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X-ray Absorption Spectroscopy on Copper Trace Impurities on Silicon Wafers

Published online by Cambridge University Press:  01 February 2011

Andy Singh ,
Katharina Baur ,
Sean Brennan ,
Takayuki Homma ,
Nobuhiro Kubo  and
Piero Pianetta
Andy Singh
Affiliation:
Stanford Synchrotron Radiation Laboratory, 2575 Sand Hill Rd, Stanford, CA 94309, USA
Katharina Baur
Affiliation:
Stanford Synchrotron Radiation Laboratory, 2575 Sand Hill Rd, Stanford, CA 94309, USA
Sean Brennan
Affiliation:
Stanford Synchrotron Radiation Laboratory, 2575 Sand Hill Rd, Stanford, CA 94309, USA
Takayuki Homma
Affiliation:
Waseda University, Dept. of Applied Chemistry, Shinjuku, Tokyo 169-8555, Japan
Nobuhiro Kubo
Affiliation:
Waseda University, Dept. of Applied Chemistry, Shinjuku, Tokyo 169-8555, Japan
Piero Pianetta
Affiliation:
Stanford Synchrotron Radiation Laboratory, 2575 Sand Hill Rd, Stanford, CA 94309, USA
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Abstract

Trace metal contamination during wet cleaning processes on silicon wafer surfaces is a detrimental effect that impairs device performance and yield. Determining the chemical state of deposited impurities helps in understanding how silicon surfaces interact with chemical species in cleaning solutions. However, since impurity concentrations of interest to the semiconductor industry are so low, conventional techniques such as x-ray photoelectron spectroscopy cannot be applied. Nonetheless, chemical information on trace levels of contaminants can be determined with x-ray absorption near edge spectroscopy (XANES) in a grazing incidence geometry. In this study, silicon samples were dipped in ultra pure water (UPW) and 2% hydrofluoric (HF) solutions with copper concentrations of 5 and 1000 ppb, respectively. These samples were then analyzed using XANES in fluorescence yield mode to determine the oxidation state of deposited copper contaminants. It was found that copper impurities on the silicon surface from HF solution were metal in character while copper impurities deposited from the spiked UPW solution were deposited as an oxide. These results show that XANES can provide information on the chemical state of trace impurities even at surface concentrations below a few thousandths of a monolayer.

Type
Research Article
Information
MRS Online Proceedings Library (OPL) , Volume 716: Symposium B – Silicon Materials-Processing, Characterization, and Reliability , 2002 , B1.4
Copyright
Copyright © Materials Research Society 2002

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