Electrical and spectroscopic comparison of HfO2/Si interfaces on nitrided and un-nitrided Si(100)

Abstract

The interfacial chemistry of the high-k dielectric HfO2 has been investigated on nitrided and un-nitrided Si(100) using x-ray photoelectron spectroscopy (XPS) and secondary ion mass spectroscopy (SIMS). The samples are prepared by sputter depositing Hf metal and subsequently oxidizing it. A 600 °C densification anneal is critical to completing Hf oxidation. These spectroscopic data complement electrical testing of metal oxide semiconductor capacitors fabricated with ∼50 Å HfO2 on nitrided and un-nitrided Si(100). Capacitors with interfacial nitride show reduced leakage current by a factor of 100 at a −1 V bias. Concurrently, interfacial nitride increased capacitance 12% at saturation. XPS shows that an interfacial layer composed of nonstoichiometric hafnium silicate (HfSixOy), forms at both the HfO2/Si and HfO2/SiNx interfaces. Differences in the Si 2p and O 1s XP spectra suggest more silicate forms at the un-nitrided interface. HfO2 films on un-nitrided Si show more O 1s and Si 2p photoemission intensity characteristic of HfSixOy. SIMS depth profiles through the buried interface are consistent with interfacial silicate formation, as shown by a HfSiO+ ion signal, that is sandwiched between HfO2 and SiNx. SiNx is suggested to minimize interfacial HfSixOy formation by limiting the amount of Si available to interact with the HfO2 layer.