Genji Nakamura

Effective Schottky Barrier Height modulation using dielectric dipoles for source/drain specific contact resistivity improvement

We demonstrate statistically significant data for specific contact resistivity (ρ_c) of sub-10^-8Ω-cm² and sub-2×10^-8Ω-cm² for N-type and P-type Si respectively on 300mm wafer by introducing ultra-thin ALD high-k dielectric layer(s) between the metal and Si. A 6-terminal Cross-Bridge Kelvin (6T-CBK) structure was used for the extraction to achieve excellent resolution in this small ρ_c range. With the help of measurements from multiple dielectric stacks and Non-Equilibrium Greens Function (NEGF) based quantum transport calculations, we clearly show that the suppression of evanescent metal induced gap states (MIGS) and formation of interface dipole play significant role to reduce the ρ_c as long as the tunneling resistance of the dielectric stack is small. Finally, transient response, break down mechanism and technology benchmarking are discussed which show promise for sub-14nm node applications.

Physical and Electrical Effects of the Dep-Anneal-Dep-Anneal (DADA) Process for HfO2 in High K/Metal Gate Stacks

The use of anneals between interspersed during hafnium oxide deposition to optimize electrical properties of the resulting films has recently been reported (1-4). In particular, Professor Toriumi’s group has reported anneals after every cycle (layer-by-layer deposition and anneal) to optimize ALD hafnium oxide films. We have extended this approach by performing multiple deposition cycles before each anneal to produce optimized hafnium oxide films in a process that is demonstrable and manufacturable on 300 mm wafers for advanced high K/metal gate stacks. The proposed mechanism for film growth on an SiO2 interlayer is illustrated in Figure 1. The electrical improvements observed in highly scaled gate first devices using this process have recently been reported (5,6).

Evaluation of high thermal stability cyclopentadienyl Hf precursors with H2O as a co-reactant for advanced gate logic applications

For the purpose of extending the upper temperature limit of metallorganic atomic layer deposition, mixed ligand precursors containing cyclopentadienyl (Cp, C5H5) ligands have been shown to exhibitsuperior thermal stability compared to the widely adopted tetrakis(ethylmethylamino)hafnium (TEMAH) precursor while also possessing adequate vapor pressure characteristics for use in atomic layer deposition (ALD) processing. In order to prevent the deleterious oxidation of the underlying Si from O3 the use of a milder oxidant such as H2O is preferred. Accordingly in this study, we investigated ALD using the liquid precursors CpHf(NMe2)3 and (CpMe)2Hf(OMe)Me in the temperature range 305 – 410 °C with H2O as a co-reactant and compared the film growth and electrical properties with films deposited using a conventional TEMAH/H2O process at 305 °C as well as the same process with an optimized annealing scheme. The CpHf(NMe2)3/H2O process was observed toexhibit a growth-per-cycle (GPC) in the range 0.23 – 0.36 A/cycle ...

HfxZr1−xO2 compositional control using co-injection atomic layer deposition

As a replacement for SiO2 based gate dielectrics, HfO2 with an admixture of ZrO2 has the potential to provide a higher dielectric constant than pure HfO2 by means of stabilization of higher-k phases. Accordingly, in this study the authors have pursued a means to control composition of HfxZr1−xO2 films grown by atomic layer deposition by simultaneously flowing Hf and Zr metal precursors during the precursor exposure step and varying the molar flow ratio. Using the tetrakis(ethylmethylamino) Hf and Zr precursors, TEMAH and TEMAZ, with either H2O or O3 co-reactants, the co-injection approach for HfxZr1−xO2 was compared with alternating HfO2 and ZrO2 growth cycles and was observed to allow uniform and tunable composition control. For the co-injection process, deviation from the cycle ratio trendline suggests more efficient chemisorption of TEMAZ compared to TEMAH. The authors have also evaluated these films in metal–oxide–semiconductor capacitor structures and verified the electrical equivalence and similar w...

Physical and Electrical Properties of MOCVD Grown HfZrO4 High-k Thin Films Deposited in a Production-Worthy 300 mm Deposition System

The continued scaling of MOSFET devices necessitates the scaling of the gate dielectric in terms of equivalent oxide thickness (EOT) and associated k-value. As a replacement for SiO2 based gate dielectrics, which have reached their fundamental scaling limit, Hf-based dielectrics including HfO2, Hf silicate and nitrided Hf silicate have been chosen as viable materials.[1] Though the HfO2-based materials have generally been preferred, recent studies have shown that HfO2 with an admixture of ZrO2, which are both fully miscible, has the potential to provide a higher dielectric constant by means of stabilization of higher-k phases.[2,3] Moreover, the mixed oxide HfxZr1-xO2 has been shown to exhibit improved device performance and reliability compared to HfO2.[4] For the deposition of ultra-thin high-k gate dielectric films on planar structures, chemical vapor deposition may offer advantages in terms of wafer throughput, manufacturability, cost of ownership, and process flexibility compared to the alternately pursued atomic layer deposition based approaches. In this study we investigated the process characteristics and film properties of HfZrO4 (HfO2:ZrO2=1) thin films deposited using metallorganic chemical vapor deposition on a 300 mm production-worthy deposition chamber. The mixed oxide films were deposited using a mixture of Hf-t-butoxide and Zr-t-butoxide (1:1 molar ratio) at a wafer temperature of either 380°C or 480°C using O2 as a co-reactant. The Si wafers had a thin (~8A) layer of chemically grown SiO2. The physical properties of the films were analyzed using various characterization techniques including spectroscopic ellipsometry, corona-oxide-semiconductor (Quantox) leakage measurements, XRR, angle-resolved XPS, RBS, ICP-AES, and TEM. MOS capacitor structures featuring HfZrO4 dielectric were fabricated and tested using C-V and I-V measurements. Key electrical parameters (EOT, leakage current density, VFB) were compared with structures featuring HfO2 deposited using the same deposition system and process conditions used for the HfZrO4 process. The HfZrO4 growth rate (Fig.1) was observed to be the same for both deposition temperatures, thus indicating a mass transport limited growth rate regime. Density was observed to increase with deposition temperature in line with reported values for ALD-deposited HfZrO4 from metal chloride sources.[3] The increase in film density (and possibly decrease in film impurities) is also corroborated by improved Quantox measured leakage (Fig.2) as well as increase in metal coverage rates (Fig.3). Improvements in Jg vs EOT trends were observed when comparing HfZrO4 with HfO2 in MOS capacitor structures. Additionally, no measurable difference in CV hysteresis was observed for HfZrO4 compared to HfO2. In our deposition system an excellent wafer-to-wafer repeatability (0.86%) was observed for a mean thickness of 19 A over a 50 wafer run. These results indicate that MOCVD HfZrO4 is a promising material for advanced high-k applications. Figure 1. XRR measured thickness values and densities for HfZrO4 films deposited at 380°C and 480°C and associated growth rates determined from linear fits.