Characterization of the influence of the sample shape on accuracy, statistics and reproducibility in TXRF Analysis of semiconductor surfaces

01.01.2009 - 31.12.2010
Scholarship
The International Standardization Organization / Technical Committee 201 / Working Group 2 (ISO/TC201/WG2) is working on the standardization of Total Reflection X-ray Fluorescence Analysis (TXRF) in semiconductor industry since 1993. As reported at the 12th Conference on TXRF Analysis and Related Methods by Yohichi Gohshi, convener of the ISO/TC201/WG2, one of the major problems for standardization of TXRF is the large statistical uncertainty of quantification. Due to its outstanding properties TXRF is widely used in the semiconductor industry for the analysis of silicon wafer surfaces. The presence of metal contamination on the wafer surface is a serious limiting factor to process yields for the production of integrated circuits. TXRF offers a nondestructive qualitative and quantitative analysis of trace elements. It is extremely surface-sensitive and is deemed to be matrix-independent. The use of synchrotron radiation (SR) as excitation source for TXRF offers several advantages over X-ray tube excitation, such as better detection limits (in the fg-range). TXRF allows spatially resolved surface mapping and actually the determination of the type of the contamination. A lot of measurements are needed to obtain a representative analysis of the whole wafer surface. Hence TXRF is often combined with preconcentration methods such as vapor phase decomposition¿droplet collection (VPD-DC) or vapor phase treatment (VPT). In general TXRF is known to allow for linear calibration typically using an internal standard for quantification. For small sample amounts (low ng region) the thin film approximation is valid neglecting absorption effects of the exciting and the detected radiation. However, for higher total amounts of samples deviations from the linear relation between fluorescence intensity and sample amount have been observed. Aim of the project is an investigation of TXRF sample parameters (e.g. shape, density) and their influence on absorption effects and hence the fluorescence intensity to improve the statistical quality of TXRF quantification. Sample shapes on different reflector materials, as a result of drying, different preparation techniques and reflector materials will be investigated by micro-XRF and confocal white light microscopy. A mathematical model will be developed to simulate fluorescence intensities and absorption effects with respect to the sample parameters. The results of the measurements and the simulations will be used to characterize the ideal TXRF sample and to improve the sample preparation techniques.

People

Project leader

Project personnel

Institute

Grant funds

  • Österr. Akademie der Wissenschaften (National) Austrian Academy of Sciences

Research focus

  • Materials Characterization: 100%

Keywords

GermanEnglish
TXRFTXRF
Halbleitersemiconductor
OberflächenanalyseSurface Analysis

Publications