Photolithography

Photolithography uses patterned light to transfer a design into a light-sensitive material, typically creating a mask for etching or other processing of a surface.

Photoresist: A light-sensitive polymer film whose solubility changes when exposed to radiation. Its exposure-dependent solubility turns the projected pattern into a developable mask.
Rayleigh criterion: A rule describing the ability of an optical system to distinguish nearby image features. Its resolution relationship helps explain optical limits in projection lithography.
Integrated circuit: An electronic circuit whose components are fabricated together on a semiconductor substrate. Repeated photolithography steps define the device’s microscopic layers and structures.
Electron-beam lithography: A lithographic method that writes patterns directly with a focused electron beam. It avoids a photomask but writes patterns serially rather than exposing whole fields.
Photomask: A patterned plate that selectively blocks or transmits radiation during photolithographic exposure. It carries the design that exposure transfers into the photoresist.
Numerical aperture: A dimensionless measure of an optical system’s ability to collect or focus light. Higher numerical aperture can resolve smaller printed features.
Semiconductor device fabrication: The sequence of processes used to build semiconductor devices on wafers. Photolithography supplies patterned masks throughout wafer processing.
Nanoimprint lithography: A patterning method that presses a nanoscale mold into a deformable material. It transfers features by mechanical contact instead of patterned-light exposure.
Photolithography exposure: The step in which patterned radiation changes the chemical properties of photoresist. Exposure determines which regions of resist will remain after development.
Diffraction: The spreading and interference of waves as they pass openings or encounter obstacles. Diffraction blurs mask patterns as light is projected onto resist.

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