Performance Piezoelectric Airframes for Nano Air Vehicles

As the semiconductor industry continues to evolve rapidly to meet the growing demand for high-performance, low-power chips driven by technologies such as artificial intelligence (AI) and 5G, process nodes have progressed to sub-nanometer scales. This advancement introduces increased challenges in terms of structural complexity, material diversity, and precision requirements. In this context, etching plays a critical role in enabling accurate pattern transfer and the formation of nanoscale structures throughout device fabrication. This paper reviews the development of semiconductor etching technologies by systematically introducing the working principles, key advantages, application scenarios, and inherent limitations of three mainstream dry etching methods: Reactive Ion Etching (RIE), Inductively Coupled Plasma Reactive Ion Etching (ICP-RIE), and Atomic Layer Etching (ALE). Through comparative analysis, ALE demonstrates significant advantages due to its atomic-level precision and low-damage characteristics. The paper highlights ALEs unique strengths and its potential as a next-generation mainstream etching technology, while also discussing current limitations and future research directions.

Silicon nanostructures with high aspect-ratio (AR) features have played an important role in many fields. In this study, we report the fabrication of high AR silicon nanostructures using an inductively coupled plasma reactive ion etching (ICP-RIE) process by controlling the voltage bias at the substrate. The results show that by reducing the radio frequency (RF) bias power to 10 W, the etch selectivity of silicon to photoresist can be enhanced up to 36 times. Using the photoresist as a mask, this process can fabricate 300 nm-period one-dimensional (1D) grating structures with a height up to 807 nm, an improvement of 3.75-fold compared with structures fabricated by normal bias power. Furthermore, the analysis of the etch rate shows that the etch rate decreases over time in 1D gratings but remains constant in 2D pillar arrays, which can be attributed to the removal of the sidewall passivation. By including an O2 ICP-RIE step to remove the remaining polymer mask, the highest AR of 2D pillar structures that can be achieved is 8.8. The optical characterization of the fabricated structures demonstrates effective antireflection properties, where the measurements show that the reflectivity can be suppressed from 35% to 0.01% near normal incidence and 35% to 2.4% at 65° incident angle. The demonstrated low-RF power ICP-RIE process can create high AR nanostructures without the need for an inorganic mask and can find applications in integrated circuits, photonics, and functional nanostructures.

Design and fabrication of scanning mirror for laser display

The effect and influence of dry plasma etching processes of Si/SiGe using HBr for the formation of diode mesa structures has been investigated to minimise sidewall leakage current. To characterise sidewall damage electrically, Si-based resonant interband tunnel diodes (RITD) were processed and the completed RITDs compared by their peak-to-valley current ratio (PVCR) and valley current density (VCD), which are sensitive to defect related currents. Dry processed RITDs were compared to reference RITDs fabricated by wet chemical etching (HNO3:HF:H2O=100:1:100). The combination of HBr process gas and very low substrate bias power (10 W) for inductively coupled plasma reactive ion etching (ICP-RIE) yielded the better results. The resulting RITDs processed by ICP-RIE using HBr chemistry show high PVCR of 4.02 with VCD of 32 A/cm2 while wet etched RITDs show a PVCR of only 2.81 with VCD of 40 A/cm2. Hydrogen passivation during the HBr plasma process may play a role that overcomes the slightly higher surface roughness compared to wet etching.

We report a novel method of fabricating gallium nitride (GaN) nanorods of controllable dimension and density from GaN epitaxial film using inductively coupled plasma reactive ion etching (ICP-RIE). The GaN epitaxial film was grown on a sapphire substrate by metal-organic chemical vapor deposition. Under the fixed Cl2/Ar flow rate of 10/25 sccm and ICP/bias power of 200/200 W, the GaN nanorods and array were fabricated with a density of 108–1010 cm-2 and dimension of 20–100 nm by varying the chamber pressure from 10 to 30 mTorr. The technique offers one-step, controllable method for the fabrication of GaN nanostructures and should be applicable for the fabrication of GaN-based nano-optoelectronic devices.

A method for the reduction of defect density in GaN epilayer using nanoscale patterned sapphire substrates (NPSS) was proposed. The sapphire substrates were patterned by natural lithography and inductively coupled plasma reactive ion etching (ICP-RIE). The undoped GaN films were grown on NPSS through metal organic chemical vapor deposition. The pits density was analyzed by atomic force microscope (AFM) and threading dislocation distribution was observed by scanning electron microscopy (SEM). The optical characteristics were measured from X-ray diffractometry and photoluminescence spectroscopy. These results indicate NPSS can improve crystalline quality by effectively reducing threading dislocations.

Impact of etching process on Al2O3/GaN interface for MOSc-HEMT devices combining ToF-SIMS, HAXPES and AFM

In this work, an alternative dry etching approach for parylene AF4 is presented based on a photoresist soft mask, which results in a relatively simpler, faster, cheaper and environmentally friendly process in comparison to the typical dry etching process with a hard mask. 2.5 µm thick parylene AF4 was deposited on a silicon (Si) substrate by vapor deposition polymerization (VDP). A 5 µm thick photoresist was used as a soft mask, while parylene AF4 patterning was done using an oxygen (O <inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</inf> )-argon (Ar) inductively coupled plasma reactive ion etching (ICP-RIE) process. The AF4:photoresist selectivity was around 1 while the AF 4 etching rate was roughly 275 nm/min for an Ar/02 ratio of 0.1 at 20mTorr and ICP:CCP powers of 1000W:50W respectively. The influence of the ICP plasma parameters on the AF 4 etching rate was investigated and the results suggested a predominant oxygen radicals-based reactive chemical etching mechanism.

In this work, two-section, coupled cavity, mid-IR quantum cascade lasers (QCLs) were characterized in terms of their tuning range and emission stability under operation towards potential application in detection systems. Devices were processed by inductively coupled plasma reactive ion etching (ICP-RIE) from InP-based heterostructure, designed for emission in the 9.x micrometer range. Single mode devices were demonstrated with a better than 20 dB side mode suppression ratio (SMRS). The fabrication method resulted in improved yield, as well as high repeatability of individual devices. Continuous, mode-hop-free tuning of emission wavelength was observed across ~4.5 cm−1 for the range of temperatures of the heat sink from 15 °C to 70 °C. Using the thermal perturbation in the lasing cavity, in conjunction with controlled hopping between coupled-cavity (CC) modes, we were able to accomplish tuning over the range of up to ~20 cm−1.

Selective etching of GaN over AlGaN is a critical process step in GaN-based high electron mobility transistor (HEMT) fabrication, where precise removal of GaN is required without damaging the thin AlGaN barrier. In this study, we developed a high-selectivity, low-damage etching process using a customized BCl₃/SF₆ inductively coupled plasma reactive ion etching (ICP-RIE) system. Specifically, a 27.12 MHz helical resonance ICP source was utilized to generate high-density radicals and maximize gas dissociation efficiency, while the substrate temperature was precisely controlled using an external oil-circulating bath. The effects of gas composition and substrate temperature on etch rates, selectivity, and surface properties were systematically investigated. By optimizing the gas ratio to 30% SF₆, a record-high GaN-over-AlGaN selectivity of 78:1 was obtained while maintaining a fast GaN etch rate. Temperature-dependent studies revealed that Al-F passivation was stable at low temperatures, whereas it degraded above 40 ℃, resulting in a significant decrease in selectivity. Although low temperatures enhanced passivation, they also promoted AlCl₃ residue oxidation, resulting in unintended surface roughening. At an intermediate temperature of ∼30℃, the etched surface exhibited the best overall characteristics, including smooth morphology, stable chemical states, and minimized leakage current. These results demonstrate that selective, high-throughput, and low-damage GaN etching can be realized by combining optimized BCl₃/SF₆ chemistry with precise substrate temperature control and high-frequency ICP operation.

Channel waveguides have been fabricated in x-cut lithium niobate (LiNbO3) by proton exchange (PE) method and optically measured. The thickness and the optical constants of the thin PE layer were characterized using a prism coupling technique. The PE area was plasma etched and a 2.775-μm total etching depth was achieved. The measured average etching rate is 92.5 nm/min. One- and two-dimensional dense arrays of LiNbO3 nanostructures have also been fabricated by using interference lithography (IL) and inductively coupled plasma reactive ion etching (ICP-RIE) techniques.

GaN-based blue light-emitting diodes grown and fabricated on patterned sapphire substrates by metalorganic vapor-phase epitaxy

Multifunctional antireflective coatings have practical applications as important optical components in many fields, particularly for optical devices and imaging systems. However, a good antireflection application in the visible region is often unsatisfactory for mid-infrared devices, and the difficulty in obtaining multiple capabilities simultaneously is one of the main factors limiting their applications. In this work, hierarchical moth-eye structures with superhydrophobicity were fabricated via inductively coupled plasma reactive ion etching (ICP-RIE) using nanodisk-array masks, which were formed by three-beam laser interference lithography (LIL), for improving the ultra-broadband optical properties. The uniform antireflection efficiency, which was close to 1% reflectivity covering over the visible and mid-infrared wavelength range, was exhibited by the moth-eye structures with high-quality pillar arrays. Additionally, irregular nanostructures were tailored onto the top of the pillars to generate hierarchical moth-eye structures for simultaneously obtaining both the superhydrophobic and anticorrosive properties. The fabricated antireflective structures, with the features of self-cleaning and durability, have the advantage of being for long-term use in harsh environments.

A novel fabrication process to etch, to passivate, and to release single-crystal silicon structures totally in just only one process by inductively coupled plasma reactive ion etching (ICP-RIE) has been presented in this paper. Several kinds of movable actuators such as relay, comb-drive, and capacitance with thickness of 30 μm have been fabricated successfully to demonstrate this fabrication process. Here, experimental investigations about fabrication parameters to get well profile and suspension structures are performed in a STS ICP-RIE system.

Production method for aluminum beam leads on ceramic substrates : R. E. McMahon, F. J. Bachner, R. A. Cohen, W. S. Franklin and J. D. Impey. Proc. 21st Electronic Components Conf., Washington DC, USA, 10–12 May (1971), p. 96