Analysis of Buried-Oxide Dielectric Breakdown Mechanism in Low-Dose Separation by Implanted Oxygen (SIMOX) Substrates Fabricated by Internal Thermal Oxidation (ITOX) Process

Buried-oxide (BOX) dielectric breakdown behavior of low-dose separation by implanted oxygen (SIMOX) substrates fabricated by the internal thermal oxidation (ITOX) process was analyzed. From the time-zero dielectric breakdown (TZDB) characterization of the metal-oxide-semiconductor (MOS) capacitors using BOX as a dielectric, of various areas, BOX breakdown was found to be dominated by the electrically weak spots (EWS's) distributed randomly in the BOX layer. The densities of EWS's show good correlation with those of Si islands in the BOX for several samples, indicating that the Si islands are the main cause of BOX breakdown. A model for extracting the EWS density as a function of breakdown field is proposed, the appropriateness of which is verified by its application to the experimental results. Using the proposed model, the dependence of Si island density and their thickness distribution on oxygen ion dose and ITOX layer thickness was investigated, indicating that both dose reduction and ITOX enhancement can effectively reduce the Si island density. By combining the dose reduction and ITOX enhancement, BOX breakdown characteristics, almost comparable to that of the thermally grown oxide were attained, even for a relatively large capacitor area of 7.85×10 -3 cm 2 , revealing the high performance of ITOX-SIMOX technology.