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

Stress tensor mesostructures for freeform shaping of thin substrates

Stress-induced shaping, which deforms thin substrates utilizing stressed surface coatings, has enabled and enhanced a host of applications in past decades. Owing to the touchless fabrication process compatible with modern planar technology, the method has been applied from microscale to macroscale applications such as self-assembled micro-structures and space mirrors. However, the deformations created by existing stress-control schemes are limited to certain classes of geometries (such as sphere, coma and astigmatism) or rely on boundary constraints and hinges because the stress is unary, e.g., equibiaxial stress or uniaxial stress with fixed orientation. Here, we present novel stress tensor mesostructures to spatially control the three required stress tensor components, i.e., two normal stresses and a shear stress, over the surface of thin substrates. Three different mesostructure types have been created, each offering distinct advantages. For demonstration, we patterned these mesostructures on the back sides of silicon wafers for freeform shape generation and correction which are not achievable by conventional methods. Stress tensor mesostructures will unleash the value of fields related to stress-induced bending from microscale to macroscopy, such as thin freeform substrates that will become increasingly important with the rise of wearable and space optics

Toward large-area sub-arcsecond x-ray telescopes II

In order to advance significantly scientific objectives, future x-ray astronomy missions will likely call for x-ray telescopes with large aperture areas (≈3 m[superscript 2]) and fine angular resolution (≈1[superscript 2 ]). Achieving such performance is programmatically and technologically challenging due to the mass and envelope constraints of space-borne telescopes and to the need for densely nested grazing-incidence optics. Such an x-ray telescope will require precision fabrication, alignment, mounting, and assembly of large areas (≈600 m2) of lightweight (≈2 kg/m[superscript 2] areal density) high-quality mirrors, at an acceptable cost (≈1 M$/m[superscript 2] of mirror surface area). This paper reviews relevant programmatic and technological issues, as well as possible approaches for addressing these issues-including direct fabrication of monocrystalline silicon mirrors, active (in-space adjustable) figure correction of replicated mirrors, static post-fabrication correction using ion implantation, differential erosion or deposition, and coating-stress manipulation of thin substrates

High-precision figure correction of x-ray telescope optics using ion implantation

ABSTRACT Achieving both high resolution and large collection area in the next generation of x-ray telescopes requires highly accurate shaping of thin mirrors, which is not achievable with current technology. Ion implantation offers a promising method of modifying the shape of mirrors by imparting internal stresses in a substrate, which are a function of the ion species and dose. This technique has the potential for highly deterministic substrate shape correction using a rapid, low cost process. Wafers of silicon and glass (D-263 and BK-7) have been implanted with Si+ ions at 150 keV, and the changes in shape have been measured using a Shack-Hartmann metrology system. We show that a uniform dose over the surface repeatably changes the spherical curvature of the substrates, and we show correction of spherical curvature in wafers. Modeling based on experiments with spherical curvature correction shows that ion implantation could be used to eliminate higher-order shape errors, such as astigmatism and coma, by using a spatially-varying implant dose. We will report on progress in modelling and experimental tests to eliminate higher-order shape errors. In addition, the results of experiments to determine the thermal and temporal stability of implanted substrates will be reported

Dimensinal metrology for nanometre-scale science and engineering: Towards sub-nanometre accurate encodders

Abstract Metrology is the science and engineering of measurement. It has played a crucial role in the industrial revolution at the milli-inch length scale and in the semiconductor revolution at the micrometre length scale. It is often proclaimed that we are standing at the threshold of another industrial revolution, brought by the advent and maturing of nanotechnology. We argue that for nanotechnology to have a similarly revolutionary effect a metrology infrastructure at and below the nanometre scale is instrumental and has yet to be developed. This paper focuses on dimensional metrology, which concerns itself with the measurement of lengths and its applications such as pattern placement and feature size control. We describe our efforts to develop grating-and grid-based scales with sub-nanometre accuracy over 300 mm dimensions using the nanoruler-a scanning-beam interference lithography tool

Physics of the Cosmos (PCOS) Program Technology Development 2018

We present a final report on our program to raise the Technology Readiness Level (TRL) of enhanced chargecoupleddevice (CCD) detectors capable of meeting the requirements of Xray grating spectrometers (XGS) and widefield Xray imaging instruments for small, medium, and large missions. Because they are made of silicon, all Xray CCDs require blocking filters to prevent corruption of the Xray signal by outofband, mainly optical and nearinfrared (nearIR) radiation. Our primary objective is to demonstrate technology that can replace the fragile, extremely thin, freestanding blocking filter that has been standard practice with a much more robust filter deposited directly on the detector surface. Highperformance, backilluminated CCDs have flown with freestanding filters (e.g., one of our detectors on Suzaku), and other relatively lowperformance CCDs with directly deposited filters have flown (e.g., on the Xray Multimirror MissionNewton, XMMNewton Reflection Grating Spectrometer, RGS). At the inception of our program, a highperformance, backilluminated CCD with a directly deposited filter has not been demonstrated. Our effort will be the first to show such a filter can be deposited on an Xray CCD that meets the requirements of a variety of contemplated future instruments. Our principal results are as follows: i) we have demonstrated a process for direct deposition of aluminum optical blocking filters on backilluminated MIT Lincoln Laboratory CCDs. Filters ranging in thickness from 70 nm to 220 nm exhibit expected bulk visibleband and Xray transmission properties except in a small number (affecting 1% of detector area) of isolated detector pixels ("pinholes"), which show higherthanexpected visibleband transmission; ii) these filters produce no measurable degradation in softXray spectral resolution, demonstrating that direct filter deposition is compatible with the MIT Lincoln Laboratory backillumination process; iii) we have shown that under sufficiently intense visible and nearIR illumination, outofband light can enter the detector through its sidewalls and mounting surfaces, compromising detector performance. This 'sidewall leakage' has been observed, for example, by a previous experiment on the International Space Station during its orbitday operations. We have developed effective countermeasures for this sidewall leakage; iv) we developed an exceptionally productive collaboration with the Regolith Xray Imaging Spectrometer (REXIS) team. REXIS is a student instrument now flying on the Origins Spectral Interpretation Resource Identification Security - Regolith Explorer (OSIRISREx) mission. REXIS students participated in our filter development program, adopted our technology for their flight instrument, and raised the TRL of this technology beyond our initial goals. This Strategic Astrophysics Technology (SAT) project, a collaboration between the MKI and MIT Lincoln Laboratory, began July 1, 2012, and ended on June 30, 2018

Precision microcomb design and fabrication for x-ray optics assembly

Silicon microcombs developed at our laboratory for the precision alignment and assembly of large-area foil optics have previously been demonstrated to achieve submicron-level assembly repeatability with submillimeter-thick flat substrates. In this article we report on a double-side deep reactive-ion etch fabrication process using silicon-on-insulator wafers which was developed to improve the microcombs' manufacturing accuracy