Chemical states and electrical properties of a high-k metal oxide/silicon interface with oxygen-gettering titaniummetal-overlayer Appl.We present theoretical and experimental results regarding the thermodynamic stability of the high-k dielectrics ZrO 2 and HfO 2 in contact with Si and SiO 2 . The HfO 2 /Si interface is found to be stable with respect to formation of silicides whereas the ZrO 2 /Si interface is not. The metal-oxide/SiO 2 interface is marginally unstable with respect to formation of silicates. Cross-sectional transmission electron micrographs expose formation of nodules, identified as silicides, across the polycrystalline silicon/ZrO 2 /Si interfaces but not for the interfaces with HfO 2 . For both ZrO 2 and HfO 2 , the x-ray photoemission spectra illustrate formation of silicate-like compounds in the MO 2 /SiO 2 interface.

and PMOS (AQi is negligible. However, AVfb does not reach OV We report here for the first time that Fermi pinning at the because Si-Hf and Si-0-Hf bonds co-exist at the polySi interface. The polySilmetal oxide interface causes high threshold voltages in AVfb saturation value depends only on the bond number ratio. A MOSFET devices. Results indicate that pinning occurs due to the comparison of AVfb for HfOz (ALD or MOCVD) and HfSixOy interfacial Si-Hf and Si-0-AI bonds for HfO, and AIzO,, respectively. (MOCVD) films deposited with different precursors and dopant This fundamental characteristic also affects the observed polySi activation anneals produce, the universal curve in Fig. 11. The slight depletion. Device data and simulation results will be presented. variation in AVb for Hf02 can be attributed to differences in Keywords: Hf02, AI203, Fermi pinning, polYd, gate dielectric. processing conditions. Our data indicates that the shifts of Vfb(n+) INTRODUCTION and Vfb(pt) from the characteristic values for SiO, NMOS and Scaling MOSFETs to improve performance results in PMOS are a fundamental characteristic of the PolySilMeOx interface. higher gate leakage as the SiOz gate melectic becomes thinner. To These shifts are responsible for the observed high Vts. address this issue, there has been much interest in hafnium-based The impact of the sub-monolayer HfOz on the CETacc is dielectrics as a potential gate dielectric [1-3]. Two major issues shown in Figs. 12 and 13. Although the p+ gate CETacc increases evident in numerous publications [1-3] that must be addressed to with each subsequent cycle, the n+ gate has a CETacc minimum at IO fabricate useful devices for CMOS circuit applications are (1) the cycles, The n+ gate is in depletion and the minimum indicates Si-Hf high threshold voltages and (2) the large CETinv difference between bonds reduce the polySi depletion. To investigate this further, CMOS NMOS and PMOS. To date, a PolySiIMeOx CMOS process with devices were fabricated (Fig. 14). The polySi depletion for ntgate acceptable Vts for both NMOS and PMOS has not been reported. NMOS (p+ gate PMOS) is decreased (increased) when SiOz is capped Defects and charge within the gatestack (Fig. I ) can result with HfO,. This tradeoff in polySi depletion is attributed to Fermi in substantial Vt shifts. At the top interface, Fermi pinning is a pinning near (Fig. 8). Less band bending occurs for n+ polySi mechanism known to cause high Vts for metal gates [41. Considering because the polySi interface is pinned close to the bulk polySi Fermi the polySi/MeOx interface shown in Fig. 2, the question arises, 'Are level. For p+ gates, more band bending occurs because the interface is the metal atoms at the interface part of the dielectric or part of the pinned further away from the bulk. This effect occurs for low and gate electrode?' This raises the issue as to whether the interface bonds high temperame activation anneals (Fig. 15). This effect is the likely affect the Vt. In this work, we examine the role of the polySiIMeOx cause...

We report on the development of a hafnium zirconate (HfZrO4) alloy gate dielectric for advanced gate stack applications. The HfZrO4 and hafnium dioxide (HfO2) films were formed by atomic layer deposition using metal halides and heavy water as precursors. The HfZrO4 material properties were examined and compared with those of HfO2 by a wide variety of analytical methods. The dielectric properties, device performance, and reliability of HfZrO4 were investigated by fabricating HfZrO4/tantalum carbide (TaxCy) metal-oxide-semiconductor field effect transistor. The HfZrO4 dielectric film has smaller band gap, smaller and more uniform grains, less charge traps, and more uniform film quality than HfO2. The HfZrO4 dielectric films exhibited good thermal stability with silicon. Compared to HfO2, the HfZrO4 gate dielectric showed lower capacitance equivalent thickness value, higher transconductance, less charge trapping, higher drive current, lower threshold voltage (Vt), reduced capacitance-voltage (C-V) hysteresis, lower interface state density, superior wafer level thickness uniformity, and longer positive bias temperature instability lifetime. Incorporation of zirconium dioxide (ZrO2) into HfO2 enhances the dielectric constant (k) of the resulting HfZrO4 which is associated with structural phase transformation from mainly monoclinic to tetragonal. The tetragonal phase increases the k value of HfZrO4 dielectric to a large value as predicted. The improved device characteristics are attributed to less oxygen vacancy in the fine grained microstructure of HfZrO4 films.

No abstract

Oxynitride films grown on preoxidized (100) silicon surfaces in a nitric oxide (NO) ambient at 950 °C have been investigated using x-ray photoelectron spectroscopy (XPS), secondary ion mass spectrometry (SIMS), atomic force microscopy (AFM), and cross-sectional transmission electron microscopy (XTEM). Compared to N2O oxynitride, NO oxynitride exhibits very different surface chemistry, interface properties, and growth mechanisms. The etch back of NO and N2O oxynitride films allows control of sample thickness for the XPS measurements. NO oxynitride has the interfacial nitrogen (Nint) sharply peaked on the Si substrate side of the interface, while it is broad and on the dielectric side of the interface for the N2O oxynitride. The N(1s) XPS results reveal a clear distinction between N2O oxynitride and NO oxynitride. Near the Si/dielectric interface the NO oxynitride shows primarily Si≡N bonds, while the N2O films showed a N(1s) binding energy peak that is in-between that of Si≡N bonds and Si2=N—O bonds. Furthermore, the NO oxynitride surface roughness as determined by AFM is lower than that of the Si/SiO2 interface.