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Large Area Distributed Electronics

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Microelectronics and, particularly, silicon integrated circuit microelectronics, has produced amazing capabilities over the last 40 years. There are numerous indicators of this, but best summarized as “Moore's Law.” While more transistors/ cm2 is the driving force, the microelectronics-based display industry has, for over a decade also explored alternate directions – larger and larger “chips” and/or alternative substrates. Thus, displays have grown from several in2 to several ft2 while the number of transisors/cm2 has remained small. Further, major R & D investment has been made in migrating from a glass substrate “chip” to a plastic one in order to achieve increased functionality (again without increasing the transistors/ cm2).

The relatively low cost manufacturing process used for displays has created significant interest in applying this form of microelectronics to other classes of problems. An example is an image array. Here the amorphous TFT can also be used as a light sensor. This leads to digital x-rays with many advantages over the conventional film based methods. The sensor function might also cover other parts of the EM spectrum to provide a large area IR imager or RF antenna array (communications and radar). Other sensor techniques would provide the capability to monitor stress or corrosion while integration of actuators would lead to the capability to not just monitor the environment, but to respond to it (modification of a property in response to a stimulus).

To accomplish such sensor applications, more transistors/ cm2 is not the issue. Rather the ability to cost effectively fabricate modest numbers of integrated devices (<105) over large areas (>ft2) is essential. Even then, other attributes may also be required (such as flexible substrate). Perhaps the most demanding feature that has not been developed by either the integrated circuit or display industries is a high performance TFT.

Transistor performance is determined by materials properties and critical dimensions. Microelectronics progress has been based on the favorable material characteristics of silicon (and its oxide) and the drastic scaling (from 10's of microns to tenths of microns) that has been achieved. Cost effective manufacture of TFTs over large areas limits both the material and dimensional properties that can be achieved and results in a 10-100x reduction in device performance. While not a significant limitation for displays, it is for applications that require performance in the MHz and higher regime.

One approach to achieving higher performance TFTs is to improve the process conditions that are currently used to fabricate poly TFTs. This might be achieved by better recrystallization and oxidation methods or by processing “off line” and then transferring onto the preferred substrate. While such methods are well known, there are still challenging technical hurdles. A novel means to circumvent many of these problems might be accomplished via printing of Si nanowires or C nanotubes as the active material of TFTs. Both materials have significant issues, which must be overcome.

DARPA is currently funding work in a variety of areas expected to impact the migration of microelectronics from “smaller is better” to “bigger is better”. Status and objectives of these efforts will be presented especially from the perspective of opportunities to achieve the desired results with digital fabrication methods.

Document Type: Research Article

Publication date: 2005-01-01

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  • For more than 30 years, IS&T's series of digital printing conferences have been the leading forum for discussion of advances and new directions in 2D and 3D printing technologies. A comprehensive, industry-wide conference that brings together industry and academia, this meeting includes all aspects of the hardware, materials, software, images, and applications associated with digital printing systems?particularly those involved with additive manufacturing and fabrication?including bio-printing, printed electronics, page-wide, drop-on-demand, desktop and continuous ink jet, toner-based systems, and production digital printing, as well as the engineering capability, optimization, and science involved in these fields. In 2016, the conference changed its name formally to Printing for Fabrication to better reflect the content of the meeting and the evolving technology of printing.

    Please note: For purposes of its Digital Library content, IS&T defines Open Access as papers that will be downloadable in their entirety for free in perpetuity. Copyright restrictions on papers vary; see individual paper for details.

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