Specific Process Knowledge/Lithography/Aligners/Aligner: Maskless 04 processing: Difference between revisions
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Aligner: Maskless 04 offers not only two exposure modes, but also two autofocus modes; optical or pneumatic. The defocus process parameter is used to compensate for offsets between the autofocus mechanism and the focal point of the exposure light, and simultaneously optimize print quality in different resists and varying thicknesses. | Control of the exposure dose differs between the two available exposure modes. In Raster mode, the dose is directly controlled by the on-time of the DMD mirrors during exposure, and the dose process parameter is thus simply given in units of mJ/cm<sup>2</sup>. As the intensity of the exposure light at the substrate surface cannot easily be measured, this dose is indirectly calibrated at the factory, by adjusting the optimal dose to match the known dose of a particular resist. | ||
<br>In Vector mode, however, the exposure dose is determined by combination of four different process parameters: | |||
*Pen [1, 2, 5, 10, or 25 µm], the size of pinhole projected onto the substrate surface | |||
*Transmission [30, or 100 %], the transparency of the filter in front of the pinhole | |||
*Laser Power [0-120 mW], the output power of the diode laser | |||
*Exposure Velocity [0-200 mm/s], the movement speed of the stage during exposure | |||
The Pen determines the size of the spot on the substrate surface and thus the ultimate resolution. It may also affect the intensity available at the substrate. For highly sensitive resists, the Transmission can be used to lower the Exposure Velocity to a reasonable value. The Laser Power directly affects the intensity available at the substrate. The Exposure Velocity determines the dwell time at each point on the substrate, and thus the effective dose received by the resist at the intensity determined by the three other parameters. | |||
Aligner: Maskless 04 offers not only two exposure modes, but also two autofocus modes; optical or pneumatic. The defocus process parameter is used to compensate for offsets between the autofocus mechanism and the focal point of the exposure light, and simultaneously optimize print quality in different resists and varying thicknesses. The "defoc" parameter us a unitless value, representing ±100% of the available correction available above and below the initial focus point established during loading of the substrate. One defoc step is approximately 0.25µm. Positive defoc is into the resist, i.e. writehead moves down when defoc is increased. | |||
'''Optical autofocus:''' Uses red laser light to focus on the substrate surface. Works for substrates down to 3x3 mm. | '''Optical autofocus:''' Uses red laser light to focus on the substrate surface. Works for substrates down to 3x3 mm. | ||
'''Pneumatic autofocus:''' Uses compressed air flowing through the nozzle of the writehead to focus on the substrate surface. Substrates must be at least 5x5 mm to be successfully loaded. The pneumatic AF fails at some distance from the substrate edge, which means that in order to have any useful area in the center of the sample when using the pneumatic AF, the substrate must likely be larger than 5x5 mm. When using the pneumatic autofocus, we recommend a substrate size of at least 10x10 mm. | '''Pneumatic autofocus:''' Uses compressed air flowing through the nozzle of the writehead to focus on the substrate surface. Substrates must be at least 5x5 mm to be successfully loaded. The pneumatic AF fails at some distance from the substrate edge, which means that in order to have any useful area in the center of the sample when using the pneumatic AF, the substrate must likely be larger than 5x5 mm. When using the pneumatic autofocus, we recommend a substrate size of at least 10x10 mm. | ||
==Exposure dose and defocus== | ==Exposure dose and defocus== | ||