Crystallographic texture and phase metrology during damascene copper processing

Abstract

The rapid adoption of damascene copper technology has brought about an increased need to understand and control microstructure in the barrier and metal layers during processing. We have developed and implemented a methodology for rapidly characterizing thin film polycrystalline microstructures on 200 mm Si substrates using an X-ray diffraction (XRD) based metrology tool to measure crystallographic texture and phase in a time frame suitable for in-line applications. The acquired data can be used as a direct measure of the deposition process in terms of film quality, reproducibility and stability over time. The spatial distribution of crystallographic texture and phase can be measured on a single wafer in order to check within wafer uniformity. These same measurements can also be carried out at predetermined intervals on wafers from single deposition tools, with the results used to create a database that can be applied to process control trend charting and to the establishment of acceptance criteria. The methodology developed makes use of several novel data analysis and collection techniques, such as the use of a direct matrix transformation method to determine the orientation distribution function (ODF) from a group of truncated pole figures. Useful quantitative outputs of the ODF, such as volumetric fractions of crystallographic texture components, can be used in quantifying texture evolution within and between wafers. On-the-fly texture compensation can also be used to generate useful quantitative phase and film thickness measurements. We present the principles of operation of this metrology tool and selected examples collected in the IBM's Advanced Semiconductor Technology Center (ASTC), East Fishkill, NY.