Specific Process Knowledge/Lithography/EBeamLithography/JEOLAlignment: Difference between revisions

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 To get started using the prealigner, place the cassette front side down and the hook away from yourself. Log in on the computer and load PAMS Metrology Tool and PAMS Image Viewer. Verify that the coordinate output is correct by moving to the stage zero marker mounted on the bottom right of the prealigner, zero it on the coordinate display panel if it is more than a few µm off.
-Move the stage to the center of your substrate, use the coordinates posted on the wall to find it easily. Find a feature that allows you to gauge the rotation, this can be a long straight line or two features that have the same Y-coordinate. Minimize the rotation by either rotating the slot using the set screws (not all cassettes have this) or by removing the substrate cover and rotate the substrate inside the slot. Rotation should be so low that the Y-coordinate difference between the P and Q marks is less than 500 µm.
+Move the stage to the center of your substrate, use the coordinates posted on the wall to find it easily. Find a feature that allows you to gauge the rotation, this can be a long straight line or two features that have the same Y-coordinate. Minimize the rotation by either rotating the slot using the set screws (not all cassettes have this) or by removing the substrate cover and rotate the substrate inside the slot. In the example below we have a cross (the P mark) which is obviously rotated relative to the red cross hair and the substrate should be rotated counter clockwise to compensate. Rotation should be so low that the Y-coordinate difference between the P and Q marks is less than 500 µm.
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 Prealignment using the PAMS Metrology Tool and PAMS Microscope view. Image: Thomas Pedersen.
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-It is usually a good idea to deal with substrate rotation first. Move the stage to the center of your substrate. Use the coordinate guide posted on the wall next to the prealigner and the coordinate read out on the table. Once you find the center of your substrate move to a horisontal feature like a cross or waveguide that will allow rotation adjustment. In the example below we have a cross (the P mark) which is obviously rotated relative to the red cross hair.
-If the cassette has a slot rotation screw, use this to roughly correct rotation. If the slot does not have a rotation screw, remove the substrate cover and rotate your substrate. The rotation screw is fragile, NEVER USE A TOOL TO ROTATE IT. Only use your fingers. The slot is spring loaded, if it is hard to turn the screw you can release tension in the springs by firmly presseing down on the outer ring as illustrated below.
 Once the substrate rotation is fine it is time to find the actual alignment marks (P and Q marks). In the Metrology tool choose “JBX-9500FS” on the “Workpiece Window” dropdown and choose the substrate size and slot ID of your substrate. Enter the design coordinates of the P and Q marks in the “PQ design Local” fields.
-Now find your P mark, align it to the red cross hair at 8X digital zoom and click “Get P”. Click it a few times as the first time always inputs an incorrect coordinate. Move to your Q mark, align to the cross hair and click “Get Q” a few times. Now click “Calculate”. The software will now calculate the rotation and gain. Verify that rotation is better than ± 0.5°, if not you should rotate the slot as described above. Substrate rotation and finding the P and Q marks can be an iterative process and you should continue to ensure that rotation is better than ± 0.5°. Also verify that the gain is close to 1. The gain is the ratio of measured distance between P and Q marks versus the design distance, ideally it should be 1.
+Now find your P mark, align it to the red cross hair at 8X digital zoom and click “Get P”. Click it a few times as the first time always inputs an incorrect coordinate. Move to your Q mark, align to the cross hair and click “Get Q” a few times. Now click “Calculate”. The software will now calculate the rotation and gain. Verify that rotation is better than ± 1° and that the Y-coordinate difference is less than 500 µm, if not you should rotate the slot as described above. Also verify that the gain is close to 1. The gain is the ratio of measured distance between P and Q marks versus the design distance, ideally it should be 1.
 Finally press “Log result” to produce a text output. Copy and paste the output into a text file and save it with your exposure files, for instance to your M-drive. The procedure must naturally be carried out for all substrates that need alignment exposure.
 When you are done with the alignment station, please close the programs, log off the computer and turn the microscope illumination down. Alert a member of the loading team to have your prealigned substrates loaded to the auto stocker.