Chang-gong Wang

Atomic Layer Deposition of Hafnium Silicate from HfCl4, SiCl4, and H2O

Atomic layer deposition of Hf-Si-O and Hf O2 using Hf Cl4, Si Cl4, and H2 O was studied. The growth per cycle and composition of Hf-Si-O films were analyzed as a function of the growth temperature, the pulse sequence, and the precursor doses. The growth of Hf-Si-O from Hf Cl4 Si Cl4 H2 O appeared to be determined not only by the -OH density but also by the -OH bonding mode. The Hf Cl4 Si Cl4 H2 O chemistry results in carbon-free films with low chlorine impurity content. The Hf-Si-O films of Hf-rich composition are meeting the leakage-current requirements for 45 nm technology node and below.

Highly scalable ALD-deposited hafnium silicate gate stacks for low standby power applications

The electrical performance of hafnium silicate (HfSiOx) gate stacks grown by atomic layer deposition (ALD) has been evaluated in capacitors and transistors. First, scaling potential of HfSiOxlayers was studied as function of composition and thickness. It is shown that the equivalent oxide thickness scales down with decreasing layer thickness and increasing Hf-content. The gate leakage (at Vfb-1V), however, is mainly determined by the physical layer thickness. For the same equivalent oxide thickness (EOT) target, the lowest leakage is observed for the layers with the highest Hf-content. Leakage values as low as 1×10-3 A/cm 2 for an equivalent oxide thickness of 1.3 nm have been obtained, Second, the thermal stability against crystallization of the ALD HfSiO x has been studied and related to their electrical properties. The thermal stability of HfSiOx decreases with increasing Hf-content that necessitates the use of nitridation. The influence of various annealing conditions on the nitrogen incorporation is also studied, Finally, the effect of HfSiOx composition and postdeposition nitridation is discussed on transistor level. TaN metal gate transistor data indicate that nitridation reduces the gate leakage and that Hf-rich HfSiOx layers show the best scaling potential, i.e., highest performance for the lowest gate leakage.

X‐ray Photoelectron Spectroscopy of High‐κ Dielectrics

Photoelectron spectroscopy is a powerful technique for the analysis of gate dielectrics because it can determine the elemental composition, the chemical states, and the compositional depth profiles non‐destructively. The sampling depth, determined by the escape depth of the photoelectrons, is comparable to the thickness of current gate oxides. A maximum entropy algorithm was used to convert photoelectron collection angle dependence of the spectra to compositional depth profiles. A nitrided hafnium silicate film is used to demonstrate the utility of the technique. The algorithm balances deviations from a simple assumed depth profile against a calculated depth profile that best fits the angular dependence of the photoelectron spectra. A flow chart of the program is included in this paper. The development of the profile is also shown as the program is iterated. Limitations of the technique include the electron escape depths and elemental sensitivity factors used to calculate the profile. The technique is als...