AVS 46th International Symposium
    Manufacturing Science and Technology Group Monday Sessions
       Session MS-MoA

Paper MS-MoA10
A Comparison of VPD, TXRF, and Surface SIMS to Detect Fe, Ni, Cu, and Al on Silicon Wafers

Monday, October 25, 1999, 5:00 pm, Room 611

Session: Ultra-Clean Society and Contamination Free Manufacturing
Presenter: V.K.F. Chia, Charles Evans & Associates
Authors: V.K.F. Chia, Charles Evans & Associates
J. Metz, Charles Evans & Associates
M.J. Edgell, Charles Evans & Associates
Correspondent: Click to Email
The emphasis on contamination free manufacturing (CFM) continues within the manufacturing environment through the use of cleanrooms and the practice of contamination-free procedures. Stringent contamination limits for polished and epitxial substrates and surface preparation (i.e. before gate oxide growth) are suggested by the National Technology Roadmap for Semiconductors (NTRS). Today's requirement for surface metals is typically in the range of 10@super 10@ at/cm@super 2@. Future needs are anticipated to be in the mid-10@super 9@ at/cm@super 2@. The transition metals Fe, Ni, and Cu are considered to be very damaging at the gate oxide level, and therefore requirements for these are becoming more stringent. Al is important to monitor because at concentrations below 10@super 11@ at/cm@super 2@ it can increase the oxide growth in the very thin gate oxide regime. This is a different effect compared to higher levels of Al (e.g. >10@super 12@ at/cm@super 2@), which decreases gate oxide thickness for thicker gate oxides. VPD, TXRF and SurfaceSIMS are commonly used in surface clean technology. VPD is a collection/scanning procedure that concentrates the metal contaminants on a wafer surface into a droplet. VPD procedure is popular because it improves the detection limit of the final analytical measurement technique. TXRF is well established as a surface sensitive technique. It can detect medium- and high-Z elements (sulfur to uranium) on silicon wafers at very low concentration levels. Routine detection limit is approximately 10@super 10@ at/cm@super 2@ or better. SurfaceSIMS is a powerful analytical technique for substrate engineering. Typical detection limit of this technique is 10@super 8@ to 10@super 10@ at/cm@super 2@. SurfaceSIMS complements TXRF by detecting low-Z elements, such as Li, Na, K, and Al. This presentation provides an overview of VPD, TXRF, and SurfaceSIMS and their application to detect Fe, Ni, Cu, and Al.