Improved burst pressure of LPCVD Si3N4 membranes by nanometer thick compressive adlayers

Si3N4 is a material widely used in MEMS technology. Its high mechanical strength makes Si3N4 attractive for applications where there is a need for ultrathin, yet robust, freestanding films, such as nanometer thick X-ray windows and support films for TEM. In this work, mechanical properties of Si3N4 and B-coated Si3N4 membranes were studied using a bulge test method. Burst pressure and corresponding membrane stress in Si3N4 layers were found to be significantly increased when a 3nm thick B layer was deposited on the top side of 25nm thick Si3N4 membranes, whereas a B layer applied to the bottom side of the membranes did not have an effect on the membrane strength. Using FEM simulations, we show that the B layer deposited at the top side decreases the maximum tensile stress in Si3N4 near the membrane edge, where a significant contribution to the total stress comes from bending. From this, we conclude that failure in single layer Si3N4 membranes during bulge test is dominated by fracture at the edge. The burst pressure of B-coated Si3N4 membranes was found to be higher for membranes with lower (more compressive) residual stress in B, which indicates that failure of bilayer membranes is caused by fracture initiated in the B layer. Please click Additional Files below to see the full abstract

Crystal surface characterization

Characterization of the structure of the crystal surface is essential for next generation electronics devices. Such as spin injection structures and topological insulators, to name a few. We have studied the advantages of characterization of the crystal surface based on the analysis of modulations of specular X-ray reflection occurred during the azimuthal scan in grazing incidence X-ray diffraction (GID) geometry

Modeling of XUV-induced damage in Ru films:The role of model parameters

We perform a computational study of damage formation in extreme ultraviolet (XUV)-irradiated ruthenium thin films by means of combining the Monte Carlo approach with the two-Temperature model. The model predicts that the damage formation is most affected by ultrafast heating of the lattice by hot electrons, and is not very sensitive to the initial stage of the material excitation. Numerical parameters of the model were analyzed, as well as different approximations for the thermal parameters, showing the importance of the temperature dependence of the electron thermal conductivity and the electronphonon coupling factor. Our analysis reveals that the details of photoabsorption and ultrafast non-equilibrium electron kinetics play only a minor role in the XUV irradiation regime.</p

High reflectance La/B based multilayer mirrors for 6.x nm wavelength

For future photolithography processes, the wavelength of 6 nm may offer improved imaging specs. The perspective of this technology however, will depend critically on the performance of multilayer reflective mirrors, which are likely to be based on La/B. One of the issues is formation of LaxBy compounds at the interfaces, which decreases the optical contrast and reduce the reflectivity. To prevent such chemical interaction, passivation of La by nitrogen has been investigated. We successfully synthesized LaN layers that resulted in a new world record reflectivity of 64% at 6.6 nm at near normal incidence. This reduces the gap to the target of 70%, desired for a next generation lithography.</p

Control of YH₃ formation and stability via hydrogen surface adsorption and desorption

Yttrium is known to form two hydrides: YH2, a metal, and YH3, which is dielectric. However, the stability of YH3 is not fully understood, especially in the context of thin films, where the yttrium layer must be coated to protect it from oxidation. In this work, we show that the stability of a YH3 thin film depends on the capping layer material. Our investigation reveals that YH3 appears to be stabilized by hydrogen that is adsorbed to the capping layer surface. This is evidenced by the YH3-YH2 transition temperature, which was found to be correlated with the desorption temperature of hydrogen from the surface. We posit that surface-adsorbed hydrogen prevents hydrogen from diffusing out of the thin film, which limits YH3 dissociation to the solubility of hydrogen in the YH2/YH3 thin film