[paper] Analysis of aging effects - From transistor to system level

Analysis of aging effects - From transistor to system level

Maike Taddiken*, Nico Hellwege, Nils Heidmann, Dagmar Peters-Drolshagen, Steffen Paul

Institute of Electrodynamics and Microelectronics,
University of Bremen, Otto-Hahn-Allee 1, Bremen 28359,Germany

ABSTRACT: Due to shrinking feature sizes in integrated circuits, additional reliability effects have to be considered which influence the functionality of the system. These effects can either result from the manufacturing process or external influences during the lifetime such as radiation and temperature. Additionally, modern technology nodes are affected by time-dependent degradation i.e. aging. Due to the age-dependent degradation of a circuit, processes on the atomic scale of the semiconductor material lead to charges in the oxide silicon interface of CMOS devices, altering the performance parameters of the device and subsequently the behavior of the circuit. With the continuous downscaling of modern semiconductor technologies, the impact of these atomic scale processes affecting the overall system characteristics becomes more and more critical. Therefore, aging effects need to be assessed during the design phase and actions have to be taken guaranteeing the correct system functionality throughout a system’s lifetime. This work presents methods to investigate the influence of age-dependent degradation as well as process variability on different levels. An operating-point dependent sizing methodology based on the gm/ID method extended to incorporate aging, which aims at developing aging-resistent circuits is presented. The basic idea of the gm/ID sizing method is the dependence of the operating point of a MOS transistor on the state of inversion in the channel, its strong relation to circuit performance and the possibility to calculate transistor dimensions.The inversion coefficient IC is a fundamental metric within the gm/ID method and numerically represents the inversion level of a MOS device formally described in the EKV MOS model. Additionally, the sensitivity of circuit performances in regard to aging can be determined. In order to investigate the reliability of a complex system on behavioral level, a modeling method to represent the performance of system components in dependence of aging and process variability is introduced. [read more...]