Maskless lithography

In maskless lithography, light used to expose the photosensitive emulsion (or photoresist) is not projected from, or transmitted through, a photomask. Instead, most commonly, the radiation is focused to a narrow beam. The beam is then used to directly write the image into the photoresist, one or more pixels at a time. An alternative method, developed by Micronic Laser Systems, is to scan a programmable reflective photomask, which is then imaged onto the photoresist. This has the advantage of higher throughput and flexibility. Both methods are used to define patterns on photomasks.

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Strictly speaking, interference lithography is another form of maskless lithography, but is limited to forming periodic patterns only.

For improved image resolution, ultraviolet light, which has a shorter wavelength than visible light, is used to achieve resolution down to around 100 nm. Besides light, electrons, X-rays, protons, and other radiation can also be used to print patterns in the sensitive layer.

IBM has developed an alternative maskless lithography technique based on atomic force microscopy see here.

The main advantage of maskless lithography is the ability to change lithography patterns from one run to the next, without incurring the cost of generating a new photomask. This may prove useful for double patterning.

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