As industry trends drive increased integration and speed, Cuilow-k structures are the desired choice for advanced IC circuits. A simulation methodology has been developed to study the flip-chip packaging effect on the Cullow-k structures. Multi-level submodeling techniques have heen used to bridge the scale difference between the flip-chip packages and the metalidielectric stacks. Interface fracture mechanics-based approach is used to determine the crack driving force at each interface. The impact of the die-attach process on interconnect reliability has been evaluated.To achieve smaller feature size and higher speed in future chips, we can replace Si02 with low-k dielectric material in all via and trench layers, or increase the number of metal layers. This paper evaluates the effect of placing low-k as last metal dielectric and low-k at all via and trench layers, as well as the effect of eight-layer metal/dielectric stack compared with the four-layer metal stack.The future flip-chip Cuilow-k packages are facing higher possibilities of adhesive or cohesive failure near the low-k interface. This paper provided a quantitative evaluation of the increased risk, thus providing guidelines to the next level of low-k flipchip packages.
MEMS switches provide high isolation when open and low insertion loss vhen closed. They also Iuve the advantages of low p o w r consumption. Thcrefore, RF MEMS switches are an attractive solution to switch antenna bands and transmit/rcceive switching for future multi-band. high bandwidth cell phones. However: Stiction is a major concern for resistive sn-itchcs with metal-to-mctal contact.An iterative-coupled electrostatic-structuml analysis is utilized to evaluate the effect of design parameters on restoring force of MEMS switches. Parameters including mctal thickness, diclcctric thickness. beam-to-ground gap height: metal and dielectric width. and cantilcvcr beam length can be evaluated. The clcctrostatic force is first calculated based on the clcctrical field component. A strnctural analysis is then performed to determine the cantilever beam deflection due to the electrostatic force. A unique integrated empiricalnumerical method is used to qualitativel?-dctcrminc the stiction force bascd on measured actuation \'ohages for real dcviccs. The analysis can provide quick evaluation and screenings of proposed designs to dctcnnine if their actuation voltage falls in the acceptable range. Simulation prediction agrees ver?. well with test measurements.Although increasing cantilever thickncss and shortening cantilever length both increasc restoring force, the actuation vollage will increase significantly as a result. The most favorable moditication is to increase the clcctrode area. A short and wide smctnre with a large area can increase rcstoring force while maintaining low actuation voltage. Compared to similar bi-layer designs, sandwich designs can be actuated at fulther reduced voltages without changing the beam restoring force. In addition, the sandwich structure:being thermal-stress-balanced, is less sensitive to temperature excursion. With the properly selected design parameters, the new designs will be able to achieve the break awav restoring force of the original design at much lower actuation voltages.Switches with good electrical as well as mechanical performances have been successfully fabricated.
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