Search Results (12)

A multi-mode interferometer (MMI) spectrometer is a type of reconstructive micro-spectrometer based on imaging light propagation patterns in MMI waveguides. A waveguide scattering surface accentuates imaging light patterns in the multi-mode interferometer. This technology has been proven with an SU-8 core waveguide with an etched SU-8 nanograss scattering surface. This paper describes our creation of a fully silicon-based spectrometer using a silica core MMI waveguide. Scattering features were created in silica using SU-8 nanograss as an etch mask in a reactive ion etch (RIE). With optimized etch parameters, the silica core MMI spectrometer achieved an SNR of three with an incident light power of −68 dBm, which was almost 6 dB lower than designs with an SU-8 core. Full article

We report on the fabrication and characterization of InGaN-based ridge-waveguide laser diodes employing spin-on-glass (SOG) as the insulation and planarization layer. In contrast to conventional silicon dioxide (SiO₂) isolation deposited by PECVD, the SOG approach provides improved surface planarity, reduced processing complexity, and lower fabrication cost. The laser structures were grown on GaN substrates by MOCVD, with the active region consisting of In_0.11Ga_0.89N quantum wells. Following ridge formation and SOG deposition, an etch-back process was used to form the electrical contacts. We have demonstrated the formation of high-quality insulating surfaces with strong adhesion to the ridge sidewalls. When using a Ni protective layer, the fabricated devices exhibited favorable electrical and optical characteristics and achieved stable laser operation under both pulsed and continuous-wave conditions. These results indicate that the SOG-based insulation process represents a promising alternative for the scalable and cost-effective fabrication of InGaN laser diodes targeting advanced photonic applications. Full article

Inorganic gap filling technology is an effective method to improve reliability and heterogeneous integration density in 2.5D and 3D integration. It uses plasma-enhanced chemical vapor deposition (PECVD) to deposit silicon dioxide (SiO₂) filler layers in gaps between chiplets. This technology is used to replace the Epoxy Mold Compound (EMC) commonly used in traditional packaging. However, as an inorganic filling material, SiO₂ poses reliability challenges such as cracking and peeling during or after deposition. Furthermore, there lacks quantitative characterization and modeling of the microscale mechanical properties, thermal stress distribution, and fracture failure risk in the filler layer. By combining nanoindentation technology with three-point bending tests, this study reports a comprehensive characterization route for quantitative characterization of mechanical behavior of the filler. A finite element method (FEM) model was also established to predict the thermomechanical reliability of the gap filling process. Raman spectroscopy measured data confirm the model’s reliable predictive ability. The results reveal the impact of filler thickness on the stress. The microscale SiO₂ mechanical characterization method and the thermal stress and fracture risk FEM prediction model in this study not only address the limitations of traditional testing and simulation but also provide support for process optimization and structural design of gap filling in high-density 2.5D/3D packaging. This work promotes the understanding of inorganic filling process reliability in chiplet integration. Full article

Mesoporous silicon dioxide films have been shown to be well suited as adhesion-promoting interlayers for generating high-strength polymer–metal interfaces. These films can be fabricated via microwave plasma-enhanced chemical vapor deposition using the precursor hexamethyldisiloxane and oxygen as working gas. The resulting mesoporous structures enable polymer infiltration during overmolding, which leads to a nanoscale form-locking mechanism after solidification. This mechanism allows for efficient stress transfer across the interface and makes the resulting adhesion highly dependent on the morphology of the deposited film. To gain a deeper understanding of the underlying deposition mechanisms and improve process stability, this work investigates the growth behavior of mesoporous silica films using a multiple regression analysis approach. The seven process parameters coating time, distance, chamber pressure, substrate temperature, flow rate, plasma pulse duration, and pause-to-pulse ratio were systematically varied within a Design of Experiments framework. The resulting films were characterized by their free surface area, mean agglomerate diameter, and film thickness using digital image analysis, white light interferometry, and atomic force microscopy. The deposited films exhibit a wide range of morphological appearances, ranging from quasi-dense to dust-like structures. As part of this research, the free surface area varied from 15 to 55 percent, the mean agglomerate diameter from 17 to 126 nm, and the film thickness from 35 to 1600 nm. The derived growth model describes the deposition process with high statistical accuracy. Furthermore, all coatings were overmolded via injection molding and subjected to mechanical testing, allowing a direct correlation between film morphology and their performance as adhesion-promoting interlayers. Full article

Silicon oxynitride (SiO_xN_y, hereafter denoted as SiON) thin films represent an intermediate phase between silicon dioxide (SiO₂) and silicon nitride (Si₃N₄). Through systematic compositional ratio adjustments, the refractive index can be precisely tuned across a wide range from 1.45 to 2.3. However, the underlying mechanism governing the influence of elemental composition on film structural quality remains insufficiently understood. To address this knowledge gap, we systematically investigate the effects of key industrial plasma-enhanced chemical vapor deposition (PECVD) parameters—including precursor gas selection and flow rate ratios—on SiON film properties. Our experimental measurements reveal that stoichiometric SiO_xN_y (x = y) achieves a minimum surface roughness of 0.18 nm. As oxygen content decreases and nitrogen content increases, progressive replacement of Si-O bonds by Si-N bonds correlates with increased structural defect density within the film matrix. Capacitance–voltage (C-V) characterization demonstrates a corresponding enhancement in device capacitance following these compositional modifications. Recent studies confirm that controlled modulation of film stoichiometry enables precise tailoring of dielectric properties and capacitive behavior, as demonstrated in SiON-based power electronics, thereby advancing applications in related fields. Full article

The influence of Ar + SiH₄ + O₂ plasma formulation on the phase composition and optical properties of amorphous SiO_x films with silicon nanoclusters obtained using PECVD with DC discharge modulation was studied. Using a unique technique of ultrasoft X-ray emission spectroscopy, it was found that at a 0.15 mol.% plasma oxygen content, amorphous silicon a-Si films are formed. At a high oxygen content (≥21.5 mol.%), nanocomposite films based on SiO_x silicon suboxide containing silicon nanoclusters ncl-Si are formed. It was found that the suboxide matrix consists of a mixture of SiO_1.3 and SiO₂ phases, and the average oxidation state x in the SiO_x suboxide matrix is ~1.5. An increase in the concentration of O₂ in the reactor atmosphere from 21.5 to 23 mol.% leads to a decrease in ncl-Si content from 40 to 15% and an increase in the average oxidation state x of SiO_x from 1.5 to 1.9. In this case, the suboxide matrix consists of two phases of silicon dioxide SiO₂ and non-stoichiometric silicon oxide SiO_1.7. Thus, according to the experimental data obtained using USXES, the phase composition of these films in pure form differs in their representation in both random coupling and random mixture models. A decrease in the ncl-Si content of SiO_x films is accompanied by a decrease in their sizes from ~3 to ~2 nm and a shift in the photoluminescence band from 1.9 eV to 2.3 eV, respectively. Full article

Unique electronic properties of graphene offer highly interesting ways to manipulate the functional properties of surfaces and develop novel structures which are sensitive to physical and chemical interactions. Nano-crystalline graphene is frequently preferable to crystalline monolayer in detecting devices. In this work, nano-crystalline graphene layers were synthesized directly on SiO₂/Si substrates by plasma-enhanced chemical vapour deposition (PECVD). The influence of the deposition time and temperature on the characteristics of the structures were studied. The optical properties and evaporation kinetics of pure water droplets were analysed, along with arrangement and composition of the grown layers. The nano-crystalline graphene layers grown at 500 °C were characterised by the refraction index 2.75 ± 0.35 and the normalised excess Gibbs free energy density 0.85/γ_water 10⁻⁴ m, both being similar to those of the monolayer graphene. The changes in the refraction index and the excess Gibbs free energy were related to the parameters of the Raman spectra and a correlation with the technological variables were disclosed. Full article

We utilized a plasma-enhanced atomic layer deposition (PEALD) process to deposit an AlN passivation layer on AlGaN/GaN surface to enhance the polarization effects, which enabled the fabrication of an enhancement-mode (E-mode) AlGaN/GaN metal-insulator-semiconductor heterojunction field-effect transistor (MIS-HFET) without the need for a gate recess process. The AlN film deposited by PEALD exhibited a crystalline structure, not an amorphous one. The enhanced polarization effect of introducing the PEALD AlN film on a thin AlGaN barrier was confirmed through electrical analysis. To fabricate the E-mode AlGaN/GaN MIS-HFET, the PEALD AlN film was deposited on a 4.5 nm AlGaN barrier layer and then a damage-free wet etching process was used to open the gate region. The MIS-gate structure was formed by depositing a 15 nm plasma-enhanced chemical vapor deposition (PECVD) silicon dioxide (SiO₂) film. The fabricated thin-AlGaN/GaN MIS-HFET demonstrated successful E-mode operation, with a threshold voltage of 0.45 V, an on/off ratio of approximately 10⁹, a specific on-resistance of 7.1 mΩ·cm², and an off-state breakdown voltage exceeding 1100 V. Full article

Peri-implantitis leads to implant failure and decreases long-term survival and success rates of implant-supported prostheses. The pathogenesis of this disease is complex but implant corrosion is believed to be one of the many factors which contributes to progression of this disease. A nanostructured titanium dioxide layer was introduced using anodization to improve the functionality of dental implants. In the present study, we evaluated the corrosion performance of silicon carbide (SiC) on anodized titanium dioxide nanotubes (ATO) using plasma-enhanced chemical vapor deposition (PECVD). This was investigated through a potentiodynamic polarization test and bacterial incubation for 30 days. Scanning electron microscopy (SEM) and transmission electron microscopy (TEM) were used to analyze surface morphologies of non-coated and SiC-coated nanotubes. Energy dispersive X-ray (EDX) was used to analyze the surface composition. In conclusion, SiC-coated ATO exhibited improved corrosion resistance and holds promise as an implant coating material. Full article

SiO₂ thin films are deposited by radio frequency (RF) plasma-enhanced chemical vapor deposition (PECVD) technique using SiH₄ and N₂O as precursor gases. The stoichiometry of SiO₂ thin films is determined by the X-ray photoelectron spectroscopy (XPS), and the optical constant n and k are obtained by using variable angle spectroscopic ellipsometer (VASE) in the spectral range 380–1600 nm. The refractive index and extinction coefficient of the deposited SiO₂ thin films at 500 nm are 1.464 and 0.0069, respectively. The deposition rate of SiO₂ thin films is controlled by changing the reaction pressure. The effects of deposition rate, film thickness, and microstructure size on the conformality of SiO₂ thin films are studied. The conformality of SiO₂ thin films increases from 0.68 to 0.91, with the increase of deposition rate of the SiO₂ thin film from 20.84 to 41.92 nm/min. The conformality of SiO₂ thin films decreases with the increase of film thickness, and the higher the step height, the smaller the conformality of SiO₂ thin films. Full article

Silica (SiO_2, silicon dioxide—a dielectric layer commonly used in electronic devices) is widely used in many types of sensors, such as gas, molecular, and biogenic polyamines. To form silica films, core shell or an encapsulated layer, silane has been used as a precursor in recent decades. However, there are many hazards caused by using silane, such as its being extremely flammable, the explosive air, and skin and eye pain. To avoid these hazards, it is necessary to spend many resources on industrial safety design. Thus, the silica synthesized without silane gas which can be determined as a silane-free procedure presents a clean and safe solution to manufactures. In this report, we used the radio frequency (rf = 13.56 MHz) plasma-enhanced chemical vapor deposition technique (PECVD) to form a silica layer at room temperature. The silica layer is formed in hydrogen-based plasma at room temperature and silane gas is not used in this process. The substrate temperature dominates the silica formation, but the distance between the substrate and electrode (D_STE) and the methane additive can enhance the formation of a silica layer on the Si wafer. This silane-free procedure, at room temperature, is not only safer and friendlier to the environment but is also useful in the fabrication of many types of sensors. Full article

Aimed at the problem of the small wet etching depth in sapphire microstructure processing technology, a multilayer composite mask layer is proposed. The thickness of the mask layer is studied, combined with the corrosion rate of different materials on sapphire in the sapphire etching solution, different mask layers are selected for the corrosion test on the sapphire sheet, and then the corrosion experiment is carried out. The results show that at 250 °C, the choice is relatively high when PECVD (Plasma Enhanced Chemical Vapor Deposition) is used to make a double-layer composite film of silicon dioxide and silicon nitride. When the temperature rises to 300 °C, the selection ratio of the silicon dioxide layer grown by PECVD is much greater than that of the silicon nitride layer. Therefore, under high temperature conditions, a certain thickness of silicon dioxide can be used as a mask layer for deep cavity corrosion. Full article