The pursuit of ever smaller DRAM cell sizes is still active and ongoing. DRAM cell size is projected to approach 0.0013 um2 for the D12 node. Patterning challenges are significant whether considering the use of DUV or EUV lithography. In particular, ASML reported that when center-to-center values reached 40 nm, single patterning… Read More
Author: Fred Chen
Application-Specific Lithography: Sub-0.0013 um2 DRAM Storage Node Patterning
Secondary Electron Blur Randomness as the Origin of EUV Stochastic Defects
Stochastic defects in EUV lithography have been studied over the last few years. For years, the Poisson noise from the low photon density of EUV had been suspected [1,2]. EUV distinguishes itself from DUV lithography with secondary electrons functioning as intermediary agents in generating reactions in the resist. Therefore,… Read More
Predicting EUV Stochastic Defect Density
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
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
IEDM 2025 – TSMC 2nm Process Disclosure – How Does it Measure Up?