Effects of electrical, thermal and thermal gradient stress on reliability of metal interconnects

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Patra, Srijita
Major Professor
Randall Geiger
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Electrical and Computer Engineering

The Department of Electrical and Computer Engineering (ECpE) contains two focuses. The focus on Electrical Engineering teaches students in the fields of control systems, electromagnetics and non-destructive evaluation, microelectronics, electric power & energy systems, and the like. The Computer Engineering focus teaches in the fields of software systems, embedded systems, networking, information security, computer architecture, etc.

The Department of Electrical Engineering was formed in 1909 from the division of the Department of Physics and Electrical Engineering. In 1985 its name changed to Department of Electrical Engineering and Computer Engineering. In 1995 it became the Department of Electrical and Computer Engineering.

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  • Department of Electrical Engineering (1909-1985)
  • Department of Electrical Engineering and Computer Engineering (1985-1995)

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This thesis focuses on the reliability modeling of metal interconnects under time-dependent stress. Whereas most existing reliability models are based upon the assumption that stress is constant throughout the useful life of a system, this thesis considers the more general and more realistic situation where the stress is time-dependent. In this work the stress is defined by temperature and current density variables. It is assumed that the Cumulative Density Function (CDF) is characterized by a single stress parameter that incorporates all stress-dependent variables. A closed-form expression that can be used to calculate the CDF under time-varying stress is presented and this can be used to determine the corresponding Median Time to Failure (MTF). A single parameter which can be represented as a real number is used to incorporate the total effects of the stress history making this approach applicable for dynamic power/thermal management algorithms.

A reliability model that includes the effects of thermal gradient stress in the presence of temperature and current stress is also introduced. With these models, temperature measurement accuracy requirements are developed that are necessary if power/thermal management circuits are to be successful in achieving 10% accuracy in the MTF. Incorporation of a time-dependent stress model that incorporates the user-dependent electrical and thermal stress history in the power/thermal management module of a large integrated circuit offers potential for significantly improving system performance while maintaining a target reliability throughout the operating life of the integrated circuit or for improving the reliability when operated at a user-determined stress level.

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Wed Jan 01 00:00:00 UTC 2014