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

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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


Adding Random Secondary Electron Generation to Photon Shot Noise: Compounding EUV Stochastic Edge Roughness

Adding Random Secondary Electron Generation to Photon Shot Noise: Compounding EUV Stochastic Edge Roughness
by Fred Chen on 04-26-2022 at 6:00 am

Compounding EUV Stochastic Edge Roughness 2

The list of possible stochastic patterning issues for EUV lithography keeps growing longer: CD variation, edge roughness, placement error, defects [1]. The origins of stochastic behavior are now well-known. For a given EUV photon flux into the resist, a limited fraction are absorbed. Since the absorption is less than 5% affected… Read More


EUV Resist Absorption Impact on Stochastic Defects

EUV Resist Absorption Impact on Stochastic Defects
by Fred Chen on 04-03-2022 at 10:00 am

EUV Resist Absorption Impact on Stochastic Defects 1

Stochastic defects continue to draw attention in the area of EUV lithography. It is now widely recognized that stochastic issues not only come from photon shot noise due to low (absorbed) EUV photon density, but also the resist material and process factors [1-4].

It stands to reason that resist absorption of EUV light, which is … Read More


Pattern Shifts Induced by Dipole-Illuminated EUV Masks

Pattern Shifts Induced by Dipole-Illuminated EUV Masks
by Fred Chen on 12-19-2021 at 10:00 am

Pattern Shifts Induced by Dipole Illuminated EUV Masks

As EUV lithography is being targeted towards pitches of 30 nm or less, fundamental differences from conventional DUV lithography become more and more obvious. A big difference is in the mask use. Unlike other photolithography masks, EUV masks are absorber patterns on a reflective multilayer rather than a transparent substrate.… Read More


Revisiting EUV Lithography: Post-Blur Stochastic Distributions

Revisiting EUV Lithography: Post-Blur Stochastic Distributions
by Fred Chen on 11-14-2021 at 10:00 am

Revisiting EUV Lithography Post Blur Stochastic Distributions

In previous articles, I had looked at EUV stochastic behavior [1-2], primarily in terms of the low photon density resulting in shot noise, described by the Poisson distribution [3]. The role of blur to help combat the randomness of EUV photon absorption and secondary electron generation and migration was also recently considered… Read More


Stochastic Effects from Photon Distribution Entropy in High-k1 EUV Lithography

Stochastic Effects from Photon Distribution Entropy in High-k1 EUV Lithography
by Fred Chen on 08-04-2021 at 10:00 am

Stochastic Effects from Photon Distribution Entropy in High k1 EUV Lithography

Recent advances in EUV lithography have largely focused on “low-k1” imaging, i.e., features with pitches less than the wavelength divided by the numerical aperture (k1<0.5). With a nominal wavelength of 13.5 nm and a numerical aperture of 0.33, this means sub-40 nm pitches. It is naturally expected that larger… Read More


CD-Pitch Combinations Disfavored by EUV Stochastics

CD-Pitch Combinations Disfavored by EUV Stochastics
by Fred Chen on 11-29-2020 at 6:00 am

CD Pitch Combinations Disfavored by EUV Stochastics

Ongoing investigations of EUV stochastics [1-3] have allowed us to map combinations of critical dimension (CD) and pitch which are expected to pose a severe risk of stochastic defects impacting the use of EUV lithography. Figure 1 shows a typical set of contours of fixed PNOK (i.e., the probability of a feature being Not OK due… Read More


Application-Specific Lithography: 20nm Flash, 3D XPoint, 3D NAND Bit Lines

Application-Specific Lithography: 20nm Flash, 3D XPoint, 3D NAND Bit Lines
by Fred Chen on 08-10-2020 at 6:00 am

Application Specific Lithography SemiWiki

Nonvolatile memory capacity reached 64 Gb levels when NAND Flash half-pitch reached 20 nm [1]. Having reached 14 nm [2], NAND Flash half-pitch is no longer being reduced, now that it has entered the 3D era. However, recently, 3D XPoint has found applications within the Optane platform [3]. The lithography for patterning 20 nm half-pitch… Read More


Online Class: Advanced CMOS Technology 2020 (The 10/7/5 NM Nodes)

Online Class: Advanced CMOS Technology 2020 (The 10/7/5 NM Nodes)
by Daniel Nenni on 04-12-2020 at 9:00 am

3D Finet Model

Our friends at Threshold Systems have a new ONLINE class that may be of interest to you. It’s an updated version of the Advanced CMOS Technology class held last February. This is normally a classroom affair but to accommodate the recent COVID-19 travel restrictions it is being offered virtually.

As part of the previous class we did… Read More