Chandrasekhar Narayan

Scaling tape-recording areal densities to 100 Gb/in 2

We examine the issue of scaling magnetic tape-recording to higher areal densities, focusing on the challenges of achieving 100 Gb/in2 in the linear tape format. The current highest achieved areal density demonstrations of 6.7 Gb/in2 in the linear tape and 23.0 Gb/in2 in the helical scan format provide a reference for this assessment. We argue that controlling the head-tape interaction is key to achieving high linear density, whereas track-following and reel-to-reel servomechanisms as well as transverse dimensional stability are key for achieving high track density. We envision that advancements in media, data-detection techniques, reel-to-reel control, and lateral motion control will enable much higher areal densities. An achievable goal is a linear density of 800 Kb/in and a track pitch of 0.2 µm, resulting in an areal density of 100 Gb/in2.

A one-megapixel reflective spatial light modulator system for holographic storage

A prototype reflective spatial light modulator (SLM) system has been developed for writing megabit pages of data into a holographic medium at a rate of 12 pages per minute. The SLM is based upon a crystalline-silicon reflective active-matrix array with integrated data drivers, using liquid crystal (LC) electrooptics and a personal computer system with an interface to provide data. The LC has been optimized for high contrast and efficiency with coherent illumination. The resolution-limited contrast was measured at 4:1, which was high enough to provide bit-error-free charge-coupled-device images using modulation and error-correction codes.

Design and fabrication of a prototype projection data monitor with high information content

A prototype 28-in.-diagonal desktop data monitor capable of displaying 2048 × 2048- pixel images has been designed, built, and evaluated. The monitor uses optical projection technology. A reflective, crystalline silicon active-matrix light valve using liquid crystal electro-optics and a digital electronic interface architecture is described. This rear-projection monitor has four million resolvable pixels, uses three light valves to achieve color, has a low-gain surface diffuser screen, and functions as a fully interactive, color personal computer monitor with motion video capability. The monitor is 20 in. deep.

Thin film transfer process for low cost MCM-D fabrication

This paper describes a unique, highly flexible cost competitive method to fabricate microelectronic packages that require thin film interconnections. The method involves fabricating thin film metal/polymer structures multi-up on a reusable temporary glass carrier; the thin film stack is transferred later onto product substrates of choice. The final product substrate can be silicon, co-fired alumina or glass-ceramic, aluminum nitride, diamond, or a printed wiring board. Optionally, one can also use the released thin film decal as a flexible high wireability interconnect by itself, as an interposer, or in applications like wafer level testing for known good die (KGD). The thin film wiring structure can be fabricated multi-up on a standardized form factor carrier (independent of the characteristics of the final product substrate) in a thin film interconnect foundry, thus significantly reducing cost both from the economies of scale and full utilization of the thin film factory for a variety of customer needs. >

Laser release process to obtain freestanding multilayer metal-polyimide circuits

Some applications in microelectronics call for freestanding polyimide films with fine metallic wiring patterns that are thinner than commercially available copper-clad polyimide sheets, which are typically greater than 25 μm in thickness. This work describes a laser-assisted technique to fabricate freestanding multilayer thin-film wiring with polyimide dielectric insulating layers that are less than 10 μm thick. A release layer consisting of a thin polymeric film is first deposited on an optically transparent carrier and the multilayer thin-film structure is then fabricated on this substrate, with the polymeric release layer sandwiched between the transparent carrier and the multilayer structure. Excimer laser light passes through the transparent carrier and ablates the polymeric layer at the transparent carrier/polymer interface, resulting in separation of the sacrificial carrier from the multilayer structure. The optimal release process is carried out using a 308-nm XeCI excimer laser operating at a fluence of about 100 mJ/Cm 2 .

Active line repair for thin-film-transistor liquid crystal displays

A new method for repairing line defects during panel fabrication is described for high-resolution thin-film-transistor liquid crystal displays (TFT/LCDs). This approach uses electronic means in conjunction with physical rewiring to supply the appropriate data signal to the undriven segment of an open data line. Active line repair is simple and inexpensive, with the capacity for repairing numerous line defects. We have successfully implemented this repair approach on 10.4-in.-diagonal, 157-dpi prototype TFT/LCDs. This method is particularly suited for lower-volume, large-area, high-resolution TFT/LCDs, which are difficult to produce with high yield.

A Non-Destructive Technique to Measure the Extent of Inter-Diffusion in Oxide Solid Solution Interfaces Between Metals and Ceramics

Adhesion of metals to ceramics is an area of extreme importance for packaging of electronic devices. In one of the several adhesion schemes that can be employed to promote adhesion between metals and ceramics, the metal is preferentially oxidized at the interface and there is solid solution mixing between the substrate and the oxidized metal at the interface. An example is the Ni/MgO system. Estimation of the extent of mixing at the interface is often difficult and time consuming. This work describes a simple non-destructive method to estimate the extent of interdiffusion between the oxides using a standard x-ray diffraction measurement. This technique relies on the changes in the peak shapes and positions as a function of the nature and extent of interdiffusion. The technique is precise enough to allow one to estimate interdiffasion coefficients in some oxide/oxide systems. The diffusion and intermixing phenomena in the NiO/MgO system will be examined as an illustrative example.