Specific Process Knowledge/Lithography/EBeamLithography: Difference between revisions
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= Alignment of exposure to existing pattern on wafer = | = Alignment of exposure to existing pattern on wafer = | ||
[[Image:GlobalMark.png|200px|thumb| | [[File:P and Q marks.png|400px]] | ||
[[Image:GlobalMark.png|200px|thumb|Text around the global mark is NOT recommended.]] | |||
A set of global marks are needed in order to align an exposure to an existing pattern on a wafer. These marks should be clearly visible in a 100keV SEM, i.e. preferably defined by Ti/Au or another 'heavy' metal. Etched global marks or global marks defined by a light metal as Al can be hard to locate manually as well as automatically. | A set of global marks are needed in order to align an exposure to an existing pattern on a wafer. These marks should be clearly visible in a 100keV SEM, i.e. preferably defined by Ti/Au or another 'heavy' metal. Etched global marks or global marks defined by a light metal as Al can be hard to locate manually as well as automatically. | ||
The global marks should either be crosses or L-shaped and be quite large, i.e. 500 - 1000 microns in length. If the wafer contains a number of identical marks, the marks should be marked in order to identify the 'right' alignment marks (the scan width of the SEM is 1 mm x 1 mm). | The global marks should either be crosses or L-shaped and be quite large, i.e. 500 - 1000 microns in length. If the wafer contains a number of identical marks, the marks should be marked in order to identify the 'right' alignment marks (the scan width of the SEM is 1 mm x 1 mm). | ||
The marks should be as narrow as possible. | The marks should be as narrow as possible. | ||