Letter to the Editor
Staff -- Semiconductor International, 4/1/2004
I just saw your story on NBTI ("NBTI: A Growing Threat to Device Reliability ," Semiconductor International, March 2004). Agere Systems had two IEDM (International Electron Devices Meeting) papers this year — both on transistor reliability. A key recent reliability concern for core and I/O transistors has been the rapid shift of PMOS drive current and threshold voltage as a function of time under normal operating conditions. However, the theoretical and experimental understanding of the physics of this degradation remain poor.
The two papers Ashraf Alam wrote this year for IEDM attempt to fill this gap by providing a more complete theoretical and experimental framework for understanding of this problem. Our message is mixed — we find that the degradation will increase as devices are scaled (paper 1, S. Mahapatra and M.A. Alam). However, under actual operating condition, we find that there is a significant recovery of the drive current and threshold voltage shift that may make the situation better then originally anticipated (paper 2, M.A. Alam). I think this understanding will help us with 90 nm technology from TSMC, because without it the NBTI margin may be too small to unconditionally qualify the technology.
Agere qualified its 130 nm DSP chips with copper and low-k dielectrics in April 2003, and demonstrated 90 nm devices with low-k technology in November 2003.
See Ashraf's work on breakdown behavior (www.agere.com/NEWS/PRESS2002/120402a.html).
Steven Goldsmith
Senior Manager, Corporate Communications
Agere Systems
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Article is nice!
Ashok - 9/2/2004 12:14:00 AM CDT
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