Specific Process Knowledge/Lithography/Aligners/Aligner: Maskless 01 processing: Difference between revisions
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=Optimal use of the maskless aligner= | =Optimal use of the maskless aligner= | ||
==Writing speed | ==Writing speed== | ||
The site acceptance test performed during the installation of the Aligner: Maskless 01 showed an exposure time/speed of 0.025 min/mm<sup>2</sup>, which is slightly lower than the 0.02 min/mm<sup>2</sup> given in the specifications. At such speeds, a full 4" design would take 2:30-3:15 hours to expose. In practice, we observe exposure times in excess of 2 hours for a full 4" design. | The site acceptance test performed during the installation of the Aligner: Maskless 01 showed an exposure time/speed of 0.025 min/mm<sup>2</sup>, which is slightly lower than the 0.02 min/mm<sup>2</sup> given in the specifications. At such speeds, a full 4" design would take 2:30-3:15 hours to expose. In practice, we observe exposure times in excess of 2 hours for a full 4" design. | ||
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Alternatively, the development after first exposure can be skipped. This enables the use of chemically amplified positive tone resists, such as AZ MiR 701, without the drop in sensitivity usually associated with the post-exposure bake. The contrast of the alignment mark, however, is greatly reduced, making alignment more difficult. AZ MiR 701 shows more contrast than AZ 5214E, but in both cases the focus and brightness has to be optimized in order to make automatic alignment possible. The design may also have to be adapted, as the poor contrast makes navigation using the overview camera difficult. Also, a less reflective substrate than Si, e.g. oxidized Si, may complicate alignment further. | Alternatively, the development after first exposure can be skipped. This enables the use of chemically amplified positive tone resists, such as AZ MiR 701, without the drop in sensitivity usually associated with the post-exposure bake. The contrast of the alignment mark, however, is greatly reduced, making alignment more difficult. AZ MiR 701 shows more contrast than AZ 5214E, but in both cases the focus and brightness has to be optimized in order to make automatic alignment possible. The design may also have to be adapted, as the poor contrast makes navigation using the overview camera difficult. Also, a less reflective substrate than Si, e.g. oxidized Si, may complicate alignment further. | ||
In the case of negative tone resist, such as AZ nLOF 2020, there is no contrast after exposure, making alignment impossible. Performing post-exposure bake before the second exposure yields a slight contrast, but in the case of nLOF the automatic alignment failed. Manual alignment was possible, but the alignment accuracy | In the case of negative tone resist, such as AZ nLOF 2020, there is no contrast after exposure, making alignment impossible. Performing post-exposure bake before the second exposure yields a slight contrast, but in the case of nLOF the automatic alignment failed. Manual alignment was possible, but the alignment accuracy may suffer. | ||