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In photolithography, photoresist compounds are used create a mask on the surface of a silicon wafer. The mask allows for precise control over the doping and etching processes used to form devices on silicon wafers. It is important for the mask to hold up to chemical attack during the etching process.
In photolithography, several masks are used in turn, each one reproducing a layer of the completed design, and together known as a mask set. A curvilinear photomask has patterns with curves, which is a departure from conventional photomasks which only have patterns that are completely vertical or horizontal, known as manhattan geometry.
The etch chemistry is dispensed on the top side when in the machine and the bottom side is not affected. This etching method is particularly effective just before "backend" processing ( BEOL ), where wafers are normally very much thinner after wafer backgrinding , and very sensitive to thermal or mechanical stress.
In both cases, the mask covers the entire wafer, and simultaneously patterns every die. Contact printing/lithography is liable to damage both the mask and the wafer, [38] and this was the primary reason it was abandoned for high volume production. Both contact and proximity lithography require the light intensity to be uniform across an entire ...
A benefit of using phase-shift masks in lithography is the reduced sensitivity to variations of feature sizes on the mask itself. This is most commonly used in alternating phase-shift masks, where the linewidth becomes less and less sensitive to the chrome width on the mask, as the chrome width decreases.
An illustration of OPC (Optical Proximity Correction). The blue Γ-like shape is what chip designers would like printed on a wafer, in green is the pattern on a mask after applying optical proximity correction, and the red contour is how the shape actually prints on the wafer (quite close to the desired blue target).
A SÜSS MicroTec MA6 mask aligner. An aligner, or mask aligner, is a system that produces integrated circuits (IC) using the photolithography process. It holds the photomask over the silicon wafer while a bright light is shone through the mask and onto the photoresist. The "alignment" refers to the ability to place the mask over precisely the ...
A key advantage of maskless lithography is the ability to change lithography patterns from one run to the next, without incurring the cost of generating a new photomask. This may prove useful for double patterning or compensation of non-linear material behavior (e.g. when utilizing cheaper, non-crystalline substrate or to compensate for random ...