Electrical and spectroscopic comparison of HfO_(2)/Si interfaces on nitrided and un-nitrided Si(100)

摘要

The interfacial chemistry of the high-k dielectric HfO_(2) 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℃ densification anneal is critical to completing Hf oxidation. These spectroscopic data complement electrical testing of metal oxide semiconductor capacitors fabricated with ～50 A HfO_(2) 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 (HfSi_(x)O_(y)), forms at both the HfO_(2)/Si and HfO_(2)/SiN_(x) interfaces. Differences in the Si 2p and O 1 s XP spectra suggest more silicate forms at the un-nitrided interface. HfO_(2) films on un-nitrided Si show more O 1 s and Si 2p photoemission intensity characteristic of HfSi_(x)O_(y). SIMS depth profiles through the buried interface are consistent with interfacial silicate formation, as shown by a HfSiO~(+) ion signal, that is sandwiched between HfO_(2) and SiN_(x). SiN_(x) is suggested to minimize interfacial HfSi_(x)O_(y) formation by limiting the amount of Si available to interact with the HfO_(2) layer.