Evaluation of surface analysis methods for characterization of trace metal surface contaminants found in silicon integrated circuit manufacturing

Abstract

We report a preliminary investigation of surface analytical methods used to evaluate trace metal contaminants on silicon wafer surfaces. The methods discussed include sputter induced postionization methods, backscattering spectrometry, total reflection x-ray fluorescence, and a sample preparation method known as vapor phase decomposition. In order to initiate the evaluation, a series of silicon wafers was dosed with transition metal contaminants Cu and Fe and then analyzed with total reflection x-ray fluorescence, sputter induced resonant ionization spectroscopy, and heavy ion backscattering spectroscopy. One wafer with low concentrations of Fe was analyzed by time of flight secondary ion mass spectrometry. As a result of this study, we are pursuing improved capability in several areas including standards. Heavy ion backscattering spectrometry is suggested as a means of verifying surface dosed silicon wafer standard.

Accurate calibration of TXRF using microdroplet samples

“…The straight TXRF data are spot checks on a few sites of limited number and dimension of a diameter of 8 mm (∅ SSD) from an information depth of 2-10 nm, however, 100 nm has also been reported [9]. The information depth is depending on the incident angle [23].…”

“…Sputter-or vapor-phase-deposited Ni layer on Si wafers [6] 5. Microdroplets of controlled dimensions on clean and planar Si surfaces [7] Spin-coated and IAP standard reference samples must be certified with complementary methods such as nitrogenbeam Rutherford backscattering (RBS) [8] or secondary ion mass spectrometry (SIMS) [9] or vapor phase decomposition (VDP) [10][11][12]. The dose of ion-implanted metals or the amount of sputter-deposited metals can be controlled by adjusting the process parameters.…”

Results of a pilot study and a proposal to build a high current pulsed nanosecond low energy Si ion beam for the detection of trace amounts of heavy impurities in silicon

“…In addition, a carefbl selection of the thickness of the carbon foil will prevent ions backscattered off the silicon substrate atoms from hitting the ion detector (the Sandia group is using ion beams lighter (C and N) than that of 3 the silicon substrate atoms (see Eq. 1)). The use of the carbon foil causes some energy straggling of the backscattered ions with the result of some degradation of time and therefore mass resolution of their spectrometer.…”

An Electronics Division Retrospective (1952-2002) and Future Opportunities in the Twenty-First Century

“…20͒ co-editor of the NIST series on Characterization and Metrology for ULSI Technology, and colleagues to range between 10 8 -10 10 atoms/cm 2 for a variety of transition metals. 253 A useful qualitative diagnostic technique to detect the presence of metals was accomplished by monitoring the etch pit density with a large concentration of metals present, conventionally referred to as ''haze'' as measured by the modulated optical reflectance technique. 254 More quantitative results were available by monitoring the carrier lifetime and electron beam induced current ͑EBIC͒.…”