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For high-volume production of 3D-stacked chips with through-silicon-vias (TSVs), wafer-scale bonding offers lower production cost compared with bump bond technology and is promising for interconnect pitches smaller than 5 µ using available tooling. Prior work has presented wafer-scale integration with tungsten TSV for low-power applications. This paper reports the first use of low-temperature oxide bonding and copper TSV to stack high performance cache cores manufactured in 45 nm Silicon On Insulator-Complementary Metal Oxide Semiconductor (SOI-CMOS) embedded DRAM (EDRAM) having 12 to 13 copper wiring levels per strata and upto 11000 TSVs at 13 µm pitch for power and signal delivery. The wafers are thinned to 13 µm using grind polish and etch. TSVs are defined post bonding and thinning using conventional alignment techniques. Up to four additional metal levels are formed post bonding and TSV definition. A key feature of this process is its compatibility with the existing high performance POWER7™ EDRAM core requiring neither modification of the existing CMOS fabrication process nor re-design since the TSV RC characteristic is similar to typical 100–200 µm length wiring load enabling 3D macro-to-macro signaling without additional buffering Hardware measurements show no significant impact on device drive and off-current. Functional test at wafer level confirms 2.1 GHz 3D stacked EDRAM operation.

A new interaction between TSV processes and devices in close proximity, different from mechanical stress, is identified, studied and mitigated. Detailed characterization via Triangular Voltage Sweep (TVS) and SIMS shows the role of mobile ion penetration from BEOL layers. An improved process is presented and confirmed in test structures and DRAM.

Differential thermal expansion mismatch between Cu and Si along with high aspect ratios required for TSV pose unique challenges to the integration and reliability of Cu TSV. A TSV structure that successfully mitigates these concerns has been integrated into CMOS with high K/metal gates. Data from test structures demonstrate no ‘Cu pumping’ or other deleterious effects to neighboring devices or interconnects. Functional 3D prototypes utilizing stacked embedded DRAMs were demonstrated showing no impact from TSV processing.