The document discusses four topics related to transistors: 1. Threshold voltage is the minimum gate voltage needed to create a conducting path between source and drain, and depends on oxide thickness, temperature, and random dopant fluctuations. 2. Latchup refers to a short circuit formed between power and ground rails in an integrated circuit, caused by interaction between parasitic bipolar transistors. 3. Electromigration is the forced movement of metal ions due to an electric field, with atoms traveling toward the positive conductor end and vacancies toward the negative end. 4. Mobility degradation occurs due to lateral and vertical electric fields scattering carriers, reducing surface mobility as channel lengths shrink.

1. Threshold Voltage
• The threshold voltage is the minimum gate-to-source voltage VGS
differential that is needed to create a conducting path between the
source and drain terminals. It is abbreviated as Vth.
• Dependence on oxide thickness
• Dependence on temperature
• Dependence on random dopant fluctuation

2. Latchup
• Latchup refers to short circuit formed between power and ground
rails in an IC leading to high current and damage to the IC.
• Latch up is the phenomenon of low impedance path between power
rail and ground rail due to interaction between parasitic pnp and npn
transistors.

3. Electromigration (EM)
• Electromigration is the forced movement of metal ions due to an electric
field.
• Ftotal = Fdirect +Fwind
• Metal atoms(ions) travel toward the positive end of the
conductor while vacancies move toward the negative end.

4. Mobility Degradation
• Mobility is important because the current in MOSFET depends upon
mobility of charge carriers(holes and electrons).
• Lateral Field Effect: In case of short channels, as the lateral field is
increased, the channel mobility becomes field-dependent and
eventually velocity saturation occurs .
• Vertical Field Effect: As the vertical electric field also increases on
shrinking the channel lengths, it results in scattering of carriers near
the surface. Hence the surface mobility reduces .