Total reflection x-ray fluorescence analysis of planarized semiconductor product wafers

Abstract

The use and effectiveness of total reflection x-ray fluorescence (TXRF) have been widely reported. The application of this technique in semiconductor fabrication has become popular and several instrument vendors now make equipment optimized for this particular purpose. Because sample surfaces must be optically flat in order to achieve the total reflectance condition, the majority of the work in investigating semiconductor processing is performed on monitor wafers. The use of TXRF for in-line process control, therefore, has been limited to silicon or dielectric film substrates, either on the surface or the backside of the wafer. This article details the use of TXRF analysis for monitoring the contamination present on production-wafer surfaces, after planarization techniques have been used. The wafer surfaces at several of these planarization steps meet the criteria for the application of the TXRF technique using the normal operating conditions of the TXRF instrument. This technique can be used as process-monitoring tool to study wafer surfaces for particular contaminants that affect wafer yield. TXRF is being used on IBM’s state-of-the-art DRAM and logic circuits.