Thermostability of amorphous zirconium aluminate high-k layers

One challenge in the development of high-k dielectric films is to preserve their amorphous nature during the processing of CMOS. In this work, the feasibility of using ZrO2–Al2O3 binary alloys to obtain a stable homogeneous amorphous structure in a high-k layer is investigated. In situ high temperature X-ray diffraction tests show that the onset crystallisation temperature of the binary alloy with 42 and 61 mol% Al2O3 is 900, 400 C higher than that of the pure ZrO2. After rapid thermal process anneals up to 900 C, the ZrAlxOy film remains amorphous. At 1000 C, tetragonal ZrO2 forms in the ZrAlxOy film. In addition, it is demonstrated that there is no undesirable amorphous phase separation during annealing at temperatures below and equal to 900 C in the ZrO2–Al2O3 system. 2002 Elsevier Science Ltd. All rights reserved.