Ryan M. Martin

Plasma enhanced atomic layer deposition of HfO2 and ZrO2 high-k thin films

A plasma enhanced atomic layer deposition (PEALD) process was developed to deposit high-k dielectric constant materials using alternative metal t-butoxide and oxygen plasma exposures. The deposited thickness increased linearly with an increasing number of precursor/oxygen plasma cycles, and the growth rates of HfO2 and ZrO2 were determined to be 1.1 and 2.8A∕cycle, respectively. The as-deposited films were determined to be fully oxidized and amorphous by the x-ray photoelectron spectroscopy (XPS) and Fourier transformed infrared spectroscopy (FTIR). The PEALD films were found to have high concentrations of bridging oxygen bonds with metals (M–O–M) as the film thickness increased, in contrast to the high concentrations of M–O–H in the films deposited by plasma enhanced chemical vapor deposition (PECVD). The M–O–M bonds in the PEALD films were further increased upon annealing at 250 °C in atmosphere with a corresponding decrease in M–O–H concentrations, suggesting the elimination of hydroxyl groups upon annealing. The PEALD HfO2 and ZrO2 films showed higher dielectric constants (25, 22) than those of PECVD deposited films (21, 19), likely due to the enhanced ionic contribution from the M–O–M bonds in the PEALD films. The smallest equivalent oxide thickness (EOT) of 13 A was achieved by PEALD HfO2 with a leakage current density of 0.2A∕cm2, several orders of magnitude below that of thermally grown SiO2 films with the same EOT.A plasma enhanced atomic layer deposition (PEALD) process was developed to deposit high-k dielectric constant materials using alternative metal t-butoxide and oxygen plasma exposures. The deposited thickness increased linearly with an increasing number of precursor/oxygen plasma cycles, and the growth rates of HfO2 and ZrO2 were determined to be 1.1 and 2.8A∕cycle, respectively. The as-deposited films were determined to be fully oxidized and amorphous by the x-ray photoelectron spectroscopy (XPS) and Fourier transformed infrared spectroscopy (FTIR). The PEALD films were found to have high concentrations of bridging oxygen bonds with metals (M–O–M) as the film thickness increased, in contrast to the high concentrations of M–O–H in the films deposited by plasma enhanced chemical vapor deposition (PECVD). The M–O–M bonds in the PEALD films were further increased upon annealing at 250 °C in atmosphere with a corresponding decrease in M–O–H concentrations, suggesting the elimination of hydroxyl groups upon ann...

Plasma etching of Hf-based high-k thin films. Part II. Ion-enhanced surface reaction mechanisms

The mechanism for ion-enhanced chemical etching of hafnium aluminate thin films in Cl2/BCl3 plasmas was investigated in this work, specifically how the film composition, ion energy, and plasma chemistry determine their etch rates. Several compositions of Hf1−xAlxOy thin films ranging from pure HfO2 to pure Al2O3 were etched in BCl3/Cl2 plasmas and their etch rates were found to scale with Eion in both Cl2 and BCl3 plasmas. In Cl2 plasmas, a transition point was observed around 50 eV, where the etch rate was significantly enhanced while the linear dependence to Eion was maintained, corresponding to a change in the removal of fully chlorinated to less chlorinated reaction products. In BCl3 plasma, deposition dominates at ion energies below 50 eV, while etching occurs above that energy with an etch rate of three to seven times that in Cl2. The faster etch rate in BCl3 was attributed to a change in the dominant ion from Cl2+ in Cl2 plasma to BCl2+ in BCl3, which facilitated the formation of more volatile etch...

Bilateral variation of subclavius muscle resembling subclavius posticus.

During routine anatomical dissection, a bilateral variation of the muscle subclavius was discovered with additional morphological features consistent with the muscle subclavius posticus. Attached medially to the first rib by tendon and to the clavicle by fibrous bands, the long triangular shaped muscle ran dorsal-laterally to attach onto the transverse scapular ligament and the coracoid process. The scapular insertion of the omohyoid muscle was just medial to this muscle, with some intermingling of fibers close to their insertions. In addition, the muscle on the left was split into two heads before inserting onto the scapula. Innervation was supplied by the nerve to the subclavius. We believe this muscle to be a hybrid of subclavius and subclavius posticus muscles, and we discuss the developmental origin of this rare subclavius variant, as well as the potential role this muscle may play in the development of thoracic outlet syndrome.

Characteristics of Hf-silicate thin films synthesized by plasma enhanced atomic layer deposition

Hafnium silicate films were grown by alternating the deposition cycles of hafnium oxide and silicon oxide using a plasma enhanced atomic layer deposition process. The as-deposited and 900 °C annealed hafnium silicate films were determined to be amorphous using grazing incidence x-ray diffraction. This suggested that the formation of hafnium silicate suppressed the crystallization of HfO2 at high temperatures. The dielectric constants increased from ∼5 to ∼17 as the hafnium content increased from 9 to 17 at. % in the hafnium silicate films. The leakage currents through the Hf-rich Hf-silicate films were two to three orders of magnitude lower than that of SiO2 with the same equivalent oxide thickness in the range of 1.6–2.3 nm. The estimated band gap of Hf-silicate films from the O 1s plasma loss spectra increased with the increasing Si content due to the higher band gap of SiO2 than that of HfO2.

Plasma etching of Hf-based high-k thin films. Part I. Effect of complex ions and radicals on the surface reactions

The effect of ion and radical compositions in BCl3/Cl2 plasmas was assessed in this work with a focus on the formation of etch products in patterning hafnium aluminate, a potential high-k gate oxide material. The plasma composition became increasingly more complex as the percentage of boron trichloride was increased, which led to the formation of a significant amount of boron-containing species including B+, BCl+, BCl2+, BCl3+, B2Cl3+, and B2OCl3+ in the plasma. The BCl2+ ions were found to be the dominant species in BCl3 containing plasmas at most conditions; however, increasing the pressure or decreasing the power led to an increase in the formation of higher mass ions. Several compositions of Hf1−xAlxOy thin films ranging from pure HfO2 to pure Al2O3 were etched in BCl3/Cl2 plasmas as functions of ion energy and plasma composition. The etch product distributions were measured and the dominant metal-containing etch products were HfClx and AlClx in a Cl2 plasma and HfClx, HfBOCl4, and AlxCly in a BCl3 pl...

Plasma etching of Hf-based high-k thin films. Part III. Modeling the reaction mechanisms

A generalized etch rate model was formulated to describe metal oxide etching in complex plasma chemistries, based on the understanding gained from detailed plasma characterization and experimental investigation into the metal oxide etching mechanisms. Using a surface site balance-based approach, the correct etch rate dependencies on neutral-to-ion flux ratio, ion energy, competing deposition and etching reaction pathways, and film properties were successfully incorporated into the model. The applicability of the model was assessed by fitting to experimental etch rate data in both Cl2 and BCl3 chemistries. Plasma gas phase analysis as well as etch and deposition rate measurements were used to calculate initial values and appropriate ranges for model parameter variation. Physically meaningful parameter values were extracted from the modeling fitting to the experimental data, thereby demonstrating the applicability of this model in assessing the plasma etching of other complex materials systems.

Feature profile evolution during shallow trench isolation etching in chlorine-based plasmas. III. The effect of oxygen addition

The effect of oxygen addition to chlorine plasma during shallow trench isolation etching is quantified in this work. Specifically, the electron density and the electron temperature in an electron cyclotron resonance reactor were characterized by a Langmuir probe and were found to remain relatively constant upon O2 addition. The silicon etching rates were found to increase with the square root of the ion energy, suggesting the etching reaction is limited by the momentum transfer from ions to the surface. A relatively small amount of oxygen addition (<10%) to the chlorine plasma simultaneously changes the reactor wall conditions and surface kinetics, since oxygen becomes actively involved in the surface reactions. The change in the chamber wall conditions and surface kinetics leads to the change in both the amount of etch products and the etched feature profile. The incorporation of oxygen on the surface results in a significant change of the etched surface morphology and its composition. This work suggests...