Silicon Wafers Research Articles

Silanization Strategies for Tailoring Peptide Functionalization on Silicon Surfaces: Implications for Enhancing Stem Cell Adhesion.

Biomaterial surface engineering and the integration of cell-adhesive ligands are crucial in biological research and biotechnological applications. The interplay between cells and their microenvironment, influenced by chemical and physical cues, impacts cellular behavior. Surface modification of biomaterials profoundly affects cellular responses, especially at the cell-surface interface. This work focuses on enhancing cellular activities through material manipulation, emphasizing silanization for further functionalization with bioactive molecules such as RGD peptides to improve cell adhesion. The grafting of three distinct silanes onto silicon wafers using both spin coating and immersion methods was investigated. This study sheds light on the effects of different alkyl chain lengths and protecting groups on cellular behavior, providing valuable insights into optimizing silane-based self-assembled monolayers (SAMs) before peptide or protein grafting for the first time. Specifically, it challenges the common use of APTES molecules in this context. These findings advance our understanding of surface modification strategies, paving the way for tailoring biomaterial surfaces to modulate the cellular behavior for diverse biotechnological applications.

Fabrication of a sharp Si protrusion with a faceted apex grown from a surface-melted silicon wafer under high electric and magnetic fields: application to field emission electron sources

A silicon (Si) protrusion, grown on a narrow path of a Si(001) wafer by surface melting via resistive heating, was sharpened by applying a local high electric field under a magnetic field during the growth. The electric field caused local stress to the surface-melted Si, which was pulled upward along the field. Consequently, the melted Si formed a sharper protrusion on solidification, with an apex surrounded by {001}, {113}, and {111} facets. The field emission from the protrusions was measured. The onset voltage of the emission from protrusions was lower when they were grown under the electric field. We used Fowler–Nordheim plots to characterize the emission current and voltage conversion factor, β. The results indicated that the application of electric field is beneficial to sharpening Si protrusions grown from Si melt. Such protrusions surrounded by facets are suitable for field emission electron sources with a high local electric field.

Suppressing The Blistering of Silicon Nitride in PERC Solar Cells for High Industrial Yield

Passivated emitter and rear contact (PERC) solar cells possess the highest photovoltaic market share at present. In industrial production, blistering of the rear silicon nitride (SiNx) passivation layer significantly affects the yield. In order to solve this problem, the relevant processes for manufacturing the PERC solar cells have been carefully studied. It was found that polishing of the silicon wafer rear surface, aluminum (AlOx) thickness, and the deposition process of the SiNx layer will affect the blistering ratio. By optimizing the manufacturing process mentioned above, the blistering ratio of the PERC solar cells has been effectively suppressed. This work not only provides reliable technical support for the yield improvement of the PERC solar cells but also provides some useful reference for the tunnel oxide passivated contact (TOPcon) and back contact (BC) solar cell industrial manufacture.

Use of plasma process diagnostic sensors for the monitoring of in situ dry cleaning of plasma enhanced chemical vapor deposition chamber

A potential source of particle contamination due to poorly maintained PECVD chamber condition forces to perform in situ dry cleaning also actively employed before the wet-cleaning chamber maintenance period. In this paper, we demonstrate the use of plasma process diagnostic sensors, optical emission spectroscope, and quadrupole mass spectrometer for in situ plasma monitoring of the dry-cleaning step. It is worthwhile to know the thin film residue on the chamber’s inner wall, but it is difficult to collect the deposited thin film sample from the wall since the preparation of the sample from the equipment is impossible. To alleviate the concern, we prepared silicon wafer samples mounted on the chamber sidewall over the prolonged exposure of the SiO2 deposition process, and the collected sensory data were investigated under the dry-cleaning condition. The residue film obtained through the experiment was characterized by Fourier transform infrared, x-ray photoelectron spectroscopy, atomic force microscopy, and scanning electron microscopy. We found a useful insight into the chamber dry-cleaning end point detection application through residual gas analysis, and the results contribute to process engineers setting up the in situ dry-cleaning recipe to make sure that subsequent deposition can be consistently maintained.

Three-Dimensional Profile Reconstruction and Internal Defect Detection of Silicon Wafers Using Cascaded Fiber Optic Fabry–Pérot Interferometer and Leaky Field Detection Technologies

Abstract Wafer quality control is one of the important processes to improve the yield rate of semiconductor products. Profile quality and defects in the wafer are two key factors that should be taken into consideration. In this research, we introduce a method that measures the profile of the upper surface and the thickness of the wafer at the same time using an optical fiber cascaded Fabry–Pérot interferometer working at wavelength of 1550 nm. Therefore, the 3D profile of the wafer can be reconstructed directly. Testing results show that both accuracy and precision of the Fabry–Pérot interferometer are within a nanometer scale. Defects, especially those embedded inside the wafer, will be detected by monitoring the leaky field with treating wafers as slab waveguides. With the leaky field detection, defects on the lower surface of the wafer were successfully detected by monitoring the leaky field above the upper surface of the wafer. Compared with traditional methods such as radiographic testing or computed tomography testing, the proposed methods provide a cost-effective alternative for wafer quality evaluation.

Fractal analysis on the surface topography of Monocrystalline silicon wafers sawn by diamond wire

The direct impact of diamond wire slicing on the cost of subsequent silicon wafer processing underscores the significance of reducing slicing costs for both the integrated circuit and photovoltaic industries. Effectively and reasonably evaluating monocrystalline silicon wafer quality is thus a crucial challenge. In this paper, fractal theory was used to analyze the monocrystalline silicon wafer sawn surfaces combining with surface roughness measurement. The findings reveal the presence of scratches, pits, and prominent saw marks on the sawn surface. Notably, the surface roughness is significantly higher along the feed direction compared to that along the wire direction. Moreover, an increase in the ratio of feed speed to wire speed leads to a rougher surface. The fractal dimension of the sawn surface is inversely proportional to its roughness, indicating that a higher fractal dimension corresponds to a finer surface texture. Moreover, the two dimensional fractal dimension can effectively capture the anisotropic characteristics of monocrystalline silicon wafers. The two dimensional fractal dimension of the wafer surface obtained by removing materials in ductile mode has a strong symmetry. However, the two dimensional fractal dimension of the surface obtained in brittle mode fluctuates obviously and is weakly symmetric. By combining traditional surface roughness analysis with fractal methods, we can gain insights into the material removal mechanisms involved in slicing monocrystalline silicon wafers using diamond wire, which is of great significance for optimizing diamond wire slicing.

52‐2: Invited Paper: 1µm Nanowire Based MicroLED Chips for Efficient and High Performance Smart Watch Displays

One of the microLED direct view display major challenges is to find ways of drastically dropping the cost, for instance by reducing the microLED size, simplifying the assembly process, and improving the assembly yield.Aledia has developed a 3D nanowire (NW) microLED technology on 8” silicon wafers which has the outstanding capability to keep the same efficiency for <4µm size devices containing only 1NW as for larger devices containing hundreds of NWs. This technology provides similar efficiency as well as electro‐optical parameters (I‐V and Emission Spectra) whatever the microLED size. Over 30% Wall Plug Efficiency (WPE) is obtained and 3% WPE standard deviation is measured at wafer level as well as a wavelength standard deviation as low as 1.5 nm. Those results show that our technology allowsthe manufacturing of micron size microLEDs on a Si platform without experiencing a loss of efficiency with size reduction. We will present our technology and its performance. Based on our microLED we will also propose a cost competitive and energy efficient direct‐view smartwatch display architecture.

Ion motion above a biased wafer in a plasma etching reactor

The behavior of ions in the plasma is an essential component in the process of industrial etching. We studied the motions and energy distribution of argon ions in a inductively coupled plasma (ICP) etching tool, by the method of laser induced fluorescence (LIF). The silicon wafer clamped to a chuck at the bottom of the chamber was biased with a 1 MHz 1–1.2 kV peak-to-peak sinusoidal voltage. The plasma is formed with a 2 MHz ICP coil pulsed at 10 Hz. Sheath thickness was measured at different phases of the bias waveform. The experiment also compared the ion motions with and without wafer bias, as well as different switch-on time of wafer bias. For all cases, ion energy distribution functions and the two-dimensional flow pattern were studied near the center and edge of the wafer. Significant vortex flows were observed near the wafer edge. Experiments in which the wafer was biased in the plasma afterglow resulted in a narrow distribution of ion energy close to the bias voltage at the vicinity of the wafer, and the ion incident angle on the wafer was the smallest. The results were compared to simulations using the Hybrid Plasma Equipment Model code.

Low-loss α-tantalum coplanar waveguide resonators on silicon wafers: fabrication, characterization and surface modification

The performance of state-of-the-art superconducting quantum devices is currently limited by microwave dielectric loss at different interfaces. α-tantalum is a superconductor that has proven effective in reducing dielectric loss and improving device performance due to its thin low-loss oxide. Here, we demonstrate the fabrication of high-quality factor α-tantalum coplanar-waveguide resonators directly on pristine 300 mm silicon wafers over a variety of metal deposition conditions and perform a comprehensive material and electrical characterization study. Additionally, we apply a surface treatment based on hydrofluoric acid that allows us to modify different resonators surfaces, leading to a reduction in two-level system loss in the devices by a factor of three. This loss reduction can be entirely attributed to the removal of surface oxides. Our study indicates that large scale manufacturing of low-loss superconducting circuits should indeed be feasible and suggests a viable avenue to materials-driven advancements in superconducting circuit performance.

Resonant Ring with a Gain of 36 for Use with a 1 MW 110 GHz Gyrotron

A 110 GHz quasi-optical ring resonator, designed for use with a 1 MW pulsed gyrotron, has been built and successfully tested using a 100 mW solid-state source. A low reflectance (2.4%) input coupler and a low-loss, four-mirror ring demonstrated a compression ratio, defined as the ratio of output to input power, of 36. The 6 ns output pulses were generated from the 2 m length ring using a silicon laser-driven semiconductor switch (LDSS). The quasi-optical ring resonator was designed with large waist sizes so that input pulses of up to 1 MW will stay under the 35 kV/cm electric field limit for ionization in ambient air. Maximum compression gain was achieved by matching the input coupling fraction to the round trip loss in the ring, achieving close to critical coupling. The experimental output pulse shape obtained after firing the LDSS was modeled using the reflectance, transmittance, and absorptance of the switch vs. time and vs. laser pulse fluence, with good agreement found with theory. The timing for the peak energy efficiency of 32% was found and the main loss mechanism limiting that efficiency was found to be the absorptance in the silicon wafer.

Controllable Fabrication of Silicon Solar Cells with Inverted or Upright Pyramid Structures by a One-Step Copper Catalysis Method

Silicon has garnered significant attention as the primary material for solar cell preparation. Traditional alkaline etching solutions are limited to creating an upright pyramid structure on monocrystalline silicon surfaces. However, research indicates that an inverted pyramid structure exhibits superior light-trapping properties compared to the upright pyramid structure. In this study, we employed a one-step copper ion metal-assisted chemical etching process to fabricate an inverted pyramid structure on monocrystalline silicon wafers. This method allows for the customization of either inverted or upright pyramid structures by adjusting the concentration of specific solution components. Characterization of the textured silicon wafers reveals that the inverted pyramid structure exhibits lower reflectivity than both the upright pyramid structure and polished silicon. By integrating this texturing technique into the solar cell production line, we successfully produced solar cells with both inverted and upright pyramid structures. Evaluation of various solar cell parameters demonstrates that the inverted pyramid structure outperforms the upright pyramid structure, showcasing lower reflectivity and higher photoelectric conversion efficiency.

Facile preparation of zwitterionic core-shell nanogels for dual-functional coatings: Combining antifouling and antibacterial features in silicon implant model surface modification

To develop surface-coating technology for fabricating functionalized biomedical implant and overcome implant-associated bacterial infections, this study presented an innovative antifouling and antibacterial dual-functional nanogel coating methodology for engineering silicon-based biomedical implants/biochips. Firstly, zwitterionic core-shell PAA@(GMA/SBMA) nanogels were designed and prepared via reflux-precipitation polymerization and were characterized through NMR, FTIR, DLS, AFM and TEM. The nanogels exhibited uniform and spherical morphology, salt-ion responsiveness, and high lysozyme loading capability. Subsequently, the PAA@(GMA/SBMA) nanogels were covalently grafted onto the surface of silicon wafers, via an epoxy-amine ring-opening reaction, to prepare nanogel-coated silicon wafers (Si@nanogels). A comprehensive array of characterization techniques, including SEM-EDS, contact angle measurements, and XPS, validated the effective nanogel-coating. These coatings demonstrated notable resistance to protein adsorption, highlighting their robust antifouling properties. Upon loading with the antibacterial agent lysozyme, the nanogel coating displayed remarkable antibacterial efficacy against both Gram-negative (E. coli) and Grampositive (S. aureus) bacteria and effectively inhibited biofilm formation. Furthermore, the nanogel coatings exhibited good biocompatibility and dynamic stability, thus facilitating the surface-mediated adhesion and growth of fibroblast 3T3 cells. Significantly, this work provided a facile, economic and efficient surface modification approach to fabricate nanogel-coated antifouling/antibacterial dual-functional biomedical implant model towards potential clinical applications.

Formation of Black Silicon in a Process of Plasma Etching with Passivation in a SF6/O2 Gas Mixture.

This article discusses a method for forming black silicon using plasma etching at a sample temperature range from -20 °C to +20 °C in a mixture of oxygen and sulfur hexafluoride. The surface morphology of the resulting structures, the autocorrelation function of surface features, and reflectivity were studied depending on the process parameters-the composition of the plasma mixture, temperature and other discharge parameters (radical concentrations). The relationship between these parameters and the concentrations of oxygen and fluorine radicals in plasma is shown. A novel approach has been studied to reduce the reflectance using conformal bilayer dielectric coatings deposited by atomic layer deposition. The reflectivity of the resulting black silicon was studied in a wide spectral range from 400 to 900 nm. As a result of the research, technologies for creating black silicon on silicon wafers with a diameter of 200 mm have been proposed, and the structure formation process takes no more than 5 min. The resulting structures are an example of the self-formation of nanostructures due to anisotropic etching in a gas discharge plasma. This material has high mechanical, chemical and thermal stability and can be used as an antireflective coating, in structures requiring a developed surface-photovoltaics, supercapacitors, catalysts, and antibacterial surfaces.

High-performance CsPbBr3-silicon heterojunction photodetectors fabricated by chemical vapor deposition

Inorganic perovskite cesium lead halide (CsPbBr3) has attracted extensive research attention due to its excellent photoelectric properties and long-term stability to water, oxygen, light and heat. In this work, high crystallinity CsPbBr3 microcrystals with different morphologies and grain sizes were synthesized by one-step chemical vapor deposition (CVD) on silicon (Si) wafers and silicon nanowires (SiNWs), respectively. Characterization results show that the CsPbBr3 microcrystals grown on SiNWs (CsPbBr3-SiNWs) display more compact and uniform morphologies than those grown on Si wafer (CsPbBr3-Si). Moreover, CsPbBr3-SiNWs exhibits higher detectivity and larger on/off ratio than CsPbBr3-Si, which are 5.1 × 1012 Jones over 3.4 × 1012 Jones, and 51.3 over 14.7, respectively. Furthermore, CsPbBr3-SiNWs shows a faster photo response with a rise/fall time of 0.22 s/0.28 s than 0.26 s/0.32 s in CsPbBr3-Si. In addition, the CsPbBr3-SiNWs photodetector maintained 90% of its original photocurrent after 60 days of exposure to air, showing excellent stability. These results strongly suggest a promising fabrication approach for constructing perovskite-based heterojunction optoelectronic devices with high performance and excellent stability.

Designing PEDOT: PSS/Si hybrid solar cells via numerical simulation: optimum selection of the absorber and hole transport layer thickness and defect density

Numerical investigation of PEDOT: PSS/Si heterostructures was carried out using solar cell capacitance simulation (SCAPS 1D) in which experimentally observed absorbance of PEDOT: PSS was incorporated. The defect density of PEDOT: PSS, the defect density of n-Si, and the donor doping density of n-type silicon wafer were investigated based on the optimized absorption coefficient of n-type silicon wafer. The optimized value of PEDOT: PSS thickness, doping density, and the defect density of both PEDOT: PSS and n-Si were determined. The contour colour mapping tool was used to predict the efficiency region of the heterojunction solar cell. 21.2% efficient PEDOT: PSS/n-Si hybrid solar cells resulted after optimizing the parameters.

DNA Origami Plasmonic Nanoantenna for Programmable Biosensing of Multiple Cytokines in Cancer Immunotherapy.

Herein, we report a DNA origami plasmonic nanoantenna for the programmable surface-enhanced Raman scattering (SERS) detection of cytokine release syndrome (CRS)-associated cytokines (e.g., tumor necrosis factor-α (TNF-α) and interferon-γ (IFN-γ)) in cancer immunotherapy. Typically, the nanoantenna was made of self-assembled DNA origami nanotubes (diameter: ∼19 nm; length: ∼90 nm) attached to a silver nanoparticle-modified silicon wafer (AgNP/Si). Each DNA origami nanotube contains one miniature gold nanorod (AuNR) inside (e.g., length: ∼35 nm; width: ∼7 nm). Intriguingly, TNF-α and IFN-γ logically regulate the opening of the nanotubes and the dissociation of the AuNRs from the origami structure upon binding to their corresponding aptamers. On this basis, we constructed a complete set of Boolean logic gates that read cytokine molecules as inputs and return changes in Raman signals as outputs. Significantly, we demonstrated that the presented system enables the quantification of TNF-α and IFN-γ in the serum of tumor-bearing mice receiving different types of immunotherapies (e.g., PD1/PD-L1 complex inhibitors and STING agonists). The sensing results are consistent with those of the ELISA. This strategy fills a gap in the use of DNA origami for the detection of multiple cytokines in real systems.

Continuously tunable uniaxial strain control of van der Waals heterostructure devices

Uniaxial strain has been widely used as a powerful tool for investigating and controlling the properties of quantum materials. However, existing strain techniques have so far mostly been limited to use with bulk crystals. Although recent progress has been made in extending the application of strain to two-dimensional van der Waals (vdW) heterostructures, these techniques have been limited to optical characterization and extremely simple electrical device geometries. Here, we report a piezoelectric-based in situ uniaxial strain technique enabling simultaneous electrical transport and optical spectroscopy characterization of dual-gated vdW heterostructure devices. Critically, our technique remains compatible with vdW heterostructure devices of arbitrary complexity fabricated on conventional silicon/silicon dioxide wafer substrates. We demonstrate a large and continuously tunable strain of up to −0.15% at millikelvin temperatures, with larger strain values also likely achievable. We quantify the strain transmission from the silicon wafer to the vdW heterostructure, and further demonstrate the ability of strain to modify the electronic properties of twisted bilayer graphene. Our technique provides a highly versatile new method for exploring the effect of uniaxial strain on both the electrical and optical properties of vdW heterostructures and can be easily extended to include additional characterization techniques.

Metal-organic decomposed lanthanum cerium oxide thin films: A study of chemical and surface properties

Lanthanum cerium oxide thin films have been deposited on n-type (100) silicon wafers using the spin coating technique. The post-deposition annealing was performed over spin-coated films. The compositional studies were conducted by performing Fourier transform infrared spectroscopy, Energy dispersive X-ray spectroscopy, and X-ray diffraction. Ellipsometry was used to determine the thickness and atomic force microscopy was performed to understand the surface morphology of the deposited thin films. The effect of rapid thermal annealing at different temperatures over the structural and chemical properties of the LaCeO2 thin films was observed. The FTIR spectra show the formation of silicates at the interface of the oxide and semiconductor, while XRD results show that the films become crystalline with increased annealing temperature. The refractive index was observed to be reduced with an increase in the annealing temperature and a minor reduction in the physical thickness as per the sample standard deviation of 0.2981[Formula: see text]nm.

Photovoltaic Manufacturing Factories and Industrial Site Environmental Impact Assessment

Life cycle inventories (LCIs) and life cycle assessments (LCAs) of photovoltaic (PV) modules and their components focus on the operations of PV factories, but the factories and industrial site product and construction stages are either not or only partially tackled. This work contributes through the bottom-up, model-based generation of LCIs and LCAs for setting up a vertically integrated 5 GWp/a PV industrial site, including the manufacturing of silicon ingots, wafers, solar cells, and PV modules, on a 50 ha greenfield location. Two comparative LCAs are performed. The first compares the annualized environmental impacts of the developed LCI sets with four existing inventories in the Ecoinvent v3.8 database. The second comparative LCA explores the environmental impact differences concerning the industrial site when using different building systems for the factories. Here, the reference system with a steel structure is compared with two alternative building systems: precast concrete and structural timber. The results show that the wafer, cell, and module factories’ annualized environmental impacts with the Ecoinvent LCIs are strongly overestimated. For the ingot factory, the opposite result is identified. The impacts of all four factories show reductions of between 11.7% and 94.3% for 14 of the 15 impact categories. High mean environmental impact shares of 79.0%, 78.2% and 79.2% for the steel, precast concrete and timber structural building systems, respectively, are generated at the product stage. The process and facilities equipment generates 54.2%, 54.4% and 58.2% of the total product and construction stages’ mean environmental impact shares. The proposed alternative timber building system reduces the environmental impacts in 14 of the 15 evaluated categories, with reductions ranging from 1.1% to 12.4%.

Development of rigid polishing materials for use in microelectronics

The paper presents the results of development of conditions for obtaining hard polishing materials based on polyetherurethane solutions for chemical-mechanical planarization of semiconductor silicon wafers.