Luxtron and Lucent Technologies Develop In-Situ, Real-Time, Temperature Measurement System for IC Wafer Processing; Lucent and Luxtron Reach Cross-Licensing Agreement for Accurate Temperature Measurement System for In-Situ RTP Wafer Processing and Other Applications

Business Wire, April 17, 1997

SANTA CLARA, Calif.--(BUSINESS WIRE)--April 17, 1997--Luxtron Corporation announced today it reached a cross-licensing agreement with Lucent Technologies to commercialize an in-situ, real-time wafer temperature measurement system for rapid thermal processing (RTP), using Luxtron's patented ripple technique, acknowledged as being significantly more precise than anything else available.

Until now, the method used for monitoring the progress of wafers during processing has been using imprecise techniques. When the estimate of the processing time is arrived at, everything is stopped and the wafer is removed to be measured by off-line metrology. This indirect, dead-reckoning monitoring process sometimes results in wafer damage and loss, and leads to low throughputs caused by stopping and restarting the process until desired results are achieved. Accurate, in situ measurements are therefore crucial.

As device geometries shrink and wafer diameters grow, the use of RTP will increase in many device-processing steps. RTP use today is noted for improved process results and the advantages of single-wafer processing and thermal budget reduction. A critical factor in RTP's application has been reproducible temperature control, which is now expected to improve significantly with the widespread use of the ripple technique.

"Ripple technology solves many long-standing problems with RTP temperature measurement and control," said Bob Goodman, president and CEO of Luxtron. "We expect the system to be sold worldwide, not only to semiconductor device manufacturers and OEM equipment vendors, but also to those working with non-semiconductor, industrial applications where emissivity is a problem."

Goodman explained that anywhere a pyrometer is used, ripple techniques will measure emissivity.

"Ripple applications will work with substances such as molten steel," he said. "We have even done some work for NASA aircraft in the detection of micro-cracks, for example."

"Ripple techniques can be used in heavy industrial applications such as aluminum-rolling mills, since this is a very temperature-dependent process demanding great measurement accuracy," said Chuck Shietinger, Luxtron's manager of strategic business development, and one of the technology's originators. He added that another use being studied is for gas-fired power plants. "The heat exchangers inside boilers get very dirty, making it impossible to track inside temperatures with current technology. This means plants must be run cooler than they could, to avoid failures. Being able to run such a plant even one degree hotter can result in millions of dollars in additional power."

The ripple technique is a powerful optical method that measures both temperature and emissivity by tracking AC-modulated light. Artificial light has a unique, 60-Hertz signature, which allows predictions about how it will be modified by the object it is reflected from, such as a wafer undergoing processing, for example.

In RTP, "ripple signals" originate from changes in heating lamp output, due to AC powering. By observing the ratio of wafer and lamp ripple, emissivity can be measured with plus or minus 0.001 precision. Wafer temperatures can be measured from about 350 degrees C to 1,200 degrees C from outside the process chamber. In 1991, Luxtron began working with Lucent -- at that time AT&T -- to develop a measurement system using the ripple technique.

At the project's beginning, Lucent Technologies obtained a number of ripple systems from Luxtron, for use on AG Associates RTP furnaces. Lucent recognized the value of this type of measurement process, and the need to improve hardware design. Over the past two years, Lucent and Luxtron invested considerable resources developing and testing improved designs. Under license from Luxtron, Lucent has built a number of ripple measurement systems mostly for AG Associates furnaces. SEMATECH has also supported this development.

"Prototype systems using the ripple technique have demonstrably improved the manufacturing margin of our IC process," said Dale Ibbotson, VLSI Process Development Department Head for Lucent Technologies. He added that as more ripple systems come on line, the reduction of waste and increase in yields will be considerable.

The RTP ripple system is composed of a small detector box with two short pieces of sapphire fiber that run directly to two cooled photodetectors, and a pair of amplifiers. One lightpipe "looks" at the wafer, the other at the background lamp light. The detector box, which can be bolted underneath an AG or AST furnace, is connected to a processor with a high-speed analog-to-digital (A/D) converter, and the data is processed by software developed by Lucent and Luxtron. Under the cross-licensing agreement, Luxtron will manufacture, sell, and support the ripple measurement product.

Seven patents have been granted protecting this system, with others yet pending. The technique has been used by SEMATECH, its member companies, and most RTP equipment companies, to measure emissivities of filmed wafers and help further develop RTP processes. Luxtron Corporation, founded in 1978 with headquarters and ISO 9001-certified manufacturing facilities located in Santa Clara, Calif., develops, manufactures and markets unique sensors and instrumentation, based on optical and heat flow technologies, for a wide range of industrial, medical, semiconductor, and R&D applications. Luxtron is a wholly owned subsidiary of the Fairey Group. Luxtron has four product lines including: -0-