Lecture%202-Nanofabrications%20and%20Materials%20for%20Biomedical%20Applications

Lecture%202-Nanofabrications%20and%20Materials%20for%20Biomedical%20Applications

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BME 551 Lecture #2 force Viscous force Force of gravity Length scale icro nd Nano cale Micro- and Nano-Scale Fabrications and Materials for Biomedical Applications T. K. Hsiai
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Semiconductor Technology Major processing steps in integrated circuit fabrication Dicing Dicing procedures involve slicing/cutting silicon wafers with microprocessor controlled high speed d iamond saws. Depending upon the material and requirement, kerf may be as small as 20 μ, and dies ay be diced as small as 01" (250 μ) may be diced as small as .01 (250 μ). Packaging The packaging of the micro structures or devices meets the following requirements: · Enable the user to handle the device easily · Protects the device in harsh environments · Prevents it from mechanical damage, chemical attack, or high temperatures
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High -Resolution Lithography Lithography a) electron beam: deflection fields at 100 x 100 µ m electron beam resist=polymethyacrylate (PMMA) b) photolithography positive vs negative photoresists (PR) Materials Etching A) Chemical etching of silicon -pros and cons B) Dry Etching - chemistry and mechanisms 1) Physical etching )y g 2) Chemical etching 3) Physical -chemical etching 4) Photochemical etching C) Etching Induced Damage ) gg
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Lithography 1. Photolithgraphy -IC industry -A technique used to transfer shapes and designs onto a surface of photoresist materials -MASKS -stencils to generate desired patterns in resisted oated wafer coated wafer -optically flat glass or quartz plate -direct contact with wafer for exposure to UV radiation -Spin coating of photo resist (PR)-1.5 µ m in thickness ± 5 nm -polarity (tone): positive vs. negative - U- PR; high aspect ratio(>10:1 at >200 in SU 8 PR; high aspect ratio( 10:1 at 200 µ m in thickness)( HW ) -Polyimide(>200 µ m)( HW ) - Photolithography (also called optical lithography ) is a process used in microfabrication to selectively remove parts of a thin film (or the bulk of a substrate). It uses light to transfer a geometric pattern from a photomask to a light-sensitive chemical ( photoresist , or simply "resist") on the substrate. A series of chemical treatments then engraves the exposure pattern into the material underneath the photoresist. In a complex integrated circuit (for example, modern CMOS ), a wafer will go through the photolithographic cycle up to 50 times.
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Basic IC Process steps on an oxidized Si Wafer SiO 2 ~1 μm n-type silicon A) Oxidation Photor Resist (PR) ±1 μm B) Lithography Preparation UV light Glass Plate C) Exposure Opaque pattern Hardened resist Positive PR D) Removal of unexposed R by delveloper Negative PR PR by delveloper E) SiO 2 etched with NH4 + HF F) Exposed PR removed with H 2 SO 4
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Photoresits (PR) Photoresist is a light -sensitive material used in several industrial processes, such as photolithography and photoengraving to form a patterned coating on a surface.
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Lecture%202-Nanofabrications%20and%20Materials%20for%20Biomedical%20Applications

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