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

The rough scan conditions are used to scan over several 100 µm to find the mark while the fine scan conditions are used to accurately determine the center in as small a window as possible. Edit the P mark rough conditions by clicking its '''Setting''' button. Set the scan position x and y to about half the size of the mark, in this case 250 µm. Set the scan width in x and y to 400 µm to scan a large area with a high chance of finding the mark. If the contrast of the mark is not optimal the number of scans or the scan clock (beam dwell time) can be increased. Go to the '''Offset''' pane and make sure all offsets are set to zero. Go to the '''Scan type''' pane and set the mark width and mark length according to the mark, in this case 20 µm and 500 µm, respectively. The mark width is the most important as the system will only acknowledge a feature of the stated dimension to be the mark. Close the window on '''OK'''.

Also edit the fine scan conditions of the P mark. The windows are essentially identical, the only difference is the dimensions as we now want to scan a much smaller area in order to pinpoint the mark center with as high accuracy as possible. Ideally the mark should be similar to the one shown below with a wide part for the rough scan and a narrow part at the center for fine scan. In the fine scan define the scan position to be 20-30 µm from the center and set the width to 10 µm or less. The scan is made with 4000 datapoints along the scan axis, thus for a 10 µm wide scan the position resolution is 2.5 nm. The maximum resolution is 1 nm, thus if one defines a scan width less than 4 µm there will simply be less datapoints along the scan axis.

Once the P mark conditions are set up, setup the Q mark conditions in the same way. From the '''SETWFR''' window click '''Save''' and '''Execute'''. The mark scan will start with the P mark rough scan, if the mark is found it will continue to P mark fine scan, if successful the system will continue with Q mark rough scan and finally Q mark fine scan. Below is a few examples of an mark scan routine. In the left image the system has scanned the mark in the x-direction and found a nice feature, the yellow line indicates the system is currently scanning in y. Observe that in a y-axis scan the beam scans along the y-axis to determine the x-coordinate of the mark and vice versa. The center image shows a completed fine scan in a 10 µm window. The last image shows the data output after successfull mark detection. The important parameter is the P mark observation position offset. In this case the offset is (88,-335), this is entered in the SDF file '''OFFSET''' command to make sure the mark is easily found during job execution.