Norhayati Soin 05 KEEE 4426 WEEK 2 06/01/2006 KEEE 4426 VLSI WEEK 2 REVIEW.

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Norhayati Soin 05 KEEE 4426 WEEK 2 06/01/2006

KEEE 4426 VLSI

WEEK 2

REVIEW

MOSFET

Technology evolution

ITRS(1)

ITRS(2)

ITRS(3)

ITRS(4)

Feature size

Capacitance Modeling

Gradual Channel Approximation

Classification of deviceand circuit simulators

Design flow

Process and Device simulator(1)

Process and Device simulator(2)

Circuit simulators

MOSFETS Mode of Operation(1)

Memory technology(1)

P-N Junction

Equilibrium(1)

•The -ve acceptor atoms in the P-type material repel the mobile electrons on the N-type side of the join (Junction). The +ve donors in the N-type material also repel the holes on the P-type side of the junction.

•The free electrons inside the N-type material need some extra energy to overcome the repulsion of the P-type's acceptor atoms. If they don't have enough energy, they can't cross the depletion zone & reach the P-type material. If they do manage to get past this energy barrier some of their kinetic energy will have been converted into potential energy

Equilibrium(2)

The free electrons inside the N-type material need some extra energy to overcome the repulsion of the P-type's acceptor atoms. If they don't have enough energy, they can't cross the depletion zone & reach the P-type material. If they do manage to get past this energy barrier some of their kinetic energy will have been converted into potential energy

This means the amount of energy converted from kinetic to potential form (or vice versa) when an electron crosses the depletion zone is where e is the charge on a single electron.

Depletion Zone

depletion zone •is free of charge carriers •the electrons/holes find it difficult to cross this zone. •very little current to flow when we connect an external voltage supply & apply a small potential difference between the two pieces of semiconducting material. (Here, ‘small’ mean small compared with , which an electron requires to get over the potential barrier.)

Reversed Biased

•The effect of applying a bigger voltage depends upon which way around it's connected.

•When we make the N-type side more +ve (i.e. drag some of the free electrons out of it) & the P-type more -ve (drag holes out of it) will increase the difference in potential across the barrier.

•This makes it even harder for a stray electron or hole to cross the barrier.

Forward biased

When we make to N-type side more -ve & the P-type side more +ve we force lots of extra electrons & holes into the two pieces of material. To understand the effect of this, let's concentrate on the electrons.

The electrons in the N-type region near the junction are repelled by the fixed acceptor atoms in the P-type. However, they're also repelled by the other electrons drifting around inside the N-type material.

Norhayati Soin 05 KEEE 4426 WEEK 2 06/01/2006 KEEE 4426 VLSI WEEK 2 REVIEW.

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