Specific Process Knowledge/Lithography/Aligners/Aligner: Maskless 01 processing: Difference between revisions
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==Writing speed[[Image:section under construction.jpg|70px]]== | ==Writing speed[[Image:section under construction.jpg|70px]]== | ||
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. | ||
The exposure time increases linearly with exposure dose and writing area. However, due to the stepped nature of the exposure, the exposure time as a function of fill factor is highly nonlinear. It takes the same time to expose a single pixel as an entire 300µm X 400µm writing field, so the exposure time depends on the number of addressed writing fields, rather than on the fill factor of the design. In practice, there will probably not be much variation in exposure time with fill factor. Exposure tests using a 50mm<sup>2</sup> design have shown that the exposure time increases linearly from 40s at 10mJ/cm<sup>2</sup>, to 257s at 1000mJ/cm<sup>2</sup>. The fill factor of the design is 20%, but 80% of the area is addressed by the writing fields. Scaled to a full 4" wafer, the exposure time is estimated to 2:37 hours at dose of 100mJ/cm<sup>2</sup>. | |||
At these exposure speeds, we would quickly run into a bottleneck as more and more users expose more and more wafers, if full 4" designs are used all the time. Another concern is that the exposure dose seems to be unstable over long exposure times, as consecutive exposures using the same parameters have been observed to yield different lithographic results. The conclusion is that exposure using the maskless aligner requires a different design philosophy than when a mask aligner is used for the exposure. | At these exposure speeds, we would quickly run into a bottleneck as more and more users expose more and more wafers, if full 4" designs are used all the time. Another concern is that the exposure dose seems to be unstable over long exposure times, as consecutive exposures using the same parameters have been observed to yield different lithographic results. The conclusion is that exposure using the maskless aligner requires a different design philosophy than when a mask aligner is used for the exposure. | ||