Control of laser induced interface traps with in-line corona charge metrology

Abstract

Laser annealing is an ideal activation step for ultra shallow junctions (USJ). But it can increase the density of interface traps (Dit) of the gate dielectric, resulting in degraded NBTI reliability. Therefore the influence of anneal conditions is studied with corona charge metrology. SiO2 is used as a reference gate dielectric for which recovery solutions are worked out to reduce the laser induced Dit. But, on the other hand, the recovery can cause degradation of the USJ, limiting the choice of process conditions for recovery. The reduction in Dit by spike anneal can be explained by stress relaxation in case of SiO2 and SiON. For HiK gate dielectrics the behaviour is more complex due to possible chemical interactions and crystallization. Recovery can be done by spike anneal and mulitscan laser anneal. The latter is better towards USJ properties.