100 years of x rays: Impact on micro- and nanofabrication

Abstract

Hard x-ray phase zone plate fabricated by lithographic techniquesIn November of 1895 Wilhelm C. Röntgen observed fluorescence caused by invisible rays emanating from a discharge tube. This discovery of x rays was not a mere happenstance; Röntgen was a highly skilled experimentalist, well prepared to launch a series of clever experiments and startle the world with the announcement of ''a new kind of ray.'' The practice of medicine was transformed, and the era of modern physics inaugurated. X rays have proven essential to the probing of atomic, molecular, and solid-state structures. X-ray astronomy has revealed some of the most exotic and violent phenomena in the universe, including the black holes. X-ray microscopy provides information complementary to what is obtainable from optical and electron microscopies. In microand nanolithography x rays provide high quality aerial images and simple processing, in part because of an absence of spurious scattering, something that Röntgen himself observed. However, application in ultralarge scale integrated ͑ULSI͒ manufacturing is still uncertain for a variety of reasons, primarily because ultraviolet optical-projection lithography continues to satisfy commercial needs. X-ray lithography may find application in areas outside the ULSI industry, for example in optoelectronics, flat-panel displays, and magnetic data storage. It has the intrinsic resolution to reach the practical limits of the lithographic process, around 20 nm. However, to approach this limit diffraction blurring must be avoided by reducing the mask-sample gap below 5 m, which may not be acceptable in manufacturing. In this event, and in order to retain the lithographic qualities of 1 nm wavelength radiation, projection with Fresnel zone plate arrays could be employed.

Arrays of magnetic nanoindentations with perpendicular anisotropy

“…1 In conventional lithography a pattern is typically created in a resist layer which is subsequently transferred to a magnetic film. The pattern generation can be accomplished with a number of technologies such as electron beam lithography, 2,3 ion beam lithography, [4][5][6][7][8] near field lithography, 9,10 laser interference lithography, [11][12][13][14] x-ray lithography, 15,16 or nanoimprint. 17,18 Unfortunately, most methods may not be suitable for largescale device fabrication because they are multistep, expensive, and involve time-consuming procedures.…”

High‐Precision Temperature‐Controllable Metal‐Coated Polymeric Molds for Programmable, Hierarchical Patterning

“…However, with increasing demand for much smaller feature sizes, this technique has been faced with limited resolution and depth‐of‐focus that is caused by a defined light wavelength (krypton fluoride (KrF) laser; 248 nm) and its diffraction limit . Meanwhile, alternative techniques involving electron‐beam (e‐beam), X‐ray, extreme UV, scanning probe lithography, etc. have been developed to significantly improve the resolution for sub‐100 nm scale features.…”

Microzone plates with high-aspect ratio fabricated by e-beam and x-ray lithography

“…1 Fresnel zone plates ͑FZP͒ were of particular interest for focusing soft x-rays, since the refractive index of most materials in those wavelength regions is nearly unity, 2,3 making conventional refractive or reflective optics impractical. 4,5 FZP used as excellent focusing elements in x-ray regions have stimulated strong interests and efforts in developing various techniques for fabrication.…”