Here are the all short channel effects that you require.It consist of:- Drain Induced Barrier Lowering Hot electron Effect Impact Ionization Surface Scattering Velocity saturation

1. SHORT CHANNEL EFFECTS
By:
Ashish A Bait
Sagar Paarcha
Nilesh Narkhede
Suraj More

2. OVERVIEW
• Pre-requisite
• What is Short Channel
• What are Short Channel Effects
• DIBL
• Surface scattering
• Hot electron effect
• Impact Ionisation
• Velocity saturation

3. PRE-REQUISITE
• Threshold voltage:- The minimum voltage
across gate and source which allows current
flow through the transistor.
• Sub-threshold current:- The current flowing
through the transistor before threshold
voltage is called sub-threshold current.
• Pinch-off voltage :- It is a voltage after which
there is no effect of increase in drain to
source voltage on the current flowing
through transistor.

4. WHAT IS SHORT CHANNEL
• Channel length ~= depletion width of source
and drain

5. SHORT CHANNEL EFFECTS
• Short channel MOS has good processing
speed, requires low operating potential and
increases transistor density on the chip.
• Although the performance degrades with
decrease in channel length.
• It faces some serious issues like DIBL, surface
scattering, velocity saturation, impact
ionisation, hot electron effect.

6. DRAIN INDUCEDBARRIER LOWERING(DIBL)
• Increase in drain voltage reduces the barrier
face by electrons or holes in the source
allowing them to go from source to drain
where gate voltage remain unchanged.
• Gate looses the control of flow of current
through MOS and become as good as
redundant.

7. DRAIN INDUCEDBARRIER LOWERING(DIBL)

8. DRAIN INDUCEDBARRIER LOWERING(DIBL)
Long Channel Short Channel

9. SURFACE SCATTERING

10. SURFACE SCATTERING
• In long channel Ex>>Ey,but in short channel
Ex is not negligible.
• Ex and Ey field makes electron to travel in zig-
zag path, reducing their mobility.
• As the channel length becomes shorter
electric field Ey increases causing surface
mobility to become field dependent.

11. HOT ELECTRON EFFECT

12. HOT ELECTRON EFFECT
• At high velocity carriers drifting near the drain
gains extra energy called hot carriers.
• These hot carriers tunnel through gate oxide
thus reducing the total current flow from
source to drain.
• Reduces the input impedance.

13. HOT ELECTRON EFFECT
• The technique is used in floating gate devices
to increase the threshold by trapping the
electrons in the floating gate
• To reduce hot electron effect:- drain is lightly
doped, resulting in less electric field created
for carriers.

14. IMPACT IONISATION

15. IMPACT IONISATION
• Electron travelling to the drain creates
electron-hole pair by impact ionisation.
• Secondary electrons are collected at drain
causing current to increase in saturation.
• Secondary holes are collected at substrate
causing to increase latch up.

16. VELOCITY SATURATION

17. VELOCITY SATURATION
• Up to certain point velocity is directly
proportional to electric field.
• But after the point velocity saturates and has
no effects of increase in electric field.