TSB Award for Revolutionary Laser Measurement Technology

A measurement method developed by scientists at the Institute for Spectrochemistry and Applied Spectroscopy (ISAS) is revolutionizing microelectronics. Researchers at ISAS have developed a technique for characterizing laser beams, which enables the production of computer chips with much greater precision than before. The method, which is already being marketed with great success in the USA in collaboration with a Berlin-based laser company, received the “Transferpreis WissensWerte” from the TSB Förderverein Technologiestiftung Berlin e.V. on July 1, 2003.

Microelectronic components for information and communication technology are produced using photolithographic methods. The circuit design is miniaturized and projected onto a silicon wafer coated with a light-sensitive layer. In several steps (etching, sputtering, deposition), the maze of electronic circuits with millions of switching functions is transferred onto the wafer, which is later cut into individual chips. This process demands high purity and precision. Advances in physical research have made it possible to further reduce the width of the circuit structures, resulting in the number of circuits that can be integrated into a chip doubling every 18 months, in accordance with Moore’s Law.

Key to the minimal structure width is the sharpness of the image with which the circuit design is projected onto the wafer for exposure by an excimer laser. High spectral purity of the lasers is required, which is ensured using spectrometric measurement techniques. This is where the expertise of ISAS scientists comes in. The Institute for Spectrochemistry and Applied Spectroscopy (ISAS), based in Dortmund, has a branch in Berlin’s Adlershof science and technology park, which was established in 1992 from the former Central Institute for Optics and Spectroscopy of the Academy of Sciences of the GDR.

A team led by ISAS physicists Dr. Helmut Becker-Roß and Dr. Stefan Florek has been conducting fundamental research on spectrometer devices to measure light spectra and their application in various spectral analysis methods. In 1998, for example, they developed an extremely high-resolution spectrometer in collaboration with the Society for the Promotion of Applied Optics, Optoelectronics, Quantum Electronics, and Spectroscopy e.V. (GOS), which was later used by scientists at ETH Zurich for atmospheric research.

ISAS’s work was also known to LTB Lasertechnik Berlin, an Adlershof-based company seeking a solution to the problem of spectral characterization of lasers. In an unprecedented short development time of less than 18 months, ISAS, GOS, and LTB jointly developed a concept and turned it into a market-ready device: the “Echelle Spectrometer for Laser Radiation Characterization for Microlithography,” which is now sold under the brand name ELIAS (Emission Line Analyzing Spectrometer). The project pushed both optical and mechanical precision to the limits of what was physically and technically possible.

The device quickly became a success in the electronics industry. In 2002, LTB signed an agreement with Cymer Inc., the largest manufacturer of exposure lasers for the chip industry, based in San Diego, to acquire the Adlershof technology. To date, more than 70 ELIAS devices have been sold worldwide.

According to Dr. Becker-Roß, the ISAS measurement technology will fundamentally impact the further development of microelectronics. By improving the use of the current “workhorse” of microlithography, the 193 nm wavelength, the transition to the next, even shorter wavelength laser—157 nm—can be postponed by several years. This will save the chip industry billions in investments, or at least delay them. “In this way, we’ve helped ensure that Moore’s Law will remain valid for a few more years,” says ISAS researcher Becker-Roß with pride.