ELECTRICAL AND COMPUTER ENGINEERING

NEW TECHNOLOGY EXTENDS THE REACH OF PLASMA PROCESSING

Plasma processing is the dominant silicon etching technology used in making semi-conductors. While the conventional paradigm of immersing one or more silicon wafers in a single plasma chamber has been successful,it does not fully meet the needs of future microsystems. Working with microplasmas, Associate Professor Yogesh Gianchandani (left) and graduate student Chester Wilson (right) are developing a silicon etching strategy that confines plasmas in a range from a few tens of microns to more than a centimeter.

With traditional plasma etching, a single plasma acts over a wafer's entire surface. Creating several different etch depths requires the use of a like number of masking steps. With microplasmas, relatively small electrode areas permit high power densities without drawing high currents. Several microplasmas with different etch characteristics could operate on different regions of a single wafer. "They can be used as in-situ processing tools," says Gianchandani. "Microplasmas could simplify the production of structurally complex microsystems and offer significant potential in chemical sensing and other applications."

SEEKING THE "HOLY GRAIL" OF COMPUTING POWER

Clockwise from top left: Dan van der Weide, Bob Joynt, Mark Eriksson and Max Lagally are leading a team of researchers in an effort to build a semiconductor-based quantum gate or qubit. (26K JPG)

An interdisciplinary team of UW-Madison engineering and physics researchers plans to use silicon germanium quantum dots to build a semiconductor-based quantum gate or qubit, to serve as the foundation for a new generation of computers. A working quantum computer could be so powerful that it would solve in seconds certain problems that would take the fastest existing supercomputer millions of years to complete.

A quantum dot is a nanometer-scale "box" that holds a distinct number of electrons. The number can be manipulated by changing electrical fields near the dot. A quantum computer would use these dots to take advantage of a quantum phenomenon known as superposition, in which, for example, an electron would have its spin state both up and down at the same time.

Where a classical computer uses an on or off state to represent bits of information in the "zeros" and "ones" of binary code, a quantum computer uses the superposition as qubits. With superposition, a qubit is in neither the zero nor the one state before being measured, but exists as both zero and one simultaneously. This quality could allow a quantum computer to perform massively parallel calculations enabling certain "hard" problems, like encryption, to be resolved in mere seconds.

The team consists of principal investigator Dan van der Weide, Erwin W. Mueller Professor and Bascom Professor of Surface Science Max G. Lagally, physics professors Mark Eriksson and Bob Joynt, postdoctoral researcher Mark Friesen, staff scientist Don Savage and graduate student Paul Rugheimer.

BUILDING THE FUTURE OF INFORMATION TECHNOLOGY

Associate Professor Mikko Lipasti and Professor James Smith share a role in a new National Science Foundation (NSF) awards program to mold the future of information technology. With $450,000 over three years, Smith and Lipasti plan to develop methods for dynamic error detection in parallel computer systems. These methods will be able to detect both hardware failures and design errors. The key principle is that checking a complex computation can be performed with simple hardware, provided the check is delayed in time with respect to the primary computation.

This method will be applied first to memory intercommunication hardware in multiprocessor systems and will be extended later to other parts of parallel systems.

The NSF grant is part of the new Information Technology Research (ITR) initiative. A presidential committee created the ITR program, which is intended to fund higher-risk emerging technologies that could have greater payoff in the high-tech economy.