Mismatch characterisation of chip interconnect resistance

Many analog circuits use matched resistors on chip. The resistors have two components: the resistive elements and the interconnects. The resistive elements have good matching properties. However, the resistance of the interconnects - especially of the contacts and vias - is only guaranteed to be within certain wide limits. If the matched resistors are low-ohmic, then the interconnect dominates the mismatch equations. This is often solved by oversizing the interconnect or by avoiding structures with lots of interconnect. We prefer to characterize these interconnects or even to build resistors using only interconnects. The measurement results show that the interconnect resistance can match as well as poly resistors in the same 0.18 μm technology.