Engineering topics

Smith, Henry I.

Publications and source records attributed to Smith, Henry I..

7 records

DOE OSTI2017

Direct Writing of X-ray Gratings Using Zone-Plate-Array Lithography (ZPAL)

With the objective of providing the synchrotron and free-electron-laser communities with rapid turnaround and low prices for the highest quality and most advanced gratings and diffractive-focusing optics, LumArray has made specific improvements to its ZP-150 maskless photolithography system, which is based on Zone-Plate-Array Lithography (ZPAL), a technology unique to Lumarray. ZPAL’s advantages include an ability to correct in software for systematic patterning errors. Emphasis was placed on interferometric measurements of various contributors to patterning errors using Fizeau interferometry and a Mireau technique that was developed specifically for measuring errors within a micron-scale area. Average line-placement error was reduced below 20 nm using both pattern-file distortion and address-grid modification. The preferred implementation, address-grid modification, is hardware-based and requires no user intervention while also correcting more types of error. With continued iteration and refinement of the error measurements, we anticipate achieving global line-placement error below10nm. In order to investigate line-edge smoothness and high-frequency line-placement errors, a scheme for inspecting micron-sized areas was invented and implemented based on Mireau interferometry. This enabled the various contributions to be separately evaluated and measured. These included: exposure-dose variation, pattern-writing strategy and errors in the positioning of the microlenses. Deleterious crosstalk between microlenses was minimized via a pattern-dependent software modification. The impact of exposure threshold was revealed and adjustment made. The impact of address-grid fineness on line-edge roughness was likewise shown. Lastly, techniques were developed to measure and correct errors in the positioning of microlenses within the array. We expect final calibration of microlens positions to within 5nm.

42 ENGINEERING↗

DOE OSTI2012

Three-dimensional photonic crystals by large-area membrane stacking

We designed and analyzed a “mesh-stack” three-dimensional photonic crystal of a 12.4% bandgap with a dielectric constant ratio of 12:1. The mesh-stack consists of four offset identical square-lattice air-hole patterned membranes in each vertical period that is equal to the in-plane period of the square lattice. This design is fully compatible with the membrane-stacking fabrication method, which is based on alignment and stacking of large-area single-crystal membranes containing engineered defects. A bandgap greater than 10% is preserved as long as the membranes are subjected to in-plane misalignment less than 3% of the square period. By introducing a linear defect with a nonsymmorphic symmetry into the mesh-stack, we achieved a single-mode waveguide over a wide bandwidth.

36 MATERIALS SCIENCE↗

DOE OSTI2012

Nanocrystal structures

A structure including a grating and a semiconductor nanocrystal layer on the grating, can be a laser. The semiconductor nanocrystal layer can include a plurality of semiconductor nanocrystals including a Group II-VI compound, the nanocrystals being distributed in a metal oxide matrix. The grating can have a periodicity from 200 nm to 500 nm.

36 MATERIALS SCIENCE↗

NASA NTRS1998

X-ray lithography masking

X-ray masking apparatus includes a frame having a supporting rim surrounding an x-ray transparent region, a thin membrane of hard inorganic x-ray transparent material attached at its periphery to the supporting rim covering the x-ray transparent region and a layer of x-ray opaque material on the thin membrane inside the x-ray transparent region arranged in a pattern to selectively transmit x-ray energy entering the x-ray transparent region through the membrane to a predetermined image plane separated from the layer by the thin membrane. A method of making the masking apparatus includes depositing back and front layers of hard inorganic x-ray transparent material on front and back surfaces of a substrate, depositing back and front layers of reinforcing material on the back and front layers, respectively, of the hard inorganic x-ray transparent material, removing the material including at least a portion of the substrate and the back layers of an inside region adjacent to the front layer of hard inorganic x-ray transparent material, removing a portion of the front layer of reinforcing material opposite the inside region to expose the surface of the front layer of hard inorganic x-ray transparent material separated from the inside region by the latter front layer, and depositing a layer of x-ray opaque material on the surface of the latter front layer adjacent to the inside region.

Smith, Henry I.↗

NASA NTRS1992

The MIT high resolution X-ray spectroscopy instruments on AXAF

The general design and performance characteristics of MIT's two dispersive spectrometers, the Bragg Crystal Spectrometer (BCS) and the High Energy Transmission Grating Spectrometer (HETG), now being developed for the Advanced X-ray Astrophysics Facility (AXAF), are described. Particular attention is given to the development of the critical technologies incorporated into these instruments, including BCS diffractors, imaging gas flow proportional counters, and grating elements for the HETG. The principal stages and the current status of the developments are reviewed.

Canizares, C. R.↗

NASA NTRS1992

An anti-reflection coating for use with PMMA at 193 nm

An antireflection coating (ARC) for use with poly(methyl methacrylate) (PMMA) resist for ArF excimer laser lithography (193 nm) was formulated. It consists of PMMA and a bis-azide, 4.4-prime-diazidodiphenyl sulfone (DDS) which crosslinks the film after deep UV (260 nm) irradiation and subsequent annealing. The reacted DDS then serves as the absorber for the 193 nm radiation and also prevents mixing of the ARC and PMMA during PMMA spin-coating and development. The effectiveness of the ARC was demonstrated by exposing, in PMMA, using achromatic holographic lithography, gratings of 100 nm period (about 50 nm linewidth) that are almost entirely free of an orthogonal standing wave.

Yen, Anthony↗

NASA NTRS1990

X-ray/VUV transmission gratings for astrophysical and laboratory applications

This paper describes the techniques used to fabricate deep-submicron-period transmission gratings for astrophysical and laboratory applications, with special attention given to the major steps involved in the transmission grating fabrication. These include the holographic lithography procedure used to pattern the master transmission grating, the fabrication of X-ray mask, the X-ray lithography step used to transfer the X-ray mask pattern into a substrate, and the electroplating of the substrate to form the final grating pattern. The various ways in which transmission gratings can be used in X-ray and VUV spectroscopy are discussed together with some examples of experiments reported in the literature.

Schattenburg, M. L.↗