Curve Fitting Results

Ray

Log(Id)

VGS

Sqrt(Id)

VGS

Weak-Inversion Fitting

Chip #1

Chip #2

Weak-Inversion Fitting Temperature Effect

Chip #1

T = 65F

T = 80F

T = 90F

Sqrt(Id)

VGS

Curve Fittings from Square Root of Drain Current

Threshold voltage

Slope1

Slope2

slope drops due to the degradation of mobility

Depletion region charge

Threshold Voltage Fitting results

Chip #1T = 65FT = 80FT = 90F

Chip #2

T = 69F

Leakage when Vgs = 0V

VDS

Punch-through

GIDL

DIBL

Mobility Ratio Fitting results

Chip #1T = 65FT = 80FT = 90F

Chip #2

T = 69F

Slope1 Slope2 K3

For chip#1, mobility will drop fourfold while it drops 2.5 times for chip #2

Velocity Saturation

Chip #1

T = 65F

T = 80F

T = 90FChip #2T = 69F

further to velocity saturation

closer to velocity saturation

Mobility ratio Fitting Velocity Saturation Dominant Case

Chip #1

Chip #2Mobility only drops 1.1 times!

Mobility only drops 1.04 times!

Problems So Far

• In mobility ratio fitting results, the difference in two slopes lying only in the assumption of mobility difference under standard square law equation.

• However, as the previous slide show, if velocity saturation kicks in, square law doesn't hold and the index can also be an coefficient. Thus, the mobility degradation effect will be reduced.

• Nevertheless, the temperature effect is not affected.

We need to understand the physics here to choose which phenomenon is here presented.