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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) ... The depth of focus restricts the thickness of the photoresist and the depth of the topography on the 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 ]
Good depth of focus requires diffracted light traveling at comparable angles with the optical axis, and this requires the appropriate illumination angle. [4] Assuming the correct illumination angle, OPC can direct more diffracted light along the right angles for a given pitch, but without the correct illumination angle, such angles will not ...
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.
Moreover, STI has a higher degree of planarity making it essential in photolithographic applications, depth of focus budget by decreasing minimum line width. To planarize shallow trenches, a common method should be used such as the combination of resist etching-back (REB) and chemical mechanical polishing (CMP).
C. Welborne Piper may be the first to have published a clear distinction between Depth of Field in the modern sense and Depth of Definition in the focal plane, and implies that Depth of Focus and Depth of Distance are sometimes used for the former (in modern usage, Depth of Focus is usually reserved for the latter). [5]
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.