Silicon-rich Nitride Layers Research Articles

Hot electron engineering for boosting electroluminescence efficiencies of silicon-rich nitride light emitting devices

The combination of a SiO2 electron accelerator layer with a silicon-rich nitride layer forming a bilayer embedded in a metal-oxide-semiconductor structure has proved to enhance the integrated visible-infrared EL intensity by more than two orders of magnitude in comparison to the single-layer electroluminescent device approach. The origin of such an improvement is attributed to the massive ionization of defects in the silicon-rich nitride layer by direct impact of injected hot electrons coming from the SiO2 conduction band. Our premises are further corroborated by performing a thorough study of the charge transport in the bilayer structure. This study displays a main electrical mechanism at steady state that combines hot-electron tunneling injection from the SiO2 accelerator layer and space charge-limited current enhanced by Poole-Frenkel conduction from the silicon-rich nitride electroluminescent layer. The proposed electrical mechanism is validated by numerical simulations that provide good agreement with the experimental behavior. These results point out the feasibility of boosting electroluminescence efficiency of Si-based light emitting devices by performing an adequate gate stack engineering that maximizes the hot-electron injection into the electroluminescent layer.

Study of Silicon Nanoparticles Formation in Silicon Nitride

We present results of the study on the silicon nanoparticles formation in multilayer silicon nitride structures. These structures consist of pairs of stoichiometric silicon nitride dielectric layers (SiNx) and silicon rich nitride layers (SRN). Silicon nanocrystals precipitate from the SRN layer during annealing at high temperatures (1000 °C or 1100 °C). High resolution transmission electron microscopy has been applied for investigation of the nanocrystals formation. Surface photovoltage spectroscopy technique was used for the spectral characterization of prepared structures

Crystallization Behavior of Silicon Quantum Dots in a Silicon Nitride Matrix

Silicon quantum dot superlattice was fabricated by alternating deposition of silicon rich nitride (SRN) and Si3N4 layers using RF magnetron co-sputtering. Samples were then annealed at temperatures between 800 and 1,100 degrees C and characterized by grazing incident X-ray diffraction (GIXRD), transmission electron microscopy (TEM), Raman spectroscopy, and Fourier transform infrared spectroscopy (FTIR). GIXRD and Raman analyses show that the formation of silicon quantum dots occurs with annealing above 1,100 degrees C for at least 60 minutes. As the annealing time increased the crystallization of silicon quantum dots was also increased. TEM images clearly showed SRN/Si3N4 superlattice structure and silicon quantum dots formation in SRN layers after annealing at 1,100 degrees C for more than 60 minutes. The changes in FTIR transmission spectra observed with annealing condition corresponded to the configuration of Si-N bonds. Crystallization of silicon quantum dots in a silicon nitride matrix started stabilizing after 60 minutes' annealing and approached completion after 120 minutes'. The systematic investigation of silicon quantum dots in a silicon nitride matrix and their properties for solar cell application are presented.

Spark protection layers for CMOS pixel anode chips in MPGDs

In this work we have investigated the functioning of high resistivity amorphous silicon and silicon-rich nitride layers as a protection against discharges in Micro-Patterned Gaseous Detectors (MPGDs). When the anode is protected by a high resistivity layer, discharge signals are limited in charge. A signal reduction is expected when the layers are too thick; simulations presented in this paper indicate that layers up to 10 μm thick can be applied without significantly degrading the detector performance. Layers of amorphous silicon and silicon-rich nitride have been deposited on top of Timepix and Medipix2 chips in GridPix detectors; with this, chips survive naturally occurring as well as intentionally produced discharges.

Fabrication of a silicon oxide stamp by edge lithography reinforced with silicon nitride for nanoimprint lithography

The fabrication of a stamp reinforced with silicon nitride is presented for its use in nanoimprint lithography. The fabrication process is based on edge lithography using conventional optical lithography and wet anisotropic etching of ⟨1 1 0⟩ silicon wafers. SiO2 nano-ridges of 20 nm in width were fabricated. A silicon rich nitride layer is deposited over the original SiO2 nano-ridges to improve the ridge strength and to achieve a positive tapered shape which is beneficial for nanoimprinting. A replica of the nano-ridges with silicon rich nitride shield is obtained by imprinting the stamp into thermoplastic nanoimprint polymer mr-I 7010E.

Spontaneous direct bonding of thick silicon nitride

Wafers with LPCVD silicon-rich nitride layers have been successfully direct bonded to silicon-rich nitride and boron-doped silicon surfaces. A chemical - mechanical polishing treatment was necessary to reduce the surface roughness of the nitride before bonding. The measured surface energies of the room-temperature bond were comparable to values found for Si - Si hydrophilic bonding. A mechanism similar to this bonding is suggested for silicon nitride bonding.

Vacuum sealing of microcavities using metal evaporation

A new encapsulation technique to seal a vacuum-tube microcavity hermetically at low pressures, based on aluminium evaporation, is presented and its performance is compared to conventional low-pressure chemical vapour deposition (LPCVD) reactive sealing. The microdiode consists of an in-cavity recessed single-crystalline silicon cathode tip above which a polycrystalline silicon anode is suspended on a silicon-rich nitride layer. The diode cavity is cleared from the sacrificial oxide in buffered HF through the horizontal etch-access channels between the polysilicon anode and the silicon-rich nitride isolation layer. Vacuum sealing of the cavity using LPCVD polycrystalline silicon results in polysilicon deposits ( > 50 nm) inside the cavity, and thus in a non-acceptable degradation of the cathode-tip curvature. When sealing is performed using aluminium evaporation, no deposits inside the cavity are observed and pressures below 10 Pa can be expected. Applications of the technique presented are not restricted to micro vacuum diodes, but also include various type of hermetically sealed micromechanical structures, where deposits inside the sealed cavity are undesirable.

Optimization of fully-implanted NPNs for high-frequency operation

With a very straightforward (low-cost) process flow as basis, fully-implanted washed-emitter-base (WEB) NPNs have been optimized for operation in the 10-30 GHz range. Above 20 GHz the best overall performance is achieved by heavy doping of the epi. A low-stress silicon rich nitride layer is proven effective as surface isolation before contact window dip-etch.

Amorphous silicon thin-film transistors with two-layer gate insulator

Hydrogenated amorphous silicon (a-Si:H) thin-film transistors (TFTs) which utilize two layers of amorphous silicon nitride with different composition as a gate insulator have been studied. The field-effect mobility, subthreshold slope, and stability of an a-Si:H TFT are enhanced by inserting a thin silicon-rich nitride layer between the a-Si:H and the gate insulator. The improvement of these characteristics appears to be due to both the decrease of the interface state density between the a-Si:H and the top silicon-rich nitride layer, and the good dielectric quality of the bottom nitride layer.

In situ Auger electron spectroscopy investigation of the chemical bonding of ion-beam-deposited silicon nitride

The necessity of knowing the atomic ratio of nitrogen to silicon and the contamination of silicon nitride to obtain layers with reproducible physical, chemical and electrical properties is reviewed. Ion-beam-sputtered thin films of various nitrogen-to-silicon ratios with an oxygen content of less than 1% are analysed by in situ Auger electron spectroscopy. By deliberately allowing a pure silicon-rich nitride layer to become oxidized, the different signals contributing to the line shape of the derivative Si LVV peak are unambiguously identified. Assuming the peak-to-background ratio to be an intrinsic measurement, we propose a method to evaluate the composition of non-stoichiometric silicon nitride layers from the study of the Si LVV peak recorded in the EN( E) mode. This peak is reconstituted by using a linear combination of experimental Si LVV peaks from pure silicon and completely nitrided silicon. A realistic background is deduced from a step-by-step deposition of Si 3N 4 onto carbon. The results are compared with Rutherford backscattering spectrometry measurements and discussed.