Lin, Y., Li, H. Y., & Tan, C. S. (2021). Structural Integrity of 3-D Metal–Insulator–Metal Capacitor Embedded in Fully Filled Cu Through-Silicon via. IEEE Transactions on Components, Packaging and Manufacturing Technology, 11(6), 918–921. https://doi.org/10.1109/tcpmt.2021.3067322
Abstract:
A novel way to implement integrated metal-insulator-metal (MIM) capacitor with ultra-high capacitance density of up to 5,621.8 nF/mm2 has been proposed earlier. This technology embeds three-dimensional metal-insulator-metal (3-D MIM) capacitor into the existing trench of through-silicon via (TSV) prior to Cu filling to achieve > 90% planar surface area reduction. However, the previous study was on the early-stage test vehicles without Cu filling. In this work, the complete test vehicles with fully-filled Cu TSVs have been successfully fabricated whose trench diameters are 0 (D00), 10 (D10), 20 (D20), and 30 μm (D30), respectively. Firstly, the design layout and the process flow are disclosed in details. Then under scanning electron microscope (SEM) and transmission electron microscope (TEM), it is found that the peak of the Si scallop on the sidewall is deformed for the D30 test vehicle. For the first time, the damage is found in Si substrate, instead of TSV SiO2 liner, due to the thermo-mechanical stress between the TSV Cu core and the surrounding
structures. In addition, the Al2O3 dielectric layer is also impaired at the damaged Si peaks. Lastly, the leakage current density is measured and normalized at a bias of 1.5 V: 4.0 × 10-9 A/cm2 for D00, 4.1 × 10-8 A/cm2 for
D10, 1.1 × 10-6 A/cm2 for D20, and 7.4 × 10-1 A/cm2 for D30, respectively. Therefore, the structural integrity of D10 and D20 test vehicles with fully-filled Cu TSVs is preserved, but the D30 test vehicle is not intact due to
higher stress. Capacitance density of 6,547.1 and 7,091.7 nF/mm2 is recorded for D10 and D20 test vehicles, respectively.
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Publisher Copyright
Funding Info:
This research / project is supported by the Agency for Science, Technology and Research - Individual Research Grant
Grant Reference no. : A1783c0004