High accuracy and rapid dose measurements for ultra-low energy ion implantation using low energy x-ray emission spectroscopy

This paper reports on the development and use of low energy x-ray emission spectroscopy (LEXES) for non-destructive dosimetry of low energy ion implants. Secondary Ion Mass Spectrometry (SIMS) is often considered the technique of choice for ion implant characterization. Unfortunately, SIMS measurements are time consuming and often require multiple measurements to build statistical confidence in the data. In addition, the complex surface ion yield transients-a fact of life in SIMS-can only be addressed by careful analytical protocols which add to the complexity of the analysis. Low energy high dose implants result in very high dopant concentrations (10%) in the first few nanometers that can compromise the quantitative accuracy of SIMS. LEXES is relatively immune to such matrix effects. For ion implant dosimetry, tool matching and wafer mapping, the LEXES technique will be shown to provide a greater than 10× improvement in throughput compared to SIMS for B, P, As and Ge. Repeatability for LEXES will be shown to be <1% for acquisition times of 1-8 minutes across a range of technologically relevant implant conditions.