THIN FILMS

The development of pulsed-laser-deposition (PLD) technology has brought about a revolution in the application of high-quality ceramic thin films onto appropriate substrates, but the technique is still not used routinely in industry. At a workshop last May organized by the National Institute of Standards and Technology (NIST; Gaithersburg, MD) together with the Naval Research Laboratory (NRL; Washington, DC), almost 100 experts from industry, US government laboratories and agencies, and academia

THIN FILMS

Laser deposition holds promise, needs development

John W. Hastie and Douglas B. Chrisey

The development of pulsed-laser-deposition (PLD) technology has brought about a revolution in the application of high-quality ceramic thin films onto appropriate substrates, but the technique is still not used routinely in industry. At a workshop last May organized by the National Institute of Standards and Technology (NIST; Gaithersburg, MD) together with the Naval Research Laboratory (NRL; Washington, DC), almost 100 experts from industry, US government laboratories and agencies, and academia discussed the remaining technological barriers that are preventing full industrial use of PLD.

Thin-film deposition using pulsed-laser ablation has provided researchers with a powerful and flexible tool for preparing chemically and structurally complex inorganic thin films of materials that are otherwise difficult or impossible to produce by conventional physical or chemical-vapor-deposition ap proaches (see figure on p. 20). Use of PLD, particularly for research applications, has increased dramatically over the last 10 years. Next-generation thin-film applications, such as electronics, sensors, and protective/functional/ hard coatings, will require films of increasing chemical complexity that will themselves require more-versatile and controllable processing techniques.

Most current researchers and technologists have had to develop their own PLD facilities and procedures because there are few commercial installations or production facilities available, reflecting the infancy of this technology. To address the technology barriers that limit wider industrial application of PLD, recognized leaders from different sectors of the PLD community attended the workshop--Pulsed Laser Deposition (PLD) Technological Barriers: Research Needs and Opportunities. Discussion covered key topics such as process tool development and scale-up, process monitoring and control, promising commercial applications, and supporting fundamental research.

Venky Venkatesan and Jim Greer, representing major manufacturers of PLD systems--Neocera (Beltsville, MD) and Epion (Bedford, MA), respectively--each indicated the importance of having in situ monitoring and feedback control for large-scale industrial applications. They and others also indicated that, for certain anticipated applications, control of particulates will be needed. Greer noted that development of PLD process-monitoring technology was beyond the scope of small companies. In response, participants from government laboratories and academia presented their ongoing research in process monitoring and other areas.

Andy Tam from IBM Almaden Research Center (San Jose, CA) provided a large-company perspective and noted that the adoption of new processing technologies such as PLD is constrained by competition from existing technologies. Tam and others suggested that future applications would need to be based on new materials with dramatically improved properties--such as electrical, magnetic, optical, or physical--that would lead to a more serious consideration of PLD for production applications by large companies.

Peter Norris of N¥Applied Technologies (Woburn, MA) led a discussion on the lessons learned from metal-organic chemical-vapor deposition. He noted that a major barrier to the adoption of a new deposition technology was the need for either the cost or performance advantage of the new technology to exceed current manufacturing technology by at least a factor of five--or the new technology must produce a unique product. The need for a "product unique to PLD" was widely echoed, and several new materials systems were cited, such as gallium nitride (GaN) for optoelectronics, ferrites for filters and circulators, colossal magnetoresistive materials for bolometry and switching, and ferroelectrics for tunable microwave devices and piezoelectric actuators. Other product areas mentioned and actively being pursued include tribological and protective coatings, high-temperature superconductor coated tapes, biomaterials, phosphors, polymers, and organics.

An informal working group was established among the lead participants to develop approaches to implement the workshop recommendations. A comprehensive report on the workshop prepared by NIST and NRL will be available soon from NIST.

JOHN W. HASTIE is a supervisory research chemist at the National Institute of Standards and Technology (Gaithersburg, MD), and DOUGLAS B. CHRISEY is head of the plasma-processing section at the National Research Laboratory (Washington, DC).

More in Research