Justin C. Hackley

Graphitic carbon growth on Si(111) using solid source molecular beam epitaxy

Solid source molecular beam epitaxy is used to explore the growth of carbon films directly on Si(111). It is shown that graphitic carbon is grown by the implementation of a thin amorphous carbon film that suppresses the formation of SiC precipitates. Raman scattering measurements show the D and G vibrational phonon modes, indicating graphitic ordering in the carbon film. X-ray photoelectron spectroscopy is used to verify the formation of sp2 bonds in the graphitic carbon films and confirms the suppression of SiC.

Interface of atomic layer deposited HfO2 films on GaAs (100) surfaces

HfO2 films have been deposited by using a tetrakis(dimethylamino)hafnium/H2O atomic layer deposition (ALD) process on GaAs. X-ray photoelectron spectroscopy measurements show that the HF and NH4OH predeposition surface treatment results in efficient removal of the Ga and As native oxides. No interface oxidation is detected after 15cycles of HfO2 ALD implying effective passivation of the GaAs surface. Spectroscopic ellipsometry confirms linear growth at 1.0A∕cycle on both starting surfaces, while Rutherford backscattering spectrometry indicates steady-state coverage after about 10 ALD cycles. For films grown on native oxide GaAs, complete removal of the As oxide is observed after 20 ALD cycles.

Nucleation of HfO2 atomic layer deposition films on chemical oxide and H-terminated Si

HfO2 thin films have been deposited by an atomic layer deposition (ALD) process using alternating pulses of tetrakis-ethylmethylamino hafnium and H2O precursors at 250 °C. The as-deposited films are mainly amorphous and nearly stoichiometric HfO2 (O/Hf ratio ∼1.9) with low bonded carbon content (∼3 at. %). A comparison of the nucleation stage of the films on OH- and H-terminated Si(100) surfaces has been performed using Rutherford backscattering spectrometry, x-ray photoelectron spectroscopy (XPS), and spectroscopic ellipsometry (SE). We find for the initial 5–7 process cycles that the film nucleates more efficiently on the OH-terminated surface. However, after the 7th cycle both surfaces exhibit similar surface coverage, which takes about 40 cycles to reach a steady growth rate per cycle. Angle resolved XPS measurements reveal the formation of a ∼6 A interfacial layer after four ALD cycles on the H-terminated surface and the thickness of the interfacial layer does not change substantially between the 4th...

Growth and Interface Evolution of HfO2 Films on GaAs(100) Surfaces

The initial film growth 2–100 cycles and the interface evolution of HfO2 thin films on GaAs surfaces were investigated for an atomic layer deposition chemistry that utilizes tetrakis ethylmethyl amino hafnium and H2O at 250°C. Starting surfaces include native oxide and HF or NH4OH-etched substrates. X-ray photoelectron spectroscopy shows that deposition on native oxide GaAs surfaces results in the gradual consumption of the arsenic and gallium oxides. Arsenic oxides are easier to remove, leaving some metallic arsenic–arsenic suboxide at the interface. The removal of the gallium oxides is slower, and some residual Ga2O3 and Ga2O are detected after 100 process cycles. High resolution transmission electron microscopy confirms the presence of an almost sharp interface for the 100 cycle 12 nm film and indicates that the as-deposited film is polycrystalline. The depositions on either HF or NH4OH-etched substrates result in a sharp interface with very little residual gallium oxide and arsenic suboxide present. Rutherford backscattering spectroscopy shows that steady-state growth comparable to that achieved on SiO2 is reached after 20 ALD cycles for all GaAs surfaces; however, high initial surface activity is detected for the etched surfaces.

Growth and interface of HfO2 films on H-terminated Si from a TDMAH and H2O atomic layer deposition process

HfO2 thin films have been deposited by an atomic layer deposition (ALD) process using alternating pulses of tetrakis(dimethyl)amino hafnium and H2O precursors at a substrate temperature of 200–325°C. The initial stage of film growth on OH- and H-terminated Si(100) surfaces is investigated using Rutherford backscattering spectrometry (RBS), x-ray photoelectron spectroscopy (XPS), and spectroscopic ellipsometry (SE). The authors observe an initial growth barrier on the Si–H surface for the first approximately four process cycles, where film growth is more efficient on the OH-terminated surface. Both starting surfaces require about 15cycles to reach a steady growth rate per cycle, with the OH-terminated surface displaying a slightly higher growth rate of 2.7×1014Hf∕cm2 compared to 2.4×1014Hf∕cm2 for Si–H. Combining the RBS and SE data we conclude that the films deposited on the OH-terminated surface are denser than those deposited on the Si–H surface. Angle-resolved XPS measurements reveal the formation of a...

Antimony-assisted carbonization of Si(111) with solid source molecular beam epitaxy

The carbonization of an antimony-terminated Si (111) surface in a solid source molecular beam epitaxy system is presented. Reflection high-energy electron diffraction, atomic force microscopy, x-ray photoelectron spectroscopy, and cross-sectional transmission electron microscopy are used to characterize samples grown with and without antimony termination. It is shown that the antimony-terminated surface promotes the formation of thin, smooth and continuous SiC films at a relatively low temperature of 800 °C.

Atomic Layer Deposition of HfO 2 Thin Films on Si and GaAs Substrates

The atomic layer deposition of HfO 2 thin films is studied on Si(100) and GaAs(100) surfaces. The films are grown using tetrakis(dimethylamido)hafnium (TDMAH) and H 2 O precursors at a deposition temperature of 275°C. The Si surfaces used include a H-terminated surface and an OH-rich chemical oxide. GaAs substrates are subjected to two different pre-deposition treatments involving an HF and a NH 4 OH wet chemical etch that has been shown to remove most of the Ga and As native oxides. Spectroscopic ellipsometry (SE) confirms linear growth rates of 1.05±0.05 A/cycle for all surfaces. Rutherford backscattering spectrometry (RBS) shows that steady-state growth of 2.6×10 14 Hf/cm 2 /cycle is reached after 10 ALD cycles for the HF-etched GaAs surface. X-ray photoelectron spectroscopy (XPS) indicates the presence of native oxides on both GaAs starting surfaces after 10 cycles due to postdeposition surface oxidation. However, the presence of the native oxide is not detected for thicker 15 and 20 cycle samples indicating passivation of the surface and suppression of the interfacial layer formation.

Atomic Layer Deposition of Metal Oxide Films on GaAs (100) surfaces

Atomic Layer Deposition is used to deposit HfO 2 and TiO 2 films on GaAs (100) native oxides and etched surfaces. For the deposition of HfO 2 films two different but similar ALD chemistries are used: i) tetrakis dimethyl amido hafnium (TDMAHf) and H 2 O at 275°C and ii) tetrakis ethylmethyl amido hafnium (TEMAHf) and H 2 O at 250°C. TiO 2 films are deposited from tetrakis dimethyl amido titanium (TDMATi) and H 2 O at 200°C. Rutherford Back Scattering shows linear film growth for all processes. The film/substrate interface is examined using x-ray Photoelectron Spectroscopy and confirms the presence of an “interfacial cleaning” mechanism.

Nucleation Studies of HfO 2 Thin Films Produced by Atomic Layer Deposition

A hot wall Atomic Layer Deposition (ALD) flow reactor equipped with a Quartz Crystal Microbalance (QCM) has been used for the deposition of HfO 2 thin films with tetrakis (dimethylamino) hafnium (TDMAH) and H 2 O as precursors. HfO 2 films were deposited on H-terminated Si and SC1 chemical oxide starting surfaces. Spectroscopic ellipsometry (SE) and QCM measurements confirm linear growth of the films at a substrate temperature of 275°C. FTIR spectra indicate the films are amorphous as-deposited. Two distinct growth regimes are observed: from 1-50 cycles, both surfaces display similar growth rates of about 1.0A/cycle; from 50-200 cycles, HfO 2 growth is decreased by about 15% to ~0.87A/cycle on both surfaces. Nucleation and initial growth behavior of the films on Si-H were examined using X-ray photoelectron spectroscopy (XPS). Angle-resolved XPS, at take-off angles of θ=0, 15, 30, 45 and 60° measured from the normal to the sample surface, is used to probe the interfacial region of thin films (4, 7, 10, 15 and 25 cycles) on H-terminated samples. Initially, an interfacial layer comprised of a SiO x /HfSiO x mixture is grown between 1-10 ALD cycles. We observe that the Si/HfO 2 interface is unstable, and oxidation continues up to the 25 th ALD cycle, reaching a thickness of ~18A.