The MA6 Mask Aligner is designed to provide the maximum flexibility required in a R&D laboratory environment. It can handle regular semiconductor wafers up to 6 inches in diameter as well as irregularly shaped pieces (starting from 1 cm2) of different thicknesses (up to 6 mm). Variety of mask holders can accommodate masks from 4 to 6-inch with the following “exposure windows”: 2, 3, 4, and 6-inch round, and 3-inch square. Broad spectrum light from mercury lamp is used for the exposure illumination. The light intensity is stabilized using two constant intensity (CI) channels: 2W/ cm2 at 365nm wavelength (CI1) and 3.5 W/cm2 at 405nm (CI2). The aligner performs exposures in vacuum (vacuum between substrate and mask), low vacuum (vacuum level between substrate and mask can be adjusted), hard (nitrogen pressure under the substrate), soft (vacuum under the substrate) modes. Line space resolution up to 0.6 micron can be achieved under optimum conditions in vacuum mode. Both vacuum modes can be used only with a special vacuum 4” wafer. In addition, the aligner has a proximity contact mode that reduces the damage to the mask by leaving an adjustable gap between the substrate and the mask when exposing. The drawbacks are that anything smaller than 10 microns will not be resolved accurately, the mode requires special mask holder with proximity sensors, and only relatively large samples can be exposed.
The instrument is equipped with a splitfield microscope (5x, 10x and 20 x objectives) and an automated stage for a high precision alignment. Two separate focus adjustment can be performed for mask and substrate surface. Reference points can be stored thus the stage will automatically drive between them allowing the alignment to be checked at different locations. A capturing option is provided to further improve alignment accuracy at the high magnification. Using this options one can, first, focus on the mask, capture the image of the mask, and then, second, switch focus to the substrate surface and align the substrate fiducials to the virtual mask fiducials on the stored image.
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