A high sensitivity and process tolerant digital thermal sensing scheme for 3-D Ics

Abstract

Thermal sensing is a pressing need in stacked 3-D chips with limited number of vertical heat conduits. In 3-D systems with active temperature control, the controller is reliant on sensors placed on individual planes to provide the necessary thermal feedback. To this end we propose a delay-line based thermalsensor which provides a high temperature-sensitivity, high level of process-robustness and is amenable to the TSV-based communication paradigm used in 3D systems. The temperaturesensitive piece mitigates the high process-susceptibility of 3-D circuits through usage of multiple logic-stages composed of longchannel devices and elimination of common-mode noise on the delay-line pair. The thermal information is conveyed to the controller in the form of a signal-frequency and hence is insensitive to path-mismatch in TSV wires. A high postdigitization temperature sensitivity of 0.82%/°C was achieved. The 1-σ accuracy loss due to process-variations and supply-noise was limited to 0.78°C and 1.06°C respectively indicating a high level of process-tolerance.