Enabling Advanced Lithography: The Challenges of Storing and Transporting EUV Reticles
This paper explains the challenges inherent in designing pods for EUV lithography and proposes solutions that will allow more fabs to implement advanced lithography nodes at their facilities.
PROTECTING EUV RETICLES
The finer the lithographic patterns, the greater the risk reticle contamination poses. Potential contamination sources include both foreign particles and chemical residues. Reticle coatings are delicate and easily damaged. Anything that touches a reticle, whether it is an expected part of the process such as a robot arm in the fab or an unexpected contaminant such as a human hair, has the potential to cause damage.
Immersion lithography relies on pellicles to act as “dustcovers” that protect reticles from particle contamination during pattern exposure. Pellicles need to be optically transparent, which in the case of EUV lithography means that they must be transparent to light in the EUV spectrum with wavelengths around 13.5 nm. Most existing pellicle film materials absorb EUV light, but the semiconductor industry is starting to implement EUV-specific pellicles (see Figure 1).