Predicting EUV Stochastic Defect Density

Predicting EUV Stochastic Defect Density
by Fred Chen on 12-04-2022 at 6:00 am

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

Electron Blur Impact in EUV Resist Films from Interface Reflection
by Fred Chen on 11-08-2022 at 6:00 am

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?

Where Are EUV Doses Headed?
by Fred Chen on 10-11-2022 at 6:00 am

Where Are EUV Doses Headed 1

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

Application-Specific Lithography: 5nm Node Gate Patterning
by Fred Chen on 09-08-2022 at 6:00 am

Blur Limitations for EUV Exposure

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

Read More

Spot Pairs for Measurement of Secondary Electron Blur in EUV and E-beam Resists

Spot Pairs for Measurement of Secondary Electron Blur in EUV and E-beam Resists
by Fred Chen on 08-14-2022 at 8:00 am

Spot Pairs for Measurement of Secondary Electron Blur in EUV

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

EUV’s Pupil Fill and Resist Limitations at 3nm
by Fred Chen on 08-08-2022 at 10:00 am

EUV Pupil Fill and Resist Limitations at 3nm p1

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

Read More

Obscuration-Induced Pitch Incompatibilities in High-NA EUV Lithography

Obscuration-Induced Pitch Incompatibilities in High-NA EUV Lithography
by Fred Chen on 06-19-2022 at 10:00 am

High NA EUV Lithography 1

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

The Electron Spread Function in EUV Lithography
by Fred Chen on 06-07-2022 at 6:00 am

Electron Spread EUV

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

Double Diffraction in EUV Masks: Seeing Through The Illusion of Symmetry
by Fred Chen on 05-22-2022 at 7:00 am

Double Diffraction in EUV Masks

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

Demonstration of Dose-Driven Photoelectron Spread in EUV Resists
by Fred Chen on 05-08-2022 at 10:00 am

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