Soft mask-based dry etching of parylene AF4 for advanced packaging applications

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.

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.

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.

Balancing reinforcement and etch stability: SiC whisker effects in plasma-exposed AlN ceramics

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.

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.

Design and fabrication of scanning mirror for laser display

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.

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.

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

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

Reactive ion etching (RIE) and inductively coupled plasma (ICP) Cr etch processes have been evaluated for fabrication of extreme ultraviolet lithography masks on 200 mm substrates. Experiments were completed to optimize the Cr etch rate, etch rate uniformity, and Cr to resist selectivity for both etch processes. The best ICP process was found to have superior etch rate, etch rate uniformity, and comparable Cr to resist selectivity to the RIE process. The effect of exposed Cr area on the Cr to resist selectivity, critical dimension (CD) bias, and CD bias 3σ was also investigated. A decrease in exposed Cr area from 95% to 7% was found to dramatically increase the Cr etch rate, leading to an increase in the Cr to resist selectivity. Lower Cr loading was also found to decrease the CD bias and CD bias 3σ. The average CD bias was very high for both processes, with the ICP etch process having a higher CD bias (143 nm) than the RIE process (89 nm). The CD bias uniformity was significantly lower for the ICP process (32 nm, 3σ) when compared to the RIE process (71 nm, 3σ).

Among rare-earth ion-doped crystals that are of high interest for quantum technologies, yttrium orthosilicate [Y2SiO5 (YSO)] crystal has demonstrated the longest coherence times. Etching optical guiding structures enables the creation of complex structures offering the advantage of technological scalability. We report on the dry etching of YSO crystal wafers performed by inductive coupled plasma (ICP) reactive ion etching. The material etching rate, the etch rate selectivity versus the material mask, and the etched side wall’s shape have been measured for various ICP process parameters and gas combinations including Ar-alone, Cl2:Ar, and Cl2:N2 plasma chemistry. These gas-combination choices have enabled identifying the etching mechanisms involved. Etching results have evidenced that Ar ions are the primary contributors for YSO etching, with Cl ions being also efficient, while Cl neutrals play a marginal role. ICP YSO etching is predominantly a physical process carried out by ions. Several ICP powers and RF powers have been investigated. The highest 80 nm/min etch rate is obtained under the Ar-alone plasma, but at the expense of trenching, while chlorine-based etching provides no trenching and smooth side walls. The choice of the dielectric material mask is also discussed.

ICP-RIE etching of self-aligned InP based HBTs with Cl 2/N 2 chemistry

Dry-etching processes for high-temperature superconductors