Specific Process Knowledge/Lithography/Aligners/Aligner: Maskless 02 processing: Difference between revisions
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The alignment accuracy of the Aligner: Maskless 02 is a combination of the position accuracy of the stage, the accuracy of the alignment mark detection, the accuracy of the pattern already on the wafer (first print), and the calibration of the machine (correction of offset between the exposure light axis and the center of the cameras). | The alignment accuracy of the Aligner: Maskless 02 is a combination of the position accuracy of the stage, the accuracy of the alignment mark detection, the accuracy of the pattern already on the wafer (first print), and the calibration of the machine (correction of offset between the exposure light axis and the center of the cameras). | ||
The calibration of the machine was performed during installation, but can also be corrected if systematic offsets are observed in alignment tests. This calibration also compensates errors in the detection of the alignment marks (at least on the standard samples used for calibration and alignment tests). By measuring the stitching accuracy between two layers printed on the same substrate (without unloading the substrate), we may be able to assess the stage accuracy. By aligning to a pattern previously exposed by the Aligner: Maskless 02, or ideally by another machine, we can assess the mask-less aligner's ability to compensate for any scaling and orthogonality errors between the two prints. | The calibration of the machine was performed during installation, but can also be corrected if systematic offsets are observed in alignment tests. This calibration also compensates errors in the detection of the alignment marks (at least on the standard samples used for calibration and alignment tests). By measuring the stitching accuracy between two layers printed on the same substrate (without unloading the substrate), we may be able to assess the stage accuracy. By aligning to a pattern previously exposed by the Aligner: Maskless 02, or ideally by another machine, we can assess the mask-less aligner's ability to compensate for any scaling (gain) and shearing (orthogonality) errors between the two prints. | ||
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. | ||