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
The list of possible stochastic patterning issues for EUV lithography keeps growing longer: CD variation, edge roughness, placement error, defects . 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
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
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
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 . 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
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
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
Nonvolatile memory capacity reached 64 Gb levels when NAND Flash half-pitch reached 20 nm . Having reached 14 nm , 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 . The lithography for patterning 20 nm half-pitch… Read More
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