Juan R. Maldonado

High speed replication of submicron features on large areas by X-ray lithography

To achieve the high throughput necessary for a practical X-ray lithographic system, we have devised a new overall approach to X-ray lithography based on the use of X-rays with wavelengths of 4-6 Å rather than the 8.34-Å wavelength used in previous work. The principal advantage of the shorter wavelengths is that they allow a system to have X-ray windows so that large area patterns can be replicated under ambient conditions. In addition, the shorter wavelengths simplify the selection of mask substrate materials; thus we have developed a new X-ray mask structure using an optically transparent Mylar substrate. This permits realignment to be done by optical means. We also report results obtained with a new negative resist with high sensitivity to the shorter wavelength X-rays. We have achieved the replication of submicron size features using a 4.6-Å rhodium X-ray source, a Mylar mask with 7000-Å thick gold patterns, and the new resist, and have demonstrated the practicality of this system by the fabrication of propagating magnetic bubble structures with small features.

PLZT ceramic display devices for slow-scan graphic projection displays

A projection display device for slow-scan graphics has been developed using the scattering properties of PLZT ferroelectric ceramics. The device consists of a ferroelectric-photoconductor sandwich in which a Cd 1-x Zn x S mixture is used as a photoconductive film. The composition of the film is controlled to provide peak photosensitive response at 441.6 nm, corresponding to the blue line from a He-Cd laser. Any image can be written into the device with a combination of steered laser beam (less than 1 mW) and electrically applied pulses, held for an indefinite time without sustaining power and erased electrically. Because of the properties of the photoconductive film, selective erase and simultaneous reading and writing are possible. The all-solid-state structure of the device combined with the scattering properties of the ceramic permit the device to be used as a slide in a conventional 35-mm projector.

Strain-biased ferroelectric-photoconductor image storage and display devices operated in a reflection mode

The display properties of previously described strain-biased ferroelectric-photoconductor devices that operate in a transmission projection mode can be improved by operating them in a double-pass or reflection mode in which the reading light is reflected off an opaque interface between the ceramic and the photoconductor. Such an arrangement offers better resolution (because of the thinner ceramic), isolation between reading and writing light, and greater flexibility in the choice of photoconductor, which need not be transparent to the reading light. Simple reflection mode structures have been fabricated that use either PVK or CdS photoconductive layers and show a resolution of 250 lines/in.

High speed replication of sub-micron features on large areas by X-ray lithography

We have developed, and describe herein, a new approach to X-ray lithography based on the use of X-rays with wavelengths of 4–6 A rather than the 8–34 A wavelength used in previous work. The principal advantage of the shorter wavelengths is that they allow the exposure system to have X-ray windows for increased throughput. We have achieved the replication of submicron size features in metal films using a 4.6 A Rh L α source, a new X-ray mask and new X-ray resist with high sensitivity to the shorter wavelengths and improved ion milling techniques.