Current Conduction and Charge Trapping in Thin Interpoly Dielectrics Prepared by In Situ Multiple Rapid Thermal Processing

Abstract

In this paper we report a systematic and comprehensive study of the effects of post‐oxidation anneals on the electrical properties of thin polyoxide films. Thin (≤20 nm) interpoly dielectrics have been grown on phosphorus implanted polysilicon by in situ multiple rapid thermal processing (RTP) including rapid thermal oxidation (RTO1), rapid thermal nitridation (RTN), and subsequent rapid thermal reoxidation (RTO2). In comparison with polyoxides grown in conventional furnace, RTO1 polyoxides exhibit a significantly reduced leakage current. In addition, both the dielectric breakdown strength and breakdown field distribution have been improved. It is found that RTN of RTO1 results in polyoxides with an unusual polarity asymmetry dependence of electrical conduction and trapping properties, i.e., a higher electrical conduction and electron trapping rate for electrons injected from the top poly‐Si electrode than for electrons injected from the bottom poly‐Si electrode. Subsequent RTO2 of nitrided polyoxides results in a reduction of both the leakage current and electron trapping rate. Longer RTO2, however, increases the leakage current due to the progressively deteriorated poly‐Si/ polyoxide interfacial texture.