Electron beam lithography is commercially used to directly write submicron patterns onto advanced node masks. With the advent of EUV masks and nanometer-scale NIL (nanoimprint lithography), multi-beam writers are now being used, compensating the ultralow throughput of a single high-resolution electron beam with the use… Read More
Introduction
The ever-growing demand for faster, smaller, and more efficient electronic devices has fueled the semiconductor industry’s relentless pursuit of innovation. One crucial technology at the heart of semiconductor manufacturing is Extreme Ultraviolet Lithography (EUVL) to achieve smaller feature sizes… Read More
The point spread function is the basic metric defining the resolution of an optical system [1]. A focused spot will have a diameter defined by the Airy disk [2], which is itself a part of the diffraction pattern, based on a Bessel function of the 1st kind and 1st order J1(x), with x being a normalized coordinate defined by pi*radius/(0.5… Read More
For a leading-edge lithography technology, EUV (extreme ultraviolet) lithography is still plagued by some fundamental issues. While stochastically occurring defects probably have been the most often discussed, other issues, such as image shifts and fading [1-5], are an intrinsic part of using reflective EUV optics. However,… Read More
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
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
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
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.
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
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 [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
