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An on-chip test circuit has been developed to directly measure substrate and line-to-line coupling noise. This test circuit has been manufactured in a 0.35 μm double-well double polysilicon CMOS process and consists of noise generators and switched-capacitor signal processing circuitry. On-chip analog-to-digital conversion and calibration are used to eliminate off-chip noise and to extend the measurement accuracy by removing system noise. A scan circuit is described that enables the noise waveform to be reconstructed. On-chip generators ranging in area from 0.25 μm2 to 1.5 μm2 produce noise at the receiver decreasing from 3.14 mV/μm to 0.73 mV/μm. Open and closed guard rings reduce the noise by 20% and 85%, respectively. Measurement of test circuits manufactured with an epitaxial process-5.5-μm-thick epitaxy with 20 Ω·cm resistivity on top of a 120 μm bulk with 0.03 Ω·cm-exhibits a frequency limit of 50MHz below which coupling is insensitive to substrate noise. The difference between experimental results and an analytic model of the line-to-line coupling capacitance ranges from 8.5% to 17.7% for different metal layers.
Date of Publication: Feb. 2006