IDDQ and Reliability Indicators

 EPSRC GR/L98404
Defect Detection Techniques for Deep Sub Micron Designs
   
 

Summary

IDDQ or static current testing has become a mainstream test technique within the microelectronics industry. Its use has been mainly to supplement functional/scan vectors to improve interconnect and oxide short detection. In deep sub-micron (DSM) devices, the future of IDDQ is uncertain as static sub-threshold leakage current is increasing, reducing the effectiveness of IDDQ by masking faults. In addition, the relative importance of fault types is changing, making for example opens detection more important in new technologies.

A number of interesting techniques have been proposed to replace IDDQ testing for DSM devices. In all cases, the defect detection potential is not fully understood and the practical implementation issues have not yet been properly studied. We are hence interested in investigating these and new ideas more fully. In summary, various companies and research groups have proposed the following techniques:

1

IDDT - This technique monitors the supply current transients caused by clock and logic transitions. It has been shown that sub-threshold leakage and the effect of process variations can be filtered from the measurements.1,2,3

2

IDDQ- Back Bias - This technique requires a triple well process and a separate well to substrate supply. For IDDQ measurements on core logic, a back bias is applied reducing effective Vt and hence reducing sub-threshold leakage. The technique requires library redesign.4

3

Energy Consumption Ratio (ECR) - The average dynamic current consumed by a circuit during a logic transition will be affected by the majority of defects. The ratio of these currents for two measurements with different input vectors will cancel contributions to the absolute measurements due to process variation and sub-threshold leakage. The technique has also been proposed to detect node coupling faults.5

4

BIC Sensors - A technique involving the fabrication of on-chip current sensors into the Vdd or Vss lines. The technique allows distributed high speed IDDQ measurements on-chip at the expense of silicon area. BIC sensors do not however eliminate the fundamental problem of high sub-threshold leakage and cause a number of problems including degraded effective supply, resistive and inductive losses during supply transients, noise injection and verification problems.6,7

5

DIDDQ_f(temp. oxide stress) - Two techniques. One involving repeated IDDQ measurements before and after an oxide stress and the other, a standard IDDQ test at reduced temperature. The first technique is designed to activate oxide defects and then detect through an IDDQ change relative to the initial measurement. The second technique reduces sub-threshold leakage through temperature reduction to improve sensitivity.8,9

   
 

References

 
1

Dorey, A.P., Jones, B.K., Richardson, A.M. and Xu,Y.Z.
Rapid reliability assessment of VLSICs
Plenum press ISBN 0-306-43492X, 1990.

2 Dorey, A.P., Jones, B.K., Richardson, A.M., Russell, P.C. and Xu, Y.Z.
Reliability Testing by Precise Electrical Measurement
IEEE International Test Conference, paper 21.1, pp. 369-374, Sept 1988.
3 Manoj Sachdev, Peter Janssen, and Victor Zieren
Defect detection with transient current testing and Its potential for deep sub-micron CMOS ICs
Proceedings of ITC, pp204-214, Oct. 18th - 23rd 1998, Washington
4

M. Sachdev
IDDQ Test and Diagnosis in Deep Sub-micron
IDDQ Test Workshop, pp. 84-89, 1995.

5 Bapiraju Vinnakota, Wanli Jiang & Dechang Sun
Process-Tolerant Test With Energy Consumption Ratio
Proceedings of ITC, pp1027-1037, Oct. 18th - 23rd 1998, Washington DC.
6 T.-L. Shen, J.C. Daly and J.-C. Lo
A 2-ns detecting time, 2mm CMOS built-in current sensing circuit
IEEE J.Solid-State Circuits,Vol.28,No.1, pp.72-77, 1993.
7 Maidon, Deval, Tomas, Verdier, Begueret & Dom
On-line CMOS BICS: An experimental study
Proceedings of the IEEE IDDQ workshop, pp85-90, Nov 5-6th 1997.
8 Anne E. Gattiker and Wojciech Maly
Current Signatures: Application
Proceedings of ITC, pp156-166, Nov. 1st- 6th 1997, Washington DC
9 C. Thibeault & L. Boisvert
Diagnosis method based on DIDDQ probabilistic signatures: Experimental results
Proceedings of ITC, pp1019 - 1027, Oct. 18th - 23rd 1998, Washington
   
  Project Manager - Dr A Richardson
Project Duration - Oct. 1998 to Sept 2001
   
  Homepage