Aligner (semiconductor)

It holds the photomask over the silicon wafer while a bright light is shone through the mask and onto the photoresist.

The "alignment" refers to the ability to place the mask over precisely the same location repeatedly as the chip goes through multiple rounds of lithography.

[1][2] Currently, mask aligners are still used in academia and research, as projects often involve devices made using photolithography in smaller batches.

Used only briefly, proximity aligners held the mask slightly above the surface to avoid this problem, but were difficult to work with and required considerable manual adjustment.

Finally, the Micralign projection aligner, introduced by Perkin-Elmer in 1973, held the mask entirely separate from the chip and made the adjustment of the image much simpler.