While stochastic defects link yield with the practical resolution of EUV lithography resulting from its quantum nature [1], very low yields of EUV processes are more readily linked to the use of EUV masks without pellicles. Pellicles are thin film membrane covers on masks (regardless of wavelength: EUV and DUV and i-line) used… Read More
Author: Fred Chen
EUV Lithography Without Pellicles: Accounting for Low Yields
EUV Resist Degradation with Outgassing at Higher Doses
Dosing for EUV lithography walks a fine line between productivity and defectivity. Fabs can choose higher-dose exposures to suppress photon shot noise [1]. However, higher doses require EUV machines to scan the wafer at slower speeds, degrading throughput [2].
On the other hand, there is the threat of resist thickness loss that… Read More
IMEC’s Advanced Node Yield Model Now Addresses EUV Stochastics
It lays the foundation for the Stochastics Resolution Gap
Chris Mack, the CTO of Fractilia, recently wrote of the “Stochastics Resolution Gap,” which is effectively limiting the manufacturability of EUV despite its ability to reach resolution limits approaching 10 nm in the lab [1,2]. As researchers have inevitably found, … Read More
Edge Roughness Differences Among EUV Resists
EUV resists are a key component in the implementation and optimization of EUV lithography. By converting a limited number of absorbed EUV photons into a variable number of released migrating electrons, the resist becomes the final determinant of resolution. There are two kinds of resist which are seriously considered: chemically… Read More
Facing the Quantum Nature of EUV Lithography
The topics of stochastics and blur in EUV lithography has been examined by myself for quite some time now [1,2], but I am happy to see that others are pursuing this direction seriously as well [3]. As advanced node half-pitch dimensions approach 10 nm and smaller, the size of molecules in the resist becomes impossible to ignore for… Read More
High-NA Hard Sell: EUV Multi-patterning Practices Revealed, Depth of Focus Not Mentioned
In High-NA EUV lithography systems, the numerical aperture (NA) is expanded from 0.33 to 0.55. This change has been marketed as allowing multi-patterning on the 0.33 NA EUV systems to be avoided. Only very recently have specific examples of this been provided [1]. In fact, it can be shown that double patterning has been implemented… Read More
Impact of Varying Electron Blur and Yield on Stochastic Fluctuations in EUV Resist
A comprehensive update to the EUV stochastic image model
In extreme ultraviolet (EUV) lithography, photoelectron/secondary electron blur and secondary electron yield are known to drive stochastic fluctuations in the resist [1-3], leading to the formation of random defects and the degradation of pattern fidelity at advanced
Stitched Multi-Patterning for Minimum Pitch Metal in DRAM Periphery
In a DRAM chip, the memory array contains features which are the most densely packed, but at least they are regularly arranged. Outside the array, the regularity is lost, but in the most difficult cases, the pitches can still be comparable with those within the array, though generally larger. Such features include the lowest metal… Read More
A Perfect Storm for EUV Lithography
Electron blur, stochastics, and now polarization, are all becoming stronger influences in EUV lithography as pitch continues to shrink
As EUV lithography continues to evolve, targeting smaller and smaller pitches, new physical limitations continue to emerge as formidable obstacles. While stochastic effects have long been… Read More
Variable Cell Height Track Pitch Scaling Beyond Lithography
Two approaches compared
With half-pitch approaching 10 nm, EUV patterning is heavily impacted by stochastic effects, which are aggravated from reduced image contrast from electron blur [1]. A two-mask (“LELE”: Litho-Etch-Litho-Etch) approach was proposed to pattern core features for self-aligned double patterning (SADP)… Read More
Rapidus, IBM, and the Billion-Dollar Silicon Sovereignty Bet