TXRF results for continued processing on semi-clean tools...

Robert Huang roberth at quswami.com
Fri Sep 4 14:29:59 PDT 2009


Dear SNF Specmat Committee Members:

I would like to ask for the committee’s approval to run 4” silicon wafers on SNF semi-clean tools (mainly the AG4100 RTA machine) that have been deposited with titanium oxide via e-beam evaporation through an external vendor.  We have worked with this vendor to reduce metal contamination levels below the 1e12/cm2 “semi-clean” specification limit.  As you will see in the attached file, prior to taking corrective action, there were locations on a test wafer that clearly exhibited Fe and Cu levels above the 1e12/cm2 limit.  However, after detailed investigation, several steps were taken to clean up the tool with the positive results shown in the attached file from the last test wafer.  Note that the TXRF results were provided by Evans Analytical Group (EAG) using a W source which can detect elements from S-Zn and Mo-Hf.  If an element is not listed in the table, it was not detected in the analysis.  Evans has a detailed procedure for calibration of their TXRF equipment and guarantee reproducibility to within the reported results (uncertainty values in the table are 1sigma standard deviations) through use of calibrated Vanadium and Nickel references.  Also note that due to overlap in emission energies, EAG can only report upper bounds for some of the elements (specifically the Cu and Hf energy peaks overlap) and the background matrix Ti energy peak interferes with the Cl, K, and Ca peaks.

If there are any questions, please do not hesitate to contact me.

Sincerely,

Robert Huang
Director, Process and Device Technology
QuSwami, Inc.
505 Montgomery St., Suite 300
San Francisco, CA 94111
415-834-9910 (Office)
408-854-0450 (Cell)
roberth at quswami.com<mailto:roberth at quswami.com>
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