All-Digital PMOS and NMOS Process Variability Monitor Utilizing Shared Buffer Ring and Ring Oscillator

Tetsuya IIZUKA  Kunihiro ASADA  

IEICE TRANSACTIONS on Electronics   Vol.E95-C   No.4   pp.627-634
Publication Date: 2012/04/01
Online ISSN: 1745-1353
DOI: 10.1587/transele.E95.C.627
Print ISSN: 0916-8516
Type of Manuscript: Special Section PAPER (Special Section on Solid-State Circuit Design – Architecture, Circuit, Device and Design Methodology)
process variability,  all digital,  on-chip monitor,  buffer ring,  

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This paper proposes an all-digital process variability monitor based on a shared structure of a buffer ring and a ring oscillator. The proposed circuit monitors the PMOS and NMOS process variabilities independently according to a count number of a single pulse which propagates on the ring during the buffer ring mode, and an oscillation period during the ring oscillator mode. Using this shared-ring structure, we reduce the occupation area about 40% without loss of process variability monitoring properties compared with the conventional circuit. The proposed shared-ring circuit has been fabricated in 65 nm CMOS process and the measurement results with two different wafer lots show the feasibility of the proposed process variability monitoring scheme.