of all-wafer etching meant to clean, smoothen, and planarize the entire wafer in preparation for subsequent lithographic steps. Modeling of CMP is complex because both mechanical abrasion and chemical reaction are involved. 

Kumar, S. and Pike, W.T. (2005) Technique for eliminating notching in through-wafer etching. 16th MME Micromechanics Eur. Workshop P15, 8 8-91... 

Figure S-A2. Silicon wafer etched using the microplasma etcher for 1 min. VHF (very-high-frequency) power, substrate bias power, and Ar-SFe flow rates are 150 W, 4 W, 200 seem, and 100 seem, respectively.

Plasma Etching, Fig. 6 Cross-sectional SEM micrographs of (a) high aspect ratio microstructure of holes with the same nominal diameter of 1.5 pm and nearly the same etching depth of 69.5 pm, (b) through-wafer etching... 

One can make a direct measurement of the effect of size on the glass transition temperature of a thin polymer film by measuring the film s thickness as the temperature is increased or decreased the glass minsition temperature then is marked by a discontinuity in expansivity. Such measurements may be conveniently carried out by ellipsometry or x-ray or neutron reflectivity. Figure 2.29 shows results obtained for thin polystyrene films heated in air on silicon wafers etched to remove the native oxide (Keddie et al. 1994). At thicknesses... 

Figure 10.11 Electron micrograph of (A) the surface of an microelectrode array prepared from a microporous polycarbonate host membrane (diameter of 1 pm) (reprint with permission from reference (7)) (B) Pt fibrils obtained after the polycarbonate host membrane is dissolved away from the microelectrode array (reprint with permission from reference (7)) (C) SEM micrograph of the surface of a microchannel glass wafer etched but unfilled (reprint with permission from reference (125)) (D) etched and with Rh-filled array (125) (reprint with permission from reference (125)).

Figure 1.13 Patterned SOIMUMPS wafer. Through-wafer etches are performed from the front side of the wafer 10 or 25 pm deep to form device layer holes, and from the back side 400 pm deep to form through-wafer holes.

Figure 8.10 Through-wafer etch holes to enable back-side release. The backside etch holes eliminate the need for etch holes in the Poly2 mirror membrane. (Reprinted with permission from IEEE Journal of Selected Topics in Quantum Electronics, Microelectromechanical deformable mirrors, 1967 IEEE.)...

Note that the etch velocity is also dependent on the crystallographic orientation. Figure 10.18 shows the typical shape of the etched cavity as a function of the orientation of the Si wafer. It shows that the edge of the cavity for (110) Si wafer etching has vertical orientation compared to the (100) Si wafer because of higher etching velocity of the (110) orientation compared to that of the (100) orientation. 

Also considered for future work is the application of etched quartz as a contact surface. In this process, the wafer etched with micro-features is placed in contact with part free surfaces during contact infiltration in order to impart desired surface textures. Of particular concern in this investigation are the geometrical limits of feature size and accuracy in micro-feature rephcation. The resulting 3D-printed metal parts containing micro-feature projections could be used as a durable and low cost rapid tooling for applications such as micro-fluidics. 

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