Magazine autumn99 non contact

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Non-Contact Copper and Cobalt Detection For 0.18 µm Technology by Janet Benton, Bell Labs, Lucent Technologies This article is based on a transcription of a paper presented at the KLA-Tencor YMS seminar at SEMICON/WEST 1999.

This article addresses the effect of copper and cobalt use in back-end processing trace contamination on the front end. This article will discuss the results of a collaboration between Bell Laboratories, the Silicon

F i g u re 1. Qua ntox funda mental silicon m e a s u re m e n t s .

Research Department of Bell Labs at Murray Hill, and KLA-Tencor. A unique window of opportunity was available just prior to the upgrade of the research fab line at Murray Hill. We were able to have the last lot of wafers that went through the line be intentionally contaminated. This enabled us to decide how we could measure trace contamination, whether it would F i g u re 2. Cobalt ki lls bulk lifetime.

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Autumn 1999

Yield Management Solutions

make any difference, and what it would do to the electrical properties of either the silicon or the SiO2 gate oxide. The contamination was introduced two different ways. First, it was implanted using one MeV implant of either copper or cobalt on the back of the wafer after the oxide had been grown on the wafers. We used both floatzone and epitaxial silicon. We then annealed the wafers at either 600°C or 1000°C. After processing, we used a KLA-Tencor Quantox to measure deep level transient spectroscopy (DLTS), total internal reflection X-Ray fluorescence (TXRF), and charge-tobreakdown (QBD) on polydots, for both cobalt and copper. In the case of cobalt, we did a second method, using the dip method. After we grew an oxide on our silicon that was either 40Å, 100Å, or 1000Å of SiO2, we dipped the wafers into a standard cobalt solution. We then followed that with a 900°C anneal for 30 minutes, and did similar techniques for characterization. What we found was that


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Magazine autumn99 non contact by KLA Corporation - Issuu