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Hot carrier effect dependence on channel length

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rajesh13

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Can somebody tell me how the Hot carrier effect is minimised when the channel length is increased. I am interested only on the dependence of Hot carrier effect and channel length.( and not on the introduction of LDD)
 

Hot carrier are produced by excessive high electric field along the channel. Since E=V/L, longer channel length reduce the electric field intensity and thus reduce the effect of hot carrier.
 
terryssw said:
Hot carrier are produced by excessive high electric field along the channel. Since E=V/L, longer channel length reduce the electric field intensity and thus reduce the effect of hot carrier.
Click to expand...

Is it that simple.
I tried to use this concept to drive the dpendence of L on the hot carrier effect. I found that the final velocity with which electron reaches drain is independent of channel length.

Please find the derivation below:

E = Vds/L (electric field lateral)

F = e E (force on electron)

now F = m a ( m is the mass of the electron , a is the acceleration)

V*V = U*U +2 a L ( V is the final velocity & U is the initial velocity)

asssume U = 0, so the final velocity is independent of L.
 

I suggest the following explanation (not quite sure)

I think the formula can only (very rougly) calculate the drift velocity of the electron, not the absolute velocity (electron drift from source to drain, but still go randomly at any moment). The drift velocity is far lower than the absolute velocity that the electron process at any moment, and it is this velocity that determine if a electron become hot carrier. Since the hot carrier effect cause electrons to be trapped in the oxide, lateral drift velocity certainly cannot direct electron to enter the oxide region.
 

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