Hartmut Prinz

Texture and Stress Study of Sub-Micron Copper Interconnect Lines Using X-ray Microdiffraction

In addition to standard reliability tests, both a careful process control based on a large number of data to reach statistically relevant conclusions and the study of solid-state physical degradation mechanisms at representative samples are needed to understand weaknesses in the interconnect technology and to exclude reliability-related failures in copper interconnects. In addition, numerical simulation will help forecast the effect of process and material changes on interconnect reliability.

Potential and Limits of Texture Measurement Techniques for Inlaid Copper Process Optimization

For future technology nodes with shrunken interconnect dimensions, a thorough texture analysis of the metal interconnects becomes increasingly important in order to optimize and to control the inlaid‐copper process. In comparison to plane metal layers deposited on wafers, the microstructure of the metal is more complicated in copper lines and vias which were produced using an inlaid process. Therefore, advanced texture‐measurement techniques like X‐ray microdiffraction, electron backscatter diffraction (EBSD), and TEM combined with automated crystallography analysis (ACT) are needed to obtain the required microstructure information. These complementary methods are suitable to pick up local as well as integral information on the crystallographic orientation of the copper interconnects and liner materials. Potential and limits of the available techniques and the respective instrumentation are discussed in this paper. Examples of process‐monitoring capabilities and of development support, especially with reg...

Temperature‐Dependent Stress Measurements at Inlaid Copper Interconnect Lines

The 3‐dimensional stress state of inlaid copper line structures in low‐k dielectrics was measured using synchrotron micro X‐ray diffraction (μ‐XRD) at temperatures between 25°C and 450°C. The barrier layer (Ta or TaN/Ta) had only a low impact on the stress‐temperature behaviour. However, an additional thick SiOxFy capping layer lowered the room temperature stress significantly compared to copper lines with a thin SiCxNy passivation. The effect of this thick capping layer on the slope of the stress‐temperature curve was even more dramatic. Samples without a thick SiOxFy capping layer showed a transition from in‐plane tensile stress to compressive stress between 150°C and 250°C, while samples capped with thick SiOxFy reached this point at higher temperatures or in some cases even stayed tensile up to 400°C. This shift was also dependent on the copper line width. Furthermore, in 4μm wide lines with thick SiOxFy cap the out‐of‐plane stress became more tensile with increasing temperature, leading to a reverse ...

Microstructure Effect on Electromigration‐Induced Degradation of Inlaid Copper Interconnects

Electromigration‐induced degradation processes in via/line dual inlaid copper interconnect test structures are discussed based on experimental studies. Void formation, growth and movement, and consequently interconnect degradation, depend on both interface bonding and copper microstructure. Void movement along the copper line and void growth in the via are discontinous processes, wherein their step‐like behavior is caused by copper microstructure. Microstructure studies and microstructure monitoring are becoming more important for strengthened top interfaces of copper lines, e. g. by local alloying of the copper or by applying an additional coating on top of the polished copper lines. As a result of this interface engineering, the contribution of grain boundary diffusion becomes increasingly important for the directed mass transport and for electromigration‐induced degradation.

Parabolic Capillary Optics with less than 50 μm Focus and Large Focal Distance for Synchrotron Radiation Scattering

We report the design and performance of a unique parabolic focusing optics for a general purpose materials research station at the bending magnet BM20 (ROBL‐CRG) at ESRF. The measured gain between 8–12 keV was >1000, the focal spot <40 μm at a focal length of 235 mm (8 keV) and 244 mm (11.5 keV), respectively, which allows the use of special sample environments around the focus spot. The low divergence of <0.15° especially permits the in situ characterization of stress states in copper dual inlaid interconnect micro‐structures as well as the measurement of far‐field diffraction patterns of planar waveguides. First test results will be shown and the advantages of the parabolic focusing optics discussed.

Micro-XRD Stress And Texture Study Of Inlaid Copper Lines - Influence Of ILD, Liner And Etch Stop Layer

The influence of ILD, liner and etch stop layer on the room temperature stress state of copper line test structures was examined by micro‐XRD. Test structures consisted of large arrays of parallel lines with line widths of 0.18 μm and 1.8 μm. All these parameters have an influence on the room temperature stress state, whereas the variation of the liner and the ILD showed the largest effects. The change from a full low‐k stack to a hybrid stack, where SiO2 ILD is use for the ‘via layer’ only and low‐k material for the ‘line layer’ results in completely different parameter dependencies. The relationship between copper microstructure and the resulting stress in copper lines is discussed.