Influences of Dummy Metal Fills on CMOS VCO

In this paper, influences on CMOS voltage controlled oscillator (VCO) caused by dummy metal fills are investigated. Two fully integrated VCOs are fabricated, tested and verified in 0.18-mum 1P6M bulk CMOS technology. The area-consuming inductors and capacitors of the VCOs are implemented by multilayer complementary-conducting- strip transmission lines (CCS TLs) and metal-oxcide-metal (MOM) capacitors, respectively. The two-dimensional (2-d) and multilayer CCS TL provides miniaturized design and facilitate the chip to satisfy the metal density rules required by foundry process. The two identical X-band VCOs are merely with different dummy metal patterns inserted by designers and foundry, respectively, for frequency tuning and power level comparisons. The comparisons demonstrate that the existence of the dummy metal fills inside and beside the CCS TL has significant influences on the VCO. Therefore, compared with the VCO whose dummy metal fills inserted randomly by foundry, the other VCO whose dummy metal fills inserted by designers is more predictable and reliable.