In recent years a significant progress has there been made in applying X-ray diffraction (XRD) for in-line measurement of crystallographic phase and texture in conductors for process monitoring. One of the enabling factors is the usage of a large area 2-D- detector which has the sensitivity, stability, and reliability suitable for in-line applications in semiconductor fabs. We present the principles of operation and a summary of results from using an automated XRD metrology in support of copper damascene production. The principles of operation include a model of a diffractometer that translates the detector space to the reciprocal space and subsequently through a series of corrections to the orientation distribution space of the crystallites.
The automated XRD tool equipped with a 2D detector is capable of rapid mapping of 200/300 wafers (with a throughput rate of up to 50 wafers/hour) and delivering quantitative information about the film crystallographic composition and texture.
The major applications of in-line XRD include process development for the 65 nm node and beyond, and BEOL process monitoring-control for 130 and 90 nm nodes. The presented examples concentrate on the TaN/Ta/Cu seed/ECP Cu processes. Monitoring of film microstructure has proven to be a sensitive indicator of deposition tool stability and a useful method in defining the process windows. The examples of applications, based on three years of experience in the fabs, show a clear correlation between the yield loss, poor parametrics, resistivity, electromigration and stress migration performance of copper interconnects and TaNx/Ta phase, Cu seed texture and ECP Cu texture. The microstructure of barrier layers, copper seed, and ECP copper may be tailored for improved reliability and monitored throughout the process by means of XRD on both blanket and patterned wafers with a spatial resolution down to 30 microns.

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