OPTICAL DIELECTRIC FUNCTION DATABASE FACILITATES COMPOUND SEMICONDUCTOR MATERIAL QUALITY CONTROL

摘要

A NIST researcher is providing for the first time, date on the optical dielectric function of epitaxial thin films of compound semiconductors at growth temperatures. These data, measured using in situ spectroscopic ellipsometry, make it possible to reliably determine the composition and thickness of these thin films in real-time, during the growth by molecular beam epitaxy. Unlike silicon, wafers of compound semiconductors combine layers of more than one element and are more difficult and expensive to fabricate. Therefore, materials suppliers must rely on methods of real-time analysis to detect flaws early in the process, before more costly device fabrication takes place. Conventional in situtechniques based on electron diffraction decay exponentially in time and, therefore, cannot be used in real-time throughout the growth.At the request of a private company, NIST provided the optical dielectric function data for distribution in their optical dielectric function data for distribution in contains ellipsometry sofrware for a wide range of materials including semiconductors, metals, and oxides. Availability of the date, which incorporates composition and temperature dependence, makes it possible for the first time to determine reliably the composition, temperature, and thickness in real-time during the sequential growth of each layer. NIST's contribution to this ever expanding dielectric function database is enabling vendors of ellipsometer equipment to impact broader telecommunications and high-performance electronics markets, which depend on low-cost availabiliy of complex multilayered compound semiconductor heterostructures. Continued product maturity and introduction of the software into commercial markets are expected to leverage impact of the NIST database in industry at large.