lets understand what is Yield and what is Reliability
yield is kind of a probability of failure say a processed device, whereas Reliability is a probability of failure over the period of time, initially while we were testing the device is functioning fine or good, over the period of time, it has failed .
what all could be reasons for it not being reliable ?
NBTI [negative bias temperature inversion]
courtesy : Cadence
Due to electric field stress and temperature, the hydrogen gets detached from Si dangling bond, creating interface traps. This problem is mainly noticed in PMOS transistors.
TDDB [ Time dependent Dielectric Breakdown] : some defects which are random, form a path from gate to channel through gateoxide.
Image courtesy : purdue Univ
HCI [Hot carrier injection] : The electrical field around the drain, generates injection of hot-carriers into SiO2 gate oxide layer. These carriers causes changes the charge distribution in the oxide-interface area.
courtesy : Cadence
picture courtesy : Sciencedirect/Elsevier
References:
1. Reliability Simulation in integrated Circuit Design , Cadence whitepaper
2. lecture notes by Ninad Pimparkar, Microelectronics Reliability phenomena
3. A comprehensive model of PMOS NBTI degradation by M.A. Alam, S. Mahapatra
For Reading of Chip Design Articles,
2 responses so far ↓
shivakumar revanna // May 7, 2008 at 1:50 pm |
Could you please tell me is there any relation between yeild and test coverage?
Thanks,
Shivakumar
ankit khare // July 12, 2008 at 7:23 pm |
which coverage you are asking? Mostly frequency based testing, current leakage and stress based are mostly the criteria which decide the faulty parts not to escape. Hence deciding yield