Deviation of the light from the ideal path in an optical system. Aberrations are classified into six elements: Seidel's five aberrations (coma, spherical aberration, curvature, astigmatism, distortion) and chromatic aberration.
ADC
Automatic Defect Classification
A function that an inspection machine automatically classifies defects.
Aerial Image
Pattern image of a photomask projected onto a wafer where resist is to be placed.
Developed resist is not always formed like the pattern of the aerial image.
AFM
Atomic Force Microscopy
A microscope capable of observing 3D surface feature of samples by detecting atomic force between sample surface and a probing stylus called cantilever.
Aligner
A photolithography tool that transfers the patterns of a photomask onto a resist-coated wafer on which an electronic circuit is to be formed.
This tool utilizes a UV lamp for the exposure and typically the pattern size of the photomask is equal to the pattern to be formed on wafer.
Alt-PSM
Alternating Phase Shift Mask
One type of phase shift mask.
Levenson type phase shift Masks (all the phase shift mask other than the Half Tone type phase shift mask).
AOD
Acoustic Optical Deflector
A device that deflects laser light by diffraction at ultrasonic wave front generated at the surface of the optical medium. Because of no mechanical moving part in this device, it enables a very high speed scanning of the light.
APC
Advanced Process Control
A kind of lithographic process control which utilizes feedback and/or feedforward of the process.
ArF
Argon Fluoride
ArF excimer laser used as an exposure light source
Laser wavelength: 193nm
Att-PSM
Attenuated Phase Shift Mask
One type of phase shift mask.
It is also called Half Tone type phase shift mask.
