Single Crystalline Silicon Wafers Research Articles

Peculiarities in XPS spectra of Sn/SiO2 layers as an effect of surface charge

X-ray photoelectron spectroscopy based on synchrotron radiation was used to investigate the composition of the observed SnO2-x/Sn:SiO2-x thin layer grown by organometallic chemical vapour deposition on single-crystalline silicon wafer with additional argon ions etching treatment. Due to the formation of a thermodynamic anomaly during in situ layer growth, an efficient oxygen exchange between silicon and tin oxide phases occurs. The present study addresses the effect of localized surface charging and its influence on the obtained XPS core level spectra. We found that due to the high electrical conductivity of metallic tin and the direct coupling of tin particles to the silicon wafer, the XPS Sn 3d5/2 core level spectrum is not affected by the surface charge compared to the highly charged dielectric silicon oxide matrix, as observed for the XPS O 1 s and Si 2p core level spectra. Our results show that the core level spectra of Si 2p and O 1 s are shifted up to 3 eV due to the presence of uncompensated positive charge on the surface of the silica matrix. These results provide insight into the influence of surface charge effects on the analysis of conductor/insulator composite materials and contribute to the application of Sn-based materials in various application concepts related to energy and surface functionalization.

Quantitative shear stress imaging in high throughput in-line Si wafer inspection

Defect inspection methods are basic steps in electronic chip manufacturing and power device production processes in the semiconductor industry. Based on stress induced photoelastic anisotropy, in-line polarized stress imaging (PSI) and quantitative determination of the local shear stress component are possible in single crystalline silicon wafers. Hereafter, such polarization stress images are compared and validated quantitatively with results of finite element simulations based on different 3D elastic models. Uniquely, high resolution at high throughputs is achieved for 300 mm wafer size in the present quantitative stress imaging study.

ELECTRON IRRADIATED PI2610 POLYIMIDE FILMS ON MONOCRYSTALLINE SILICON

The optical and strength properties of electron-irradiated films of a polyimide composition (polyimide PI2610) deposited on the surface of single-crystalline silicon wafers of the KDB-10 grade by centrifugation were studied. Irradiation with electrons with an energy of 5 MeV was carried out on a linear accelerator U-003 in the dose range 1·1014 – 2·1015 cm–2. It has been experimentally established that at an irradiation dose of Ф = 1∙1014 cm–2, relaxation of elastic stress fields in the polyimide film is observed, which is expressed in modification of the shape of bands with maxima at 1349 and 1700 cm–1, caused by vibrations of the C–N–Cst bond and the C=O double bond imide ring. Polyimide PI-2610 films on silicon are quite stable when irradiated with electrons. A noticeable transformation of the ATR spectrum at a dose of 2∙1015 cm–2 was observed only in the region of stretching vibrations of C–H and O–H bonds, which is due to radiation-induced processes on by-products of polyimide synthesis and residual solvents. No noticeable decrease in the intensity of absorption bands caused by vibrations of the skeleton of the aromatic ring, imide ring, single and double C–C and C–O bonds, and imide C=O bonds was observed.

STRENGTH PROPERTIES OF ELECTRON IRRADIATED FILMS OF NEGATIVE NOVOLAC
 PHOTORESISTS ON MONOCRYSTALLINE SILICON

The adhesive and strength properties of electron-irradiated NFR 016D4 photoresist films for explosive lithography
 deposited on the surface of KDB-10 single-crystalline silicon wafers by centrifugation have been studied.
 It has been experimentally established that electron irradiation leads to warping and partial detachment of the
 NFR 016D4 photoresist film from the silicon substrate. Irradiated photoresist films behave like brittle materials.
 A significant decrease in crack resistance and adhesion to the silicon substrate of irradiated photoresist films was
 observed. caused by radiation-induced processes at the photoresist/silicon interface.

Electrochemically-stimulated nanoscale mechanochemical wear of silicon

AbstractMechanochemical reactions at the sliding interface between a single-crystalline silicon (Si) wafer and a silica (SiO2) microsphere were studied in three environmental conditions: humid air, potassium chloride (KCl) solution, and KCl solution with an applied voltage. Compared to that from humid air, mechanochemical material removal from the silicon surface increased substantially in the KCl-immersed condition, and further increased when electrochemistry was introduced into the tribological system. By measuring the load dependence of the material removal rate and analyzing the results using a mechanically assisted Arrhenius-type kinetic model, the activation energy (Ea) and the mechanical energy (Em), by which this energy is reduced by mechanical activation, were compared qualitatively under different environmental conditions. In the KCl-immersed condition, mechanochemistry may decrease the required effective energy of reactions (Eeff = Ea − Em) and promote material removal mainly through improved catalysis of the mechanochemical reactions facilitated by greater availability of water molecules compared to the humid air condition. Thus, the effectiveness of the mechanochemistry is improved. In the electrochemical condition, electrochemically-accelerated oxidation of the silicon surface was confirmed by the X-ray photoelectron spectroscopy (XPS) characterization. The results strongly suggest that electrochemistry further stimulates mechanochemical reactions primarily by increasing the initial energy state of the surface via the facilitated formation of interfacial bonding bridges, i.e., a surface oxidation/hydroxylation process.

Stability of Wafer-Scale Thin Films of Vertically Aligned Hexagonal BN Nanosheets Exposed to High-Energy Ions and Reactive Atomic Oxygen.

Stability of advanced functional materials subjected to extreme conditions involving ion bombardment, radiation, or reactive chemicals is crucial for diverse applications. Here we demonstrate the excellent stability of wafer-scale thin films of vertically aligned hexagonal BN nanosheets (hBNNS) exposed to high-energy ions and reactive atomic oxygen representative of extreme conditions in space exploration and other applications. The hBNNS are fabricated catalyst-free on wafer-scale silicon, stainless steel, copper and glass panels at a lower temperature of 400 °C by inductively coupled plasma (ICP) assisted chemical vapor deposition (CVD) and subsequently characterized. The resistance of BNNS to high-energy ions was tested by immersing the samples into the plasma plume at the anode of a 150 W Hall Effect Thruster with BNNS films facing Xenon ions, revealing that the etching rate of BNNS is 20 times less than for a single-crystalline silicon wafer. Additionally, using O2/Ar/H2 plasmas to simulate the low Earth orbit (LEO) environment, it is demonstrated that the simulated plasma had very weak influence on the hBNNS surface structure and thickness. These results validate the strong potential of BNNS films for applications as protective, thermally conductive and insulating layers for spacecrafts, electric plasma satellite thrusters and semiconductor optoelectronic devices.

Formation of inverted pyramid-like structures on surfaces of single crystalline silicon solar cells by chemical wet etching

We present a new, simple, and cost-effective etching method for forming inverted pyramid-like structures on the surfaces of single-crystalline diamond-wire sawn silicon wafers. The method follows a three-step process for etching silicon wafers without metal-assisted chemical etching involved. We used acidic etching to produce nano-to-micro-structured caves in the first two steps followed by anisotropic etching with an alkaline solution. This paper shows that the size of the opening of the inverted pyramid could vary from several hundred nanometers to about 4 μm, depending on the etch time periods in the second and the third steps. The cell performance was, however, only evaluated here for cases of smaller sizes of inverted pyramids. That is, solar cells were manufactured following an almost commercially standard procedure by using wafers with inverted pyramids of ∼900 nm in size. The best cell with this type of structure has a conversion efficiency of 19.22%, which is higher relative to the cells with smaller inward recessed caves or upright pyramids on the surfaces.

Design, Fabrication, and Experiment of a Decoupled Multi-Frame Vibration MEMS Gyroscope

A z-axis decoupled multi-frame vibration MEMS gyroscope (DMFVMG) is presented in this paper. Firstly, the decoupled principle is employed and the sense frame, Coriolis frame and drive frame are arranged through inner fame, intermediate frame and outer frame, and the movement characteristic analysis indicates that the structure is fully decoupled. The structure is simulated through mode analysis, harmonic response and drop shock response. The simulation results show that the resonant frequencies of the Sense Mode and Drive Mode are 10094Hz and 10162Hz, and the maximum deformation and stress with the shock analysis is 7.14 μ m and 235.19MPa (among three different directions). Then, the structure is fabricated through MEMS processing, and P-type single-crystalline silicon wafer and 7740 glass wafer are used. After that, the structure is packaged in a ceramic vacuum tube shell and the resonant frequencies and quality values of the sense and drive mode are 10354.21Hz and 5364, 10438.23Hz and 5219, the error between fabrication and simulation is 2.58% and 2.72%. And the monitoring system of DMFVMG prototype is established by analog circuit with drive closed-loop and sense open-loop. Then, the DMFVMG prototype is tested through turntable, and the range, scale factor and intercept are ±300°/s, -19.06mV/°/s and 95.43mV respectively. Finally, five repeated bias tests are arranged and the angular random walking values and bias stability are 0.2408°/√h, 0.2358°/ √h, 0.2413°/√h, 0.2397°/√h and 0.2480°/√h, 2.858°/h, 3.159°/h, 3.428°/h, 1.891°/h and 3.467°/h respectively.

Comparative Study of Silicon Nanowires Grown From Ga, In, Sn, and Bi for Energy Harvesting

A high density of silicon nanowires for solar cell applications was fabricated on a single crystalline silicon wafer, using low eutectic temperature metal catalysts, namely, gallium, indium, tin, and bismuth. The use of silicon nanowires is exploited for light trapping with an aim to enhance the efficiency of solar cells. Additionally, we have optimized the deposition parameters so that there is merely deposition of amorphous silicon along with the growth of silicon nanowires. Thus, it may improve the stability of silicon-based solar cells. The different catalysts used are extensively discussed with experimental results indicating stable growth and highly efficient silicon nanowires for photovoltaic applications. To test the stability, we measured the open-circuit voltage for four hours and the change in voltage was ±0.05 V. The fabrication of all-crystalline silicon solar cells was demonstrated using the conventional mature industrial manufacturing process that is presently used for the amorphous silicon solar cells. To summarize, this research compares various post-transition metals as a catalyst for the growth of nanowires discussing their properties, and such silicon nanowires can be utilized in several other applications not only limited to photovoltaic research.

Cytotoxicity of Mitomycin C-Porous Silicon in Human Prostate Carcinoma Cells

Porous silicon (pSi) microparticles with pore diameter 15 to 20 nm were fabricated by electrochemical etching of single-crystalline silicon (Si) wafers (n-type) to be used as delivery systems for the anticancer drug mitomycin C (MMC). The in vitro toxicity of the mitomycin-loaded pSi carrier was investigated on human prostate carcinoma (DU145) cells. The cells showed a decrease in viability of ~80% over a 6 hours period, when using mitomycin. Meanwhile, a ~55% decrease in cell viability was observed, when using the pSi carrier to deliver the drug. The drug-loaded carrier showed a sustained release throughout 24 hours, with an 80% decrease in cell viability after 16 hours. This observed controlled release of mitomycin from the pSi carrier suggests a superior therapeutic effect than the direct administration of mitomycin, as it potentially minimizes the drug side effects. Results showed that the strong cytotoxic effect towards the prostate cancer cells was due to the drug and not the carrier since the mitomycin-loaded pSi carrier affected cell viability, but the pSi carrier showed no toxicity. Furthermore, it was observed that with a higher amount of drug-loaded carriers, the toxicity effect was higher, thus, allowing further control of the therapeutic effect of the carrier.

In Situ Formation of Nanoporous Silicon on a Silicon Wafer via the Magnesiothermic Reduction Reaction (MRR) of Diatomaceous Earth.

Successful direct route production of silicon nanostructures from diatomaceous earth (DE) on a single crystalline silicon wafer via the magnesiothermic reduction reaction is reported. The formed porous coating of 6 µm overall thickness contains silicon as the majority phase along with minor traces of Mg, as evident from SEM-EDS and the Focused Ion Beam (FIB) analysis. Raman peaks of silicon at 519 cm−1 and 925 cm−1 were found in both the film and wafer substrate, and significant intensity variation was observed, consistent with the SEM observation of the directly formed silicon nanoflake layer. Microstructural analysis of the flakes reveals the presence of pores and cavities partially retained from the precursor diatomite powder. A considerable reduction in surface reflectivity was observed for the silicon nanoflakes, from 45% for silicon wafer to below 15%. The results open possibilities for producing nanostructured silicon with a vast range of functionalities.

Radiation tolerance of nanostructured TiAlN coatings under Ar+ ion irradiation

The radiation tolerance of TiAlN coatings under irradiation with 200 keV Ar+ ions is studied at room temperature. The ion fluence varied in the range of 1·1016–2·1017 ions/cm2. The TiAlN coatings were deposited by reactive magnetron sputtering on single crystalline silicon wafers as well as on AISI 304 stainless steel bars. Elemental composition of the coatings was investigated using Rutherford backscattering spectrometry with He+ ions of 2.53 MeV and 4.53 MeV as well as by energy-dispersive X-ray spectroscopy using 18 keV electrons. Phase composition and structure of TiAlN coatings were examined by X-ray diffraction and scanning electron microscopy. Mechanical properties of TiAlN coatings were evaluated by nanoindentation using a nanohardness tester with a Berkovich diamond tip and applying the Oliver-Pharr method. Some selective nitrogen sputtering was detected caused by the Ar+ ion irradiation. The TiAlN coatings crystallites refined under argon ion irradiation. It was found that the irradiation fluence of 2·1017 ions/cm2 is a threshold fluence, at which the solid solution decomposition starts. Ion irradiation causes mechanical properties improvement up to the fluence of 5·1016 ions/cm2. No destruction processes of the coatings such as blistering or flaking were detected for all irradiation fluences used in this study.

Evaporation-Induced Hierarchical Assembly of Rigid Silicon Nanopillars Fabricated by a Scalable Two-Level Colloidal Lithography Approach.

Periodic arrays of silicon nanowires/nanopillars are of great technological importance in developing novel electrical, optical, biosensing, and electromechanical devices. Here, we report a novel two-level colloidal lithography technology for making periodic arrays of single-crystalline silicon nanopillars (or nanocolumns) over large areas. Spin-coated monolayer silica colloidal crystals with unusual nonclose-packed structures are utilized as first-level etching masks in generating ordered polymer posts whose sizes can be much smaller than the templating silica microspheres. These polymer posts can then be used as second-level structural templates in fabricating highly ordered silicon nanopillars with broadly tunable geometries by employing metal-assisted chemical etching. As the silicon nanopillars are produced by direct wet etching on the surface of a single-crystalline silicon wafer, they are relatively free of volume defects and thus their bending strength approaches the predicted theoretical maximum. Most importantly, the unique nonclose-packed structure of the original colloidal template and the close-to-ideal mechanical property enables the formation of unusual open-structured hierarchical assemblies of rigid silicon nanopillars during water evaporation. Both experiments and numerical finite-difference time-domain modeling confirm the importance of high aspect ratios of the templated silicon nanopillars in achieving superior broadband antireflection properties. The large fraction of entrapped air in the hierarchically assembled silicon nanopillars further facilitates to accomplish superhydrophobic surface states, promising for developing self-cleaning antireflection coatings for many important optoelectronic applications.

Hydrophobic nanostructures fabricated by ferric nitrate etching method on single crystalline silicon surface

To improve the hydrophobicity of the surfaces of single crystalline silicon (sc-Si) wafers, hierarchical structures were fabricated on the surfaces of sc-Si wafers by using Fe(NO3)3/HF mixed solution as an etchant. Scanning electron microscope, atomic force microscope and water contact angle were used to characterize the etching of sc-Si wafers. It was found that after the etching process the surface micro/nano-structures having hemispherical etched pits with needle-like folds can be formed and the surface of sc-Si wafers possess hydrophobicity. The concentration of Fe(NO3)3, etching temperature and etching time have important impacts on surface morphology and surface hydrophobicity of the sc-Si. Results showed that the surface water contact angle of etched sc-Si wafers decreased with the increase of the concentration of Fe(NO3)3. The surface water contact angle of the sc-Si wafer treated with 0.2 M of Fe(NO3)3 is highest (124.37°) and increased by 145.89% compared to that of control sc-Si wafers due to the smallest surface roughness and the most smooth surface. Surface wettability of sc-Si wafers varied from hydrophobic to hydrophilic as the etching temperature increasing from 30 °C to 70 °C. When the etching temperature was 30 °C and 70 °C, the surface water contact angle of sc-Si wafer was 142.32° and 13.86°, respectively. With the increase of the etching time, rough grooves formed on the surface of sc-Si wafers and the roughness changed larger. Hydrophobic surfaces with a water contact angle up to 144.50° were obtained at etching time of 30 min.

Silicon and germanium nanostructures formed by spark discharge plasma

Formation of semiconductor nanostructures on the surface of single crystalline silicon and germanium wafers by spark discharge plasma in air was investigated. The prepared nanostructures were analyzed by means of the scanning and transmission electron microscopy and optical spectroscopy of the photoluminescence and Raman scattering. The formed nanostructures exhibit a fractal-like morphology with interconnected nanocrystals of 2-200 nm sizes that is explained by repeated processes of spark ablation and subsequent condensation. While the size and morphology of the nanostructure depend on power sources of the spark discharge, short interaction times of spark discharge plasma and target determine a relatively low efficiency of the chemical oxidation of germanium and silicon, as well as low ionic temperatures of the plasma.

Temperature field modeling and cut formation in laser micromachining of silicon in ice layer

Several hybrid laser machining processes have been proposed in recent years to eliminate and/or prevent the deposition of material debris, formation of recast layer and thermal damage in the laser-ablated region. Laser micromachining process performing in an ice layer is a novel technique which is of potential to limit these negative effects in work materials. In this paper, the thermal modeling of the laser ablation in ice is presented to advance the understanding of heat transfer and cut formation induced by the process. A nanosecond-pulse laser was used in this study for grooving a single-crystalline silicon wafer shielded by an ice layer. A 3D numerical simulation associated with the finite element method was performed and then verified by a set of experiments. Phase changes, plasma shielding effect and energy losses caused by thermal conduction and convection were also included in the model. The simulation results obtained under the different levels of laser power were found to have a good agreement with the experiments. The evolution of temperature field and cut formation in the workpiece can be realized at the different heating and cooling cycles of the pulsed laser irradiation. The model developed in this study could facilitate the design and optimization of the ice-assisted laser micromachining process to further advance the ablation of thermally sensitive materials in manufacturing.

Ni(II) doped FeOOH 2D nanocrystals, synthesized by Successive Ionic Layer Deposition, and their electrocatalytic properties during oxygen evolution reaction upon water splitting in the alkaline medium

Nanolayers of Ni(II) doped FeOOH 2D nanocrystals were for the first time synthesized on the surface of nickel foam and single crystalline silicon wafer through Successive Ionic Layer Deposition (SILD) method by using an aqueous solution of Fe(NH4)2(SO4)2 with the equilibrium pH value, as well as the solution containing Ni(NO3)2 and NH4NO3 with pH = 9.5 reached by addition of ammonia. The obtained nanolayers were investigated by SEM, HRTEM, TEM, EDX, XRD, XPS and FTIR spectroscopy. They were stated to be formed by Ni:FeOOH 2D nanocrystals with lepidocrocite and goethite crystal structures having the morphology of nanosheets. They are 2–5 nm thick with planar dimensions of about 30–50 nm and the ratio of atomic concentrations of Ni to Fe is 25%. The nanolayers were shown to exhibit electrocatalytic properties during the oxygen evolution reaction upon water splitting in the alkaline medium. For the first time it was shown that the overpotential value can be precisely set by varying the number of SILD cycles these properties can be changed precisely. For a number of samples, synthesized after 20–80 SILD cycles, it was found for a current density of 10 mA/cm2 the lowest overpotential value of 239 mV was obtained for the sample synthesized after 60 SILD cycles. The synthesis of a wide range of electrocatalytic nanolayers by SILD with the precise structural and chemical characteristics was suggested.

A 4410-ppi Resolution Pixel Circuit for High Luminance Uniformity of OLEDoS Microdisplays

This paper proposes a pixel circuit with high resolution and high luminance uniformity for organic light emitting diode-on-silicon (OLEDoS) microdisplays. The proposed pixel circuit employs a simple structure that consists of four n-channel MOSFETs and one capacitor, resulting in high resolution. In addition, this circuit compensates for the threshold voltage ( $V_{th}$ ) variation of the driving transistor caused by the body effect, which increases the $V_{th}$ as the source-to-body voltage of the driving transistor increases, thus reducing the emission current deviation, resulting in a high luminance uniformity. Moreover, the proposed pixel circuit extends the data voltage range using the capacitive coupling of the storage capacitance and the parasitic capacitance at the gate node of the driving transistor to precisely control the emission current. To verify the performance of the proposed pixel circuit, a test pattern with an array of the proposed 4T1C pixel circuits was fabricated on a single-crystalline silicon wafer as a backplane using a 110 nm standard CMOS process with 5.5 V high-voltage devices. The proposed pixel circuit occupies a unit sub-pixel area of $5.76 \mu \mathrm {m} \times 1.92 \mu \text{m}$ , which corresponds to a resolution of 4410 pixels per inch. The measurement results show that the emission current deviation error of the proposed pixel circuit ranges between −1.16% and +1.14%, which is improved from between −45.97% to +45.42% achieved in the conventional current-source type 2T1C pixel circuit, which does not compensate for the $V_{th}$ variation of the driving transistor. Moreover, the measured data voltage range of the proposed pixel circuit is extended to 1.618 V, which is 8.17 times wider than that of the conventional pixel circuit. Therefore, the proposed pixel circuit is very suitable for high resolution and high luminance uniformity of OLEDoS microdisplays.

XPS investigations of MOCVD tin oxide thin layers on Si nanowires array

Abstract Tin oxide thin layers were grown by metal-organic chemical vapor deposition technique on the top-down nanostructured silicon nanowires array obtained by metal-assisted wet-chemical technique from single crystalline silicon wafers. The composition of the formed layers were studied by high-resolution X-ray photoelectron spectroscopy of tin (Sn 3d) and oxygen (O 1 s) atoms core levels. The ion beam etching was applied to study the layers depth composition profiles. The composition studies of grown tin oxide layers is shown that the surface of layers contains tin dioxide, but the deeper part contains intermediate tin dioxide and metallic tin phases.

A 1300 mm2 Ultrahigh-Performance Digital Imaging Assembly using High-Quality Perovskite Single Crystals.

By fine-tuning the crystal nucleation and growth process, a low-temperature-gradient crystallization method is developed to fabricate high-quality perovskite CH3 NH3 PbBr3 single crystals with high carrier mobility of 81 ± 5 cm2 V-1 s-1 (>3 times larger than their thin film counterpart), long carrier lifetime of 899 ± 127 ns (>5 times larger than their thin film counterpart), and ultralow trap state density of 6.2 ± 2.7 × 109 cm-3 (even four orders of magnitude lower than that of single-crystalline silicon wafers). In fact, they are better than perovskite single crystals reported in prior work: their application in photosensors gives superior detectivity as high as 6 × 1013 Jones, ≈10-100 times better than commercial sensors made of silicon and InGaAs. Meanwhile, the response speed is as fast as 40 µs, ≈3 orders of magnitude faster than their thin film devices. A large-area (≈1300 mm2 ) imaging assembly composed of a 729-pixel sensor array is further designed and constructed, showing excellent imaging capability thanks to its superior quality and uniformity. This opens a new possibility to use the high-quality perovskite single-crystal-based devices for more advanced imaging sensors.