1

Silicon Odometer: An On-Chip Reliability Monitor for Measuring Frequency Degradation

of Digital Circuits

NBTI impact mitigation techniques• Guard-banding

• Size up devices • Toggle circuit nodes

• Lower temperature

• Vtp and Vdd tuning

NBTI impact on digital circuits• Fmax

• Leakage current

• SRAM cell stability

• SRAM read/write margin

Bottom line: Need to accurately measure the NBTI effect and develop compact models

2

Silicon Odometer

Phase Comp.

Stressed ROSC (freq=fstress)

...

...

Reference ROSC

A

BC

PC_OUT

Measurement

Stress period

VDD_NOM

VDD_STR

0V

(freq=fref)

(freq=fref - fstress)

0

20

40

60

80

100

120

0 0.5 1 1.5 2Frequency degradation (%)

Co

un

ter

ou

tpu

t (N

)

99 98

50

33ProposedConventional

ΔN=1 @ 1%

N=50 @ 1%Δ

• Two free running ROSCs for beat frequency detection

• Count PC_OUT to determine frequency degradation

• Insensitive to environmental variations

• High delay sensing resolution

• Fully implemented by digital circuits

Labview GUI

3

Summary Measurement work bench

0.00%

0.05%

0.10%

0.15%

0.20%

0.25%

0.30%

0 2000 4000 6000Time (sec)

Fre

qu

enc

y d

egra

dat

ion

Vstress=V0, 30C

• Fully digital, minimal calibration

• Sub-picosecond sensing resolution (<0.02% or <0.8ps)

• Microsecond measurement time for minimal recovery (2us)

• Applicable as a on-chip reliability monitor