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Advanced Electrical Characterization of Charge Trapping in MOS Transistors

1.3 This Work

A wide variety of literature has amassed, devoted to reliability issues in MOSFETs. Many of these studies focus on characterizing the impact of defects on certain technologies, often using large area devices. However, as the gate area of MOSFETs continues to decrease, studying the underlying behavior of defects becomes increasingly important to explain the reliability of a technology. This is also important for investigating the feasibility of novel technologies. Ideally, a statistically significant amount of single defects should be characterized in sufficient detail to allow further studies, both using atomistic simulations to assess their underlying physical origin and to model their charge trapping dynamics, as well as device simulations to predict their detailed impact on the operating behavior of the devices. For this, more recently developed methods of defect characterization can be employed, which are currently still limited in usability due to the effort required. In this work various aspects of defect characterization including charge trapping models, experimental procedures and methods of data processing are discussed before presenting results obtained using improved methodologies on a number of technologies.

This work is divided in a number of chapters, discussing experimental and mathematical treatment of these defects and their effects in MOSFETs. The structure is as follows. Chapter 2 discusses the main types of electrically active defects found in MOSFETs, how they interact with the device and the issues they cause. Discussion is aided by examples for silicon technology. In Chapter 3, approaches to the mathematical modeling of these defects and their impact on the device are discussed. This includes concepts necessary later, such as the representation of a defect using a Markov chain with capture and emission rates. The following Chapter 4 discusses various experimental approaches available for the characterization of defects. Chapter 5 then discusses the extraction of defect parameters from measurements. This closes the gap between experimental defect characterization and defect modeling. Finally, in Chapter 6, defect characterization studies performed on three separate technologies using combinations of the methods as outlined in the previous sections will be presented.