High-frequency gratings with rectangular-groove profiles are used to generate high-efficiency beam splitters and beam deflectors. The effects of the grating design parameters, i.e., period, groove depth, duty cycle, number of phase levels, and polarization state (TE and TM) of the incoming signal, are considered. The case of the binary beam splitter grating is analyzed by using rigorous electromagnetic grating analysis. Fabrication techniques are presented in which three different lithographic techniques are considered (optical contact, deep-UV stepper reduction, and electron-beam direct write). Experimental results of 97% efficiency for the beam splitter grating and up to 80% for the beam deflector grating are reported.

The bulge test provides a convenient way to measure the mechanical properties, including fracture strength, of thin ceramic membranes. Thin (≈ 3000Å) films of non-stoichiometric SiNx, nominally defect-free and containing flaws introduced byfocused ion-beam machining, were examined. The use of such membranes in masks for projection electron-beam lithography systems makes it important to determine their ultimate strength and reliability. The mean fracture strength of the defect-free membranes was found to be 1.79±0.04GPa, and the Weibull modulus was estimated to be 49±15, giving a safe operating stress of 1.5GPa. The results of fracturing the samples containing flaws indicated that holes smaller than 15x0.5μm had no effect on the fracture strength of the membranes. By estimating the stress concentration factor for the slots, it was determined that the critical fracture stress was 16±3GPa.

We describe a variety of technologies for patterning transmissive and reflective soft x-ray projectionlithography masks containing features as small as 0.1 µm. The transmission masks fabricated for use at 13 nm are of one type, a Ge-absorbing layer patterned on a boron-doped Si membrane. Reflective masks were patterned by various methods that included absorbing layers formed on top of multilayer reflectors, multilayer-reflector-coating removal by reactive ion etching, and ion damage of multilayer regions by ion implantation. For the first time, we believe, a process for absorber repair that does not significantly damage the reflectance of the multilayer coating on the reflection mask is demonstrated.

We report on resolution experiments with the negative chemically amplified resist AZ PN114. Using soft-x-ray projection lithography at λ=14 nm, we imaged 0.1-μm lines and spaces in film thicknesses ranging from 50 to 200 nm with both a 20× reduction Schwarzschild camera and a 1× Offner ring-field optical system at doses of ∼10 mJ/cm2. High-resolution electron-beam lithography was used to study the effect of postexposure bake temperature on resist resolution and to characterize a trilayer structure. We found that at temperatures higher than 105 °C 0.1-μm features could not be resolved and patterns were distorted. Using e-beam, we resolved 0.075-μm lines and spaces in AZ PN114 and transferred the pattern to the underlying levels of the trilayer. We measured feature edge-noise for 0.1- and 0.2-μm critical dimensions (CDs) over a wide range of doses. We compared the edge noise and linewidth variation with those measured on samples written in poly(methyl methacrylate) (PMMA). We found 3σ values of 24 nm for AZ PN114 and 9 nm for PMMA. These results suggest that AZ PN114, or a resist of similar sensitivity, may be useful for CDs as small as 0.25 μm. To maintain sufficient linewidth control at smaller CDs in manufacturing, less sensitive resists will probably be required.

Using 14-nm wavelength illumination, we have imaged 0.1-µm-wide lines and spaces in single-layer thin films of the highy sensitive, negative, chemically amplified resist AZ PN114 by usingboth a Schwarzschild 20× camera and an Offner ring field 1× optical system. For soft-x-ray projection lithography the approximate 0.2-µm absorption length in resists at 14-nm wavelength necessitates a multilayer resist system. To explore further the requirements of the imaging layer of such a system, we have transferred patterns, exposed by a high-resolution electron beam in a 60-nm-thick layer of AZ PN114, into the underlying layers of a trilevel structure. Significant pattern edge noise and resist granularity were found. It remains to be determined whether the observed noise is dominated by statistical fluctuations in dose or by resist chemistry. We also investigated pinhole densities in these films and found them to increase from 0.2 cm(-2) for 380-mm-thick films to 15 cm(-2) for 50-nm-thick films.