PHT.301 Physics of Semiconductor Devices

MOSFETs

MOSFETs are the device most commonly produced by humans. Hundreds of millions of MOSFETs are used in a computer.

Reading: Sze chapter 6 or Singh chapter 9 and 10 or Thuselt 6.3, 6.4, 6.5, 6.6, and 6.8

For the exam:
• Be able to describe a MOS capacitor in terms of the flatband voltage, threshold voltage, acuumulation, depletion, and inversion.
• Draw the charge density, electric field, and electrostatic potential as a function of position in a MOS capacitor.
• Be able to draw the band diagrams for a nMOS capacitor or a pMOS capacitor.
• Know how the equation for the drain current in the linear regime is derived.
• Be able to explain 'pinchoff' and what controls the drain current in the saturation regime. Know the equation for the drain current in the saturation regime.
• Know why the simple model for MOSFETs is inadequate to describe very small MOSFETs.
• Be able to draw the electric field as a function of position along a cross section from the gate, through the oxide and into the substrate for various body voltages.

Resources:
• Turning Potential into Reality: The Invention of the Integrated Circuit, Jack S. Kilby, Nobel Prize in Physics 2000.

Student presentations:
• MOS Kondensator
  Michael Aichner, 2009
• 3-D integration Jacob Reyes 2010
• Ring oscillator (video)

Problems

Depletion width in a MOS capacitor

Flatband voltage