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Effect of oxidation temperature on the inhomogeneity of chemical composition and density in nanometric SiO2 films grown on 4H-SiC
Abstract
State-of-the-art secondary ion mass spectrometry (SIMS), X-ray reflectivity (XRR) and atomic force microscopy (AFM) have been used to determine the effect of oxidation temperature on the inhomogeneity of chemical composition...
The electrical and physical properties of the SiC/SiO2 interfaces are critical for the reliability and performance of SiC-based MOSFETs. Optimizing the oxidation and post-oxidation processes is the most promising method of improving oxide quality, channel mobility, and thus the series resistance of the MOSFET. In this work, we analyze the effects of the POCl3 annealing and NO annealing processes on the electrical properties of metal–oxide–semiconductor (MOS) devices formed on 4H-SiC (0001). It is shown that combined annealing processes can result in both low interface trap density (Dit), which is crucial for oxide application in SiC power electronics, and high dielectric breakdown voltage comparable with those obtained via thermal oxidation in pure O2. Comparative results of non-annealed, NO-annealed, and POCl3-annealed oxide–semiconductor structures are shown. POCl3 annealing reduces the interface state density more effectively than the well-established NO annealing processes. The result of 2 × 1011 cm−2 for the interface trap density was attained for a sequence of the two-step annealing process in POCl3 and next in NO atmospheres. The obtained values Dit are comparable to the best results for the SiO2/4H-SiC structures recognized in the literature, while the dielectric critical field was measured at a level ≥9 MVcm−1 with low leakage currents at high fields. Dielectrics, which were developed in this study, have been used to fabricate the 4H-SiC MOSFET transistors successfully.
We investigated the effect of nitrogen-hydrogen (NH) mixed plasma pretreatment of 4H-SiC surfaces on SiC surface properties, SiO2/SiC interface quality, and the reliability and voltage stability of metal-oxide-semiconductor (MOS) capacitors. The NH plasma pretreatment decreased the incomplete oxide and contaminants on the SiC surface and reduced the density of SiO2/SiC interface traps. Compared with the untreated sample, the dielectric insulating characteristics and reliability of samples pretreated by NH plasma were improved. We also demonstrated that the shift/hysteresis of the flat band voltage (Vfb) and the midgap voltage (Vmg) induced by bias temperature stress for SiC MOS capacitors after NH plasma pretreatment was significantly decreased. Furthermore, the mechanisms of NH plasma pretreatment to improve interface properties and device performances were determined by combining secondary ion mass spectrometry (SIMS) measurements, X-ray photoelectron spectroscopy (XPS), and first-principles calculations. The result indicates that the excessive oxidation at the SiO2/SiC interface was limited due to the reduction in the diffusion of oxygen atoms into SiC caused by the surface Si-H and Si-N; NH plasma pretreatment suppressed the generation of interfacial traps by reducing surface pollutants and passivating surface defects, and some N atoms introduced into the SiO2/SiC interface effectively passivated the interfacial electroactive traps.
As a wide and direct bandgap semiconductor material, two-dimensional (2D) graphene-like SiC has attracted extensive research attention recently. Native defects and foreign impurities often have remarkable effects on the properties of semiconductors. In this paper, the structural, mechanical and electrical properties of 2D SiC with carbon antisite (CSi), vacancy (VC), interstitial (Ci) and substitution of C by N (NC) and B (BC) have been studied systematically using first-principles calculations. It is found that defects do not cause structural reconstruction for 2D SiC. The formation energies of CSi, VC, NC and BC are not sensitive to the uniaxial strain. CSi and Ci are likely to be formed spontaneously due to the negative formation energy values. In addition, the phonon spectra and elastic constant calculations show that the properties of 2D SiC with VC and Ci are unstable. Furthermore, from the calculations of the band structures and density of states, we observed that the bandgap of 2D SiC is slightly reduced by CSi, VC, Ci, and NC, however is increased by BC. Prominent additional charge states are generated in the bandgap of 2D SiC except for NC. Moreover, the overall carrier mobility of 2D SiC could be significantly reduced by the defects.
The properties of thin Pd2Si layers fabricated by means of magnetron sputtering deposition from a stoichiometric target was examined. Optical parameters were determined using spectroscopic ellipsometry. The refraction indexes (n) and extinction coefficients (k) of a Pd2Si layer as a function of light wavelength were obtained. The microstructural properties of the Pd2Si layer were investigated using Transmission Electron Microscopy (TEM), Energy-Dispersive X-ray Spectroscopy (EDS), X-ray Diffraction (XRD), X-ray reflectivity (XRR) and Secondary Ion Mass Spectrometry (SIMS). The work function of the silicide layer was measured on the fabricated metal(Pd2Si)-insulator-semiconductor (MIS) structures using Internal Photoemission Spectroscopy (IPS). The IPS technique was used to determine the barrier energy heights at the gate/dielectric (EBG) and dielectric/substrate (EBS) interfaces of the investigated Pd2Si/SiO2/Si system. The appropriate model allowing calculations of fractions of light absorbed by the gate and transmitted to the substrate was developed. The barrier energy from the Fermi level of the silicide gate and from the substrate valence band to the dielectric conduction band are estimated to be EBG = 4.11 ± 0.05 eV and EBS = 4.34 ± 0.05 eV, respectively. Taking the measured barrier height values and reported values of Si electron affinity (χSi = 4.05 eV) and Si band gap (EG = 1.12 eV), the electron affinity of the thermally grown oxide (SiO2) was determined to be χSiO2 = 0.83 ± 0.05 eV and the Pd2Si work function equal to ϕM = 4.94 ± 0.1 eV. It is shown that the application of a single, stoichiometric sputtering target allows to obtain thin Pd2Si layers with work function value resembling that for the bulk material.
Carbon-related point defects on the 4H-SiC surface are essential for understanding the origin of defects at the SiO2/SiC interface and improving the quality of epitaxial materials. In this work, a first principle calculation was carried out to study the structural and electronic properties of carbon antisite (CSi), vacancy (VC) and interstitial defects (Ci1, Ci2, Ci3 and Ci4) on the 4H-SiC (0001) surface. The optimized structures showed that interstitial defects except Ci2 caused the surface reconstruction of 4H-SiC. The variation in formation energies with chemical potentials of the carbon for all defects indicated that the C-rich condition was beneficial to the formation of CSi, Ci1, Ci3 and Ci4, whereas the Si-rich condition was more favorable to VC. We also observed that these defects except Ci4 generated the corresponding defect energy levels in the bandgap of 4H-SiC by calculating the density of states and local charge densities. Furthermore, the effects of defect coverage and lateral lattice strain on structural and electronic properties of these defects were provided.
The wide bandgap and high carrier mobility of silicon carbide (SiC), as well as its physical and chemical stability, make it a promising material for a number of applications. One of the key requirements for these applications involves oxide formation on SiC. The usefulness of the oxide produced by anodizing is, however, limited since the anodic oxide formed on SiC in the usual dilute aqueous solution has a low density and high surface roughness. Here, we consider a new parameter in anodic oxide formation by focusing on the concentration of free water in the electrolyte, using a highly concentrated aqueous solution. In a concentrated solution, oxygen evolution, which results in a reduction in the density of the oxide, is suppressed, and the rate of formation of anodic oxide at defect sites effectively decreases to reduce the surface roughness. Furthermore, an interfacial layer with a higher density than SiO2 is formed between SiC and SiO2, buffering the difference in density between them. As a result, we successfully obtained an anodic oxide with a relatively high density and low surface roughness. This study provides a new approach to improving the properties of the anodic oxide formed on SiC.
This paper gives an overview on some state-of-the-art characterization methods of SiO2/4H-SiC interfaces in metal oxide semiconductor field effect transistors (MOSFETs). In particular, the work compares the benefits and drawbacks of different techniques to assess the physical parameters describing the electronic properties and the current transport at the SiO2/SiC interfaces (interface states, channel mobility, trapping phenomena, etc.). First, the most common electrical characterization techniques of SiO2/SiC interfaces are presented (e.g., capacitance- and current-voltage techniques, transient capacitance, and current measurements). Then, examples of electrical characterizations at the nanoscale (by scanning probe microscopy techniques) are given, to get insights on the homogeneity of the SiO2/SiC interface and the local interfacial doping effects occurring upon annealing. The trapping effects occurring in SiO2/4H-SiC MOS systems are elucidated using advanced capacitance and current measurements as a function of time. In particular, these measurements give information on the density (~1011 cm−2) of near interface oxide traps (NIOTs) present inside the SiO2 layer and their position with respect to the interface with SiC (at about 1–2 nm). Finally, it will be shown that a comparison of the electrical data with advanced structural and chemical characterization methods makes it possible to ascribe the NIOTs to the presence of a sub-stoichiometric SiOx layer at the interface.
An alternative technological approach is proposed to obtain a SiO2 film on SiC using processes that finally reduce the effective fabrication costs. Accordingly, we report achieving of a high-quality oxide on 4H-SiC substrate using a process flow that consists in a preliminary deposition by sputtering, at room temperature, of an amorphous Si thin layer, followed by its oxidation at a relative low temperature (1100 ∘C) for SiC MOS technology. The X-ray reflectivity measurements demonstrated that the resulted oxide has a comparable roughness with the one thermally grown and presents the advantage of an almost three-fold thinner interfacial layer. The improvement of the oxide/semiconductor interface was further validated by the electrical investigation of the fabricated MOS structures, where a significant diminishing of the effective oxide charge density, interface traps density and near interface oxide traps density was assessed. Thus, we demonstrated that, for a specified thickness of the oxide layer on SiC, the proposed technological flow not only significantly reduces the standard duration of the process necessary and consequently the associated fabrication cost, but, more important, leads to superior oxides and interfaces, in terms of both micro-physical and electrical properties.
The electron density and physical stress at the thermally oxidized SiC/SiO2 interface, and their change with nitrogen incorporation, were observed using x-ray reflectivity, Raman scattering, and in-situ stress measurement. There is no evidence for residual carbon species at the SiO2/SiC. Instead, a ∼1 nm thick low electron density layer is formed at this interface, consistent with interfacial suboxides (SiOx, 0.3 < x < 2), along with high interfacial stress. Nitrogen passivation, a known process to improve the interface state density and electronic properties, eliminates the low density component and simultaneously releases the interface stress. On the basis of these findings, a chemical interaction model is proposed to explain the effect of the nitrogen in terms of both stress reduction and elemental control of the dielectric/SiC interface, resulting in a higher quality gate stack on SiC.
Nanoscale windows in graphene (nanowindows) have the ability to switch between open and closed states, allowing them to become selective, fast, and energy-efficient membranes for molecular separations. These special pores, or nanowindows, are not electrically neutral due to passivation of the carbon edges under ambient conditions, becoming flexible atomic frameworks with functional groups along their rims. Through computer simulations of oxygen, nitrogen, and argon permeation, here we reveal the remarkable nanowindow behavior at the atomic scale: flexible nanowindows have a thousand times higher permeability than conventional membranes and at least twice their selectivity for oxygen/nitrogen separation. Also, weakly interacting functional groups open or close the nanowindow with their thermal vibrations to selectively control permeation. This selective fast permeation of oxygen, nitrogen, and argon in very restricted nanowindows suggests alternatives for future air separation membranes.
Using ab initio calculations, we investigate the interactions among neutral excess oxygen atoms and amorphous silica (a-SiO2), along with hole trapping on neutral excess-oxygen defects. The calculations demonstrate that the interaction of excess oxygen with the a-SiO2 network results in two distinct defect structures referred to as the oxygen bridge-bonded (OBB) and peroxy linkage configurations. The OBB configuration may relax to a lower-energy structure after trapping a hole, representing a potential relaxation channel to the peroxy radical (POR) defect. The calculated hyperfine parameters are in excellent agreement with POR defect experiments and show that the oxygen atoms trapping the unpaired spin are bound to only one silicon atom. This implies that the OBB configuration is the major precursor of POR defects.
We have attempted to establish a unified theory of SiC oxidation by reproducing all the SiC oxide growth rates on the (0 0 0 1) Si-face, (1 1 0) a-face and (0 0 0 ) C-face at various oxidation temperatures and oxide partial pressures. Growth rates were calculated using the Si and C emission model and were confirmed to fully reproduce the observed data when an enhanced surface oxide growth rate was added to the previously defined growth rate. The parameters deduced from the calculations indicated that the activation energy for the initial interfacial reaction rate corresponds to the number of Si back-bond(s) on the crystalline surface. Although the C emission ratio was found to have no significant dependence on the surface orientation, the Si emission ratio varied significantly and so likely determines the oxide growth rate. The densities of Si and C interstitials at the SiC-oxide interface were simulated both on the oxide and SiC substrate sides, and the optimal oxidation sequence is discussed in terms of the formation of the interface state.
Synthesis of porous SiO2 thin films in room temperature was carried out using plasma enhanced chemical vapor deposition (CVD) in an electron cyclotron resonance microwave reactor with a downstream configuration.The gas adsorption properties and the type of porosity of the SiO2 thin films were assessed by adsorption isotherms of toluene at room temperature.The method could also permit the tailoring synthesis of thin films when both composition and porosity can be simultaneously and independently controlled. The result shows that it is possible to control the microstructure of oxide thin films deposited by room temperature plasma enhanced chemical vapor depositon (PECVD) by scarificial polymeric organic layers.
A modified Deal Grove model for the oxidation of 4H-SiC is presented, which includes the removal of the carbon species. The model is applied to data on the oxidation rates for the (0001) Si, (000) C, and (110) a faces, which are performed in 1 atm dry oxygen and in the temperature range 950–1150 °C. Analysis within the model provides a physical explanation for the large crystal-face dependent oxidation rates observed. © 2004 American Institute of Physics.
The drive toward new semiconductor technologies is intricately related to market demands for cheaper, smaller, faster, and more reliable circuits with lower power consumption. The development of new processing tools and technologies is aimed at optimizing one or more of these requirements. This goal can, however, only be achieved by a concerted effort between scientists, engineers, technicians, and operators in research, development, and manufac turing. It is therefore important that experts in specific disciplines, such as device and circuit design, understand the principle, capabil ities, and limitations of tools and processing technologies. It is also important that those working on specific unit processes, such as lithography or hot processes, be familiar with other unit processes used to manufacture the product. Several excellent books have been published on the subject of process technologies. These texts, however, cover subjects in too much detail, or do not cover topics important to modem tech nologies. This book is written with the need for a "bridge" between different disciplines in mind. It is intended to present to engineers and scientists those parts of modem processing technologies that are of greatest importance to the design and manufacture of semi conductor circuits. The material is presented with sufficient detail to understand and analyze interactions between processing and other semiconductor disciplines, such as design of devices and cir cuits, their electrical parameters, reliability, and yield.
We investigated the interface defect engineering and reaction mechanism of reduced transition layer and nitride layer in the active plasma process on 4H-SiC by the plasma reaction with the rapid processing time at the room temperature. Through the combination of experiment and theoretical studies, we clearly observed that advanced active plasma process on 4H-SiC of oxidation and nitridation have improved electrical properties by the stable bond structure and decrease of the interfacial defects. In the plasma oxidation system, we showed that plasma oxide on SiC has enhanced electrical characteristics than the thermally oxidation and suppressed generation of the interface trap density. The decrease of the defect states in transition layer and stress induced leakage current (SILC) clearly showed that plasma process enhances quality of SiO_2 by the reduction of transition layer due to the controlled interstitial C atoms. And in another processes, the Plasma Nitridation (PN) system, we investigated the modification in bond structure in the nitride SiC surface by the rapid PN process. We observed that converted N reacted through spontaneous incorporation the SiC sub-surface, resulting in N atoms converted to C-site by the low bond energy. In particular, electrical properties exhibited that the generated trap states was suppressed with the nitrided layer. The results of active plasma oxidation and nitridation system suggest plasma processes on SiC of rapid and low temperature process, compare with the traditional gas annealing process with high temperature and long process time.
The thermal‐oxidation kinetics of silicon are examined in detail. Based on a simple model of oxidation which takes into account the reactions occurring at the two boundaries of the oxide layer as well as the diffusion process, the general relationship x 0 2+Ax 0 =B(t+τ) is derived. This relationship is shown to be in excellent agreement with oxidation data obtained over a wide range of temperature (700°–1300°C), partial pressure (0.1–1.0 atm) and oxide thickness (300–20 000 Å) for both oxygen and water oxidants. The parameters A, B, and τ are shown to be related to the physico‐chemical constants of the oxidation reaction in the predicted manner. Such detailed analysis also leads to further information regarding the nature of the transported species as well as space‐charge effects on the initial phase of oxidation.
The oxidation of single‐crystal in dry oxygen (10⁻³‐1 atm and 1200°–1500°C) followed parabolic kinetics. The oxygen partial pressure dependence of the oxidation rate of the (0001̅) carbon face decreased with increasing temperature (from 0.6 at 1200°C to 0.3 at 1500°C). A kinetic model based on parallel transport of oxidants through the oxide via molecular and ionic oxygen diffusion mechanisms fits the observed oxidation behavior. Both diffusivity and activation energy values for oxidants permeating through the oxide derived from the model using the experimental data are similar to those for molecular oxygen permeating through vitreous . Ionic oxygen diffusion inward via the lattice presumably via a vacancy mechanism becomes more important when oxidation takes place at higher temperatures and at low oxygen partial pressures. Both diffusivity and activation energy values for the ionic oxidant diffusion derived from the model using the experimental data are similar to those values for the diffusion of oxygen through silica reported in the literature.
This article briefly summarizes the diffusion and reactions of interstitial oxygen species in amorphous SiO2 (a-SiO2). The most common form of interstitial oxygen species is oxygen molecule (O2), which is sensitively detectable via its characteristic infrared photoluminescence (PL) at 1272nm. The PL observation of interstitial O2 provides key data to verify various processes related to interstitial oxygen species: the dominant role of interstitial O2 in long-range oxygen transport in a-SiO2; formation of the Frenkel defect pair (Si–Si bond and interstitial oxygen atom, O0) by dense electronic excitation; efficient photolysis of interstitial O2 into O0 with F2 laser light (λ=157nm, hν=7.9eV); and creation of interstitial ozone molecule via reaction of interstitial O2 with photogenerated O0. The efficient formation of interstitial O0 by F2 laser photolysis makes it possible to investigate the mobility, optical absorption, and chemical reactions of interstitial O0. The observed properties of O0 are consistent with the model that O0 takes the configuration of Si–O–O–Si bond. Interstitial O2 and O0 react with dangling bonds, oxygen vacancies, and chloride groups in a-SiO2. Reactions of interstitial O2 and O0 with mobile interstitial hydrogen species produce interstitial water molecules and hydroperoxy radicals. Interstitial hydroxyl radicals are formed by F2 laser photolysis of interstitial water molecules.
Surface structures on amorphous silica with different thermal histories, i.e., the surface samples were generated at greater than (higher temperature, HT) and less than (lower temperature, LT) the glass transition temperature, were studied by molecular dynamics simulation. The charge equilibration method for taking account of charge transfer among atoms and the Ewald method were applied for calculating electrostatic interaction exactly. Radial distribution functions, bond-angle distribution of O–Si–O, coordination number of silicon and oxygen near the surface, and the surface charge distribution were calculated. The absolute value of charges of Si and O at the surface were smaller than those in the bulk. The data indicate that the near-surface region in the HT sample is more disordered than that of the LT sample: (i) Oxygen atoms are dominant in the near-surface region. (ii) Population of the defect structures, i.e. undercoordinated atoms, in the HT sample is higher than that in the LT sample and defect structures in the HT sample distributed over a wider range from the surface than those in the LT sample. (iii) The surface bond-angle distribution in the HT sample is wider than that in the LT sample and a larger amount of planar three-coordinated silicon exists on the surface than in the LT sample. (iv) The vibration amplitude in the surface region is slightly larger than that in the LT sample.
Herein we report that hierarchical electrospun SiO2 nanofibers incorporated with SiO2 nanoparticles with fiber diameters being ∼500nm and particle sizes being tens of nanometers were developed through the combination of sol–gel process and electrospinning technique followed by high-temperature pyrolysis; and their morphologies and BET surface areas were examined. The study revealed that the pre-gelation of tetraethyl orthosilicate (TEOS) in spin dopes was important to achieve the morphological consistence of the electrospun precursor nanofibers and the resulting final SiO2 nanofibers; additionally, SiO2 nanoparticles appeared to be enriched on the fiber surface, while the surface-roughness and/or porosity of the nanofibers could be controlled through adjusting the incorporation amount of SiO2 nanoparticles. The developed hierarchical electrospun SiO2 nanofibers are expected to have important applications in composites (particularly dental composites) as well as catalyst support and adsorption.
We report the results of high-level quantum-mechanical calculations on the optical transitions of a series of point defects in α quartz. We determined all electron-configuration-interaction wave functions for cluster models of the following bulk defects: neutral oxygen vacancy, ≡Si—Si≡, oxygen divacancy, ≡Si—Si—Si≡, dicoordinated Si, =Si:, E′ center, ≡Si• +Si≡, hydride group, ≡Si—H, peroxyl linkage, ≡Si—O—O—Si≡, peroxyl radical, ≡Si—O—O•, nonbridging oxygen hole center, ≡Si—O•, and silanol group ≡Si—OH. The computed transition energies and intensities have been compared with the observed absorption bands of defective silica and with the electronic transitions of molecular analogs when available. When a direct comparison of computed and experimental data is possible, a very good agreement is found. The results form the basis for a well-grounded assignment of the optical transitions of point defects in α quartz and amorphous silica.
The thermal conductivity of SiO2 thin films prepared using various procedures has been studied using a 3ω method. The thermal conductivity of SiO2 thin films of above approximately 500 nm thickness decreases as the porosity of the specimen, which is determined by infrared absorption spectroscopy, increases. Below approximately 250 nm thickness, the observed thermal conductivity of the SiO2 thin films systematically decreases as a function of film thickness. The data have been analyzed based on a SiO2-thickness-independent thermal conductivity and interfacial resistance. The total estimated interfacial resistance between the metal strip and the film, and between the film and the substrate is about 2×10−8 m2 KW−1. © 2002 American Institute of Physics.
We report on electrical and microscopic investigations aimed to clarify the origin of near-interface traps (NITs) in metal–silicon dioxide–4H-silicon carbide structures. Using capacitance–voltage and thermal dielectric relaxation current (TDRC) analysis we investigated NITs close to the 4H-SiC conduction-band edge in differently prepared thermal and deposited oxides and found that the traps give rise to two characteristic TDRC signatures belonging to two groups of trap levels. The total trapped charge exceeds 1×1013 cm−2. The observed density and energy distribution of these traps are nearly identical in all thermal and deposited oxides investigated, suggesting that the NITs belong to intrinsic defects at the SiO2/SiC interface which are readily formed during oxide deposition or thermal oxidation of 4H-SiC. Using high-resolution electron microscopy combined with nanochemical analysis (electron energy-loss near-edge spectroscopy and energy-filtered transmission electron microscopy) we investigated the SiO2/SiC interface in samples receiving reoxidation and did not find any indication of graphitic regions at or near the SiO2/SiC interface or in the bulk silicon dioxide within a detection limit of 0.7 nm. In addition, no amorphous carbon accumulation was observed near the SiO2/SiC interface. The overall results strongly suggest that the NITs near the 4H-SiC conduction band are not related to carbon structures in the SiO2/SiC interlayer.
The amount of oxygen molecules (O2) in amorphous SiO2 (a-SiO2), also called interstitial O2, was quantitatively measured by combining thermal-desorption spectroscopy (TDS) with infrared photoluminescence (PL) measurements of interstitial O2 at 1272 nm while exciting with 1064-nm Nd: yttrium aluminum garnet laser light. It was found that the amount of O2 released by the TDS measurement is proportional to the intensity decrease of the PL band, demonstrating that a-SiO2 easily emits interstitial O2 during thermal annealing in vacuum. This correlation yielded the proportionality coefficient between the absolute concentration of interstitial O2 and its PL intensity normalized against the intensity of the fundamental Raman bands of a-SiO2. This relationship was further used to determine the optical-absorption cross section of the Schumann–Runge band of the interstitial O2 located at photon energies ≳6.5 eV. This band is significantly redshifted and has a larger cross section compared to that of O2 in the gas phase.
The structures, energies, and fragmentation stabilities of silicon oxide
clusters Si_mO_n, with m = 1-5, n = 2m+1, are studied systematically by
ab initio calculations. New structures for nine clusters are found to be
energetically more favorable than previously proposed structures. Using
the ground state structures and energies obtained from our calculations,
we have also studied fragmentation pathways and dissociation energies of
the clusters. Our calculation results show that the dissociation energy
is strongly correlated with the O:Si ratio. Oxygen-rich cluster tends to
have larger dissociation energy as well as larger HOMO-LUMO gap. Our
calculations also show that SiO is the most abundant species in the
fragmentation products.
Plasma-enhanced chemical vapor deposition (PECVD) technology was considered as an excellent thin film deposition dry process in semiconductor device fabrication. Porous SiO2 film as a promising thermal insulation layer used in uncooled infrared detectors was grown directly by PECVD technology. The microstructure and elemental composition of the film were characterized by AFM, EDS, SEM and XPS. The porosity of the film was assessed according to the refractive index measured by ellipsometery. A prototype pyroelectric uncooled detector coated with a porous SiO2 film was evaluated.
We have performed in situ, energy‐dispersive x‐ray reflectivity measurements of damage layer formation and surface roughness of thin films of SiO 2 on Si and clean Si during H ion bombardment. The reflectivity was analyzed using an optical multilayer model where the variable parameters are the number of layers, the thickness and density of the layers, and the surface roughness. Room temperature ion bombardment at doses ≪5×1017/cm2 results in a buried layer between the oxide and the substrate; 300 eV bombardment produces a very thin, low‐density layer, while 1000 eV bombardment produces a thicker layer with the density of amorphous silicon. A damaged layer is not produced by equivalent bombardment at high temperature. Ion bombardment of clean Si surfaces at 500 °C resulted in roughening of the surface on the nanometer scale which is strongly dependent on the ion energy.
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