Plasma Reactive Ion Etching Research Articles

Recent Advances in Black Silicon Surface Modification for Enhanced Light Trapping in Photodetectors

The intricate nanostructured surface of black silicon (BSi) has advanced photodetector technology by enhancing light absorption. Herein, we delve into the latest advancements in BSi surface modification techniques, specifically focusing on their profound impact on light trapping and resultant photodetector performance improvement. Established methods such as metal-assisted chemical etching, electrochemical etching, reactive ion etching, plasma etching, and laser ablation are comprehensively analyzed, delving into their mechanisms and highlighting their respective advantages and limitations. We also explore the impact of BSi on the emerging applications in silicon (Si)-based photodetectors, showcasing their potential for pushing the boundaries of light-trapping efficiency. Throughout this review, we critically evaluate the trade-offs between fabrication complexity and performance enhancement, providing valuable insights for future development in this rapidly evolving field. This knowledge on the BSi surface modification and its applications in photodetectors can play a crucial role in future implementations to substantially boost light trapping and the performance of Si-based optical detection devices consequently.

Silicon nitride shadowed selective area growth of low defect density vertical GaN mesas via plasma-assisted molecular beam epitaxy

Ion bombardment during inductively coupled plasma reactive-ion etching and ion-implantation introduces irreparable crystalline damage to gallium nitride (GaN) power devices, leading to early breakdown and high leakage current. To circumvent this, a bi-layer selective area growth mask was engineered to grow up to 3.0 µm thick epitaxy of GaN using plasma-assisted molecular beam epitaxy as an ion-damage-free alternative to standard epitaxial processing routes. The masks and regrown architectures are characterized via SEM, conductive-atomic force microscopy (AFM), x-ray photo electron spectroscopy, Raman, and cathodoluminescence. Mask deposition conditions were varied to modulate and minimize the stress induced during thermal cycling. The resulting mesas exhibit low leakage, attributed to naturally terminated sidewalls as measured by an innovative perpendicular AFM measurement of the regrown sidewall. The regrown sidewall exhibited RMS (root mean square) roughness of 1.50 (±0.34) nm and defect density of 1.36 × 106 (±1.11 × 106) cm−2. This work provides a method to eliminate defect-inducing steps from GaN vertical epitaxial processing and stands to enhance GaN as a material platform for high-efficiency power devices.

Large-Scale High-Accuracy and High-Efficiency Phase Plate Machining.

In this paper, multifunctional, multilevel phase plates of quartz substrate were efficiently prepared by using a newly developed polygon scanner-based femtosecond laser photolithography system combined with inductively coupled discharge plasma reactive-ion etching (ICP-RIE) technology. The femtosecond laser photolithography system can achieve a scanning speed of 5 m/s and a preparation efficiency of 15 cm2/h while ensuring an overlay alignment accuracy of less than 100 nm and a writing resolution of 500 nm. The ICP-RIE technology can control the etching depth error within ±5 nm and the mask-to-mask edge error is less than 1 μm. An 8-level Fresnel lens phase plate with a focal length of 20 mm and an 8-level Fresnel axicon phase plate with a cone angle of 5° were demonstrated. The diffraction efficiency was greater than 93%, and their performance was tested for focusing and glass cutting, respectively. Combined with the high-speed femtosecond laser photolithography system's infinite field-of-view (IFOV) processing capability, the one-time direct writing preparation of phase plate masks of different sizes was realized on a 6-inch wafer. This is expected to reduce the production cost of quartz substrate diffractive optical elements and promote their customized mass production.

PVD decorative coatings on polycarbonate and polyamide substrates for the automotive industry

Utilizing magnetron sputtering to incorporate metal onto polymer surfaces as a substitute for metal parts in the automobile industry offers an eco-friendly alternative. In this work, decorative titanium oxynitride (TiNxOy) coatings were sputter deposited over polycarbonate and polyamide 12 substrates using a low-temperature pulsed deposition method. In order to improve coating adhesion, all substrate surfaces were pre-treated for 30 s by reactive plasma etching. Four different film thicknesses were investigated to achieve various colours. The TiNxOy coatings were quasi-amorphous, and the oxygen content decreased with increasing film thickness. Overall, four distinct colours - green, purple, magenta, and blue - were produced, and all coatings showed excellent adhesion to the polymeric substrates. Colour fastness was assessed using adapted pin-on-disk tests to evaluate the film's applicability as decorative coatings for automotive parts, with all films achieving high ratings for colour fastness. This study provides insights into the deposition of thin films on polymeric substrates, showcasing successful approaches to achieve desired colours while preserving the film's optical properties after color fastness testing.

Benchmarking diamond surface preparation and fluorination via inductively coupled plasma-reactive ion etching

Diamond, renowned for its exceptional semiconducting properties, stands out as a promising material for high-performance power electronics, optics, quantum, and biosensing technologies. This study methodically investigates the optimization of polycrystalline diamond (PCD) substrate surfaces through Inductively Coupled Plasma Reactive Ion Etching (ICP-RIE). Various parameters, including gaseous species, flow rate, coil power, and bias power were tuned to understand their impact on surface morphology and chemistry. A thorough characterization, encompassing chemical, spectroscopic, and microscopic methods, shed light on the effects of different ICP-RIE conditions on surface properties. CF4/O2 plasma emerged as a viable treatment for achieving smooth PCD surfaces with minimal etch pit formation. Most notably, surface fluorination, a critical aspect of increasing chemical and thermal stability, was successfully accomplished using CF4, SF6, and other F-containing plasmas. The fluorine concentration and surface chemistry variations were studied, with high resolution X-ray Photoelectron Spectroscopy unveiling differences amongst the sp2 C phase, sp3 C phase, C–O, CO, and C–F bonds. Time-of-flight secondary Ion Mass Spectrometry (ToF-SIMS) and depth-profile analysis unveiled a consistent surface fluorination pattern with CF4/O2 treatment. Furthermore, contact angle measurements showcased heightened hydrophobicity. This study provides valuable insights into precise diamond surface engineering, important for the development of future diamond-based semiconductor technologies.

Ion motion above a biased wafer in a plasma etching reactor

The behavior of ions in the plasma is an essential component in the process of industrial etching. We studied the motions and energy distribution of argon ions in a inductively coupled plasma (ICP) etching tool, by the method of laser induced fluorescence (LIF). The silicon wafer clamped to a chuck at the bottom of the chamber was biased with a 1 MHz 1–1.2 kV peak-to-peak sinusoidal voltage. The plasma is formed with a 2 MHz ICP coil pulsed at 10 Hz. Sheath thickness was measured at different phases of the bias waveform. The experiment also compared the ion motions with and without wafer bias, as well as different switch-on time of wafer bias. For all cases, ion energy distribution functions and the two-dimensional flow pattern were studied near the center and edge of the wafer. Significant vortex flows were observed near the wafer edge. Experiments in which the wafer was biased in the plasma afterglow resulted in a narrow distribution of ion energy close to the bias voltage at the vicinity of the wafer, and the ion incident angle on the wafer was the smallest. The results were compared to simulations using the Hybrid Plasma Equipment Model code.

Performance improvement of blue light micro-light emitting diodes (< 20 μm) by neutral beam etching process

In this study, micro-light emitting diodes array (μLEDs) with dimensions of 5 μm and 15 μm chip size were fabricated using Neutral Beam Etching (NBE) processes. Size-dependent issues of μLEDs processed by traditional inductively coupled plasma-reactive ion etching (ICPRIE) were alleviated by NBE technology, which exhibited lower equivalent resistance, turn-on voltage, and Ideality factor as compared with those of μLEDs by ICPRIE. Additionally, higher light output power of μLEDs processed by NBE with both 5 μm and 15 μm resulted in higher EQE 7.6 % and 7.7 % than those of μLEDs processed by ICPRIE. Furthermore, the size effect led to a decrease in EQEmax values of the ICPRIE sample by 0.4 %, but only a 0.1 % decay in NBE. Overall, samples fabricated by the NBE process exhibited superior optoelectronic characteristics. Finally, non-radiative recombination behaviors on the mesa sidewall were verified by cathodoluminescence analysis, showing significant decay in ICPRIE samples but not in NBE samples. These results demonstrated the potential of the NBE process for fabricating small chip sizes blue-light μLEDs required for high-brightness, high-efficiency, and high-resolution μLED displays.

Study on nanosecond laser-induced iron plasma reactive etching of single-crystal CVD diamond

Single-crystal diamond has great potential applications in national defense, military, and aerospace fields. However, the high hardness, chemical inertness, and anisotropy bring great challenges to machine microstructures on the diamond. Here, iron plasma, generated by infrared nanosecond laser ablation of a Fe target, was utilized to etch single-crystal diamond. The EDS, Raman, and XPS analysis revealed the formation of iron carbide within the sputtered layer surrounding the diamond microgrooves, thereby confirming that the iron plasma reacts chemically with the diamond. It was observed that employing a reactive metal, such as iron, for etching diamond microgrooves yields improved morphological characteristics and enhanced etching efficiency compared to the use of a non-reactive metal, such as copper. Moreover, the process of material removal through laser-induced iron plasma etching of diamond was elucidated. Subsequently, a systematic investigation was conducted on the impact of processing parameters on the laser-induced iron plasma etching of diamonds. Various periodic microstructures with regular edges and no chipping and cracks were successfully processed on the diamond using suitable laser parameters. This study furnishes a novel approach for the efficient fabrication of high-quality microstructures on single-crystal diamonds.

Fabrication of Ultralow‐Bevel Angle Mesa Structures for Vertical GaN Devices

Low‐angle bevel mesa structures are the key technological ideas needed to produce high‐quality vertical GaN devices. Nevertheless, the literature lacks sufficient information regarding the techniques that can yield the best results for obtaining the bevel angles smaller than approximately 5°.[1] Notably, for high p–n junctions NA/ND ratios, such low angles are necessary for the application of negative beveled edge termination and the efficient lowering of electric field at the surface.[1–6] In this work, the optimization of the beveled‐mesa fabrication technique for vertical GaN devices is demonstrated employing a plasma etching of the photoresist mask fabricated using a reflow process. By adjusting the resist reflow process parameters, in particular various BCl3 Cl2−1 ratios and inductively coupled plasma–reactive ion etching plasma power, a range of beveled mask angles as low as 10°–12° is achieved. However, those processes all show etching selectivity close to 1:1 between GaN and the photoresist. Even lower bevel mesa angles are reported for a novel process optimization that resulted in improving GaN to photoresist selectivity by a factor of 5–10. As a result, even smaller bevel mesa angles close to 1°–2° are able to be attained. The developed approach has the advantage of being relatively simple and cost effective.

Microstructural characterization and inductively coupled plasma-reactive ion etching resistance of Y2O3–Y4Al2O9 composite under CF4/Ar/O2 mixed gas conditions

In the semiconductor manufacturing process, when conducting inductively coupled plasma-reactive ion etching in challenging environments, both wafers and the ceramic components comprising the chamber’s interior can be influenced by plasma attack. When ceramic components are exposed to long-term plasma environments, the eroded components must be replaced. Furthermore, non-volatile reactants can form and settle on semiconductor chips, acting as contaminants and reducing semiconductor production yield. Therefore, for semiconductor processing equipment parts to be utilized, it is necessary that they exhibit minimized generation of contaminant particles and not deviate significantly from the composition of conventionally used Al2O3 and Y2O3; part must also last long in various physicochemical etching environment. Herein, we investigate the plasma etching behavior of Y2O3–Y4Al2O9 (YAM) composites with a variety of mixing ratios under different gas fraction conditions. The investigation revealed that the etching rates and changes in surface roughness for these materials were significantly less than those of Y2O3 materials subjected to both chemical and physical etching. Microstructure analysis was conducted to demonstrate the minimization of crater formation. Mechanical properties of the composite were also analyzed. The results show that the composite can be commercialized as next-generation ceramic component in semiconductor processing equipment applications.

Plasma sheath tailoring by a magnetic field for three-dimensional plasma etching

Three-dimensional (3D) etching of materials by plasmas is an ultimate challenge in microstructuring applications. A method is proposed to reach a controllable 3D structure by using masks in front of the surface in a plasma etch reactor in combination with local magnetic fields to steer the incident ions in the plasma sheath region toward the surface to reach 3D directionality during etching and deposition. This effect has the potential to be controlled by modifying the magnetic field and/or plasma properties to adjust the relationship between sheath thickness and mask feature size. However, because the guiding length scale is the plasma sheath thickness, which for typical plasma densities is at least tens of micrometers or larger, controlled directional etching and deposition target the field of microstructuring, e.g., of solids for sensors, optics, or microfluidics. In this proof-of-concept study, it is shown that E→×B→ drifts tailor the local sheath expansion, thereby controlling the plasma density distribution and the transport when the plasma penetrates the mask during an RF cycle. This modified local plasma creates a 3D etch profile. This is shown experimentally as well as using 2d3v particle-in-cell/Monte Carlo collisions simulation.

Comparative Analysis of Surface Characterization Techniques for Atomic Layer Etching

The growing demand for precise atomic level control in device fabrication has led to the rising popularity of Atomic Layer Etching (ALE).1-3 As the name implies, the process facilitates layer-by-layer material removal in an atomic scale, making low surface damage one of the key features of this process. The low-power ion bombardment and the self-limited nature of different process steps help to reduce the damage induced by ALE. However, the damage is not easy to characterize. Atomic Force Microscopy (AFM) is one of the methods that is widely used for surface characterization. However, roughness measurements of the surface using AFM may be misleading as it primarily reflects the top surface, which is typically composed of native oxide rather than the actual Si surface.In this work, we discuss how we used X-Ray reflectometry (XRR) together with ellipsometry to measure the damage induced to the Si device layer of a Silicon on Insulator (SOI) wafer.The experiments were done on an SOI wafer with a 55 nm thick device layer and 145 nm box layer. In order to remove native oxide, all samples were treated with Buffered oxide etch (BOE) 10:1 right before the etch process. The cyclic process was performed in a commercial Inductively Coupled Plasma Reactive Ion Etcher (ICP-RIE) Takachi™ tool from Plasma-Therm LLC, USA. The process gases were Chlorine to activate the Si surface and Ar to remove the activated surface. There was no plasma during activation and purging, it was only ignited during the removal step. XRR, AFM, and ellipsometry characterizations were used to monitor the damage induced by the process. These methods were used to measure the surface roughness before and after the process. In the ellipsometry model, a damage layer is incorporated to evaluate the Si surface that has undergone plasma bombardment resulting in its transformation into amorphous Si. This layer is typically referred to as the surface damage layer. The XRR can measure the roughness on Si layer right beneath the native oxide which again demonstrates the surface damage. On the other hand, AFM measures the roughness at the surface of native oxide.Our results show that while in XRR and ellipsometry, the roughness change follows the same trend, the AFM measurement is not. Results have revealed that in the case of a non-ALE process, both XRR and ellipsometry techniques exhibit a substantial level of surface damage, whereas AFM indicates lower damage. This provides evidence that AFM alone may not be a reliable approach for assessing surface damage. In addition, both XRR and ellipsometry confirm a thick native oxide on top which is very much correlated to the damage. Typically, the thickness of the native oxide is in the ranges between 15-25 Å, and our results support that the thickness of the measured native oxide layer increases with the level of surface damage.

Tuning of the Effective Refractive Index of Crystalline Si Thin Films with Controlled Modification of Nanohole Dimensions By Dry-Etching

Silicon thin films with holes are composite materials with noteworthy optical properties that can be controllably fabricated by state-of-the-art Si process technologies. For light with wavelengths larger than the hole sizes and spacing, typically by a factor of 10, the perforated Si thin films behave like an effective (refractive index) medium. Under these conditions, the optical properties of the films can be modelled by the effective medium approximation (EMA). By manipulating the volumetric air fraction (holes) of such films, the refractive index can be modified accordingly. Such a property can be exploited to tune the index contrast in various photonic devices such as filters and waveguides.This work presents a novel scalable method that combines charged sphere colloidal lithography (CSCL) and dry-etching to pattern Si thin films. We demonstrate controlled tuning of the effective refractive index by controlled lateral dry-etching of the holes. The fabricated nanoholes are spatially disordered in a 220 nm thick crystalline Si film. CSCL is performed using polystyrene particles of 60 (P60) and 100 (P100) nm diameter. The CSCL step results in a disordered arrangement of the particles with average spatial separations of 2-4 times their diameter. Using Cr as a mask, cylindrical holes are etched into Si by inductively coupled plasma-reactive ion-etching (ICP-RIE) using a pseudo-Bosch process. An additional isotropic ICP-RIE dry-etch step is introduced to widen the holes in a controlled manner, utilizing CF4 and O2 gas mixture. Importantly, this hole-widening step is time-controlled to ensure that the holes do not overlap laterally. Finally, the Cr mask is removed by wet-etching.By analyzing scanning electron microscopic (SEM) images, we estimate the lateral etch rates for the P60 and P100 samples are approximately 0.76 nm/s and 0.52 nm/s, respectively. Using this process, the average hole diameter can be increased systematically up to circa 68-97%, compared to their original diameters, while avoiding overlap. The effective refractive index of the perforated Si thin films is determined using the optical air fill factor obtained from modelling the spectroscopic ellipsometry data with Bruggeman effective medium approximation. The determined optical air fill factor varies from circa 20% to 50% with hole widening. The ellipsometry data provides the true air fill factor of the samples directly; SEM analysis could also be used, however, it is complex and cannot determine the actual porosity of the films. The ellipsometry results show that the determined refractive index is constant in the 1500 - 4000 nm wavelength range. The refractive index decreases from 3.42 for unstructured Si film to 2.9 and 2.7 for the as-etched perforated Si films of P60 and P100 samples, respectively. With controlled lateral etching of the holes, the effective refractive index systematically decreases further to approximately 2.1 for the P60 and P100 samples, which is a 39% reduction compared to Si refractive index. The determined effective indices represent averaged values accounting for possible structural birefringence, which can be used as a guideline to design photonic devices such as filters.The presented findings indicate that the effective refractive index of perforated Si thin films can be engineered by controlling the lateral dimensions of holes. While this conclusion relates specifically to crystalline Si thin films, the same concept may also be applied to other perforated dielectric thin films. Figure 1

Fluorine-Based Low-Damage Selective Etching Process for E-Mode p-GaN/AlGaN/GaN HFET Fabrication

In this study, we conducted an optimization of a low-damage selective etching process utilizing inductively coupled plasma-reactive ion etch (ICP-RIE) with a fluorine-based gas mixture. This optimization was carried out for the fabrication of p-GaN gated AlGaN/GaN enhancement-mode (E-mode) heterojunction field-effect transistors (HFETs). The optimum process conditions resulted in an etch selectivity of 21:1 (=p-GaN:Al0.2Ga0.8N) with a p-GaN etch rate of 5.2 nm/min and an AlGaN etch rate of 0.25 nm/min. In comparison with an oxygen-based selective etching process, the fluorine-based selective etching process demonstrated reduced damage to the etched surface. This was confirmed through current–voltage characteristics and surface roughness inspections. The p-GaN gated AlGaN/GaN E-mode device, fabricated using the optimized fluorine-based selective etching process, achieved a high threshold voltage of 3.5 V with a specific on-resistance of 5.3 mΩ.cm2 for the device and with a gate-to-p-GaN gate distance of 3 μm, a p-GaN gate length of 4 μm, and a p-GaN gate-to-drain distance of 12 μm. The catastrophic breakdown voltage exceeded 1350 V.

Characterization of graphene films formed using radical plasma species

Previously the authors of this paper have reported the synthesis of highly tethered, planarized graphene films on 6H-SiC(0001) using a two-step CF4-based plasma assisted synthesis (PAS) process. In the first step, silicon was selectively etched from the SiC surface to form a carbon-rich overlayer, and in the second step, a rapid thermal anneal was used to form the graphene film from this carbon-rich layer. The etch process was performed in an inductively coupled plasma-reactive ion etching system and utilized both physical etching due to ions and chemical etching due to radicals. This paper reports the plasma assisted synthesis of few-layer graphene films using only the radical species produced in a CF4-based plasma. That is, only chemical etching was involved in the selective etching process. This was achieved by placing a physical mask over the substrate to block the ion flux and allowing the microplasma formed from the ambient radical species to etch the SiC surface. This process followed by the rapid thermal anneal is referred to as microplasma assisted synthesis (MPAS) of graphene. The resulting graphene films were characterized using x-ray photoelectron spectroscopy, Raman spectroscopy and atomic force microscopy. These analyses reveal that the MPAS films are less tethered than those produced by the PAS process, and they reflect the step and terrace structure of the initial SiC substrate. Consequently, the few layer graphene films formed using MPAS show marked progress toward the quasi-freestanding graphene films formed by high temperature sublimation. Overall, these results suggest that a radical based etching process may provide a chemical route to the synthesis of quasi-freestanding graphene on SiC. Additionally, these results provide insight into the roles of radicals and ions in the etching process.

Quasiatomic layer etching of silicon nitride enhanced by low temperature

Plasma atomic layer etching is a dry etching process using a dose step to modify a material’s surface chemistry and an etch step to remove the modified surface layer. This method of etching has certain advantages over reactive ion etch due to its self-limiting etch process for highly controllable etch depth and reduced surface roughness. In this paper, we expand upon an anisotropic, plasma atomic layer etch recipe used to etch thin films of silicon nitride, which uses an H2 plasma to modify the surface layer of the material and an SF6 etch step to remove the modified surface. Several modifications are made to the recipe, including a reduction in the pressure during the SF6 step from 500 to 20 mT, to allow compatibility with modern inductively coupled plasma-reactive ion etch systems. We then explore this recipe at low wafer temperature and find a reduction of spontaneous isotropic SF6 etching. This results in an enhancement in the self-limiting aspect of the etch process, an improvement of the etched sidewall homogeneity, and a decrease in the etched surface roughness, which has the potential to be useful for reducing optical loss in silicon nitride waveguides and other nanoscale devices made in silicon nitride.

Study on effective dry etching of InGaZnO thin films under capacitively coupled plasma-reactive ion etching with a nonfluorine-based etching gas

Dry etching of InGaZnO (IGZO) thin films was performed in a capacitively coupled plasma-reactive ion etching (CCP-RIE) mode using hydrochloride (HCl) and argon (Ar) gases. Dry-etching characteristics and surface properties of IGZO films were then investigated according to gas mixture ratio, radio frequency power, and chamber working pressure. With an optimized ratio of HCl : Ar at 20 : 20 SCCM, the IGZO film showed good etch characteristics with a moderate etch rate of 6.0 nm/min and a low roughness of 0.19 nm. During the etching process of IGZO thin films, nonvolatile by-products such as GaClx, InClx, and ZnClx generated on the surface could be effectively removed by physical bombardment with Ar+ ions. As a result, we successfully conducted dry etching of IGZO thin films in the CCP-RIE system under HCl-Ar gas conditions, which demonstrated dry etching on IGZO without needing a fluorine-based etching gas.

On the low temperature limits for cryogenic etching: A quasi in situ XPS study

The cryogenic plasma etching of silicon for nano- and microelectromechanical devices is known to show an optimal operating temperature around –100 °C. The physicochemical mechanisms occurring beyond this limit, however, are not often discussed. Thus, to explore the adsorption of residual gases on the uppermost surface of a Si/SiO2 wafer at –100 ≤T≤ –147 °C, we performed a comprehensive, quasi in situ X-ray photoelectron spectroscopy (XPS) study. Precisely, the cooling down of the sample was performed in a typical plasma-etching reactor at a residual pressure of 10−4 Pa, being afterwards transferred to the XPS chamber at a constant temperature, under high vacuum. We report that water build-up on the surface becomes a major issue for T< –120 °C, as detected in the O 1 s spectra and modelled by QUASES-Generate. The thickness of the H2O layer increases exponentially as the surface temperature decreases, following an anti-Arrhenius behavior. At –147 °C, the overlayer thickness is estimated to ∼125 Å, thus, the silicon is barely probed by XPS. Adsorbed fluorine can also be detected at low temperatures, although less markedly. Finally, the effect of the temperature-dependent Fermi level change on the Si 2p peak binding energy is discussed.

Structural and Optical Properties of Vacuum‐Evaporated Mixed‐Halide Perovskite Layers on Nanotextured Black Silicon

Vacuum-Evaporated Mixed-Halide Perovskite Layers In article number 2200482, Ashok Vaseashta and co-workers investigate the structural and optical properties of mixed-halide perovskite layers deposited on black silicon by sequential and co evaporation methods. The black silicon is formed using plasma reactive ion etching. The authors demonstrate a significant reduction in the reflection of the perovskite layers. This is achieved without compromising the structural quality of the perovskite layer as a photoabsorber. The results confirm the promise of using black silicon for perovskitesilicon tandem junction solar cells.

Bias-pulsed atomic layer etching of 4H-silicon carbide producing subangstrom surface roughness

A new approach to atomic layer etching (ALE) has been demonstrated, and its application to 4H-SiC is reported here. By pulsing only the DC bias for an Ar/Cl2 inductively coupled plasma-reactive ion etching system, the etch cycle duration is reduced by more than an order of magnitude relative to conventional ALE processes. Gas flows are not changed throughout the ALE process. With this process protocol, we achieved an etch rate of 2.48±0.09 Å/cycle with 6 s cycles, an RMS surface roughness (Rq) of 0.83±0.08 Å, and an ALE synergy value of S = 99%. The parameters explored within this ALE process demonstrate effective subangstrom smoothening of 4H-SiC surfaces and is well-suited for a variety of classical and quantum device nanofabrication.