Extreme ultraviolet (EUV) lithography targets patterning pitches below 50 nm, which is beyond the resolution of an immersion lithography system without multiple patterning. In the process of exposing smaller pitches, stochastic patterning effects, i.e., random local pattern errors from unwanted resist removal or lack … Read More
Author: Fred Chen
Predicting EUV Stochastic Defect Density
Electron Blur Impact in EUV Resist Films from Interface Reflection
The resolution of EUV lithography is commonly expected to benefit from the shorter wavelengths (13.2-13.8 nm) but in actuality the printing process needs to include Pde the consideration of the lower energy electrons released by the absorption of EUV photons. The EUV photon energy itself has a nominal energy range of 90-94 eV,… Read More
Where Are EUV Doses Headed?
In spite of increasing usage of EUV lithography, stochastic defects have not gone away. What’s becoming clearer is that EUV doses must be managed to minimize the impact from such defects. The 2022 edition of the International Roadmap for Devices and Systems has updated its Lithography portion [1]. An upward trend with decreasing… Read More
Application-Specific Lithography: 5nm Node Gate Patterning
It has recently been revealed that the N5 node from TSMC has a minimum gate pitch of 51 nm [1,2] with a channel length as small as 6 nm [2]. Such a tight channel length entails tight CD control in the patterning process, well under 0.5 nm. What are the possible lithography scenarios?
Blur Limitations for EUV Exposure
A state-of-the-art
Spot Pairs for Measurement of Secondary Electron Blur in EUV and E-beam Resists
There is growing awareness that EUV lithography is actually an imaging technique that heavily depends on the distribution of secondary electrons in the resist layer [1-5]. The stochastic aspects should be traced not only to the discrete number of photons absorbed but also the electrons that are subsequently released. The electron… Read More
EUV’s Pupil Fill and Resist Limitations at 3nm
The 3nm node is projected to feature around a 22 nm metal pitch [1,2]. This poses some new challenges for the use of EUV lithography. Some challenges are different for the 0.33NA vs. 0.55NA systems.
0.33 NA
For 0.33 NA systems, 22 nm pitch can only be supported by illumination filling 4% of the pupil, well below the 20% lower limit for
Obscuration-Induced Pitch Incompatibilities in High-NA EUV Lithography
The next generation of EUV lithography systems are based on a numerical aperture (NA) of 0.55, a 67% increase from the current value of 0.33. It targets being able to print 16 nm pitch [1]. The High-NA systems are already expected to face complications from four issues: (1) reduced depth-of-focus requires thinner resists, which… Read More
The Electron Spread Function in EUV Lithography
To the general public, EUV lithography’s resolution can be traced back to its short wavelengths (13.2-13.8 nm), but the true printed resolution has always been affected by the stochastic behavior of the electrons released by EUV absorption [1-5].
A 0.33 NA EUV system is expected to have a diffraction-limited point spread… Read More
Double Diffraction in EUV Masks: Seeing Through The Illusion of Symmetry
At this year’s SPIE Advanced Lithography conference, changes to EUV masks were particularly highlighted, as a better understanding of their behavior is becoming clear. It’s now confirmed that a seemingly symmetric EUV mask absorber pattern does not produce a symmetric image at the wafer, as a conventional DUV … Read More
Demonstration of Dose-Driven Photoelectron Spread in EUV Resists
As a consequence of having a ~13.5 nm wavelength, EUV photons transfer ~90% of their energy to ionized photoelectrons. Thus, EUV lithography is fundamentally mostly EUV photoelectron lithography. The actual resolution becomes dependent on photoelectron trajectories.
Photoelectron trajectories in EUV lithography were… Read More
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