Effect of Fe impurity on performance of La2O3 as a high k gate dielectric

Abstract Lanthanum oxide (La2O3) is the most competitive alternative to gate dielectric HfO2 with its outstanding performance, such as high dielectric constant, suitable band gap and excellent stability on Si substrate. In this work, a series of Fe-doped La2O3 (LFO) films were prepared by reactive co-sputtering. The effects of Fe impurity on La2O3 as a gate dielectric were systematically investigated by surface roughness, band gap and dielectric electrical properties. Our results show that with the Fe contents increasing from 0 to 12.29%, the surface roughness of LFO films increases from 0.166 to 1.094 nm. In addition, the corresponding band gaps of LFO films decrease from 5.64 to 4.67 eV. When it comes to electrical properties, the presence of metallic Fe also destroys dielectric performance of La2O3, such as decreasing dielectric constant and increasing leakage current density. Hence, there is no doubt that metal Fe is an extremely harmful impurity for La2O3 as a gate dielectric, even if it is present in a trace amount (∼0.94%). Therefore, the content of Fe impurity in La or La2O3 should be reduced as low as possible for integrated circuits using. Finally, some methods for removing Fe impurity in La are given, which are useful for reference.