Remote Plasma Atomic Layer Deposition Research Articles

Plasma power effect on crystallinity and density of AlN films deposited by plasma enhanced atomic layer deposition

Aluminum nitride (AlN) film is a promising material which is used in various fields. In this study, AlN films with different plasma powers were grown by remote plasma atomic layer deposition. Saturation experiments have been applied in the plasma power between 1000 and 3000 W. The influence of plasma power on preferential orientation, chemical, optical, and electrical properties of AlN films are investigated. AlN films displayed multiphase hexagonal wurtzite crystal structure with (002) preferential orientation for higher plasma power, while the predominant orientation shifted toward (100) at lower plasma power. The optical emission spectroscopy analyses show that NH and NH2 radicals conduce to the deposition of AlN films and H radicals selectively dissociate Al–OH bonds which were on AlN film surface and etch deposition films. Atomic force microscopy measurements show that the 1500 W prepared AlN film with smallest surface roughness may be related to the relatively smaller concomitant crystal grains of (100) and (002). X-ray photoelectron spectroscopy investigation presents that oxygen content decreases as the plasma power increases. The obtained maximum value of dielectric constant and breakdown electrical field of AlN film deposited at 3000 W is 8.23 and 5.42 MV/cm, respectively.

Effect on passivation mechanism and properties of HfO2/crystalline-Si interface under different annealing atmosphere

Hafnium oxide (HfO2) thin film has received tremendous research interests as a passivation layer of crystalline silicon (c-Si) due to its thermal stability and positive fixed charges. HfO2 films were prepared both on P-type and N-type polished c-Si via a remote plasma atomic layer deposition process. Post annealing was carried out in oxygen, atmosphere (Air) and nitrogen (N2) at temperature of 500 °C. Electrical characterization was done through a regular metal-insulator-semiconductor structure and capacitance-voltage measurements. The oxide fixed charge (Qf) and density of interface traps (Dit) between HfO2 and c-Si were extracted. Qf and Dit reveal the potential of HfO2 for field effect and chemical passivation, respectively. Effective lifetime measurements by microwave photoconductivity decay in Si wafers passivated with HfO2 were applied to characterize surface recombination velocity to directly evaluate the overall passivation quality. The impacts of post-annealing gas ambient on passivation qualities on Si by HfO2 thin films are systematically studied. The results show that N2-annealed sample possesses the highest Qf of 1.73 × 1012 cm−2 and therefore provides the best field effect passivation. Air-annealed sample has lowest Dit of 1.0 × 1012 eV−1cm−2 and therefore provides the best chemical passivation. Air-annealed sample possesses the highest effective lifetime of 290 μs at injection level of 1 × 1015 cm−3, which means that good passivation was obtained for N-type Si wafer passivated with HfO2 after annealing in Air.

Preparation of Remote Plasma Atomic Layer-Deposited HfO2 Thin Films with High Charge Trapping Densities and Their Application in Nonvolatile Memory Devices.

Optimization of equipment structure and process conditions is essential to obtain thin films with the required properties, such as film thickness, trapped charge density, leakage current, and memory characteristics, that ensure reliability of the corresponding device. In this study, we fabricated metal-insulator-semiconductor (MIS) structure capacitors using HfO2 thin films separately deposited by remote plasma (RP) atomic layer deposition (ALD) and direct-plasma (DP) ALD and determined the optimal process temperature by measuring the leakage current and breakdown strength as functions of process temperature. Additionally, we analyzed the effects of the plasma application method on the charge trapping properties of HfO2 thin films and properties of the interface between Si and HfO2. Subsequently, we synthesized charge-trapping memory (CTM) devices utilizing the deposited thin films as charge-trapping layers (CTLs) and evaluated their memory properties. The results indicated excellent memory window characteristics of the RP-HfO2 MIS capacitors compared to those of the DP-HfO2 MIS capacitors. Moreover, the memory characteristics of the RP-HfO2 CTM devices were outstanding as compared to those of the DP-HfO2 CTM devices. In conclusion, the methodology proposed herein can be useful for future implementations of multiple levels of charge-storage nonvolatile memories or synaptic devices that require many states.

Characteristics of Hf0.5Zr0.5O2 Thin Films Prepared by Direct and Remote Plasma Atomic Layer Deposition for Application to Ferroelectric Memory

Hf0.5Zr0.5O2 (HZO) thin film exhibits ferroelectric properties and is presumed to be suitable for use in next-generation memory devices because of its compatibility with the complementary metal-oxide-semiconductor (CMOS) process. This study examined the physical and electrical properties of HZO thin films deposited by two plasma-enhanced atomic layer deposition (PEALD) methods- direct plasma atomic layer deposition (DPALD) and remote plasma atomic layer deposition (RPALD)-and the effects of plasma application on the properties of HZO thin films. The initial conditions for HZO thin film deposition, depending on the RPALD deposition temperature, were established based on previous research on HZO thin films deposited by the DPALD method. The results show that as the measurement temperature increases, the electric properties of DPALD HZO quickly deteriorate; however, the RPALD HZO thin film exhibited excellent fatigue endurance at a measurement temperature of 60 °C or less. HZO thin films deposited by the DPALD and RPALD methods exhibited relatively good remanent polarization and fatigue endurance, respectively. These results confirm the applicability of the HZO thin films deposited by the RPALD method as ferroelectric memory devices.

Effect of substrate temperature on properties of AlN buffer layer grown by remote plasma ALD

Aluminum nitride (AlN) thin film has considerable properties, which makes it advantages for a variety of applications. AlN films were prepared by remote plasma atomic layer deposition (RP-ALD) with the growth temperature of 100 to 450 °C. The properties of AlN films with various growth temperatures were studied systematically. In addition, AlN/GaN layers deposited on sapphire (Al2O3) substrates were also investigated. The AlN/GaN interfaces and AlN/Al2O3 interfaces characteristics were analyzed. The optical property of GaN films prepared on sapphire substrates with and without AlN buffer layer were identified by photoluminescence measurement. The experiment result shows that crystal AlN films became to present at 250 °C with a hexagonal wurtzite structure. X-ray photoelectron spectroscopy investigation shows that AlN films contain Al-O, Al-O-N complexes and Al-Al metallic aluminum bonds except the main Al-N bond confirmed by high resolution Al 2p and N 1 s spectra. High-resolution transmission electron microscopy measurement reveals sharp interfaces of AlN/Al2O3 and AlN/GaN. The obtained lowest lattice mismatch of AlN/Al2O3 and AlN/GaN are 11.0% and 2.1%, respectively. Photoluminescence measurement further confirms that AlN buffer layer enhances the quality of GaN grown on sapphire substrates. High quality AlN/GaN layers prepared by RP-ALD provides a promising pathway towards high quality GaN-based devices.

ALD and PEALD deposition of HfO2 and its effects on the nature of oxygen vacancies

The high-k materials are essential in thin-film transistors. A well-controlled thin film deposition that produces less electronic defects induced by charged vacancies is highly desirable for avoiding high leakage current and and providing an exceptional dielectric strength. This work addresses the use of atomic layer deposition (ALD), plasma-enhanced ALD (PEALD), and its variants to produce low-defective HfO2. The X-ray photoelectron spectroscopy (XPS) and Capacitance-Voltage (C-V) analysis revealed that the thermal ALD (TALD) samples produce electron emissions of ∼ 1 eV above the valence band maximum, negative flat band voltage shift of 1.51 V, and low dielectric breakdown strength (4.37 MV/cm). These properties confirm the high density of positive oxygen vacancies (1.2 × 1013 cm−2) acting as shallow traps, despite its O/Hf ratio (1.84) being higher than the Direct Plasma ALD (DPALD) sample. On the other hand, PEALD induces the formation of neutral vacancies promoted by the electric field of the plasma sheath. These defects are less detrimental to the capacitor performance as their flat band shifts are −0.25 and 1.01 V for remote plasma ALD (RPALD) and DPALD samples. Their dielectric breakdown strength increases by ∼ 1 MV/cm, and a reduced current density by 3 orders of magnitude less than TALD samples. The O/Hf ratio in DPALD samples is 1.80, confirming the benefits of using PEALD approaches.

Growth and characterization of Si-doped Ga2O3 thin films by remote plasma atomic layer deposition: Toward UVC-LED application

Si-doped Ga2O3 films were prepared on quartz and silicon substrates using remote plasma atomic layer deposition with trimethylgallium, Bis(diethylamino)silane and O2 plasma as the precursors. Different Si-doped concentration in films were obtained by adjusting the numbers of SiO2 circulation ratio. The effect of Si-doped concentration from 0 to 20% on the qualities of the Ga2O3 thin films were studied. The experimental results showed that Ga2O3 thin film growth per cycle increases slightly with the various cycle ratio at the same total cycles of about 600. Field emission scanning electron microscopy shows that the Ga2O3 films have very smooth surface. The spectroscopic ellipsometry tests showed that the refractive index of the Si-doped Ga2O3 thin films decreases monotonically with the doping level increases. The transmittances of all the doped Ga2O3 films are exceed 90% in the visible region. The (400) preferred orientation Ga2O3 thin films were obtained after annealing at 900 °C in N2 atmosphere. Moreover, the x-ray photoelectron spectroscopy investigation indicates that the doped Ga2O3 thin films is Ga-rich with the states of Ga3+ and Ga1+. High resolution transmission electron microscopy mapping measurement shows that the Si composition in the Ga2O3 thin films is uniform. Hall effect measurements demonstrated that the carrier concentration and mobility of the doped Ga2O3 films increase while the resistivity of the films decreases as the Si-doped concentration increases. The results of Si-doped Ga2O3 thin film with 20% cycle ratio shows high transmittance of 93% at 280 nm wavelength and low resistivity of 3.41 Ω·cm. Optical simulations show the potential for development of the Si-doped Ga2O3 films as the back electrode in the application of the ultraviolet C light-emitting diode.

Radical-Induced Effect on PEALD SiO2 Films by Applying Positive DC Bias

Multiple patterning technology has become an essential process. In the commonly used self-aligned multiple patterning process, the spacer should be dense at low temperatures and have a high elastic modulus. To meet these conditions, many thin-film deposition methods, such as plasma-enhanced atomic layer deposition, have been studied. We investigated remote plasma atomic layer deposition (RPALD) technology with a DC positive bias. After applying bias voltage to the plasma region, changes in the plasma properties, such as density and flux, were examined and applied to SiO2 deposition. When DC positive bias was applied, the sheath voltage decreased, causing an increase in the radical density, which contributed to the surface reaction. In an elastic recoil detection analysis, the application of 200 V reduced the hydrogen content of the film from 11.89% to 10.07% compared with no bias; an increase in SiO2 film density from 2.32 to 2.35 g cm−3 was also measured. The elastic modulus and hardness were shown to increase through a nano-indenter analysis and surface roughness improved with the suppression of energetic ions impinging on the film surface. Thus, the application of DC positive bias during the RPALD process effectively improved the physical, chemical, and mechanical properties of SiO2 film.

Innovative remote plasma source for atomic layer deposition for GaN devices

High-quality dielectric films could enable GaN normally off high-electron-mobility transistors (HEMTs). Plasma atomic layer deposition (ALD) is known to allow for controlled high-quality thin-film deposition, and in order to not exceed energy and flux levels leading to device damage, the plasma used should preferably be remote for many applications. This article outlines ion energy flux distribution functions and flux levels for a new remote plasma ALD system, Oxford Instruments Atomfab™, which includes an innovative, RF-driven, remote plasma source. The source design is optimized for ALD for GaN HEMTs for substrates up to 200 mm in diameter and allows for Al2O3 ALD cycles of less than 1 s. Modest ion energies of <50 eV and very low ion flux levels of <1013 cm−2 s−1 were found at low-damage conditions. The ion flux can be increased to the high 1014 cm−2 s−1 range if desired for other applications. Using low-damage conditions, fast ALD saturation behavior and good uniformity were demonstrated for Al2O3. For films of 20 nm thickness, a breakdown voltage value of 8.9 MV/cm was obtained and the Al2O3 films were demonstrated to be suitable for GaN HEMT devices where the combination with plasma pretreatment and postdeposition anneals resulted in the best device parameters.

Characteristics of carbon-containing low-k dielectric SiCN thin films deposited via remote plasma atomic layer deposition

This study investigates amorphous SiCN thin films deposited by remote plasma atomic layer deposition. Bis[(diethylamino)dimethylsilyl](trimethylsilyl)amine (DTDN-2) and N2 plasma were used as the precursor and reactant, respectively. The deposition temperature ranged from 100 to 300 °C, and the plasma power was set to 100 and 300 W. It was determined that the SiCN film carbon content increased with decreasing plasma power and deposition temperature. Likewise, decreasing the plasma power and deposition temperature lowered the dielectric constant of the film owing to the low film density and high carbon content. It was found that the composition of the SiCN film deposited at 300 °C was similar to that of the SiN film. The wet etch rate of the film deposited at 200 °C had the lowest value owing to the carbon content and high film density. The chemical bonding states of Si, C, and N were measured by x-ray photoelectron spectroscopy.

High Work Function Metallizations on Gallium Nitride for Schottky Diodes

Although silicon (Si) currently dominates the semiconductor industry, its small 1.1 eV band gap limits its maximum operating temperature, which restricts its use in high-temperature, high-power devices. Gallium nitride (GaN) is an attractive semiconductor with its wide bandgap (3.4 eV), high electron mobility (1700 cm2/Vs), high electron saturation velocity (3 x 107 cm/s), large critical breakdown field (2 MV/cm), and thermal stability. The high-power capabilities of GaN allow for a reduction in device size, which can conserve physical space if used to replace conventional Si power devices. While the semiconductor itself can endure harsh operating conditions, the reliability of the metal/semiconductor contacts can be a limiting factor for its use. Schottky contacts should provide a high barrier height and low reverse leakage current, and they must be electrically stable over the lifetime of the device.In this study, three materials reported to have high work functions are compared as Schottky diodes to n-type GaN, each selected for its anticipated thermodynamic stability with GaN1 or the potential to minimize process-induced defects in the diodes or both. Rhenium (Re) diodes fabricated via electron beam deposition, molybdenum nitride (MoNx) diodes via remote plasma atomic layer deposition (ALD), and palladium (Pd) diodes via electroless deposition were investigated. Ti/Al-based ohmic contacts were employed.The Re/n-GaN Schottky diode was chosen for study because of its thermodynamic stability against metallurgical reactions1 and high work function (4.96 eV)2. The barrier heights were investigated by current–voltage (I-V) and capacitance–voltage (C-V) measurements at room temperature. Both techniques demonstrated that the barrier height increased after an anneal at 400°C for 5 min, yielding a barrier height of 0.88 eV and ideality factor of 1.02 from by I-V measurements, while the C-V measurements revealed a barrier height of 0.91 eV. These barrier heights and reverse leakage currents remained stable upon annealing in N2 at 600°C.The MoNx/n-GaN Schottky diode was chosen for study because of the reported high work function of MoNx (5.33 eV)3, its conductive and refractory nature, and its thermodynamic equilibrium with GaN4. Films were deposited with bis (tert-butylimido)-bis (dimethylamido) molybdenum and a 300 W remote N2/H2 plasma. Four-point probe measurements and x-ray photoelectron spectroscopy (XPS) were used to measure sheet resistance and composition. Barrier heights from the I-V measurements were 0.41 eV, and ideality factors were 1.4, with good stability upon annealing at 600°C.The Pd/n-GaN Schottky diode was chosen because of its high work function (5.12 eV)2 and its potential to be electrolessly deposited, offering a gentle technique to minimize process-induced defects in the GaN, although Pd is not expected to be in thermodynamic equilibrium with GaN. A new method for electroless deposition of Pd films onto GaN surfaces used palladium dichloride with sodium L-ascorbate as the reducing agent was developed. Profilometry, four-point probe measurements, energy dispersive x-ray spectroscopy, and XPS were used to measure film thickness, sheet resistance, resistivity, morphology, and composition. The process provided conductive and pure Pd films, but some challenges with nucleation of the film on GaN makes the process less robust. Barrier heights from the I-V measurements were 1.13–1.26 eV, and ideality factors were 1.02–1.05. However, Pd is not in thermodynamic equilibrium with GaN.Among the candidates tested so far, the Re diodes were overall the strongest candidate. Future work will involve stress testing followed by materials characterization to provide more information on stable metallizations for high-power GaN devices.The authors are grateful to Sandia National Laboratories (Andrew Allerman) for providing GaN epilayers. This work was funded by the Office of Naval Research under Grant N000141812360, distribution A, approved for public release, distribution is unlimited (DCN# 43-7434-20). S. E. Mohney and X. Lin, J. Electron. Mater, 25, 811–818 (1996).H. Michaelson, J. Appl. Phys. 48, 4729-4733, (1977):H. Matsuhashi and S. Nishikawa, Jpn. J. Appl. Phys., 33, 1293, (1994).H. S. Venugopalan and S. E. Mohney, Z Metallkd., 89, 184-186, (1998).

Deposition and Characterization of RP-ALD SiO2 Thin Films with Different Oxygen Plasma Powers.

In this study, silicon oxide (SiO2) films were deposited by remote plasma atomic layer deposition with Bis(diethylamino)silane (BDEAS) and an oxygen/argon mixture as the precursors. Oxygen plasma powers play a key role in the quality of SiO2 films. Post-annealing was performed in the air at different temperatures for 1 h. The effects of oxygen plasma powers from 1000 W to 3000 W on the properties of the SiO2 thin films were investigated. The experimental results demonstrated that the SiO2 thin film growth per cycle was greatly affected by the O2 plasma power. Atomic force microscope (AFM) and conductive AFM tests show that the surface of the SiO2 thin films, with different O2 plasma powers, is relatively smooth and the films all present favorable insulation properties. The water contact angle (WCA) of the SiO2 thin film deposited at the power of 1500 W is higher than that of other WCAs of SiO2 films deposited at other plasma powers, indicating that it is less hydrophilic. This phenomenon is more likely to be associated with a smaller bonding energy, which is consistent with the result obtained by Fourier transformation infrared spectroscopy. In addition, the influence of post-annealing temperature on the quality of the SiO2 thin films was also investigated. As the annealing temperature increases, the SiO2 thin film becomes denser, leading to a higher refractive index and a lower etch rate.

Characteristics of Silicon Oxide Thin Film Deposited via Remote Plasma Atomic Layer Deposition

Recently, high-quality SiO2 thin films deposited at low temperatures have become popular because of their excellent dielectric properties. In this study, SiO2 thin films were deposited through remote plasma atomic layer deposition (RPALD) using a bis(tertiary-butylamino)silane (BTBAS) precursor and O2 plasma. The growth rate was saturated at 1.0 Å/cycle between 300 °C and 400 °C and was maintained throughout the process. The SiO2 thin film was oxygen rich according to Auger electron spectroscopy (AES), and the Si–O–Si bond structure was analyzed by measuring the binding energy differences using X-ray photoelectron spectroscopy (XPS). The leakage current density was 2.0 × 10–7 A cm−2 at 2 MV cm−1. As the deposition temperature increased from 300 °C to 400 °C, the breakdown voltage increased from 8.5 MV cm−1 to 10.5 MV cm−1 and the dielectric constant decreased from 3.85 to 3.72, which is slightly lower than for typical SiO2.

Carbon content control of silicon oxycarbide film with methane containing plasma

Deposition of silicon oxycarbide (SiCOH) thin films by remote plasma atomic layer deposition was performed. In the experiment, the recipe was composed by adjusting the ratio of Ar and CH4 plasmas to control the carbon content in the SiCOH thin film. Octamethyl cyclotetrasiloxane was used as a precursor during the deposition process at 200, 300, and 400 °C. Ar plasma was used as an activant and CH4 plasma was used as a reactant. Plasma and deposition temperatures cause a significant impact on the physical and electrical properties of the film. When CH4 plasma was used during the deposition process, the film contained carbon and exhibited a low dielectric constant. In addition, when CH4 plasma is used as a reactant, Si–C bonds in the thin film form pores and lower ionic polarization to lower the dielectric constant. Fourier-transform infrared spectroscopy data indicate that the higher the ratio of CH4 plasma, the more the cage structure in the thin film. The cage structure contributes to lowering the dielectric constant of the thin film. The film deposited with Ar plasma has the dielectric constant of 3.2 and the film deposited with CH4 plasma has the dielectric constant of 2.6. In both plasma conditions, the dielectric constant was lower than the SiO2 film with the dielectric constant of 3.9. On the other hand, x-ray photoelectron spectroscopy analysis showed that SiO1–C3 and SiC4 bonds appeared in the film deposited with CH4 plasma, which did not appear in the film deposited with Ar plasma. These bonds affected the physical and electrical properties of the thin film.

Remote Plasma Atomic Layer Deposition of SiNx Using Cyclosilazane and H2/N2 Plasma

Silicon nitride (SiNx) thin films using 1,3-di-isopropylamino-2,4-dimethylcyclosilazane (CSN-2) and N2 plasma were investigated. The growth rate of SiNx thin films was saturated in the range of 200–500 °C, yielding approximately 0.38 Å/cycle, and featuring a wide process window. The physical and chemical properties of the SiNx films were investigated as a function of deposition temperature. As temperature was increased, transmission electron microscopy (TEM) analysis confirmed that a conformal thin film was obtained. Also, we developed a three-step process in which the H2 plasma step was introduced before the N2 plasma step. In order to investigate the effect of H2 plasma, we evaluated the growth rate, step coverage, and wet etch rate according to H2 plasma exposure time (10–30 s). As a result, the side step coverage increased from 82% to 105% and the bottom step coverages increased from 90% to 110% in the narrow pattern. By increasing the H2 plasma to 30 s, the wet etch rate was 32 Å/min, which is much lower than the case of only N2 plasma (43 Å/min).

The effects of annealing and wake-up cycling on the ferroelectricity of zirconium hafnium oxide ultrathin films prepared by remote plasma atomic layer deposition

The crystalline phases and ferroelectric properties of ZrxHf1-xO2 (ZHO) ultrathin films (5.6–5.8 nm in thickness) prepared by remote plasma atomic layer deposition (RP-ALD) before and after post-annealing and wake-up cycling have been investigated in this study. For the films with high ZrO2 percentages, the plasma bombardment from RP-ALD was able to induce partial ferroelectric orthorhombic (o) crystallization during the film deposition stage. The as-deposited pure ZrO2 ultrathin film exhibited a fully developed ferroelectric polarization hysteresis after wake-up cycling. For the films containing the ferroelectric o-phase in the as-deposited state, post-annealing the films followed by a wake-up cycling procedure could greatly promote ferroelectric switching while maintaining low leakage. The ferroelectric properties of the ZHO ultrathin films were highly dependent on the ZrO2-to-HfO2 ratio and could be tailored by various combinations of post-annealing and wake-up cycling. An increase in the amount of HfO2 has been found to be detrimental to the ferroelectricity, mainly due to the high crystallization temperature of HfO2. For the post-annealed ZHO ultrathin films, the ferroelectricity was governed by the relative amounts of the ferroelectric o-phase and the non-ferroelectric monoclinic (m) phase. The Zr0.5H0.5O2 ultrathin film was the only composition which exhibited a large, stable polarization hysteresis after post-annealing but before wake-up cycling. The annealed Zr0.5H0.5O2 ultrathin film is believed to contain a suitable mix of o and m phases to produce loose grain boundaries, allowing the ferroelectric o-phase crystallites to switch freely under electrical loading.

Spatially-Resolved Remote Plasma Atomic Layer Deposition Process for Moisture Barrier Al2O3 Films

In this study, nanoscale-thickness Al2O3 layers for moisture barrier films were developed by a spatially resolved remote plasma atomic layer deposition process. The effect of various process parameters was investigated on the atomic concentration of Al2O3 films including the substrate temperature, plasma power, and scanning speed of the substrates. Carbon components were identified as major impurities in the films and is reduced at high temperature, high plasma power and low speed. Optimum conditions are maximum temperature of 80 °C to prevent plastic substrate deformation, a maximum plasma power of 150 W without surface damage and maximum speed of 125 mm/sec to maintain a low carbon contents. The water vapor transmission rate (WVTR) of 3.2 × 10 −4 g/(m2·day) was achieved with 30 nm-thick film in optimum condition.

Remote plasma atomic layer deposition of silicon nitride with bis(dimethylaminomethyl-silyl)trimethylsilyl amine and N2 plasma for gate spacer

The silicon nitride (SiNx) atomic layer deposition with bis(dimethylaminomethylsilyl)-trimethylsilyl amine precursor and N2 remote plasma was investigated. The process window ranged from 250 to 400 °C, and the growth rate was about 0.38 ± 0.02 Å/cycle. The physical, chemical, and electrical characteristics of the SiNx thin films were examined as a function of deposition temperature and plasma power. Based on the results of spectroscopic ellipsometry and x-ray photoelectron spectroscopy, the growth rate and state of binding energy showed little difference depending on the plasma power. The better film properties such as leakage current density and etch resistance were obtained at higher deposition temperatures and higher plasma power. High wet etch resistance (wet etch rate of ∼2 nm/min) and low leakage current density (∼10−8 A/cm2) were obtained. The step coverage, examined by transmission electron microscopy, was about 80% on a trench with an aspect ratio of 4.5.

Rapid thermal processing of hafnium dioxide thin films by remote plasma atomic layer deposition as high-k dielectrics

Hafnium oxide (HfO2) thin films have received significant attention due to its excellent properties, such as large band gap, good thermodynamic stability, high density and high dielectric constant. The post-annealing temperature is also essential to their properties and application possibilities. In this work, HfO2 thin films were prepared on p-type silicon (100) substrates by remote plasma atomic layer deposition using tetrakis (ethylmethylamino) hafnium and remote oxygen plasma at 250 °C. The effect of rapid thermal annealing on the properties of the thin films was investigated using grazing incidence X-ray diffraction (GIXRD), X-ray photoelectron spectroscopy and field-emission transmission electron microscope (FE-TEM). FE-TEM and GIXRD results show that the as-deposited films are mostly amorphous and the crystallization initiates at about 500 °C. They also unveil a positive correlation between interface properties of the HfO2 thin films and a dependence of the crystallinity on annealing temperature.

Simulation and Fabrication of HfO2 Thin Films Passivating Si from a Numerical Computer and Remote Plasma ALD

Recombination of charge carriers at silicon surfaces is one of the biggest loss mechanisms in crystalline silicon (c-Si) solar cells. Hafnium oxide (HfO2) has attracted much attention as a passivation layer for n-type c-Si because of its positive fixed charges and thermal stability. In this study, HfO2 films are deposited on n-type c-Si using remote plasma atomic layer deposition (RP-ALD). Post-annealing is performed using a rapid thermal processing system at different temperatures in nitrogen ambient for 10 min. The effects of post-annealing temperature on the passivation properties of the HfO2 films on c-Si are investigated. Personal computer one dimension numerical simulation for the passivated emitter and rear contact (PERC) solar cells with the HfO2 passivation layer is also presented. By means of modeling and numerical computer simulation, the influence of different front surface recombination velocity (SRV) and rear SRV on n-type silicon solar cell performance was investigated. Simulation results show that the n-type PERC solar cell with HfO2 single layer can have a conversion efficiency of 22.1%. The PERC using silicon nitride/HfO2 stacked passivation layer can further increase efficiency to 23.02% with an open-circuit voltage of 689 mV.