CALIBRATION OF REFERENCE MATERIALS FOR TOTAL-REFLECTION X-RAY-FLUORESCENCE ANALYSIS BY HEAVY-ION BACKSCATTERING SPECTROMETRY

Total-reflection X-ray fluorescence (TXRF) is widely used for the cont rol of metallic contamination caused by surface preparation processes and silicon materials. At least three companies supply a variety of TX RF systems to the silicon integrated circuit (IC) community, and local calibration of these systems is required for their day to day operati on. Differences in local calibration methods have become an issue in t he exchange of information between IC manufacturers' different FABs (F abrication Facility) and also between silicon suppliers and IC FABs. T he question arises whether a universal set of fluorescence yield curve s can be used by these different systems to scale system sensitivity f rom a single element calibration for calculation of elemental concentr ations. This is emphasized by the variety of experimental conditions t hat are reported for TXRF data (e.g. different angles of incidence for the same X-ray source, different X-ray sources, etc.). It appears tha t an instrumental factor is required. We believe that heavy ion backsc attering spectrometry (HIBS) provides a fundamental method of calibrat ing TXRF reference materials, and can be used in calculating this inst rumental factor. In this paper we briefly describe the HIBS system at the Sandia National Laboratories HIBS User Facility and its applicatio n to the calibration of TXRF reference materials. We will compare HIBS and TXRF mapping capabilities and discuss the issues associated with the restrictions of some older TXRF sample stages. We will also discus s Motorola's cross-calibration of several TXRF systems using different elements as references. (C) 1997 Elsevier Science B.V.