Record set for smallest electronic device

Researchers at Lucent Technologies--Bell Labs (Murray Hill, NJ; www.lucent.com) claim to have produced the smallest working electronic device ever made with optical lithography. This experimental device--a flash-memory cell that stores data even when power is off--has features as small as 80 nm. Currently, semiconductor manufacturers are using optical lithography to make silicon-chip features as small as 180 nm.

Record set for smallest electronic device

George Kotelly Executive Editor

georgek@pennwell.com

Researchers at Lucent Technologies--Bell Labs (Murray Hill, NJ; www.lucent.com) claim to have produced the smallest working electronic device ever made with optical lithography. This experimental device--a flash-memory cell that stores data even when power is off--has features as small as 80 nm. Currently, semiconductor manufacturers are using optical lithography to make silicon-chip features as small as 180 nm.

The research demonstrates that optical lithography can be used to produce more advanced silicon chips. Extending the limits of optical lithography also means that the semiconductor industry could postpone the costs of expensive retooling for a successor device manufacturing technology. The semiconductor industry had estimated that optical lithography would reach its physical limits at 120 nm. Mark Pinto, chief technical officer at the Lucent Technologies Microelectronics Group, says, "This achievement provides technology that Lucent`s semiconductor business can put to immediate use in developing future generations of communications integrated circuits, including ultrafast digital signal processors and high-performance systems on a chip."

To create the flash-memory device with 80-nm features, researcher Ray Cirelli and his colleagues modified how light passes through the master pattern or mask of the silicon circuit. This approach, called phase-shift lithography, greatly improves device resolution. Another technology improvement involves the development of a new class of resist materials--the photosensitive-plastic films used to form device patterns--based on cyclo-olefin maleic anhydride chemistry.

Yet another key development concerns a new light-absorbing material deposited as a thin layer between the resist and the silicon wafer during early device processing. This material absorbs the light passing through the resist and reduces unwanted reflections from the wafer.

All these chip-processing developments have resulted in a flash-memory device that has an 80-nm wide by 160-nm long central storage area or "floating gate." To produce this device, the researchers used 193-nm optical lithography. Currently, semiconductor manufacturers use 248-nm optical lithography.

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