Heavy Ion Backscattering Spectrometry Analysis of TXRF Calibration Standards

Within a relatively short period of time Total Reflection X-ray Fluorescence (TXRF) has become one of the most widely used techniques in determining trace levels of surface metallic contamination introduced by a variety of semiconductor processing procedures and equipment. Unfortunately, TXRF is not a first principles technique, and the answers one obtains are only as good as the standards used to calibrate the instrument. One of the concerns has always been the accuracy of the primary standards, as large instrument-to-instrument variations have been noted when samples have been analyzed on different TXRF systems within Motorola. Round robins involving systems outside the company have noted similar discrepancies. The most obvious approach to begin attacking this problem is to ensure that the calibration standards are accurate. Fortunately, a new non-destructive, sensitive, and precise techniqueHeavy Ion Backscattering Spectrometry (HIBS)-recently became available, and it was used to provide single-element impurity concentration measurements on the TXRF calibration standards. HIBS makes use of the familiar principles of RBS and is capable of detecting surface impurities with concentrations down to -lo9 atoms/cm2. As with RBS, concentration measurements from HIBS are based upon first principles. This HIBS analysis represents the first industrial use of the Sematech HIBS instrument located at Sandia National Laboratories. Using the results from the HIBS as well as TXRF intensities obtained from a single instrument, the certified values of the TXRF standards were adjusted so that all of them were self-consistent. The four TXRF instruments involved in the study were then recalibrated using the standards whose certified values had been adjusted to the HIBS results. As a check of the effectiveness of this common calibration procedure, wafers which had been uniformly contaminated with multiple elements by spin coating and drying were analyzed by the TXRF instruments in four different labs. The round robin results showed excellent agreement between instruments. HIBS has proven to be a valuable tool in checking with confidence the accuracy of vendorsupplied reference standards for TXRF, which has allowed for the consistent and accurate calibration of all instruments in the company. ‘Author to whom correspondence should be addressed. f’mwrinht k3 If?PnS_lntnrnatinnal Cmtre fnr niffrxtinn nntn lp1Q7 Copyright (C) JCPDS-International Centre for Diffraction Data 1997 This document was presented at the Denver X-ray Conference (DXC) on Applications of X-ray Analysis. Sponsored by the International Centre for Diffraction Data (ICDD). This document is provided by ICDD in cooperation with the authors and presenters of the DXC for the express purpose of educating the scientific community. All copyrights for the document are retained by ICDD. Usage is restricted for the purposes of education and scientific research. DXC Website – www.dxcicdd.com ICDD Website www.icdd.com