A comparative analysis of different measurement techniques to monitor metal and organic contamination in silicon device processing

Abstract

A few key techniques for the analysis of contamination in silicon are compared for their ability to detect different impurities. Both metal and organic contamination is included in this study. In addition, common contaminants and elements recently introduced in the fabrication process are considered. For what concerns metal contamination, it is shown that different approaches are required depending on the in‐depth distribution of the contaminant and hence on its diffusivity. Copper, iron, molybdenum, and tellurium are chosen as examples of contaminants with different diffusivity and solubility properties. Total reflection X‐ray fluorescence (TXRF), recombination and generation lifetime measurement techniques, deep level transient spectroscopy (DLTS) and capacitance versus voltage measurements are compared. The detection of slow diffusers is found to be very critical, because a very low dose may result in a non‐negligible concentration in the device region. As a consequence, the sensitivity per unit area required for these elements is difficult to reach with surface techniques such as TXRF. On the other hand, very fast diffusers such as copper can hardly be revealed in the solid solution in silicon. Copper in silicon can be revealed at the oxide–silicon interface by TOF‐SIMS measurements, or by surface generation velocity measurements with the Zerbst method. For what concerns organic contamination, surface recombination velocity and gate oxide integrity tests were compared. The most relevant effects of organic contamination were observed by electrical stress of the oxide. Indeed, the fraction of capacitors with degraded breakdown voltage increased dramatically in wafers with intentional organic contamination.

Dissociation and Formation Kinetics of Iron–Boron Pairs in Silicon after Phosphorus Implantation Gettering

“…The dissociation experiments were made using a powerful xenon flash (50 suns intensity and 2.5 ms period). Using Shockley-Read-Hall (SRH) model, it will be easy to demonstrate that the dissolved iron concentration [Fei] is proportional to the difference between the inverse of the lifetimes measured before and after the complete dissociation of FeB pairs [11]. This can be expressed as following:…”

“…The dissociation experiments were made using a powerful xenon flash (50 sun intensity and 2.5 ms period). Using the Shockley–Read–Hall (SRH) model, it is easy to demonstrate that the dissolved iron concentration [Fe i ] is proportional to the difference between the inverse of the lifetimes measured before and after the complete dissociation of FeB pairs . This can be expressed as the followingwhere τ 1 and τ 2 are, respectively, the measured carrier lifetimes before the dissociation of FeB pairs (100% FeB) and after their total dissociation (100% Fe i ).…”

“…The quasi-steady-state photoconductance (QSSPC) technique was used to determine [Fe i ] by measuring the effective lifetime of the minority charge carriers (τ eff ) before and after the complete dissociation of the FeB pairs. [11] Note that the lifetime measurements were carried out at an injection level Δn ¼ 1 Â 10 15 cm À3 . The dissociation experiments were made using a powerful xenon flash (50 sun intensity and 2.5 ms period).…”

2016 Atomic Spectrometry Update – a review of advances in X-ray fluorescence spectrometry and its applications

“…The implemented measurement procedures and the developed uncertainty estimation processes were validated from the agreement with results obtained from ICP-OES and/or reference/calculated values. A few key techniques, including TXRF, were compared in a critical paper by Polignano et al 71 for their ability to detect different metal and organic impurities in silicon. Copper, Fe, Mo and Te were chosen as examples of contaminants of different diffusion coefficients and solubility.…”

Analysis of Near-Surface Metal Contamination by Photoluminescence Measurements

“…In addition, the commonly used techniques based on recombination lifetime measurements frequently fail in detecting these contaminants, because the region analyzed by these techniques is usually much deeper than the region involved in molybdenum and tungsten diffusion. 7 In this work, molybdenum and tungsten-implanted wafers were analyzed by an innovative technique based upon photoluminescence measurements, with the aim to assess the ability of this technique to detect metal contamination in the near-surface region. Surface Photovoltage (SPV) measurements of carrier diffusion length were compared to the results of photoluminescence measurements.…”