Specific Process Knowledge/Lithography/Aligners/Aligner: Maskless 02 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. | ||
The measurements are used to calculate the misalignment of the second layer with respect to the first print. The median of all measurement points in X or Y (reported as "Shift") is a measure for the average overall offset between the first and second print. At each point, this error is a combination of three contributions: The translational error ("Misplacement") is the amount by which the image is shifted; | The measurements are used to calculate the misalignment of the second layer with respect to the first print. The median of all measurement points in X or Y (reported as "Shift") is a measure for the average overall offset between the first and second print. At each point, this error is a combination of three contributions: The translational error ("Misplacement") is the amount by which the image is shifted; the run-in/run-out error ("Run-out") is the amount of gain in the image; and the rotational error ("Rotation") is the angle by which the image is rotated. The unit of ppm (parts per million) is used as 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 160nm X 160nm, and the address grid size is 40nm. | ||
The deviations (±) given for the results here are calculated as half the range of measurements. If the range is smaller than the measurement uncertainty, the measurement uncertainty is used in stead. | The deviations (±) given for the results here are calculated as half the range of measurements. If the range is smaller than the measurement uncertainty, the measurement uncertainty is used in stead. | ||
The samples used for these tests are 100mm Si wafers coated with a 1.5µm layer of positive tone resist (AZ 5214E or MiR 701). | The samples used for these tests are 100mm Si wafers coated with a 1.5µm layer of positive tone resist (AZ 5214E or MiR 701). | ||