A Novel Patterned Ground Shield with Interleaved Metal Dummy for Q-Factor Enhancement in On-Chip Spiral Inductors

Abstract

A novel patterned ground shield (PGS) structure for on-chip spiral inductors is proposed to significantly enhance the quality factor (Q-factor) while adhering to advanced process design rules. The structure features an L-shaped interleaved polysilicon and active region layer, grounded through a “米”-shaped Metal-1 grid, coupled with a parallel metal dummy fill pattern distributed across all metal layers (Metal-1 to top ultra-thick metal). This dummy pattern, located in the spaces between inductor turns, minimizes the increase in parasitic capacitance to the substrate compared to conventional or bar-type dummy fills. Electromagnetic (EM) simulations demonstrate that the proposed PGS structure achieves a peak Q-factor (Qmax​) 2.5 higher​ than an inductor with an ideal shield (violating density rules) and maintains the highest Q-factor up to 8.4 GHz. Furthermore, it induces only a 0.86 GHz​ shift in the self-resonant frequency (FSR) compared to the ideal case and has negligible impact on the low-frequency inductance. This work provides an effective shielding solution that balances performance enhancement with design rule compliance for RF integrated circuits.