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 = | ||
If you need to align an exposure to an existin pattern on a wafer you need wafer marks (or global marks): | |||
[[Image:P and Q marks.png|right|250px]] | [[Image:P and Q marks.png|right|250px]] | ||
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'''1 Material:''' 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. | |||
You need at least two wafer marks, a P mark and a Q mark. It is recommended to have many P and Q marks available on the wafer to choose from. The x-coordinate of the P mark should be smaller than the X-coordinate of the Q mark. | You need at least two wafer marks, a P mark and a Q mark. It is recommended to have many P and Q marks available on the wafer to choose from. The x-coordinate of the P mark should be smaller than the X-coordinate of the Q mark. | ||