Showing papers on "Etching (microfabrication) published in 2019"

Three-dimensional femtosecond laser nanolithography of crystals

Abstract: So far, nanostructuring of hard optical crystals has been exclusively limited to their surface, as stress-induced crack formation and propagation render high-precision volume processes ineffective1,2. Here, we show that the rate of nanopore chemical etching in the popular laser crystals yttrium aluminium garnet and sapphire can be enhanced by more than five orders of magnitude (from <0.6 nm h−1 to ~100 µm h−1) by the use of direct laser writing, before etching. The process makes it possible to produce arbitrary three-dimensional nanostructures with 100 nm feature sizes inside centimetre-scale laser crystals without brittle fracture. To showcase the potential of the technique we fabricate subwavelength diffraction gratings and nanostructured optical waveguides in yttrium aluminium garnet and millimetre-long nanopores in sapphire. The approach offers a pathway for transferring concepts from nanophotonics to the fields of solid-state lasers and crystal optics. Direct laser writing is shown to dramatically enhance the chemical etch rate of laser crystals yttrium aluminium garnet and sapphire, allowing nanostructuring.

Ultrahigh-Q photonic crystal nanocavities based on 4H silicon carbide

Abstract: Photonic nanocavities with high quality (Q) factors are essential components for integrated optical circuits. The use of crystalline silicon carbide (SiC) for such nanocavities enables the realization of devices with superior properties. We fabricate ultrahigh-Q SiC photonic crystal nanocavities by etching air holes into a 4H-SiC slab that is prepared without using hydrogen ion implantation, which usually causes higher absorption losses. In addition, compared to usual designs, a relatively thin slab is utilized to avoid losses through cross-polarized mode coupling induced by the tapered air holes. We obtain a heterostructure nanocavity with a high experimental Q factor of 6.3×105, which is 16 times larger than the highest Q among the previously reported values for nanocavities based on crystalline SiC. We also show that our nanocavity exhibits a high normalized second-harmonic conversion efficiency of 1900%/W.

Engineering of Yolk–Double Shell Cube-like SnS@N–S Codoped Carbon as a High-Performance Anode for Li- and Na-Ion Batteries

Abstract: A yolk–double shell cube-like SnS@N–S codoped carbon (YDSC-SnS@NSC) was delicately tailored by a self-templated and selective etching method as well as a self-assembly strategy. Herein, the ZnSn(OH...

Gold Nanocrystal Etching as a Means of Probing the Dynamic Chemical Environment in Graphene Liquid Cell Electron Microscopy.

Abstract: Graphene liquid cell electron microscopy has the necessary temporal and spatial resolution to enable the in situ observation of nanoscale dynamics in solution. However, the chemistry of the solution in the liquid cell during imaging is as yet poorly understood due to the generation of a complex mixture of radiolysis products by the electron beam. In this work, the etching trajectories of nanocrystals were used as a probe to determine the effect of the electron beam dose rate and preloaded etchant, FeCl3, on the chemistry of the liquid cell. Initially, illuminating the sample at a low electron beam dose rate generates hydrogen bubbles, providing a reservoir of sacrificial reductant. Increasing the electron beam dose rate leads to a constant etching rate that varies linearly with the electron beam dose rate. Comparing these results with the oxidation potentials of the species in solution, the electron beam likely controls the total concentration of oxidative species in solution and FeCl3 likely controls the relative ratio of oxidative species, independently determining the etching rate and chemical potential of the reaction, respectively. Correlating these liquid cell etching results with the ex situ oxidative etching of gold nanocrystals using FeCl3 provides further insight into the liquid cell chemistry while corroborating the liquid cell dynamics with ex situ synthetic behavior. This understanding of the chemistry in the liquid cell will allow researchers to better control the liquid cell electron microscopy environment, allowing new nanoscale materials science experiments to be conducted systematically in a reproducible manner.

Area-Selective Deposition of Ruthenium by Combining Atomic Layer Deposition and Selective Etching

Abstract: • A submitted manuscript is the version of the article upon submission and before peer-review. There can be important differences between the submitted version and the official published version of record. People interested in the research are advised to contact the author for the final version of the publication, or visit the DOI to the publisher's website. • The final author version and the galley proof are versions of the publication after peer review. • The final published version features the final layout of the paper including the volume, issue and page numbers.

Recent Advances and Trends in Fan-Out Wafer/Panel-Level Packaging

Abstract: The recent advances and trends in fan-out wafer/panel-level packaging (FOW/PLP) are presented in this study. Emphasis is placed on: (A) the package formations such as (a) chip first and die face-up, (b) chip first and die face-down, and (c) chip last or redistribution layer (RDL)-first; (B) the RDL fabrications such as (a) organic RDLs, (b) inorganic RDLs, (c) hybrid RDLs, and (d) laser direct imaging (LDI)/printed circuit board (PCB) Cu platting and etching RDLs; (C) warpage; (D) thermal performance; (E) the temporary wafer versus panel carriers; and (F) the reliability of packages on PCBs subjected to thermal cycling condition. Some opportunities for FOW/PLP will be presented.

Elemental Mercury Removal by MnO2 Nanoparticle-Decorated Carbon Nitride Nanosheet

Abstract: Carbon nitride nanosheet (CNNS) is facilely synthesized via a two-step thermal oxidative etching approach and then decorated with MnO2 nanoparticles via incipient wetness impregnation method for Hg...

Etching-assisted femtosecond laser modification of hard materials

Abstract: With high hardness, high thermal and chemical stability and excellent optical performance, hard materials exhibit great potential applications in various fields, especially in harsh conditions. Femtosecond laser ablation has the capability to fabricate three-dimensional micro/nanostructures in hard materials. However, the low efficiency, low precision and high surface roughness are the main stumbling blocks for femtosecond laser processing of hard materials. So far, etching-assisted femtosecond laser modification has demonstrated to be the efficient strategy to solve the above problems when processing hard materials, including wet etching and dry etching. In this review, femtosecond laser modification that would influence the etching selectivity is introduced. The fundamental and recent applications of the two kinds of etching assisted femtosecond laser modification technologies are summarized. In addition, the challenges and application prospects of these technologies are discussed.

Large-Area Synthesis of Superclean Graphene via Selective Etching of Amorphous Carbon with Carbon Dioxide

Abstract: Contamination commonly observed on the graphene surface is detrimental to its excellent properties and strongly hinders its application It is still a great challenge to produce large-area clean graphene film in a low-cost manner Herein, we demonstrate a facile and scalable chemical vapor deposition approach to synthesize meter-sized samples of superclean graphene with an average cleanness of 99 %, relying on the weak oxidizing ability of CO to etch away the intrinsic contamination, ie, amorphous carbon Remarkably, the elimination of amorphous carbon enables a significant reduction of polymer residues in the transfer of graphene films and the fabrication of graphene-based devices and promises strongly enhanced electrical and optical properties of graphene The facile synthesis of large-area superclean graphene would open the pathway for both fundamental research and industrial applications of graphene, where a clean surface is highly needed

Uprooting defects to enable high-performance III–V optoelectronic devices on silicon

Abstract: The monolithic integration of III-V compound semiconductor devices with silicon presents physical and technological challenges, linked to the creation of defects during the deposition process. Herein, a new defect elimination strategy in highly mismatched heteroepitaxy is demonstrated to achieve a ultra-low dislocation density, epi-ready Ge/Si virtual substrate on a wafer scale, using a highly scalable process. Dislocations are eliminated from the epilayer through dislocation-selective electrochemical deep etching followed by thermal annealing, which creates nanovoids that attract dislocations, facilitating their subsequent annihilation. The averaged dislocation density is reduced by over three orders of magnitude, from ~108 cm-2 to a lower-limit of ~104 cm-2 for 1.5 µm thick Ge layer. The optical properties indicate a strong enhancement of luminescence efficiency in GaAs grown on this virtual substrate. Collectively, this work demonstrates the promise for transfer of this technology to industrial-scale production of integrated photonic and optoelectronic devices on Si platforms in a cost-effective way.

Fabrication of capacitive pressure sensor using single crystal diamond cantilever beam

Abstract: Fabrication of single crystal diamond capacitive pressure sensor is presented. Firstly, the single crystal diamond cantilever beam was formed on HPHT diamond substrate by using selective high-energy ion implantation, metal patterning, ICP etching and electrochemical etching techniques. Secondly, on this diamond cantilever beam, the desired electrode patterns were processed with photolithography and metal evaporation methods. Furthermore, the displacements of cantilever beam under different pressure conditions were investigated by atomic force microscopy. The capacitance-voltage curves of single crystal diamond cantilever beam and substrate under different force loading conditions were measured by using Agilent B1505A parameter analyzer. The results show that sensitivity increases with the enlargement of electrode area of cantilever beam, and decreases with the rise of measurement frequency.

Charge Detection in Gate-Defined Bilayer Graphene Quantum Dots.

Abstract: We report on charge detection in electrostatically defined quantum dot devices in bilayer graphene using an integrated charge detector. The device is fabricated without any etching and features a g...

Increasing the sensitivity of terahertz split ring resonator metamaterials for dielectric sensing by localized substrate etching

Abstract: We demonstrate a significant enhancement in the sensitivity of split ring resonator terahertz metamaterial dielectric sensors by the introduction of etched trenches into their inductive-capacitive gap area, both through finite element simulations and in experiments performed using terahertz time-domain spectroscopy. The enhanced sensitivity is demonstrated by observation of an increased frequency shift in response to overlaid dielectric material of thicknesses up to 18 µm deposited on to the sensor surface. We show that sensitivity to the dielectric is enhanced by a factor of up to ∼2.7 times by the incorporation of locally etched trenches with a depth of ∼3.4 µm, for example, and discuss the effect of the etching on the electrical properties of the sensors. Our experimental findings are in good agreement with simulations of the sensors obtained using finite element methods.

Optimization of photochemical machining process parameters for manufacturing microfluidic channel

Abstract: In the present study, the investigation on photochemical machining (PCM) of stainless steel (SS-304) by ferric chloride as etchant is reported. SS-304 is machined by PCM process to obtain a...

Vertical GaN Nanowires and Nanoscale Light-Emitting-Diode Arrays for Lighting and Sensing Applications

Abstract: For various lighting and monolithic sensor systems application, vertically aligned three-dimensional (3D) gallium nitride (GaN)- and indium gallium nitride (InGaN)/GaN-based LED nanowire arrays with sub-200 nm feature sizes (down to 35 nm) were fabricated using a nanosphere lift-off lithography (NSLL) technique combined with hybrid top-down etching (i.e., inductively coupled plasma dry reactive ion etching (ICP-DRIE) and wet chemical etching). Owing to the lithographic opening and well-controlled surface functionalization prior to the polystyrene nanosphere (PN) deposition, vertical GaN nanowire arrays with an area density of 9.74 × 108 cm–2 and an aspect ratio of >10 could be realized in a specified large area of 1.5 × 1.5 mm2. Optoelectrical characteristics of the nanoLEDs were further investigated in cathodoluminescence (CL) measurements, in which multiquantum well (MQW) shows a clear CL-emission at a wavelength of 465 nm. Thus, using NSLL to manufacture low-cost but highly ordered 3D GaN-based nanowir...

Design, fabrication, and optical characterization of one-dimensional photonic crystals based on porous silicon assisted by in-situ photoacoustics.

Abstract: We present a methodology to fabricate one-dimensional porous silicon (PSi) photonic crystals in the visible range by controlled etching and monitored by photoacoustics. Photoacoustic can record in-situ information about changes in the optical path and chemical reaction as well as in temperature, refractive index, and roughness during porous layers formation. Radiometry imaging can determine the carrier distribution of c-Si substrate that is a fundamental parameter to obtain high-quality PSi films. An electrochemical cell was calibrated through a series of single PSi layers that allows knowing the PA amplitude period, porosity, and roughness as a function of the current density. Optical properties of single layers were determined using the reflectance response in the UV-Vis range to solve the inverse problem through genetic algorithms. PhC structures were designed using the transfer matrix method and effective media approximation.Based on the growth kinetics of PSi single layers, those structures were fabricated by electrochemical etching monitored and controlled by in-situ photoacoustics.

Silicon nanowire pH sensors fabricated with CMOS compatible sidewall mask technology

Abstract: Silicon nanowire (SiNW) field-effect transistors (FETs) have been developed as various bio/chemical sensors due to their high sensitivity as a result of the huge surface-to-volume ratios. This paper presents a CMOS compatible sidewall mask technology (SMT) for top-down fabrication of SiNWs and a highly sensitive pH sensor based on SiNW FETs. The essence of SMT is to use stand-alone vertical sidewalls of a conformal thin film, fabricated by anisotropically etching away the planar part of the thin film deposited on a thin mesa, as hard masks for SiNW etching. As the feature size of the sidewalls, depending on the film thickness rather than lithography, can be controlled readily to tens to hundreds of nanometers by tailoring the film thickness, SMT allows high output and low cost fabrication of SiNWs without need of advanced lithography facilities. Complete SMT processes have been developed for fabrication of SiNW FETs, and pH sensors using SiNW FETs have been realized. Measurement results show that the pH sensors have good static characteristics and transient performance, and the sensitivity reaches 54.5 mV/pH for a wide range of pH values from 1 to 12, approaching the theoretical Nernstian limit.

Enhanced Light Extraction of Flip-Chip Mini-LEDs with Prism-Structured Sidewall.

Abstract: Current solutions for improving the light extraction efficiency of flip-chip light-emitting diodes (LEDs) mainly focus on relieving the total internal reflection at sapphire/air interface, but such methods hardly affect the epilayer mode photons. We demonstrated that the prism-structured sidewall based on tetramethylammonium hydroxide (TMAH) etching is a cost-effective solution for promoting light extraction efficiency of flip-chip mini-LEDs. The anisotropic TMAH etching created hierarchical prism structure on sidewall of mini-LEDs for coupling out photons into air without deteriorating the electrical property. Prism-structured sidewall effectively improved light output power of mini-LEDs by 10.3%, owing to the scattering out of waveguided light trapped in the gallium nitride (GaN) epilayer.

Area selective deposition of TiO2 by intercalation of plasma etching cycles in PEALD process: A bottom up approach for the simplification of 3D integration scheme

Abstract: A selective deposition process for bottom-up approach was developed in a modified plasma enhanced atomic layer deposition (PEALD) sequence. As a case study, a very standard PEALD TiO2 using organo-amine precursor and O2 plasma is chosen. The metal oxide selectivity is obtained on TiN versus Si-based surfaces by adding one etching/passivation plasma step of fluorine every n cycles in a PEALD-TiO2 process. Fluorine gas NF3 allows (1) to etch the TiO2 layer on Si, SiO2, or SiN surface while keeping few nanometers of TiO2 on the TiN substrate and (2) to increase the incubation time on the Si-based surface. Quasi-in situ XPS measurements were used to study the incubation time between Si/SiO2 substrates versus TiN substrate. Results show that Si–F bonds are formed on Si and lock the surface reactions. The effectiveness of this atomic layer selective deposition method was successfully tested on a 3D patterned substrate with the metal oxide deposited only at the edge of metal lines.A selective deposition process for bottom-up approach was developed in a modified plasma enhanced atomic layer deposition (PEALD) sequence. As a case study, a very standard PEALD TiO2 using organo-amine precursor and O2 plasma is chosen. The metal oxide selectivity is obtained on TiN versus Si-based surfaces by adding one etching/passivation plasma step of fluorine every n cycles in a PEALD-TiO2 process. Fluorine gas NF3 allows (1) to etch the TiO2 layer on Si, SiO2, or SiN surface while keeping few nanometers of TiO2 on the TiN substrate and (2) to increase the incubation time on the Si-based surface. Quasi-in situ XPS measurements were used to study the incubation time between Si/SiO2 substrates versus TiN substrate. Results show that Si–F bonds are formed on Si and lock the surface reactions. The effectiveness of this atomic layer selective deposition method was successfully tested on a 3...