Electrical properties of crystalline γ-Al2O3 films using conductive-AFM and MISFETs with Aluminum gates

Abstract

Introduction For future LSI applications, it has been proposed to replace the traditional SiO 2 with the high-k materials such as Al 2 O 3 , ZrO 2 , HfO 2 , Si 3 N 4 and Y 2 O 3 for gate dielectrics. In our laboratory, crystalline γ-Al 2 O 3 films have been studied and grown on Si substrate successfully using a hybrid source MBE [1]. It has a number of applications in Si devices such as quantum well devices and silicon-on-insulator technology [2]. The electrical properties of the γ-Al 2 O 3 have been reported [3], which describes no SiO 2 interface layer between Si and Al 2 O 3 , high breakdown field comparable with SiO 2 , and low leakage current compared with other insulators. Therefore, crystalline γ-Al 2 O 3 films were expected as an attractive candidate for high-k materials. However, evaluations of crystalline γ-Al 2 O 3 films might be not enough for several applications. Because crystalline films usually have crystal defects or grain boundaries, which may have a bad influence on the characteristics. In this report, we evaluated the influence of crystal defects or grain boundaries by comparison of breakdown voltage among conductive AFM's cantilevers and MIS structures that has several electrode sizes. Furthermore, we fabricated n-channel MISFETs with Aluminum gates using the crystalline film as gate dielectrics and confirmed good characteristics.