Contents I. Introduction
Hafnium oxide (HfO2), as one of the most studied high-K dielectric candidates for further scaling of CMOS devices, has demonstrated good electrical characteristics with reasonable stability and reliability on silicon substrate [1], [2]. However, in order to successfully integrate this dielectric into CMOS technology, there are a few important issues to be addressed, including degradation in channel mobility, charge trapping, and thermal stability. One approach to overcome these obstacles is by using multimetal oxides, incorporating another metal, such as Al, Ti, and Ta, into hafnium-based dielectric. This approach has already shown improvement in both electrical characteristics and thermal stability [3]–[5]. Yttrium oxide (Y2 O3) is one of the few binary metal oxides which are thermodynamically stable with silicon [6] and has shown promising results for MOSCAP and MOSFET [7], [8]. However, multimetal oxide with yttrium and hafnium has not been reported yet. In this letter, various ways to combine the two metals for oxide formation have been evaluated. The stacked Y2 O3 (top)/HfO2 (bottom) was recognized as the optimal structure and showed excellent electrical characteristics.
