In computer-chip fabrication, a silicon-crystal wafer is thoroughly cleaned before microscopic electronic components are deposited on it. Conventional cleaning techniques use caustic "wet" chemicals that could be hazardous to workers and that must be discarded after use, generating disposal costs and the potential for environmental pollution if the chemicals are not handled properly. In addition, for chips with feature sizes below a minimum, wet chemicals may not be able to get to some features, such as trenches, because of surface tension.

Potentially Safer and Less-Costly

The ATP award allowed FSI International, which provides semiconductor wafer surface conditioning equipment and support products, to develop a "dry" cleaning procedure that uses chlorine, chlorine/hydrogen and other gases to clean dirt, trace metals and other particles from wafer surfaces. Researchers completed the assembly and installation of an experimental module and developed required support processes. Although the gases are toxic, they are more easily controlled than wet chemicals. And even though the gases incur disposal costs, the amount of chemical waste generated by the FSI technology is expected to be much smaller than that created via traditional wet cleaning. Thus, the new technology should improve human and environmental safety and reduce cleaning costs during wafer processing.

FSI's methodologies for gas-phase dry cleaning were developed for use in making computer chips and have potential applications in the fabrication of printed circuit boards, disk drives and optoelectronics. If the market emerges and the FSI technology becomes widely used, substantial economic benefits would likely accrue all along the supply chain for computers and other equipment that include chips. The technology is undergoing initial testing at Texas Instruments. If the testing is successful, FSI officials say, Texas Instruments would likely buy and use systems incorporating the new technology.

ATP funding was critical to generating the gas-phase dry cleaning technology, FSI officials report. The company would not have done the research and development work at that time without it. The ATP award also enabled FSI to collaborate with Massachusetts Institute of Technology researchers during the project.

Commercialization Delayed but Still Expected

Since initiation of the ATP project, manufacturers of wafer-surface conditioning equipment have found ways to squeeze more improvements out of wet-chemical cleaning methods. Consequently, chip fabricators have less need for a dry cleaning technique than was initially anticipated. The company expected that the shift in 1997 to smaller (0.25 micron) minimum feature sizes for wafer processing would challenge the capabilities of conventional wet cleaning processes. Wet processing, however, continues to meet cleaning needs at this level and may even be viable to minimum feature sizes of 0.18 micron, which are expected to be introduced in the year 2000. Furthermore, progress has been made in reducing the amount of chemicals needed for wet cleaning processes.

Commercialization of the ATP-funded technology, therefore, depends on how much more the wet method can be extended, as well as on the remaining development work needed to demonstrate the robustness, manufacturability and reliability of the process and equipment in a chip-manufacturing environment. Although the new technology has not become a broad replacement for traditional wet cleaning in wafer processing, as originally envisioned by the ATP-project proposal, FSI anticipates the emergence of new applications requiring the unique capabilities of its technology. If the dry cleaning technology is commercialized, chip fabricators that use the new technology might achieve process improvements worth up to five times their costs for the technology, company officials say. FSI has continued to develop this technology while delaying commercialization until demand increases sufficiently. If that happens soon, the company could have a product on the market in 1999.

Go to other sections of Chapter 5: ELECTRONICS
	Expanding the Number of Light Signals in an Optical Fiber
	Manufacturing Technology for High-Performance Optoelectronic Devices
	Processes for Growing Large, Single Silicon Carbide Crystals
	Harnessing Cheap Diode Lasers to Power a Low-Cost Surgical Laser
	Lowering the Cost and Improving the Quality of Computer Chips
	A Gas Method to "Dry" Clean Computer-Chip Wafers
	Low-Cost Night-Vision Technology
	Large-Scale Diode-Array Laser Technology for X-Ray Lithography
	Using High-Temperature Superconductivity to Improve Cellular Phone Transmission
	Exploiting Alexandrite's Unique Properties for a Less-Expensive, More-Reliable Tunable Laser
	Precision Mirrors for Advanced Lithography
	Joining Several Chips Into One Complex Integrated Circuit
	Computer RAM Chips That Hold Memory When Power Is Off
	A Feedback-Controlled, Metallo-Organic Chemical Vapor Deposition Reactor
	Flat Fluorescent Lamps for Displays