X-ray Lithography and LIGA

X-ray lithography uses short-wavelength, high-energy X-rays to transfer a mask pattern into a thick resist. The short wavelength provides low diffraction and enables high-resolution, high-aspect-ratio structures.

LIGA

LIGA is a German acronym derived from Lithographie, Galvanoformung, Abformung (lithography, electroplating and molding).

Process

1. Coat a conductive substrate with a thick X-ray-sensitive resist such as PMMA.
2. Align a patterned X-ray mask.
3. Expose the resist using deep X-rays.
4. Develop the resist to form deep cavities/columns.
5. Electroplate metal into the resist mold.
6. Remove the resist to obtain a metal microstructure.
7. The metal structure can also serve as a mold for replication.

Advantages

• Very high aspect ratio.
• Nearly vertical sidewalls.
• High dimensional accuracy.
• Excellent replication capability.
• Suitable for relatively thick microstructures.
• Useful for microgears, nozzles, molds and other precision MEMS structures.

Limitation

The process requires specialized X-ray sources and masks, making it expensive and less accessible than conventional UV lithography.