Metrology development at NIST for characterizing wear-out and reliability of thin gate dielectrics

The effect known as Time-Dependent-Dielectric-Breakdown (TDDB) occurs when thin gate silicon dioxide (SiO/sub 2/) films catastrophically break down without warning during normal operation. Recently, the reliability of gate oxides has become a critical concern as the thickness of the gate oxide is reduced. Thinner films result in higher gate electric fields and direct tunneling currents passing through the gate dielectric advancing dielectric wear-out and device failure. NIST has played a key role in conducting experiments to validate the physical models of dielectric breakdown. NIST also leads standards organizations in developing new test procedures used during production monitoring and process qualification to characterize the integrity and reliability of ultra-thin gate oxides. In this paper, metrology issues relating to the reliability testing and lifetime projection of thin gate oxides will be discussed as well as the role of NIST in the development of metrology for a new generation of advanced gate dielectric materials.