A Standard Sample Preparation Method for the Determination of Metal Impurities on a Silicon Wafer by Total Reflection X-Ray Fluorescence Spectrometryt

Abstract

Total reflection X-ray fluorescence spectrometry (TXRF) is widely used for the determination of surface metal contamination on a silicon wafer. In TXRF measurements, calibration standard samples are needed to quantify the metal concentration.We propose a new method for the preparation of calibration standard samples for TXRF. The method is called "Immersion in Alkaline Hydrogen Peroxide Solution (IAP)", in which the silicon wafers are immersed in an intentionally contaminated alkaline hydrogen peroxide solution. Samples made by the IAP method are suitable calibration standard samples for TXRF because of their good depth profile reproducibility and good uniformity on the surface as well as homogeneity in a given batch. They can also be applied for making a cross-check among plural TXRF instruments as well as among different analytical methods. KeywordsTotal reflection X-ray fluorescence spectrometry (TXRF), standard sample, silicon wafer, transition metal contamination,

Study of Depth Distribution Shift of Copper on Silicon Wafer Surface Using Total Reflection X-Ray Fluorescence Spectrometry

“…The data for Fe, Ni and Zn are also plotted for comparison. 3 The surface metal concentration increased monotonically along with the added concentration.…”

“…3 Since the surface metal concentration was measured with AAS, no information about depth distribution was obtained in the above experiment. We then estimated the depth distribution of Cu by measuring TXRF angle scans.…”

“…The GF-AAS procedure was the same as that described in the previous paper. 3 The TXRF instrument used in this work was a Rigaku SYSTEM3726B using monochromatic Au-La X-ray (11.44 keY) excitation. The applied voltage and current were set at 30 kV and 300 mA, respectively.…”

“…One of the major characteristics of TXRF is its sensitivity to depth distribution.2 It has been reported that the depth distribution of the objective element affects the accuracy of TXRF measurement. 3 Recently, we reported a new method for the preparation of TXRF standard samples.3 In the method, called "Immersion in Alkaline Hydrogen Peroxide Solution (TAP)", a silicon wafer is immersed in an intentionally contaminated alkaline hydrogen peroxide solution (SC-1 solution4). The IAP wafer offers good reproducibility of depth distribution for Ca, Mn, Fe, Co, Ni and Zn.5 After this study, we applied the TAP method to Cu.…”

Standard Sample Preparation for the Analysis of Several Metals on Silicon Wafer

“…2 We have examined the depth distributions of each of the metals on the IAP wafers by measuring the angle scan profiles. Figure 3 shows the angle scan profiles of each of the metals examined in this present work.…”