MA 6 Mask

A mask aligner is a lithography tool that aligns a patterned mask to a substrate and exposes photoresist so the pattern can be transferred. Mask aligners are used in microfabrication flows where contact or proximity exposure is suitable and where direct optical alignment of mask and wafer is part of the process.

Mask aligners position a substrate beneath a mask, bring the two into a defined alignment condition, and expose the resist-coated surface with ultraviolet light. Alignment optics let the operator register mask features to wafer features before exposure, and the exposure step defines the resist image used by later development and pattern transfer steps.

Mask aligners sit at the photolithography stage of a microfabrication process. A mask aligner is typically used after substrate preparation and photoresist coating, and before resist development, etching, deposition lift-off, or other pattern transfer operations.

Mask aligners are commonly used when a process flow needs patterned resist on wafers or other flat substrates without the projection-optics architecture of a stepper or scanner. Mask aligners are often selected for process modules that depend on overlay to existing features, including flows that can benefit from backside or infrared alignment capability.

Mask aligners are used for creating patterned photoresist layers in semiconductor, microsystem, and related cleanroom fabrication. Typical uses include etch masks, implant masks, plating molds, liftoff patterns, dielectric patterning, and alignment-sensitive layers on substrates that carry previously formed structures.