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 5µm 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 5µm 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 misplacement [µm] is the amount by which the design is shifted in X and Y; 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. | |||
<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. | ||
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!colspan="2" align="center"| | !colspan="2" align="center"| | ||
!Shift median [µm] | !Shift median [µm] | ||
! | !Misplacement [µm] | ||
!Run-out (gain) [ppm] | !Run-out (gain) [ppm] | ||
!Rotation [ppm] | !Rotation [ppm] | ||
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==Overlay== | ==Overlay== | ||
In the overlay test, two | In the overlay test, two alignment accuracies are assessed: The machine-to-self overlay accuracy (MLA-MLA), and the machine-to-machine (MA6-MLA) overlay accuracy. Because alignment is possible using two marks or four marks, both are tested in each case. | ||
In the MLA-MLA overlay test, the design is the same as for stitching; ±5µm and ±1µm verniers along the X and Y axis placed in a 3 by 3 matrix covering a 60mm by 60mm area centered on the wafer. The sample is loaded, and the first layer (the linear scales) is printed. The sample is unloaded and developed. The second layer (the vernier scales) is aligned to marks contained in the first layer, and then the sample is developed again. The alignment marks used for 2 mark alignment are placed 60mm apart on the X axis, while the marks used for 4 mark alignment are placed at the corners of a 60mm by 30mm rectangle. | In the MLA-MLA overlay test, the design is the same as for stitching; ±5µm and ±1µm verniers along the X and Y axis placed in a 3 by 3 matrix covering a 60mm by 60mm area centered on the wafer. The sample is loaded, and the first layer (the linear scales) is printed. The sample is unloaded and developed. The second layer (the vernier scales) is aligned to marks contained in the first layer, and then the sample is developed again. The alignment marks used for 2 mark alignment are placed 60mm apart on the X axis, while the marks used for 4 mark alignment are placed at the corners of a 60mm by 30mm rectangle. | ||
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!Shearing [mRad] | !Shearing [mRad] | ||
!Shift median [µm] | !Shift median [µm] | ||
! | !Misplacement [µm] | ||
!Run-out (gain) [ppm] | !Run-out (gain) [ppm] | ||
!Rotation [ppm] | !Rotation [ppm] | ||
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!Shearing [mRad] | !Shearing [mRad] | ||
!Shift median [µm] | !Shift median [µm] | ||
! | !Misplacement [µm] | ||
!Run-out (gain) [ppm] | !Run-out (gain) [ppm] | ||
!Rotation [ppm] | !Rotation [ppm] | ||