Specific Process Knowledge/Lithography/EBeamLithography: Difference between revisions
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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. | ||
You need at least two wafer marks, a P mark and a Q mark. It is recommended to have | 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. | ||
The global marks should either be crosses or L-shaped, they should be as narrow as possible and 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). Text around the wafer mark is NOT recommended. | The global marks should either be crosses or L-shaped, they should be as narrow as possible and 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). Text around the wafer mark is NOT recommended. | ||