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Exposure technology

Aligner: Maskless 03 is not a direct writer. In the maskless aligner, the exposure light is passed through a spatial light modulator, much like in a video projector, and projected onto the substrate, thus exposing an area of the design at a time. The substrate is exposed by scanning the exposure field across the substrate in a succession of stripes.

The light source is a laser diode (array) with a wavelength of 405nm (8W). The spacial light modulator is a digital micro-mirror device. The individual mirrors of the DMD are switched in order to represent the design, and the laser is flashed in order to yield the desired exposure dose. This image is projected onto the substrate through a lens(system). The projected image yields a pixel size of 500nm X 500nm at wafer scale. The image is scanned across the substrate, in order to expose the entire design, each stripe overlapping (2 or 5 times depending on exposure mode) in order to minimize uniformity effects and stitching errors. The address grid size is 250nm or 100nm for Fast or High Quality exposure mode, respectively.

The writing head of the Aligner: Maskless 02 moves only in the z-direction. Using a pneumatic focusing system, the maskless aligner is able to do real-time autofocus. The defocus process parameter is used to compensate offsets in the focusing mechanism, and to optimize printing quality in different resists and varying thicknesses. The stage of the Aligner: Maskless 03 moves only in x and y. It has no theta-axis. All rotation during alignment is thus accomplished by transformation of the input design.