Modification of bounded J-Ramp method to monitor reliability and charge degradation of gate dielectric of MIS devices

Abstract

This paper suggests a novel method to control quality and reliability of thin dielectric films of the gate dielectric of MIS structures. The proposed method is based on a modification of bounded J-Ramp. This technique, besides the control of charge injected into the gate dielectric until its breakdown, gives a capability to monitor a change of charge state of the gate dielectric during all the test procedure. In order to implement this, after ending of a test (current) step we switch the test current to the measurement current level (Jm) for a short time period and this allows to monitor the voltage change across MIS structure at the constant measurement current density. The current density Jm is chosen to meet the condition that at this level a s significant charge degradation of the dielectric should not be observed. Besides, the switches to measurement level should not greatly influence on bounded J-ramp test procedure. The modified J-ramp method proposes to monitor amount of injected charge, at which irreversible degradation of MIS device characteristics takes place (Qdeg), and evaluate reliability of the dielectric film on the basis of statistical measurements of these quantities.