Experimental comparison of substrate noise coupling using different wafer types

Measurements of substrate coupled noise in a mixed-signal test IC are presented. This IC was manufactured with different types of wafers, and noise levels measured in heavily-doped epi wafers are about three times larger than those obtained in lightly doped ones. It is determined that, due to package parasitics, noise at the supply lines will easily be the major contributor to substrate-coupled disturbances, both at the digital and at the analog ends. Supply lines interact with the substrate mainly through the substrate contacts of both of the circuit core and the ring of pads. The measurements contribute to establishing a list of priorities in the actions to reduce the noise that reaches the analog section.