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The phrase depth of focus is sometimes erroneously used to refer to depth of field (DOF), which is the distance from the lens in acceptable focus, whereas the true meaning of depth of focus refers to the zone behind the lens wherein the film plane or sensor is placed to produce an in-focus image. Depth of field depends on the focus distance ...
Photolithography (also known as optical lithography) is a process used in the manufacturing of integrated circuits. It involves using light to transfer a pattern onto a substrate, typically a silicon wafer .
However, [clarification needed] the depth of focus, or tolerance in wafer topography flatness, is improved compared to the corresponding "dry" tool at the same resolution. [ 4 ] The idea for immersion lithography was patented in 1984 by Takanashi et al. [ 5 ] It was also proposed by Taiwanese engineer Burn J. Lin and realized in the 1980s. [ 6 ]
The smaller field of electron beam writing makes for very slow pattern generation compared with photolithography (the current standard) because more exposure fields must be scanned to form the final pattern area (≤mm 2 for electron beam vs. ≥40 mm 2 for an optical mask projection scanner). The stage moves in between field scans.
Optical Lithography (or photolithography) is one of the most important and prevalent sets of techniques in the nanolithography field. Optical lithography contains several important derivative techniques, all that use very short light wavelengths in order to change the solubility of certain molecules, causing them to wash away in solution, leaving behind a desired structure.
Computational lithography came to the forefront of photolithography technologies in 2008 when the semiconductor industry faced challenges associated with the transition to a 22 nanometer CMOS microfabrication process and has become instrumental in further shrinking the design nodes and topology of semiconductor transistor manufacturing.
Depth of Field is precisely the same as depth of focus, only in the former case the depth is measured by the movement of the plate, the object being fixed, while in the latter case the depth is measured by the distance through which the object can be moved without the circle of confusion exceeding 2 e.
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).