'Tennis-shoe glue' sticks circuits to chips

NEWS IBM is tinkering with a new material that could drastically slash the costs of "drawing" circuits on semiconductors, with the substance a close relative to tennis shoe glue.

At the International Electron Devices Meeting in Washington, D.C., this week IBM researchers will present a paper showing how they have developed polymer molecules that can assemble themselves into tiny, precise and predictable patterns. The resulting hexagonal pattern then serves as a stencil for mapping out circuits on silicon wafers.

To prove it works, IBM created flash-memory-like chips containing silicon nanocrystals, which give a thin layer inside a transistor that can help memory chips retain an electric charge and prevent data corruption.

"This is the first time we’ve demonstrated an electric device that uses self-assembly," said Chuck Black, a research staff member at IBM research and one of the principal scientists on the project.

If the process can eventually be used in mass production, it could help solve one of the significant problems facing semiconductor manufacturers: the cost and complexity of lithography. Currently, the millions of transistors and other features found on chips must be individually mapped out with lithographic tools -- huge pieces of machinery containing precise lasers, lenses and vibration dampeners -- that can cost $15m (£8.7m) to $18m each.

Advances in lithography are often subject to lengthy delays because of the complexity of the task.

Self-assembly would essentially turn circuit mapping into a bottom-up task, with molecules creating patterns as a result of their inherent properties. Incorporating very small structures such as nanocrystals into chips could also become far more feasible. Motorola has shown off chips containing nanocrystals, but lithographic techniques were used to make the chips.

IBM expects some form of self-assembly to be in pilot production three to five years from now. NanoInk and other start-ups are examining similar concepts. Earlier this year, researchers at the University of Wisconsin demonstrated how polymers could be used to deposit materials on lithographically created straight lines.

The patterning molecules in IBM’s experiment are called diblock copolymers, said Black. A diblock copolymer consists of two types of molecules bonded together that, in ordinary circumstances, would repel each other. The counterbalancing forces allow researchers to control their position.

"They end up forming these beautiful patterns," Black said.

Fancy as the name sounds, these sorts of polymers are fairly common. Shoe manufacturers use a variety of diblock copolymers to glue the soles of tennis shoes, Black said. Semiconductor manufacturers also use a variety of polymers in semiconductor manufacturing. The flash memory chips in this experiment were made on processes that are generally compatible with existing manufacturing tools, IBM said.

A number of companies, including Advanced Micro Devices, Intel and Motorola, will present papers at the conference, one of the principal annual gatherings of semiconductor researchers.