Back-side De-processing using CMP for bulk silicon 40-nm graphics processors
A back-side de-processing process by chemical mechanical polishing (CMP) is developed. The process has been optimized to produce repeatable results. The process is capable of exposing the circuitry of the die uniformly and is able to target more than one area for units with multiple defect locations; front-side de-processing process has difficulty achieving the same results due to the unevenness of the die
Backside failure analysis and case studies for Cu/low k technology
In this work, failure analysis (FA) challenges and new failure modes for devices of copper technology, especially for circuit-under-pad (CUP) devices are presented. Backside FA techniques including backside sample preparation, backside defect localization, backside physical analysis with both deprocessing and cross section analysis have been developed and applied to Cu/low k technology. For backside FA deprocessing, we present wet chemical etching, reactive ion etching (RIE), parallel polishing, chemical mechanical polishing (CMP) and combination of these techniques. For the backside FA cross-section analysis of copper/low k samples, focused ion beam (FIB) techniques that have been developed and studied are addressed. In addition, detailed characterization of backside silicon thinning using TMAH wet chemicals is presented.
Experimental investigation of the geotechnical properties and microstructure of lime-stabilized saline soils under freeze-thaw cycling
Abstract The Song-Nen Plain in northeastern China holds one of the three largest expanses of soda saline-alkali soil in the world. Due to its disadvantageous geotechnical properties, the saline soil in this area is unable to meet the needs of construction projects. This study evaluates the stabilizing effect of adding lime to such soils. Specifically, it investigates how the physicochemical and mechanical properties and microstructure of soda saline-alkali soil are altered by lime and how these changes are affected by both freeze-thaw cycling and the duration of curing. The results reveal that adding lime to saline soil transforms clay particles into sand and silt particles and causes the pore size distribution (PSD) to become bimodal, with small-pore and macropore populations. An increase in lime content leads to an increase in the unconfined compressive strength (UCS) but a gradual decrease in both the cation exchange capacity (CEC) and plastic index. Freeze-thaw cycles break up coarse particles and aggregate finer particles, increasing the diameter of macropores and decreasing the USC; however, the effect on specimens with >9% lime is negligible. It is further shown that the geotechnical properties of the soil change immediately after the addition of lime, indicating that the cation exchange reaction takes place very quickly. Furthermore, the pozzolanic reaction leads to an increase in the percentage of sand-sized particles and a decrease in porosity after 28 days of curing. Overall, these results indicate that it is feasible to use lime to improve the engineering properties of soda saline-alkali soil in this area.