AT89C51RD2 / AT89C51ED2 QualPack

12

Rev. 0 – 2003 July

4.3.3 Time Dependent Dielectric Breakdown

Purpose:

To evaluate the AT56800 thin gate oxide TDDB performance as follows:

a) To determine the activation energy of gate oxide failures on STI active edge capacitors

b) To determine the field acceleration factor for intrinsic gate oxide failures

c) To determine the sigma the lognormal standard deviation of the time to breakdown distribution of the

intrinsic gate oxide

Test Parameters:

Lot

9G3470 (wafers 4, 5, 18)

Min thickness:

72.9A

Max thickness:

74.7A

Capacitor size:

6.267 um

2

The stress conditions used are shown below:

Temperature/Field

9.5MV/cm

10.0MV/cm

10.5MV/cm

225C

N=5

N=5

N=5

200C

N=5

N=5

N=5

175C

N=5

N=5

N=6

Accumulated total stress time: 132 hours / 46 capacitors

Calculation Parameters:

Failure Criteria:

0.01% failures

Temp/Voltage use:

105°C / 3.3V

Oxide thickness:

63A (target –10%)

Lifetime Prediction:

The equation used to describe the breakdown of gate oxides is:

Tbd(i) = exp(SIGMA*Z(i) + GAMMA*Eox +Ea/kT + T0)

Where

Tbd(i) is the time to breakdown of the i

SIGMA is the lognormal standard deviation of the breakdown distribution,

Z(i) is the Z-score of the i

measured in standard deviations),

GAMMA is the Field acceleration constant,

Eox is the oxide field,

Ea is the activation energy of this failure mechanism,

K is Boltzmann’s constant,

T is the Kelvin Temperature, and

T0 is a fitting constant.