Lithography Glossary

Written by Chris Mack
Brought to you by the creators of PROLITH

Quadrupole Illumination
A type of off-axis illumination where four circles of light are used as the source. These four circles are spaced evenly around the optical axis.

Example: Quadrupole illumination is especially useful for improving the depth of focus of small dense lines oriented in the X or Y directions.

Quantum Efficiency
Referring to photoresist exposure, the quantum efficiency is the average number of exposure reaction products produced when one photon is absorbed by the photoreactive species.

Example: Reasonably good photoacid generators show quantum efficiencies of about 0.5.