Effect Of Post-deposition Annealing Research Articles

Negatively charged silicon nitride films for improved p-type silicon surface passivation by low-temperature rapid thermal annealing

The effect of post-deposition rapid thermal annealing (RTA) on p-type Czochralski silicon surface passivation by plasma-enhanced chemical vapor deposited nitrogen-rich silicon nitride (SiNx) films has been investigated. The effective carrier lifetime is significantly improved after annealing at low temperature (400 °C–450 °C) for 15–30 s. This improvement is associated with a decrease of N–H and Si–H bond densities in SiNx films and, a resultant decreased density of states at the SiNx/Si interface. More importantly, the polarity of fixed charges is converted from positive to negative in the annealed SiNx films. It is demonstrated that a release of hydrogen atoms to the SiNx/Si interface combined with a tuning of charges during low-temperature RTA, is very beneficial for p-type silicon surface passivation.

Post deposition annealing effect on properties of Y2O3/Al2O3 stacking gate dielectric on 4H-SiC

In this paper, the effect of post deposition annealing (PDA) on the chemical, structural, and electrical properties of the high-k Y2O3/Al2O3 stacking dielectric on p-type 4H-SiC were studied. High-k dielectric provides a physically thicker film with equivalent capacitance, therefore better exploits the high breakdown strength of 4H-SiC in its MOSFET devices. The Y2O3/Al2O3 stacking films were deposited using RF magnetron sputtering, with PDA in Ar ambient at 400 °C, 600 °C, 800 °C and 1000 °C. X-ray diffraction (XRD) and angle resolved X-ray photoelectron spectroscopy (XPS) results show that an Al5O12Y3 crystal layer was formed in between Y2O3 and Al2O3 films after annealing above 600 °C. High resolution transmission electron microscope (HRTEM) was used to investigate the atomic structure and measure the thickness of each layer. Charges and dielectric strength of the stacking films were characterized by high frequency capacitance-voltage (C-V) and current-voltage (I-V) measurements. The lower charge density and higher dielectric strength were found after PDA at 800 °C and 1000 °C.

Effects of post deposition annealing atmosphere on interfacial and electrical properties of HfO2/Ge3N4 gate stacks

Effects of post deposition annealing (PDA) atmosphere, including oxygen (O2) gas and forming gas (FG), on interfacial and electrical properties of a HfO2 gate dielectric on nitrided Ge are analyzed. Experiments to study the dielectric morphology, interface quality, and chemical composition of HfO2/Ge3N4/Ge devices were carried out using X-ray diffraction, high-resolution transmission electron microscopy (HRTEM) imaging, and X-ray photoelectron spectroscopy (XPS) measurements, respectively. The XPS study confirmed that O2 PDA effectively improves the HfO2 film stoichiometry, and the stability of the interface between HfO2/Ge3N4/Ge stacks is enhanced. Further, HRTEM images showed that the interface between HfO2/Ge3N4/Ge stacks for O2-annealed devices was smooth, uniform, and flat. The experimental results for devices annealed in O2 at 500 °C exhibited improved interfacial and electrical characteristics, such as a high dielectric constant of ~19.50; high capacitance, 1.24 nF, low equivalent oxide thickness, 1.74 nm; interface trap density, 2.18 × 1011 cm−2 eV−1; oxide charges, 2.50 × 1012 cm−2; and gate leakage currents in the order nA of 0.5 × 10−9 A/cm2, as compared with FG annealing devices. The Fowler−Nordheim tunneling current conduction mechanism was also verified. Therefore, these results are evidence that the O2 PDA process improves the interfacial and electrical properties of HfO2/Ge3N4/Ge metal-oxide-semiconductor (MOS) devices as compared with FG annealing, which is important for future Ge-based complementary MOS device performance and reliability.

F-In-codoped ZnO (FIZO) films produced by corona-discharge-assisted ultrasonic spray pyrolysis and hydrogenation as electron-selective contacts in FIZO/SiOx/p-Si heterojunction crystalline silicon solar cells with 10.5% efficiency

In this paper, we report the first results obtained by corona-discharge-assisted ultrasonic spray pyrolysis (CDA-USP), a method proposed by us for growing thin transparent conductive oxide (TCO) films. We have grown F-In-codoped ZnO (FIZO) thin films by this method and investigated their properties from the viewpoint of their potential application as electron-selective contacts to p-type silicon. In particular, we have examined the effect of film thickness and post-deposition annealing in hydrogen on the structure, morphology, elemental composition, and electrical and optical properties of the FIZO films and on the photovoltaic properties of FIZO/SiOx/p-Si heterojunctions and related solar cells. We have obtained solar cells with 10.5% conversion efficiency (total area) under 1-sun illumination, which is the highest value reported for TCO/Si heterojunction solar cells with ZnO-based TCOs.

Influence of post-deposition annealing on the chemical states of crystalline tantalum pentoxide films

We investigate the effect of post-deposition annealing (for temperatures from 848 K to 1273 K) on the chemical properties of crystalline Ta$_2$O$_5$ films grown on Si(100) substrates by radio frequency magnetron sputtering. The atomic arrangement, as determined by X-ray diffraction, is predominately hexagonal ($\delta$-Ta$_2$O$_5$) for the films exposed to heat treatments at 948 K and 1048 K; orthorhombic ($\beta$-Ta$_2$O$_5$) for samples annealed at 1148 K and 1273 K; and amorphous for samples annealed at temperatures below 948 K. X-ray photoelectron spectroscopy for Ta $4f$ and O $1s$ core-levels were performed to evaluate the chemical properties of all films as a function of annealing temperature. Upon analysis, it is observed the Ta $4f$ spectrum characteristic of Ta in Ta$^{5+}$ and the formation of Ta-oxide phases with oxidation states Ta$^{1+}$, Ta$^{2+}$, Ta$^{3+}$, and Ta$^{4+}$. The study reveals that the increase in annealing temperature increases the percentage of the state Ta$^{5+}$ and the reduction of the others indicating that higher temperatures are more desirable to produce Ta$_2$O$_5$, however, there seems to be an optimal annealing temperature that maximizes the O\% to Ta\% ratio. We found that at 1273 K the ratio slightly reduces suggesting oxygen depletion.

Effect of vacuum and sulphur annealing on the structural properties of spray deposited Cu2SnS3 thin films

Cu2SnS3 thin films have been deposited by using non-vacuum spray pyrolysis technique on soda lime glass substrates from single aqueous solution containing all the constituents. The effect of post deposition annealing of the Cu2SnS3 thin films on the composition, structural, optical and electrical properties has been studied. The XRD study reveals that vacuum annealing of the thin film gives rise to the evolution of CuxSy secondary phases by the loss of elemental tin, while the annealing held at sulphur atmosphere increases the crystallinity of the film without giving rise to any secondary phases. The Cu2SnS3 phase with preferred orientation along the (112) crystal direction grew to greater extent upon sulphur annealing associated with an improvement in the optical band gap. From the Raman analysis it was observed that as-deposited films are dominated by the presence of tetragonal crystal symmetry of the Cu2SnS3 phase. Upon vacuum annealing the peak appearing at 474 cm−1 grows to greater extent which corresponds to CuS phase, and is in good agreement with the XRD spectra. Eventually its sulphur annealing gives the pure phase of Cu2SnS3 with dominating tetragonal crystal structure.

Post-growth annealing effect on the performance of Cu2SnSe3 solar cells

In this work, the effect of post-deposition annealing in selenium environment was studied on Cu2SnSe3 thin film solar cells prepared from solid solution by doctor blade method. XRD pattern confirms deposited films are of polycrystalline nature having cubic phases with (1 1 1) orientation. The crystallinity improves with the increase in annealing temperature. At high annealing temperature surface agglomeration was found which is due to the melting and re-evaporation of the components from the surface. Electrical properties like carrier mobility, conductivity also modified with the increase in annealing temperature. Maximum efficiency of 1.17% was achieved for the sample annealed at 400 °C having barrier height (ϕb), ideality factor (n) and series resistance (Rs) nearly equal to 0.71 eV, 1.5 and 69 Ω respectively.

Effects of Post Deposition Annealing Ambient on Interfacial and Electrical Properties of HfO2/Ge3N4 Gate Stacks on Ge Mos Devices

We report the effects of post deposition annealing (PDA) ambient O2 and FG gas on interfacial and electrical properties of HfO2 gate dielectric on nitrided Ge. The morphological studies of the dielectric, interface quality and chemical composition of the HfO2/Ge3N4/Ge were studied from X-ray diffraction (XRD), High-resolution transmission electron microscopy image (HRTEM) and X-ray photoelectron spectroscopy (XPS) respectively. Experimental results of O2 annealed devices exhibit improved interfacial and electrical characteristics such as high dielectric constant (~19.50), high capacitance (1.24 nF), small EOT (1.74 nm), Dit (3.18x1010 cm2 eV-1), oxide charges (Qeff 2.60x1012 eV-1) and gate leakage currents in the order nA (0.5x10-9 A/cm-2) as compared with FG annealing devices. The Fowler−Nordheim (F−N) tunnelling current conduction mechanism was also verified. Therefore, these results are evidence for the O2 gas PDA improves the interfacial and electrical properties of HfO2/Ge3N4/Ge MOS devices as compared with FG annealing.

Effects of annealing temperature on workfunction of MoOx at MoOx/SiO2 interface and process-induced damage in indium tin oxide/MoOx/SiOx/Si stack

The workfunction of molybdenum oxide (MoOx) at the MoOx/SiO2 interface, which is referred to as the interface workfunction, and the process-induced damage at the SiO2/Si interface in an indium tin oxide (ITO)/MoOx/SiO2/Si structure are extracted by capacitance–voltage (C–V) analysis. The estimated interface workfunction is compared with that of the bulk determined by ultraviolet photoelectron spectroscopy (UPS). The interface workfunction of 5.59 eV for the as-grown ITO condition is 0.41 eV smaller than the bulk workfunction for the as-grown MoOx film. The reactive-plasma deposition (RPD) process induces damage at the SiO2/Si interface, with an estimated interface defect density (Dit) of 3.9 × 1011 cm−2 eV−1. The effects of postdeposition annealing in a forming gas on these parameters are also studied. The interface workfunction decreases with increasing temperature to 5.24 eV at 400 °C, while that of the bulk is 5.9 eV, suggesting a difference in the interface and bulk properties. The damage is almost removed at 250 °C.

Effect of Annealing of Silver Electrodes on Photolithographically Fabricated Silicon Trenches for Photodetection Applications

The photosensitivity of metal–semiconductor–metal (MSM) ultraviolet photodetectors based on recessed electrodes on silicon (Si) substrate has been enhanced. Recessed electrodes were deposited in photolithography fabricated silicon trenches. Such recessed electrodes can collect photogenerated electrons beneath the silicon surface, hence increasing the photocurrent. For metallization of Si substrates to fabricate MSM photodetectors, two interdigitated silver (Ag) contacts were deposited for each electrode by sputtering. The morphology of the sputtered contacts was studied by scanning electron microscopy. The effect of postdeposition annealing on the recessed electrodes in silicon trenches was studied. The annealing process was carried out at 300°C for 10 min. The optoelectronic characteristics of MSM ultraviolet (UV) photodetectors with such trench electrodes in silicon substrates were studied in the dark and under UV illumination, comparing photodetectors based on annealed versus as-deposited samples. The electrical characteristics of photodetectors fabricated on annealed substrates revealed enhanced sensitivity to ultraviolet radiation. It was shown that annealing silver electrodes in silicon trenches can improve photodetector quality.

Structure, optical and electronic structure studies of Ti:ZnO thin films

Ti doped ZnO (TZO) thin films are stabilized by means of sputtering on quartz substrates and their structural, optical and electronic structure studies are carried out. The effect of different substrate temperature during growth and post deposition annealing effect is emphasized in TZO films. Structural characterization reveals that the TZO films have a wurzite phase with (0001) preferred orientation and lattice strain tends to relax at higher growth temperature and lower growth rate. Crystallite size, lattice strain and the band gap demonstrate dependency on deposition parameters. Moreover, these are strongly influenced by post deposition annealing treatment. The changes induced in the electronic structure of TZO films due to varying deposition parameters and post annealing treatment are understood through X-ray absorption spectroscopy and X-ray absorption near-edge structure measurements. The secondary ion mass spectrometry predicts that concentration of Ti in TZO film is laterally homogeneous but is vertically modulated upon post annealing while the Zn and O have followed stable concentration profile.

Characterization of Low-Temperature Atomic Layer Deposited Cobalt Oxide

Cobalt oxide is of interest for applications in catalysis, energy storage, and metal/insulator/metal (MIM) tunnel diodes. Atomic layer deposition (ALD), based on purge-separated self-limiting surface reactions between precursors and oxidizing agents, enables precisely controlled deposition of highly conformal thin films. Although there have been a handful of reports of ALD of CoOx using various metal precursors and oxidizing agents, to date there have been no systematic studies of electrical performance for ALD cobalt oxide and even reports of refractive index are sparse. There is also a lack of agreement in the literature on the fundamental band gap. In this work, the structural, optical, and electrical properties of a low temperature ALD cobalt oxide are investigated as-deposited and after post-deposition annealing. CoOx thin films were deposited on p- and n-type silicon substrates via ALD. ALD was performed at 250 °C in a Picosun Sunale R-150 reactor using N2-purge separated cycles of biscyclopentadienyl-cobalt (Co(Cp)2) held at 80 oC, and a ~10% O3/O2 mixture generated with an IN-USA AC2025 ozone generator [1, 2]. CoOx films were characterized using variable angle spectroscopic ellipsometry (VASE), grazing-incident x-ray diffraction (GIXRD), x-ray reflectivity (XRR), and atomic force microscopy (AFM). Electrical test structures were formed by evaporating either Co or Al metal through a shadow mask to form top electrode areas of ~0.05 mm2. X-ray and optical analysis indicate that as-deposited cobalt oxide on silicon substrates is Co3O4. Several GIXRD peaks corresponding to Co3O4 phase orientations are found (Fig. 1) and are consistent with previously reported spectra [1, 2]. Additionally, VASE analysis (Fig. 2) yields a refractive index of ~2.8 at a wavelength of 632.8 nm, close to that of bulk Co3O4 and an earlier report of ALD Co3O4 [3]. AFM (Fig. 3) indicates that the films have an RMS roughness of ~0.4 nm, much smoother than earlier reports [1, 2]. High current density at 1 MV/cm of 1.2 mA/cm2 for a Co/Co3O4/n-Si device and 16.3 mA/cm2 for an Al/Co3O4/n-Si device is consistent with the semiconducting (p-type) nature of Co3O4. The effects of post deposition annealing in a forming gas (H2/N2) environment are expected to reduce the Co3O4 to CoO, which is expected to be the higher bandgap phase of cobalt oxide. Electrical characterization will be performed on post-deposition annealed MOS and MIM devices in an attempt to observe the transition to the insulating phase. Additionally, a discrepancy in the reported temperature versus growth behavior of the Co(Cp)2 / O3 process [1,2] will be compared to the ALD window measured in this work. [1] M. Diskus, O. Nilsen, and H. Fjellvåg, Chemical Vapor Deposition, vol. 17, no. 4–6, pp. 135–140, Jun. 2011. [2] B. Huang, K. Cao, X. Liu, L. Qian, B. Shan, and R. Chen, RSC Adv., vol. 5, no. 88, pp. 71816–71823, 2015. [3] B. Han, K. Ha Choi, J. Min Park, J. Woo Park, J. Jung, and W.-J. Lee, JVST A, vol. 31, no. 1, p. 01A145, 2013. Figure 1

Effect of reduction potential and post-deposition annealing on the structural, compositional and optical properties of electrodeposited copper(I) sulfide thin films

In the present work it is reported on the deposition of cuprous sulfide (Cu2S) by the electrodeposition technique and its characterization followed by a heat treatment. Cu2S films were deposited using reduction potentials in a range of − 600 to − 555 mV (vs. SCE) with a deposition time of 1000 s. The annealing process was performed varying the atmosphere (inert or with sulfur) and temperature (250 and 350 °C). The properties of deposited Cu2S films were analyzed using UV–Vis spectroscopy, X-ray diffraction, scanning electron microscopy and energy-dispersive X-ray spectroscopy. The deposited films had a hexagonal structure in the chalcocite phase and showed a band gap in the range of 1.61 and 1.8 eV. Characterization techniques demonstrated modifications in the properties of the material due to the presence or deficiency of sulfur in the films.

Impedance spectroscopy study of SrTiO3 pulse laser deposited photoelectrodes

Strontium titanate (STO) is an oxide that has found application in several technological areas and is a candidate electrode for photoelectrochemical cells (PECs). In this study, STO thin films were prepared via pulsed laser deposition to function as PEC electrodes. Effects of post-deposition annealing in a reducing environment on the photocatalytic activity of these electrodes are characterized by measurements of optical and electrochemical properties of the films. These observations are used to obtain insight into how the crystal and electronic properties of these electrodes are affected by the annealing process. Low annealing temperatures produce non-crystalline STO films that exhibit low photocatalytic activity. Annealing at 500 °C and higher allowed the formation of crystalline STO, which showed substantially higher ultraviolet-driven photocurrent densities. Electrochemical impedance spectroscopy reveals large decreases in charge transfer resistance that is associated with improved performance of these films. Oxygen evolution at these electrodes was confirmed with a rotating ring-disk electrode setup. Porous versions of the STO films were investigated to evaluate the effect larger surface area can have in enhancing the water oxidation performance.

Effect of post deposition annealing and post metallization annealing on electrical and structural characteristics of Pd/Al2O3/6H-SiC MIS capacitors

PurposeAl2O3 used as gate dielectric enables exploitation of higher electric field capacity of SiC, improving capacitive coupling and memory retention in flash memories. Passivation of traps at interface and in bulk which causes serious threat is necessary for better performance. The purpose of this paper is to investigate the effect of post-deposition rapid thermal annealing (PDA) and post-metallization annealing (PMA) on the structural and electrical characteristics of Pd/Al2O3/6H-SiC capacitors.Design/methodology/approachAl2O3 film is deposited by ALD; PDA is performed by rapid thermal annealing (RTA) in N2 at 900°C for 1 min and PMA in forming gas for 10 and 40 min. X-ray diffraction (XRD) and X-ray photoelectron spectroscopy (XPS) measurements data are studied in addition to capacitance-voltage (C-V) and current-voltage (I-V) characteristics for the fabricated Pd/Al2O3/SiC capacitors. Conduction mechanism contributing to the gate leakage current is extracted for the entire range of gate electric field.FindingsRTA forms aluminum silicide at the interface causing an increase in the density of the interface states and gate leakage current for devices with an annealed film, when compared with an as-deposited film. One order improvement in leakage current has been observed for the devices with RTA, after subjecting to PMA for 40 min, compared with those devices for which PMA was carried out for 10 min. Whereas, no improvement in leakage current has been observed for the devices on as-deposited film, even after subjecting to PMA for 40 min. Conduction mechanisms contributing to gate leakage current are extracted for the investigated Al2O3/SiC capacitors and are found to be trapfilled limit process at low-field regions; trapassisted tunneling in the mid-field regions and Fowler–Nordheim (FN) tunneling are dominating in high-field regions.Originality/valueThe effect of PDA and PMA on the structural and electrical characteristics of Pd/Al2O3/SiC capacitors suitable for flash memory applications is investigated in this paper.

Effect of substrate and post-deposition annealing on nanostructure and optical properties of CdTe thin films

Thermal evaporation is one of the promising methods for depositing CdTe thin films, which can obtain the thin films with the small thickness. In this work, CdTe nanoparticles have deposited on SiO2 substrates such as quartz (crystal) and glass (amorphous) at a temperature (Ts) of 150 °C under a vacuum pressure of 2 × 10−5 mbar. The thickness of CdTe thin films prepared under vacuum pressure is 100 nm. X-ray diffraction analysis (XRD) results showed the formation of CdTe cubic phase with a strong preferential orientation of (111) crystalline plane on both substrates. The grain size (D) in this orientation obtained about 7.41 and 5.48 nm for quartz and glass respectively. Ultraviolet-visible spectroscopy (UV–vis) measurements indicated the optical band gap about 1.5 and 1.52 eV for CdTe thin films deposited on quartz and glass respectively. Furthermore, to show the effect of annealing temperature on structure and optical properties of CdTe thin films on quartz and glass substrates, the thin films have been annealed at temperatures 50 and 70 °C for one hour. The results of this work indicate that the structure’s parameters and optical properties of CdTe thin films change due to increase in annealing temperature.

Atomic layer deposited HfO2 ultra-thin films on different crystallographic orientation Ge for CMOS applications

The properties of the HfO2 ultra-thin films high-k gate stack deposited on surface passivated (GeON) germanium with three different orientations viz. Ge (100), Ge (110) and Ge (111) for CMOS applications have been studied. The effect of post deposition annealing (PDA) at temperatures 350 °C and 400 °C has been investigated. The high-resolution transmission electron microscopy, X-ray photoelectron spectroscopy and atomic force microscopy were used to study the interfacial, chemical and surface properties of atomic layer deposited-HfO2 ultrathin films, respectively. The high frequency conductance method was applied to evaluate the value of interface trap density (Dit) and the lowest Dit of 6.24 × 1012 cm−2ev−1 was evaluated for (111) orientation annealed at 400 °C than (100) and (110) orientation. The effective barrier height extracted from the Fowler-Nordheim conduction transport is in the range of 0.29–0.70 eV for all samples and shows the significant dependence of the substrate orientations and PDA temperature.

Effects of post-deposition annealing on the chemical composition, microstructure, optical and mechanical properties of Y2O3 film

Reactive magnetron sputtering is an ideal technique to deposit Y2O3 films, but the existence and transformation of the physisorbed oxygen (Oδ) caused by this method were reported to have a strong impact on the films itself. In this paper, not only the Y2O3 films but powders were prepared, then the films were annealed at different temperatures (260, 350, 500, and 650 °C) according to the thermal analysis of powders. The results showed that Oδ can be transferred as desorption when the temperature increases to 260 °C, and such transformation further changes the chemical composition and the valences of O and Y elements. The post-deposited annealing can also affect the grain morphology instead of crystalline phase. The as-deposited Y2O3 films and the films annealed at higher temperature all have a cubic polycrystal with I = 100 for the (222) reflection. However, the typical orange-peel characteristics and columnar structures were only found in the Y2O3 films below 350 °C annealing. The mentioned changes including composition and grain morphology comprehensively affect the refractive index and nano-mechanical properties of Y2O3 films. This paper will provide a precise annealing temperature to obtain Y2O3 films with low physisorbed oxygen and stable micro-structure.

Effect of post-deposition annealing on the properties of ZnO films obtained by high temperature, micro-controller based SILAR deposition

The ZnO thin films were prepared by successive ionic layer adsorption and reaction (SILAR) method at elevated precursor temperature. The films were later subjected to post-deposition annealing at different temperatures. This annealing process was found to be beneficial as it improved the structural and optical properties of the films. The ZnO films obtained by SILAR were found to be polycrystalline with hexagonal crystal structure. The crystallite size of the films increased considerably after annealing. The annealed films also showed very high absorption in UV region with marginal change in band gap. Both the crystallite size and optical absorbance were found to increase proportionately with the annealing temperature.

Stress induced degradation and reliability of Al2O3 thin film on silicon

The electrical properties of metal insulator semiconductor (MIS) devices with Al2O3 as dielectric layer deposited by reactive RF (radio frequency) magnetron sputtering were investigated using Capacitance-Voltage (C-V) and Current–Voltage (I-V) to determine the quality of oxide layer and oxide/silicon interface. To assess the reliability of Al2O3/Si interface constant current stress of 1 mA for varying time period was also investigated. The effect of post deposition annealing (PDA) on electrical behavior of Al/Al2O3/Si MOS (metal oxide semiconductor) capacitors was studied. Annealed devices show substantial improvement in interface trap charge density (Dit), fixed oxide charge density (Qf) and leakage current. Improved electrical and interface properties are achieved at annealing temperature of 425 °C. Incorporation of nitrogen gas improves the thermal stability of Al2O3 films which exhibited fewer shift in flat band voltage (Vfb) as compared to the samples grown in pure argon atmosphere. Breakdown voltage for nitrogen doped Al2O3 of 30 nm thin films was enhanced from 15 V to 19 V. Results indicate that reactive sputtering in N2 containing plasma is a promising approach as reduction in gate leakage current and power dissipation is utmost essential for integrating high-k material into semiconductor processing.