Onchip Negative Bias Temperature Instability Sensor using Slew Rate Monitoring Circuitry

1
On-chip Negative Bias Temperature Instability
Sensor using Slew RateMonitoring Circuitry

• Amlan Ghosh
• (aghosh_at_ece.utah.edu)
• Dr. Rahul M. Rao, Dr. Ching-Te Chuang, Dr.
  Richard B. Brown
• Dept. of ECE, University of Utah
• IBM, T. J. Watson Research Center

IBM ACAS 2008
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Stress and Recovery of PMOS

• NBTI affects PMOS transistors when gate bias is
  negative
• Causes dissociation of Hydrogen
• More traps at the interface make the transistor
  slower

(a) Stress phase
(b) Recovery phase
J. Keane, T. Kim, and C.H. Kim, "An On-chip NBTI
Sensor for Measuring PMOS Threshold Voltage
Degradation", International Symposium on Low
Power Electronics and Design, Aug 2007
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NBTI Mechanism
M. Denais, et al., On-the-fly characterization
of NBTI in ultra-thin gate oxide PMOSFETs, IEEE
International Electron Devices Meeting, pp.
109-112, December 2004.
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NBTI R-D Model for PMOS
S. Kumar, C. Kim, S. Sapatnekar, An Analytical
Model for Negative Bias Temperature Instability,
IEEE International Conference on Computer-Aided
Design, pp. 205-210 November 2006.
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NBTI Measurement Techniques

• Measurement using various test structures
• May require precise test equipment
• Frequency degradation in a stressed ring
  oscillator
• May not be de-coupled from PBTI effect in NMOS
• Phase adjustments between multiple delay-locked
  loops

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NBTI Monitor
en
Slew monitor A
Ref ROSC
out
CP
Ctrl
Slew monitor B
Str ROSC
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Principle of NBTI Detection Circuit
Due to Str ROSC
Due to Ref ROSC
P3
PN
P2
P1
A1
Str ROSC
b
c
PR1
PR2
PR3
PRN
B1
a
out
PR1
PR2
PR3
PRN
B2
C
Ref ROSC
A2
P1
PN
P3
P2
Reset
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Slew Rate Monitor
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Charge Pump
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Normalized Output Voltage of Slew Rate Monitor
with Input Signal Slew
0.42mV/ps
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Normalized Output of Slew Rate Monitor with
Number of Input Pulses
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Sensitivity of Slew Rate Monitor with Number of
Input Pulses
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Conclusion

• NBTI measurement using rise-only slew
• Design of the NBTI monitor in IBM 65nm process
• Multiple input pulses for greater sensitivity

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Future Work

• - Determine the sensitivity of the NBTI monitor
  w.r.t stress voltage
• - Implement NBTI monitoring scheme in 65nm IBM
  process
• - Characterize circuits in real processor
  environment

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Thank You