LIGA Lithography Radiation Type: What Kind of Light Is Used?
The LIGA process (LIGA), uses X-ray lithography—i.e., X-ray radiation—to pattern a thick resist layer with very high resolution and depth. In standard multiple-choice form, the correct option is: (ii) X-ray.
A typical LIGA workflow is: X-ray exposure of a thick resist (often an electrically insulating polymer), electroforming of a metal pattern into the resist mold, and then molding to replicate structures. This “X-ray + thick resist” pairing is central to achieving deep, nearly vertical profiles suitable for micro-/nano-scale high-aspect-ratio parts.
Key terms: X-ray lithography; resist; electroforming; molding.
X-ray Lithography (Overview) for Semiconductor/ MEMS Concepts
Exam shortcut
If the question says LIGA, think X-ray lithography (not UV/visible/IR). LIGA is specifically known for deep, high-resolution X-ray patterning.
Why X-rays (and not UV/visible/infrared) are used in LIGA
LIGA relies on X-ray lithography because X-rays enable patterning through a thick resist with the kind of exposure depth and feature fidelity needed for high-aspect-ratio microstructures. UV lithography is widely used in conventional semiconductor processing, but LIGA’s defining advantage is that it uses X-rays to pattern thick resist layers more effectively for these 3D/height-demanding geometries.
Key terms: high-aspect-ratio; PMMA; synchrotron; dose.
LIGA process (conceptual flow)
- 1Step 1
A thick resist layer is patterned by X-ray lithography, creating exposed regions for subsequent development.
- 2Step 2
The exposed regions are removed to form a durable mold with high-aspect-ratio cavities.
- 3Step 3
Metal is electrochemically deposited into the mold to build the final metal microstructure.
- 4Step 4
The metal pattern can be released, and/or used as a master for molding replication.
- 5Step 5
You obtain deep, accurately patterned microstructures suitable for MEMS and related applications.
Quick answers (multiple choice)
Why LIGA is associated with X-rays (historical concept roadmap)
Need for deep patterning
Step 1Microfabrication increasingly required tall, near-vertical, high-aspect-ratio features."
Adopt X-ray lithography
Step 2X-rays enable effective exposure of thick resist layers for high-resolution 3D patterns."
Electroforming and replication
Step 3Electroforming fills the mold cavities; molding replicates the geometry."
Knowledge Check
The LIGA process utilizes which type of radiation for lithography?