Date: Mar 01, 2010 Source: DARPA Success Stories (
click here to go to the source)
Technical Challenge Addressed:
U.S. military weapons, intelligence, and communications systems employ a variety of electronic devices where performance, reliability and cost depend on the ability to precisely control the growth of their optical thin film coatings during manufacturing. As measurement and control of thinner and thinner coatings became more challenging, use of spectroscopic ellipsometry (SE) methods appeared promising if SE optical devices could be integrated with the deposition chamber to measure changes in polarization as light reflected from the coating being deposited. Existing bulky optics for SE were modified and inserted into the thin film manufacturing process chambers to detect required optical wavelengths in sequence, and then the optics were further enhanced to detect 44 wavelengths simultaneously and achieve real-time measurement and control.
Technology Description:
In the initial DARPA work, J.A. Woollam modified an existing, ex-situ variable angle spectroscopic ellipsometry (VASE) tool to achieve in-situ measurements on a molecular beam epitaxy (MBE) growth chamber. Significant improvements to the data acquisition and analysis software allowed successful in-situ characterization of aluminum gallium arsenide layers grown by MBE.
Subsequent SBIR work for DARPA and other agencies resulted in the development of a real-time spectroscopic ellipsometer to monitor and measure the thickness of film deposition in real time. To overcome the slow scanning speed of the VASE monochromator, an entirely new SE technology was developed that collected all wavelengths in parallel, using a diode array detection system. This new technology was the key to collecting 44 wavelengths at the same time rather than the single-wavelength of VASE technology. It increased the data content during in-situ growth. Real-time feedback control was demonstrated during electron-beam deposition of silicon oxynitride and mercury cadmium telluride films during metalorganic chemical vapor deposition growth.
Based on work under the multiple SBIR projects, the company developed a whole family of SE products to meet a variety of needs:
- VASE, with a spectral range of 193-2500 nm
- M-2000, with revolutionary rotating compensator technology and a spectral range of 193-1700 nm
- IR-VASE, with a spectral range of 2-30 microns
- Alpha-SE, a low-cost system for measuring index and thickness in the spectral range of 380-900 nm
- AccuMap-SE, a high-speed M-2000 with fast mapping for characterizing the thin film uniformity of large panels
Lessons Learned & Best Practices:
- Identify and develop applications for specialized measurement tools as an important part of commercialization.
- Build customer awareness of the technology and ªªapplications by joint publications with researchers and presentations at technical conferences.
- Consider patents on technology as a commercialization strategy to maintain a dominant position in the market.
Economic Impact:
When the DARPA SBIR work began, the J.A. Woollam Company had fewer than 10 employees. With the help of three successful SBIR projects, the company has grown to over 40 employees, developed a family of products, and achieved worldwide sales. J.A. Woollam is now recognized globally as a leading spectroscopic ellipsometer company, with over 90 patents and worldwide sales of nearly 2000 spectroscopic ellipsometers. The reputation of the company in hardware and software products, customer support, and applications development has been key to its place as a leader in the ellipsometry community.
Applications:
The semiconductor industry depends on lithography for manufacturing tasks that require SE measurements in the ultraviolet region. The display industry uses the visible spectrum, and the telecommunications industry uses the near infrared spectrum. J.A. Woollam's SE products cover the spectral range from 33 microns to 140 nm, and this range spans the required wavelengths required to measure thin film depositions across this entire scope of products and applications.
Partnering & Collaboration:
The roots of J.A. Woollam began in the early 1960s at the University of Nebraska, Lincoln (UNL), where ellipsometry work was undertaken in the Electric Material Laboratory. Over 80 papers were published by professors and students in the 60s and 70s, and early ex-situ VASE ellipsometers were developed.
John Woollam arrived at the University in 1979 to extend the previous ellipsometry work in the UNL laboratories. In 1987, he founded a separate company in collaboration with UNL - staffed with UNL graduates - to develop and sell a commercially viable ellipsometer on a small volume basis. The company received its first DARPA SBIR funding in 1988 to develop the SE technology needed for the thin films being used in military and commercial electronic devices.
The company's SE products were developed from the technology advancements made possible through funding from DARPA and over a dozen subsequent SBIR Phase I and II projects from the Army, Air Force, and National Science Foundation, along with internal funding generated from commercial product sales. J.A. Woollam collaborates with many companies for sales activities in over a dozen countries. The ellipsometers are offered as sensors on many deposition chambers provided by companies such as Oxford Instruments (atomic layer deposition chambers) and Von Ardenne (in-line sputter and evaporation chamber).
