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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.
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.
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 ...
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.
A general scheme for photomask lithography. Plasmonic contact lithography, a modification on the evanescent near-field lithography, uses a metal photomask, on which the SPPs are excited. Similar to common photolithographic processes, photoresist is exposed to SPPs that propagate from the mask. Photomasks with holes enable grating coupling of ...
There are several types of contact lithography masks. The standard binary intensity amplitude mask defines dark and light areas where light is blocked or transmitted, respectively. The dark areas are patterned films consisting of chromium or other metal. The light coupling mask has a corrugated dielectric surface. Each protrusion acts as a ...
A patterned mask is then applied to the surface to block light, so that only unmasked regions of the material will be exposed to light. A solvent, called a developer, is then applied to the surface. In the case of a positive photoresist, the photo-sensitive material is degraded by light and the developer will dissolve away the regions that were ...
With a proper optical imaging system between the mask and the wafer (or no imaging system if the mask is sufficiently closely positioned to the wafer such as in early lithography machines), the mask pattern is imaged on a thin layer of photoresist on the surface of the wafer and a light (UV or EUV)-exposed part of the photoresist experiences ...