Dependence of X-Ray Generation of Interface Traps on Gate Metal Induced Interfacial Stress in MOS Structures

In a series of experiments, we deliberately altered the interfacial stress distribution in MOS structures by varying the mechanical properties of the gate Al films. Subsequently, we found that the generation of interface traps resulting from exposure to X-ray was strongly correlated to this stress distribution. For a given oxide process and radiation dose, a universal curve could be established, which relates the density of radiation-induced interface traps to the interfacial stress distribution. An explanation based on the strained bond model will be proposed, which incorporates the effect of the gate-induced stress distribution on the oxide bond strain gradient near the SiO2/Si interface.