Considerations on isochronal anneal technique: From measurement to physics

The isochronal anneal technique used to predict isothermal anneal behavior of MOS devices is analyzed as a function of experimental parameters (bias during irradiation and anneal). This methodology is applied to different oxide types (hardened and unhardened) with different thickness. Net oxide trapped charge is estimated through I-V or C-V measurements, and electron and hole contributions are determined using the TSC technique. The effects of detrapping of trapped holes and compensating electrons are discussed. The prediction of long term post irradiation response can be accurately done when anneals are performed under positive bias. This prediction is more complex for other bias conditions. The difficulty is related to competitive effects of trapped hole annealing and buildup of compensating electrons as a function of temperature. To enable a precise modeling of long term annealing, a complete model must include, among other things, compensation of holes through tunneling, and/or thermally injected electrons.