Modeling,optimization And Design Of 3D On-chip TSV-inductor

Due to the imbalance scaling of board and package technology,on-chip inductors are receiving more and more attention,with compact structure and smaller parasitic effect.On the other hand,conventional on-chip 2D spiral inductor must be placed on the top metal layers,thereby consuming significant routing resources for global interconnects.Moreover,it may need more dedicated shielding to prevent unnecessary coupling,which further increases its occupied area.With the popularity of 2.5D and 3D chip architecture,Through-Silicon-Via?TSV?has been widely used,a significant portion of which are placed for thermal/manufacturability/reliability purposes.We will use these redundant TSVs to build on-chip TSV inductor that can be used in 2.5D/3D chips,which have better performance.In order to better design system circuit and quickly explore circuit design space,it is imperative to accurately and efficiently model the electrical behavior of a TSV-inductor.The traditional equivalent circuit extraction method has the issues of low accuracy and poor scalability.In this paper,a complete scheme of TSV inductor equivalent circuit extraction is proposed,which can accurately model the electrical behavior of on-chip TSV inductor.This model also can accurately capture the effects of substrate coupling,signal crosstalk,skin effect,and proximity.Experimental result shows that the proposed method can accurately model the TSV inductor with accuracy ranging from 10^-5 to 10^-4.Moreover,the simulation time of this model is reduced by about two orders of magnitude,which enhances the space exploration ability of circuit design.In order to further improve the performance of TSV inductor and adapt to the faster technology iteration trend in the field of 3D IC,magnetic core TSV inductor and corresponding optimization scheme are also proposed,which can guide the design of magnetic core TSV inductor.Experimental result shows that the optimized magnetic core TSV-inductor can achieve inductance density improvement of 7.7×and quality factor improvement of 1.3×while maintaining the same footprint.Finally,the magnetic core TSV inductor is verified in DC-DC converter.Compared with the traditional planar spiral inductor,the area of TSV inductor and magnetic core TSV inductor saved 3.4×and 12.6×respectively.In addition,applying the equivalent circuit extraction method of TSV inductor to the magnetic core TSV inductor also has a high fitting accuracy with10^-4.Finally,the air gap structure of magnetic core TSV inductor is preliminarily analyzed,which can further improve the quality factor of magnetic core TSV inductor with more flexibility.