Specific Process Knowledge/Lithography/Aligners/Aligner: Maskless 02 processing: Difference between revisions
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'''Speed vs. area:''' | '''Speed vs. area:''' | ||
During exposure of a stripe the stage moves at a constant speed. Each stripe thus includes a certain movement overhead for acceleration and deceleration. As the stripes get shorter, this overhead becomes more significant, and the normal writing speed is no longer achieved. For samples smaller than a 2" wafer, the writing speed of Aligner: Maskless 02 drops below the specified 285mm<sup>2</sup>/min. | |||
When the exposure is started on the maskless aligner, the software starts converting the design to the data needed for the exposure. When sufficient data has been generated, the hardware starts exposing the sample while more data is being generated. This simultaneous data conversion and exposure is called Online conversion. Once a design has been converted (exposed) this data may be reused for repeated exposures (Offline conversion). Due to no time lost waiting for data, offline exposure may be several tens of % faster than online. However, the converted data can only be reused if no alignment is needed, including flat alignment ("Expose with substrate angle"). | |||
Depending on the complexity and density of the pattern, the conversion process may slow down the exposure significantly. A 4" wafer exposed with a pattern consisting of 200 million 5µm circles took 65 minutes, compared to the specified 35 minutes. | |||
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The maskless aligner exposes the design in north-south oriented stripes (perpendicular to the flat). The stripes all have the same length, set by the height of the design, and only completely empty stripes are skipped. The writing speed may thus be affected by the layout of the design. | The maskless aligner exposes the design in north-south oriented stripes (perpendicular to the flat). The stripes all have the same length, set by the height of the design, and only completely empty stripes are skipped. The writing speed may thus be affected by the layout of the design. | ||
Design case: | Design case: Five 100µm wide, 40mm long lines, spaced 10mm apart (40x40mm<sup>2</sup>) | ||
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