Specific Process Knowledge/Lithography/Aligners/Aligner: Maskless 01 processing: Difference between revisions
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The results reported here use printed verniers to assess the misalignment along the two axes at different points on the wafer using an optical microscope. Two different designs were used; a ±5µm vernier and a ±1µm vernier. Both consist of a scale of 4µm lines with 10µm pitch, and a vernier scale to enable subdivision of the 5µm or 1µm scale into tenths, i.e. 0.5µm or 0.1µm. During inspection, observation of the symmetry of neighboring lines enables the observer to read the shifts with ±0.25µm or ±0.05µm accuracy. | The results reported here use printed verniers to assess the misalignment along the two axes at different points on the wafer using an optical microscope. Two different designs were used; a ±5µm vernier and a ±1µm vernier. Both consist of a scale of 4µm lines with 10µm pitch, and a vernier scale to enable subdivision of the 5µm or 1µm scale into tenths, i.e. 0.5µm or 0.1µm. During inspection, observation of the symmetry of neighboring lines enables the observer to read the shifts with ±0.25µm or ±0.05µm accuracy. | ||
<br/>The measurements are used to calculate the misalignment of the second layer with respect to the first print: The shift [µm] is the median of all measurement points in X or Y; the misplacement [µm] is the amount by which the image is shifted; the rotation [ppm] is the angle by which the image is rotated; and the run-out [ppm] is the amount of gain in the image. The unit of ppm (parts per million) is used as the rotation and run-out are generally small. A rotation of 1ppm corresponds to an angle of 0.2" (arcseconds) or a shift of 100nm across an entire 4" wafer, while a run-out of 1ppm corresponds to a shift of 50nm at the edge of a 4" wafer compared to the center. For comparison, the pixel size at the wafer surface is 500nm X 500nm. | <br/>The measurements are used to calculate the misalignment of the second layer with respect to the first print: The shift [µm] is the median of all measurement points in X or Y; the misplacement [µm] is the amount by which the image is shifted; the rotation [ppm] is the angle by which the image is rotated; and the run-out [ppm] is the amount of gain in the image. The unit of ppm (parts per million) is used as the rotation and run-out are generally small. A rotation of 1ppm corresponds to an angle of 0.2" (arcseconds) or a shift of 100nm across an entire 4" wafer, while a run-out of 1ppm corresponds to a shift of 50nm at the edge of a 4" wafer compared to the center. For comparison, the pixel size at the wafer surface is 500nm X 500nm, and the address grid size is 50nm. | ||
<br/>The deviations (±) given for the results here are calculated as half the range of measurements. If the range is small, the measurement uncertainty is used in stead. | <br/>The deviations (±) given for the results here are calculated as half the range of measurements. If the range is small, the measurement uncertainty is used in stead. | ||
<br/>The samples used for these tests are 100mm Si wafers coated with a 1.5µm layer of the positive tone resist AZ 5214E. | <br/>The samples used for these tests are 100mm Si wafers coated with a 1.5µm layer of the positive tone resist AZ 5214E. | ||