Copper/low-k process characterization for 90nm technology using SEM and TEM imaging
Artificial vertical and lateral shrinkage of different carbon-doped oxide (CDO) low-k materials is observed for electron beam exposure. The effect depends on SEM and TEM imaging conditions and sample preparation procedures. Typical artifacts include layer thinning and delamination of the CDO material from surrounding materials. TEM imaging is less critical compared to SEM. This is partly due to the favorable conditions during TEM sample preparation employing ion milling steps, which avoid the mechanical stress of conventional SEM sample cross-sectioning. Samples also absorb less energy from the electron beam during TEM scanning, which minimizes the impact of CDO shrink. Some artifacts are difficult to distinguish from real process issues, e.g. de-lamination caused by poor layer adhesion. Therefore, careful sample preparation and imaging are necessary to provide meaningful information.
Failures in copper interconnects-localization, analysis and degradation mechanisms
In this paper, we focussed about the failures in copper interconnects and on analytical techniques that are applied for physical failure analysis. Electromigration test structure after partial degradation by voiding was observed using SEM images.
In situ X‐ray Microscopy Studies of Electromigration in Copper Interconnects
Real‐time X‐ray microscopy is applied for degradation studies to understand electromigration‐induced transport processes in on‐chip copper interconnects. The material transport in inlaid Cu line/via structures is observed with about 40 nm lateral resolution. The image sequences show void formation, migration and nucleation processes. Correlation of the real‐time X‐ray images with post‐mortem SEM micrographs is used to discuss degradation mechanisms in inlaid copper interconnects. Due to the high penetration power of X‐rays through matter and its high spatial resolution, X‐ray microscopy (XRM) overcomes several limitations of conventional microscopic techniques. It utilizes the natural absorption contrast between the structures of interest, i.e. for on‐chip copper interconnects embedded in dielectrics. Due to their different X‐ray absorption characteristics at 0.52 keV, even different silicon compounds like Si, SiO2, and Si3N4 can be distinguished in X‐ray images of thinned layers as demonstrated. For fail...