ASTM F996-11

The electrical properties of gate and field oxides are altered by ionizing radiation. The method for determining the dose delivered by the source irradiation is discussed in Practices E666, E668, E1249, and Guide E1894. The time dependent and dose rate effects of the ionizing radiation can be determined by comparing pre- and post-irradiation voltage shifts, ΔV_ot and ΔV_it. This test method provides a means for evaluation of the ionizing radiation response of MOSFETs and isolation parasitic MOSFETs.

The measured voltage shifts, ΔV_ot and ΔV_it, can provide a measure of the effectiveness of processing variations on the ionizing radiation response.

This technique can be used to monitor the total-dose response of a process technology.

1.1 This test method covers the use of the subthreshold charge separation technique for analysis of ionizing radiation degradation of a gate dielectric in a metal-oxide-semiconductor-field-effect transistor (MOSFET) and an isolation dielectric in a parasitic MOSFET. ^{, ,} The subthreshold technique is used to separate the ionizing radiation-induced inversion voltage shift, ΔV_INV into voltage shifts due to oxide trapped charge, ΔV_ot and interface traps, ΔV_it. This technique uses the pre- and post-irradiation drain to source current versus gate voltage characteristics in the MOSFET subthreshold region.

1.2 Procedures are given for measuring the MOSFET subthreshold current-voltage characteristics and for the calculation of results.

1.3 The application of this test method requires the MOSFET to have a substrate (body) contact.

1.4 Both pre- and post-irradiation MOSFET subthreshold source or drain curves must follow an exponential dependence on gate voltage for a minimum of two decades of current.

1.5 The values stated in SI units are to be regarded as standard. No other units of measurement are included in this standard.

1.6 This standard does not purport to address all of the safety concerns, if any, associated with its use. It is the responsibility of the user of this standard to establish appropriate safety and health practices and determine the applicability of regulatory limitations prior to use.