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

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 degreesC densification anneal is critical to completing Hf oxidation. These spectroscopic data complement electrical testing of metal oxide semiconductor capacitors fabricated with similar to50 A 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. (C) 2002 American Institute of Physics.