Annealing effect on the formation of high-k dielectric in the W/ultrathin HfO2/Si-substrate system

Using a method of high-frequency magnetron sputtering, the structures W(150 nm)/HfO2(5 nm)/Si(100) were prepared and were further annealed either at 500A degrees C in vacuum for 30 min or in an atmosphere of argon at 950A degrees C for 12 s. Study of the capacitance-voltage characteristics of these structures showed that high-temperature annealing leads to a decrease in the maximum specific capacitance in accumulation (from 4.8 x 10(-6) to 3.2 x 10(-6) F/cm(2)) and dielectric constant (from 27 to 23). Using time-of-flight secondary-ion mass spectrometry, it is established that growth of a WO (x) phase at the W/HfO2 interface and a HfSi (x) O (y) silicate phase at the HfO2/Si (100) interface occurs during annealing. In addition, the total thickness of the intermediate oxide layer exceeds the thickness of the initial HfO2 film by 30%.