Analysis of the degradation and breakdown of thin SiO/sub 2/ films under static and dynamic tests using a two-step stress procedure

A two-step stress test is used to analyze the degradation and breakdown of thin SiO/sub 2/ films. The procedure directly relates the degradation of the oxide to the breakdown statistics, without the need of any assumption about the microscopic degradation mechanism. It partially overcomes the problems associated with dynamic tests and allows the direct comparison of different tests (static and dynamic). The evolution of the degradation of 8 nm thick oxides subjected to constant-voltage (CVS), constant-current (CCS), and bipolar square voltage stresses is analyzed using the two step stress method. The results are compared with those of conventional breakdown tests to show the feasibility of the procedure. Our test procedure is also used to study the degradation of 4 nm thick oxides when subjected to CCS. The obtained results suggest that the two-step stress test will also be a powerful tool to analyze the degradation of ultra-thin oxides.