Thermally grown ruthenium oxide thin films

Abstract

Thin ruthenium films were sputtered on oxidized silicon wafers and subsequently thermally oxidized in oxygen∕nitrogen or oxygen ambient in the temperature range from 400 to 700 °C. The morphological and structural properties of grown ruthenium oxide films were analyzed by atomic force microscopy, Raman spectroscopy, and x-ray diffraction, with electrical properties analyzed by van der Pauw technique and metal–oxide semiconductor (MOS) structures. Significant roughening of RuO2 was observed for prolonged oxidation in oxygen∕nitrogen atmosphere, or for short times in pure oxygen atmosphere. Raman spectroscopy revealed superior structural properties of thermally grown RuO2, in comparison to sputtered or metalorganic chemical vapor deposition RuO2 films. Thermally grown RuO2 is shown to have a work function of 5.1 eV, making it a suitable choice of metals, together with Ru (4.6 eV work function) for electrodes in complementary MOS n-channel and p-channel transistors.