Proc. SPIE. 8679, Extreme Ultraviolet (EUV) Lithography IV
KEYWORDS: Multilayers, Particles, 3D modeling, Atomic force microscopy, Monte Carlo methods, Photomasks, Extreme ultraviolet, Optical simulations, Extreme ultraviolet lithography, Scanning transmission electron microscopy
The EUV community has come to the conclusion that completely eliminating EUV mask defects will be nearly impossible in the near future. Instead the industry trend is to develop high performance optical simulations of the multilayer coating in order to compensate for the defects during manufacturing. In order for these simulations to be accurate the full multilayer structure of the EUV defect should be known. Currently there is no usable 3D method of simulating pit-type defects as they are relaxed during the energetic deposition of the Mo/Si multilayer. Current approximations used to model the defect's propagation are poor and have many shortcomings. Monte Carlo simulations of thin film growth are explored for this usage. They are validated using experimental data of a STEM cross section of a multilayer pit-type defect. Monte Carlo methods allow a full 3D representation of the system and have the advantage of great flexibility in deposition conditions and flux distributions. The Solid-on-Solid aggregation model is used to deposit particles onto initial substrate defects; this model does not allow overhanging particles, which replicates the smooth growth of ion-beam deposition well. Surface diffusion is simulated using Boltzmann statistics with activation energies of diffusion biased by local geometry. The growths are compared by observing the aspect ratio of the defect as a function of film thickness; the aspect ratio is defined as the depth of the defect divided by its full width at half maximum. Good fitting is observed for initial defect templates created from atomic force microscopy scans of observed initial defects. More rigorous tests of accuracy are also performed by comparing simulation predictions to AFM scans of the ending multilayer.
Microstructure of a nanostructured film is not only of fundamental scientific interest but also an important
subject from the practical point of view. In this paper we will discuss the formation of biaxially textured film
under extreme shadowing during growth. Biaxially textured films are not single crystals, but they possess
both the out-of-plane and in-plane preferred orientations. We will also discuss our newly developed reflection
high-energy electron diffraction (RHEED) surface pole figure technique and how we employ this technique to
capture the evolution of growth front texture.
Hydrogen production and delivery is critical to successful fuel cell operation. One of the most common methods to produce hydrogen is via electrolysis of water. However over-potential losses at the electrodes results in poor efficiency and an increase in power consumption. In this study we carried out experiments of water electrolysis with novel single crystal Ruthenium nano-rod arrays as the device cathode. We show that the increased active area of the nanostructured electrode serves to reduce the operating current density of the electrolyzer causing the over-potential to show a corresponding decrease. In addition to the decreased over-potential, the power needed to produce one mole of hydrogen was also reduced for the nanostructured electrolyzer compared to an electrolyzer with planar electrodes.
We investigate Tungsten (W) nanorod electrodes as gas ionizers. These W nanorods having square-base pyramidal apexes are grown using a glancing angle sputter deposition technique with substrate rotation. We show that few tens of volts of anode voltage applied to the W nanorods are sufficient to ionize a range of different gas species including Ar, CO<sub>2</sub>, N<sub>2</sub> and O<sub>2</sub>. A distinct ionization onset voltage is observed for each individual gas specie, which suggests that these nanostructured ionization devices may be useful for gas sensing applications. In addition, the low anode voltage and high ion currents observed in this study indicates that the gas ionization devices could be operated using commercially available off-the-shelf batteries.
Three-dimensional nanostructures can be fabricated by the glancing angle deposition technique. By rotating the substrate in both polar and azimuthal directions, one can fabricate desired nanostructures, such as nano-rod arrays with different shapes, nano-spring arrays, and even multilayer nanostructures. This method offers a fully three-dimensional control of the nanostructure with additional capability of self-alignment. There is almost no limitation on materials that can be fabricated into desired nanostructures. In this presentation, we will discuss the current status of the glancing angle deposition technology, its potential applications, and its future challenges.
Rensselaer is establishing an educational program, THz Science and Technology, with an interdisciplinary faculty team from Departments of Physics, Biology, and Electrical, Computer, and Systems Engineering. Doctoral level students are trained in THz electronics, THz spectroscopy, THz imaging, and THz data transfer and networking. We present examples of focus research and studio based education.
Characterizing the optical and dielectric properties of thin films in the GHz to THz range is critical for the development of new technologies in integrated circuitry, photonics systems and micro-opto-electro-mechanical systems (MOEMS). Terahertz differential time-domain spectroscopy (DTDS) is a new technique that uses pulsed terahertz (THz) radiation to detect phase changes of less than 0.6 femtoseconds (fs) and absorption changes corresponding to several molecular monolayers. This paper shows how DTDS can be combined with double modulation in the pump-probe system to improve sensitivity by an order of magnitude. The technique is experimentally verified using 1 μm thick samples of silicon dioxide on silicon.
By using a diode array detector and an in-plane scattering geometry, we have investigated the diffraction from various etch-front morphologies. We can obtain an angular distribution of light intensity profile within 30 milliseconds. A series of experimental work, including the detailed characterization of Si backside surfaces and the morphology of Al films on Si during chemical corrosion, will be presented. The corresponding roughness parameters for different surfaces were extracted from light scattering profiles, and compared with those from real-space images. Real time measurements have been performed to study the evolution of Si surface morphology during wet chemical etching. RMS roughness, pits density, correlation length, and pits formation rate can be determined in real time.
Planarization, conformal coating and etch selectivity are three key areas for successful fabrication of submicron interconnections, BCl<SUB>3</SUB> and BCl<SUB>3</SUB>/N<SUB>2</SUB> RIE (Reactive Ion Etch) are usually used to define high aspect ratio and fine edge submicron Al lines. Polymers have potential for being used as the insulator for multilevel interconnections, because of their low dielectric constants. Due to viscosity, it is difficult to coat the space between submicron metal lines with spin on formulations for polymers. Parylene is a family of conformal vapor depositable polymers with many attractive attributes, such as low dielectric constant (2.38 - 2.65), no outgassing or moisture uptake, room temperature deposition, low stress, good gap filling and local planarization properties. However, with this 'new' polymer insulator, selectivity becomes important for proper etch stop. In this paper the RIE etch selectivities of Al and parylene have been investigated and the selectivity explored to pattern micron feature size interconnections. The Al was deposited on parylene and patterned for studying etch selectivity. The planarization capability of parylene was also studied. It is demonstrated that high aspect ratio sub-micron trenches could be successfully conformally coated with parylene. The metal-polymer adhesion and diffusion characteristics are also examined; and low mechanical stress for the dielectric are demonstrated.
The limitations ofmetal interconnections in MultiChip Modules (MCM''s) are examined primarily with respect to their bandwidth arid propagation loss. Comparison is made with the alternative ofemploying optical interconnections. Some of the technical issues which lie ahead to make a Photonic Multichip Package (PMP) possible are explored. Certain organic materials are identified as promising candidates for implementing optical interconnections. These are found to be interesting because of their low deposition temperatures and because they lend themselves to fabrication by techniques that are already finding acceptance for metal interconnections in thin film MCM manufacturing.