Thermal stability and electrical properties of (La2O3)1-x(Al2O3)x composite films

(La2O3)(1-x)(Al2O3)(x) composite films (La2O3:Al2O3 = 100:0, 80:20, 67:33, 50:50) were synthesized using pulsed laser deposition. We investigated their thermal stability and electrical properties as high dielectric constant gate dielectric films. La2O3 (an Al2O3 content of 0%) films were uniformly crystallized as La-silicate after rapid thermal annealing (RTA) at 1000 degrees C for 15 s in an N-2 ambient. We found that the addition of Al2O3 suppresses crystallization, and amorphous structures are retained in the samples with an Al2O3 content of 33% or greater. Furthermore, Al2O3 addition suppresses diffusion of Si into upper composite films during RTA. The smallest capacitance equivalent oxide thickness of 1.2 nm was achieved for a sample with an Al2O3 content of 20% and with leakage current density of 3.9 x 10(-3) A/cm(2) at + 1 V relative to the flat band voltage.