3 Analytical and Numerical Investigation of the Charge Pumping

Charge pumping is a transient effect in MOS devices. It represents the transfer of charge from the source and drain terminals to the bulk by transient pulses at the terminals. A DC component of the terminal currents can be measured. In this chapter advanced analytical models of the charge-pumping effect are presented. Moreover, a general two-dimensional transient numerical model of the charge-pumping effect is described. The numerical model is applied to confirm the validity of analytical models, as well as to study the cases which cannot be described by analytical approaches. At the end of the chapter charge pumping is used to analyse the degradation of MOS devices due to hot carriers.

• 3.1 Introduction
  • 3.1.1 Charge-Pumping Techniques
  • 3.1.2 Other Techniques to Study Traps in Small MOSFETs
  • 3.1.3 Restrictions of Analytical Approaches
• 3.2 Physical Model and Numerical Approach
  • 3.2.1 Physical Model
  • 3.2.2 Discretization of the Basic Equations and Numerical Aspect
  • 3.2.3 Solution of the Trap-Dynamics Equation
  • 3.2.4 Approach to Simulate the Charge-Pumping Experiments
• 3.3 Analytical Modeling of the Large-Signal Charge-Pumping Effect
  • 3.3.1 Rigorous Analysis of the Complete Characteristics Charge-Pumping Current versus Gate Top Level
    • Processes at the Top Level:
    • Charge-Pumping Threshold and Flat-Band Voltage
    • Processes at the Falling Edge:
    • Processes at the Rising Edge:
    • Processes at the Bottom Level:
    • Charge-Pumping Current
    • Analytical Model Versus Numerical Results
    • Frequency-Dependence of the Threshold and the Flat-Band Voltage
  • 3.3.2 Emission in the Non-Steady-State Mode
• 3.4 Geometric Current Component and Other Non-Ideal Effects
  • 3.4.1 Minority Carriers Remaining in the Channel
  • 3.4.2 Carriers Emitted from the Interface States
• 3.5 Hot-Carrier Degradation Analysis
  • 3.5.1 Charge-Pumping Characteristics of MOSFETs after Hot-Carrier Stress: A Numerical Study
  • 3.5.2 Extraction of the Spatial Distribution of Interface Traps in MOSFETs
    • Symmetrical Case:
    • Non-symmetrical Case:
    • Other Large-Signal Charge-Pumping Techniques
    • Constant Amplitude Technique
  • 3.5.3 Charge-Pumping Characteristics of LDD MOSFETs before Stress
  • 3.5.4 Interface Traps Build-up in -Channel LDD MOSFETs
• 3.6 Conclusion