Removal Of Native Oxide Research Articles

Effects of Chemical Treatments and Ultrathin Al2O3 Deposition on InAlN Surface Investigated by X-ray Photoelectron Spectroscopy

The effects of chemical treatments and Al2O3 deposition on the InAlN surface were investigated by X-ray photoelectron spectroscopy (XPS). Independent of the extent of native oxide removal, the In 4d core-level binding energy was the same for untreated, HCl-treated, and HF-treated InAlN. This indicated a strong pinning tendency of the Fermi level at the InAlN bare surface. However, a 300 meV decrease in the In 4d binding energy was observed after atomic layer deposition (ALD) of Al2O3, which indicated an increase in the negative surface potential at the InAlN surface. The reduction of positive charge at the InAlN surface is discussed.

Synchrotron radiation photoemission study of the thermal annealing and atomic hydrogen cleaning of native oxide covered InAs(1 0 0) surfaces

Changes induced in the surface chemical composition of native oxide covered InAs(100) by both thermal annealing and atomic hydrogen cleaning have been investigated by soft X-ray photoemission spectroscopy. Annealing up to 450°C shows a reduction in the intensity of the In and As oxides, however this anneal is not sufficient to produce an oxide and carbon free surface. Exposure to a beam of atomic hydrogen at 360°C results in the removal of both native oxides and surface carbon contamination resulting in a clean In rich surface. The chemical stability of the cleaned InAs surface to prolonged atomic hydrogen exposure times at temperatures up to 420°C has also been investigated and shown to have no effect on the surface stoichiometry.

(Invited) III-V/Oxide Interfaces Investigated with Synchrotron Radiation Photoemission Spectroscopy

We used synchrotron radiation photoemission spectroscopy (SR-PES) to investigate the surface of GaAs and other III-V semiconductors after tri-methyl-aluminum (TMA) pulses performed at 250{degree sign}C. We observed the removal of native oxide and the growth of Al-oxide upon measuring the As3d, Ga3d, Al2p and VB spectra. After seven TMA pulses we performed one water pulse. As3d and Ga3d peaks showed almost no lineshape change, but a decrease of intensity due to the water adsorption. The valence band shows a change in the secondary electron cut-off and the decrease of work function. We conclude that water mostly adsorbs molecularly and induces the work function decrease. The molecular absorption of water indicates that the seven TMA pulses produce a passivated surface only partially terminated with OH groups.

Formation of 1.7-nm-thick-EOT Germanium Dioxide Film with a High-Quality Interface Using a Direct Neutral Beam Oxidation Process

Germanium dioxide (GeO2) films with a high-quality interface were formed using a damage-free and low-temperature neutral beam oxidation (NBO) process. Combining the NBO process with hydrogen (H) radical native oxide removal treatment creates a high-quality GeO2/Ge interface (EOT = 1.7 nm) with an extremely low interface state density (Dit) of less than 1 × 1011 cm-2eV-1.

Spectroscopic-ellipsometric study of native oxide removal by liquid phase HF process

Ex situ spectroscopic ellipsometry (SE) measurements have been employed to investigate the effect of liquid-phase hydrofluoric acid (HF) cleaning on Si<100> surfaces for microelectromechanical systems application. The hydrogen terminated (H-terminated) Si surface was realized as an equivalent dielectric layer, and SE measurements are performed. The SE analyses indicate that after a 20-s 100:5 HF dip with rinse, the Si (100) surface was passivated by the hydrogen termination and remained chemically stable. Roughness of the HF-etched bare Si (100) surface was observed and analyzed by the ex-situ SE. Evidence for desorption of the H-terminated Si surface layer is studied using Fourier transform infrared spectroscopy and ellipsometry, and discussed. This piece of work explains the usage of an ex situ, non-destructive technique capable of showing state of passivation, the H-termination of Si<100> surfaces.

Native Oxide Removal from InAlN Surfaces by Hydrofluoric Acid Based Treatment

Native Oxide Removal from InAlN Surfaces by Hydrofluoric Acid Based Treatment

Investigation of SiGe/Si heterostructures using state-of-the-art Auger Nanoprobes

The capabilities of nano-Auger were assessed for the characterization of SiGe multilayers epitaxially grown on Si(001) wafers. Reference sample consisting in stack of (300–500)-nm thick SiGe layers with a Ge content increasing in discrete steps from 6 to 30 % (as determined by X-ray diffraction) were used to that end. Composition measurements were performed on cross-sections with localized Auger Electron Spectroscopy using point analysis. The promising results obtained should enable in the near future high performance Auger mapping of real devices. The effect of native oxide removal either by argon sputtering or by HF etching was also addressed. Complementary results were otherwise obtained with Auger depth profiling using argon sputtering with Zalar rotation.

Formation of Thin Germanium Dioxide Film with a High-Quality Interface Using a Direct Neutral Beam Oxidation Process

A damage-free and low-temperature neutral beam oxidation (NBO) process is used to directly form a thin germanium dioxide (GeO2) film. A GeO2 film with only a small amount of suboxide is formed even at a low substrate temperature of 300 °C because of the extremely low-activation-energy oxidation owing to bombardment with 5-eV-energy oxygen neutral beams. We combined the NBO process with hydrogen radical native oxide removal treatment to form high-quality GeO2 films, and our fabricated Al2O3/GeO2/Ge gate stack has an extremely low interface state density (Dit) of less than 1×1011 cm-2 eV-1.

Effects of acid-treated silicon nanowires on hybrid solar cells performance

We demonstrate the efficiency improvement of hybrid solar cells based on silicon nanowires (SiNWs) and organic materials. This progress is readily achieved by acid treatments of SiNWs. Tin (Sn) catalyzed SiNWs contain residual Sn and Sn oxide drops on their top which are deleterious for a solar cell performance. Removal of this Sn and Sn oxide contamination is performed with hydrochloric acid. X-ray photoelectron spectroscopy measurement verified that the amount of Sn and Sn oxide on SiNWs array is decreased according to the immersing time. This brings open-circuit voltage and shunt resistance increase thus the hybrid solar cell performance is improved. Light intensity dependent open-circuit voltage clearly reveals that this efficiency improvement results from a reduced trap-assisted recombination through Sn and Sn oxide. In addition to the residual catalysts removal, native oxide removal by hydrofluoric acid also considerably contributes to further improvement in terms of short-circuit current and fill factor. Clearly, the improvement of SiNWs quality is essential for an optimization of hybrid solar cell performance.

Very Low Leakage Current of High Band-Gap Al2O3 Stacked on TiO2/InP Metal–Oxide–Semiconductor Capacitor with Sulfur and Hydrogen Treatments

High dielectric TiO2 film on InP treated by (NH4)2S shows improved electrical characteristics due to the removal of native oxides. Post-metallization annealing (PMA) can provide hydrogen ions, which effectively passivate defects in TiO2/InP film and interface, further improve electrical characteristics but still with high thermionic emission leakage due to low band-gap TiO2. For high band-gap Al2O3 stacked on PMA-TiO2/S–InP MOS structure with equivalent oxide thickness of 1.8 nm, the leakage current densities can be decreased as low as 1.5×10-8 and 2.2×10-7 A/cm2 at ±2 V, and the interface state density is 3.1×1011 cm-2 eV-1.

High-quality germanium dioxide thin films with low interface state density using a direct neutral beam oxidation process

High-quality germanium dioxide (GeO2) as a gate oxide is in high demand for use in future high mobility Ge-channel field-effect transistors. GeO2 thin films were directly formed by using a damage-free and low-temperature process of neutral beam oxidation (NBO) after treatment with hydrogen (H) radicals. GeO2 thin films (equivalent oxide thickness (EOT) = 1.7 nm) with a high-quality interface and an extremely low interface state density (&amp;lt;1 × 1011 cm−2 eV−1) could be formed even at low temperature (300 °C) by combining the H radical treatment, which resulted in the removal of native oxides, with the NBO process we developed.

Interface Between Atomic Layer Deposition Ta2O5 Films and GaAs(100) Surfaces

Ta2O5 films were deposited on GaAs(100) surfaces using thermal atomic layer deposition from pentakis dimethyl amino tantalum (PDMAT) and H2O. The interface between the films and native oxide covered GaAs surfaces has been examined using X-ray photoelectron spectroscopy as a function of film thickness and for deposition temperatures ranging from 200 to 350 °C. Gradual removal of the surface arsenic and gallium oxides was observed, with the removal of the arsenic oxides in general more efficient. The high oxidation states of both the arsenic and the gallium oxides were also found easier to remove. Elevation of the process temperature above 300 °C resulted in significant enhancement of the native oxide removal rate. When films were deposited on GaAs surfaces that had the surface oxides removed, a practically sharp interface between the film and the GaAs substrate was maintained.

HF Last Passivation for High Efficiency a-Si/c-Si Heterojunction Solar Cells

Amorphous/crystalline silicon heterojunction solar cells are commonly made by low temperature deposition of front and back side thin films on bare H-passivated Si wafers, obtained by HF last processes. This work discusses the impact of HF last step parameters on cell performance, considering textured and cleaned Si (100) wafers. A complete native oxide removal is mandatory and achieved in a short time (&lt; 5 min) by HF concentration higher than 1% (by weight). Above 1%, surface passivation and cells performance slightly increases with the concentration. The best process time is found to be the minimum time to deoxidize textured wafers, as seen by a good dewetting. For [H &gt; 2% this is less than 1 min. Longer process times slightly degrade surface passivation. Post rinse and drying, provided they do not reoxydize the surface, were seen to have no impact. The delay between the HF last and deposition steps is critical and depends on the efficiency of the cleaning before the HF last. With a high performance cleaning, leading to a very good surface passivation (&lt; 10 cm/s surface recombination velocity), 30 min delay has no impact and 90 min leads to about 5% relative degradation of cell performance. Regarding the HF cleanliness, HCl spiking is an efficient way to enhance robustness of surface passivation keeping &lt; 10 cm/s values when the metallic contamination, including Cu, is in the sub 50 ppb range.

Low‐Cost Post‐Growth Treatments of Crystalline Silicon Nanoparticles Improving Surface and Electronic Properties

AbstractFreestanding silicon nanocrystals (Si‐ncs) offer unique optical and electronic properties for new photovoltaic, thermoelectric, and other electronic devices. A method to fabricate Si‐ncs which is scalable to industrial usage has been developed in recent years. However, barriers to the widespread utilization of these nanocrystals are the presence of charge‐trapping defects and an oxide shell formed upon ambient atmosphere exposure hindering the charge transport. Here, we exploit low‐cost post‐growth treatment routes based on wet‐etching in hydrofluoric acid plus surface hydrosilylation or annealing enabling a complete native oxide removal and a reduction of the defect density by up to two orders of magnitude. Moreover, when compared with only H‐terminated Si‐ncs we report an enhancement of the conductivity by up to a factor of 400 for films of HF etched and annealed Si‐ncs, which retain a defect density below that of untreated Si‐ncs even after several months of air exposure. Further, we demonstrate that HF etched and hydrosilylated Si‐ncs are extremely stable against oxidation and maintain a very low defect density after a long‐term storage in air, opening the possibility of device processing in ambient atmosphere.

Processing and Characterization of GaSb/High-k Dielectric Interfaces

To obtain the suitable GaSb surface for high-k dielectric integration, the chemical and structural analysis were performed by x-ray photoelectron spectroscopy (XPS) and atomic force microscopy (AFM). The chemical analysis indicates the effective native oxide removal from GaSb surface and the resulting surface is slightly antimony rich. The structural study reveals that the surface morphology becomes rough upon the reexposure to air after the HCl-based surface treatment. GaSb metal-oxide semiconductor capacitors (MOSCAPs) with 5 nm Al2O3 by atomic layer deposition (ALD) were fabricated and electrically characterized before and after forming gas anneal (FGA).

Quality Improvements of Titanium Oxide/Gallium Arsenide MOS Capacitors by Post-Metallization Annealing and Sulfur-Treatment

The characteristics of post-metallization annealed TiO2 with various thicknesses on (NH4)2S-treated GaAs were investigated. The electrical characteristics of TiO2 films grown on (NH4)2S-treated GaAs were improved due to the removal of native oxide. The post-metallization annealing treatment can further passivate the grain boundary of TiO2 film and interface of TiO2/GaAs. With both treatments, the leakage current densities of thick TiO2 (77nm)/GaAs are 1.4 × 10-7 and 2.3 × 10-5 A/cm2 at ± 1.5 MV/cm, and that of thin TiO2 (7.5 nm) are 1.7 × 10-6 and 4.5 × 10-5 A/cm2 at ± 2 V (2.7 MV/cm). The dielectric constant and equivalent oxide thickness can reach 52 and 0.53 nm, respectively. The lowest interface state density is 3.8 × 1012 cm-2eV-1 by the high-low frequency capacitance method.

Characterization of Fluorinated-SiO2/PMA-Treated TiO2/(NH4)2S-Treated GaAs MOS Structure

The electrical characteristics of metalorganic chemical vapor deposited TiO2 films on p-type GaAs were studied. For GaAs with (NH4)2S treatment, the electrical characteristics of TiO2/GaAs are improved from native oxide removal. The electrical characteristics can be further improved by hydrogen passivation on defects, grain boundary and interface of TiO2/GaAs via post-metallization annealing, in which the active hydrogen is produced from the reaction between aluminum (Al) contact and hydroxyl groups existed on oxide surface. The stack of liquid phase deposited high band-gap SiO2 on TiO2 film can lower the thermionic emission leakage of low band-gap TiO2 and improve the quality of stacked structure by fluorination. The leakage current densities of fluorinated-SiO2/PMA-treated TiO2/(NH4)2S-treated GaAs MOS structure can reach 5.4 × 10−9 and 4.9 × 10−7 A/cm2 at ±1.5 MV/cm. The dielectric constant and the lowest interface state density are 39.7 and 4.8 × 1011 cm−2eV−1, respectively.

Effect of HF & H 2SO 4 pretreatment on interfacial adhesion energy of Cu–Cu direct bonds

Effects of HF & H 2SO 4 pretreatment conditions on the interfacial bonding strength of Cu–Cu direct bonds were systematically investigated. The evaluated interfacial adhesion energies for 3 μm-thick Cu bonding layers were 0.58, 0.46, and 4.90 J/m 2 for different HF & H 2SO 4 pretreatment times of 0, 15, and 30 s, respectively, with bonding temperature of 350 °C, which is ascribed to the effective removal of native surface oxide at optimum wet cleaning conditions before Cu–Cu bonding.

Reduction of oxygen impurity at GaN/β-Si 3N 4/Si interface via SiO 2 to Ga 2O conversion by exposing of Si surface under Ga flux

The removal of native oxide from Si (1 1 1) surfaces was investigated by X-ray photoelectron spectroscopy (XPS) and secondary ion mass spectra (SIMS) depth profiles. Two different oxide removal methods, performed under ultrahigh-vacuum (UHV) conditions, were carried out and compared. The first cleaning method is thermal desorption of oxide at 900 °C. The second method is the deposition of metallic gallium followed by redesorption. A significant decrease in oxygen was achieved by thermal desorption at 900 °C under UHV conditions. By applying a subsequent Ga deposition/redesorption, a further reduction in oxygen could be achieved. We examine the merits of an alternative oxide desorption method via conversion of the stable SiO 2 surface oxide into a volatile Ga 2O oxide by a supply of Ga metals. Furthermore, ultra thin films of pure silicon nitride buffer layer were grown on a Si (1 1 1) surface by exposing the surface to radio-frequency (RF) nitrogen plasma followed by GaN growth. The SIMS depth profile shows that the oxygen impurity can be reduced at GaN/β-Si 3N 4/Si interfaces by applying a subsequent Ga deposition/redesorption.

Controlled Oxide Removal and Surface Morphology on InSb(100) Using Gas Phase HF/H2O

The native oxide removal, surface termination, composition, and morphology of InSb(100) surfaces etched in gas phase HF/H2O mixtures at a total pressure of 100 Torr and 29 °C were investigated usin...