Dry Etching Process Research Articles

Advanced dry etching of GaAs/AlGaAs multilayer wafer with InAs quantum dot for circular defect in photonic crystal laser

We previously proposed the circular defect in two-dimensional photonic crystal (CirD) laser based on a GaAs/AlGaAs multilayer wafer, which is fabricated by dry etching. This CirD laser uses InAs quantum dot (QD) layers as the gain medium, but this inhibits vertical dry etching. We improved the dry etching process by introducing three QD layers and three-step dry etching for fabricating the CirD laser. As a result, CirD structures with good etching profiles could be fabricated and excellent optical properties were obtained. We observed lasing by a CirD laser fabricated by deep etching under photoexcitation measurement for the first time.

Xenon Difluoride Dry Etching for the Microfabrication of Solid Microneedles as a Potential Strategy in Transdermal Drug Delivery.

Although hypodermic needles are a "gold standard" for transdermal drug delivery (TDD), microneedle (MN)-mediated TDD denotes an unconventional approach in which drug compounds are delivered via micron-size needles. Herein, an isotropic XeF2 dry etching process is explored to fabricate silicon-based solid MNs. A photolithographic process, including mask writing, UV exposure, and dry etching with XeF2 is employed, and the MN fabrication is successfully customized by modifying the CAD designs, photolithographic process, and etching conditions. This study enables fabrication of a very dense MNs (up to 1452 MNs cm-2 ) with height varying between 80 and 300µm. Geometrical features are also assessed using scanning electron microscopy (SEM) and 3D laser scanning microscope. Roughness of the MNs are improved from 0.71 to 0.35µm after titanium and chromium coating. Mechanical failure test is conducted using dynamic mechanical analyzer to determine displacement and stress/strain values. The coated MNs are subjected to less displacement (≈15µm) upon theapplied force. COMSOL Multiphysics analysis indicates thatMNs are safe to use in real-life applications with no fracture. This technique alsoenables the production of MNs with distinct shape and dimensions. The optimized process provides a wide range of solid MN types to be utilized for epidermis targeting.

Assessment of STI dry etch process variability by means of dynamic time warping technique

Numerical data of two in situ optical acquisition systems were used in machine learning algorithm to evaluate an shallow trench isolation dry etch process in a dataset of more than 200 etched wafers processed during a year. Though overall recipe performance was according to specifications, the observed parameter fluctuations were characterized to check for correlation patterns in processing data by means of machine learning. Thus, dynamic time wrapping was used to analyze time series datasets to get characteristics of minimum distance’s path between signals coming of each individual wafer. Such metrics of distances could help clustering groups of wafers that appear to be in proximity. Out of eight analyzed channels, we observed the largest distance variability was in the Si main etch for spectral reflectometer dataset, which we compared to optical emission spectroscopy channels. Based on correlation assessment of distances to the etch depth uniformity data, we showed that the selected approach is a good means to analyze time series datasets of e.g. dry etch processes for monitoring process stability.

Fused silica microchannel fabrication with smooth surface and high etching selectivity

Channel fabrication technology has become increasingly important for microfluidic and nanofluidic devices. In particular, glass channels have high chemical and physical stability, high optical transparency, and ease of surface modification, so that there is increasing interest in glass microfluidic devices for chemical experiments in microfluidics and nanofluidics. For the fabrication of glass channels, especially those with a high aspect ratio (depth/width), lithography using a metal resist and dry etching have mainly been used. However, there are still issues involving the surface roughness of the etched channel and the low etching selectivity. In this study, a microchannel fabrication method with high etching selectivity that produces a smooth etched surface was developed. First, interference during dry etching by remaining Cr particles after the photolithography and Cr etching processes was assumed as the cause of the rough etched surface. Three different dry etching processes were introduced to verify this. In process 1 without removal of the Cr particles, the etched surface was not flat and had a 1 μm scale roughness. In process 2 where a cleaning process was included and high power etching was conducted, a smooth surface with a 1 nm scale roughness and a faster etching rate of 0.3 μm min−1 were obtained. For this high-power etching condition, the etching selectivity (fused silica/Cr) was relatively low at approximately 39–43. In process 3 with a cleaning process and low-power etching, although the etching rate was relatively low at 0.1 μm min−1, a smooth surface with 1 nm scale roughness (10 nm scale roughness deeper than 40 μm in the depth region) and a much higher etching selectivity of approximately 79–84 were obtained. The dry etching method presented in this study represents a significant contribution to microfluidics/nanofluidics for microchannel/nanochannel fabrication.

A broadband high-brightness quantum-dot double solid immersion lens single photon source

High-brightness single photon sources (SPSs) are key components for practical quantum information processing systems. Although the performances of recently reported high-brightness SPSs are excellent, it remains challenging to match the emission wavelength of a quantum dot (QD) to the cavity since the high-Q cavity structures have narrow spectral bandwidths. Here, we propose a highly bright and broadband QD SPS that can be deterministically fabricated with a simple yet precise method. The optimized GaAs-polymer double solid immersion lens structure is capable of a brightness of 88% at 0.5 NA and has an operation band of 65 nm with a brightness of over 80% from numerical simulations. Experimentally, we achieved a brightness of 51.6% ± 2% and pure single photon emission [g(2)(0) = 0.029 ± 0.005] at saturation. We believe that our result can pave the way to a practical high-brightness QD SPS, considering its simple QD geometry together with its low cost and precise deterministic fabrication without using expensive and complicated e-beam lithography and dry etching processes.

Process Development for Batch Production of Micro-Milling Tools Made of Silicon Carbide by Means of the Dry Etching Process

Downsized and complex micro-machining structures have to meet quality requirements concerning geometry and convince through increasing functionality. The development and use of cutting tools in the sub-millimeter range can meet these demands and contribute to the production of intelligent components in biomedical technology, optics or electronics. This article addresses the development of double-edged micro-cutters, which consist of a two-part system of cutter head and shaft. The cutting diameters are between 50 and 200 μm. The silicon carbide cutting heads are manufactured from the solid material using microsystem technology. The substrate used can be structured uniformly via photolithography, which means that 5200 homogeneous micro-milling heads can be produced simultaneously. This novel batch approach represents a contrast to conventionally manufactured micro-milling cutters. The imprint is taken by means of reactive ion etching using a mask made of electroplated nickel. Within this dry etching process, characteristic values such as the etch rate and flank angle of the structures are critical and will be compared in a parameter analysis. At optimal parameters, an anisotropy factor of 0.8 and an etching rate of 0.34 µm/min of the silicon carbide are generated. Finally, the milling heads are diced and joined. In the final machining tests, the functionality is investigated and any signs of wear are evaluated. A tool life of 1500 mm in various materials could be achieved. This and the milling quality achieved are in the range of conventional micro-milling cutters, which gives a positive outlook for further development.

All-Water Etching-Free Electron Beam Lithography for On-Chip Nanomaterials.

Electron beam lithography uses an accelerated electron beam to fabricate patterning on an electron-beam-sensitive resist but requires complex dry etching or lift-off processes to transfer the pattern to the substrate or film on the substrate. In this study, etching-free electron beam lithography is developed to directly write a pattern of various materials in all-water processes, achieving the desired semiconductor nanopatterns on a silicon wafer. Introduced sugars are copolymerized with metal ions-coordinated polyethylenimine under the action of electron beams. The all-water process and thermal treatment result in nanomaterials with satisfactory electronic properties, indicating that diverse on-chip semiconductors (e.g., metal oxides, sulfides, and nitrides) can be directly printed on-chip by an aqueous solution system. As a demonstration, zinc oxide patterns can be achieved with a line width of 18 nm and a mobility of 3.94 cm2 V-1 s-1. This etching-free electron beam lithography strategy provides an efficient alternative for micro/nanofabrication and chip manufacturing.

Development of high uniformity Al1-xScxN piezoelectric film stack dry etching process on 8-inch silicon wafers

This paper have investigated the basic properties of inductively coupled plasma reactive ion etching (ICP-RIE) of scandium doped aluminum nitride (Al1-xScxN) thin films on 8-inch silicon wafers, and presented a pretreatment scheme which can effectively improve the etching uniformity and wafer yield in the mass fabrication of Al1-xScxN-MEMS (micro-electromechanical systems) devices. Based on BCl3/Ar pretreatment and Cl2/Ar main etching scheme, an etching rate of 128 nm/min is obtained, with the low nonuniformity, and selectivity of 1.8 with respect to the loss of molybdenum (Mo) electrode is achieved, respectively. The relationship between etching parameters and etching uniformity is revealed in detail by the 5-step Al1-xScxN etching model. Meanwhile, to optimize the etching compatibility in the fabrication of Al1-xScxN-piezoelectric MEMS devices, a variety of etching masks (e.g. photoresist and silicon dioxide) are respectively used to obtain the consistent sidewall profile at different locations, with photoresist of 24° and silicon dioxide of 57°.

InGaN Laser Diodes with Etched Facets for Photonic Integrated Circuit Applications

The main objective of this work is to demonstrate and validate the feasibility of fabricating (Al, In) GaN laser diodes with etched facets. The facets are fabricated using a two-step dry and wet etching process: inductively coupled plasma-reactive ion etching in chlorine, followed by wet etching in tetramethylammonium hydroxide (TMAH). For the dry etching stage, an optimized procedure was used. For the wet etching step, the TMAH temperature was set to a constant value of 80 °C, and the only variable parameter was time. The time was divided into individual steps, each of 20 min. To validate the results, electro-optical parameters were measured after each step and compared with a cleaved reference, as well as with scanning electron microscope imaging of the front surface. It was determined that the optimal wet etching time was 40 min. For this time, the laser tested achieved a fully comparable threshold current (within 10%) with the cleaved reference. The described technology is an important step for the future manufacturing of photonic integrated circuits with laser diodes integrated on a chip and for ultra-short-cavity lasers.

Wide band UV/Vis/NIR blazed-binary reflective gratings for spectro-imagers: two lithographic technologies investigation

We report on subwavelength reflective gratings for hyperspectral applications operating in a very large spectral band (340–1040 nm). Our study concerns a blazed-binary grating having a period of 30 μm and composed of 2D subwavelength structures with size from 120 nm to 350 nm. We demonstrate the manufacturing of the gratings on 3″ wafers by two lithography technologies (e-beam and nanoimprint) followed by classical dry etching process. Optical measurements show that the subwavelength grating approach enables a broadband efficiency, polarization behaviour and wavefront quality improvement with respect to the requirements for the next generation of spectro-imagers for Earth observation missions. An outlook towards spherical substrate based on nanoimprint lithography is also reported with the results of mixed features replication (holes and pillars in the range of 160–330 nm) on a 540 mm concave substrate which demonstrate uniformity and accuracy capabilities over 3″ surface.

(Digital Presentation) Rapid Electrical Impedance Analysis to Identify Liquid Isomers Using Nanoparticle Thin Film

Chemical liquids are transparent and indistinguishable by eyes. For rapid and noncontact analysis of chemical liquids, detecting a headspace vapor from the liquids is a promising technique. Semiconductor sensor1,2, mass spectrometry with inhomogeneous electrostatic deflection3, and quartz crystal microbalance4 have been studied for vapor sensing. In these techniques, a target vapor concentration is typically lower than 100 ppm and it takes >1 min to measure the vapor electronically. On the contrary, a headspace vapor from the chemical liquids in the vessel is much concentrated. An alternative approach to measure the highly concentrated vapor is required for noncontact liquid analysis.In this study, we propose a rapid noncontact analysis to identify liquid isomers by using the concentrated headspace vapor at room temperature. The key of the analysis is to use an insulating nanoparticle thin film as a sensing layer to capture the vapor5. Figure 1(a) shows the schematic of the sensing mechanism. When a nanoparticle thin film is exposed to a chemical vapor, the vapor starts to diffuse into a void space between the nanoparticles. The driving force of the diffusion is the vapor pressure of each chemical. Due to the Kelvin effect6, nanoscale voids effectively condense a chemical vapor into liquids under the normal pressure. When the chemicals are polar molecules, the condensation is detected by monitoring ion current through the condensed liquids between insulating nanoparticles. Four butanol liquid isomers (1-butanol, 2-butanol, 2-methyl-1-propanol, and tert-butyl alcohol) are detected within 30 s for the proof-of-concept study.The microsensor chip with an insulating nanoparticle thin film was fabricated as follows. Gold interdigitated electrodes with 20μm line and spacing were prepared on a thermally oxidized silicon wafer by standard photolithography and dry-etching processes. The surface of the electrodes was cleaned by reactive-ion etching with oxygen plasma. Then, a silica nanoparticle thin film was formed by coating a colloidal solution of the nanoparticles. The average diameter of the silica nanoparticle in the solution was 50 nm. The concentration of the nanoparticle was roughly 1% (w/v) in ethanol and a 20μl of the solution was spin-coated. Figure 1(b) shows a scanning electron microscope (SEM) image of a coated nanoparticle film on the electrodes. The deposited nanoparticle film was dried at ≈50°C.Time response of the film impedance modulated by chemical vapors was evaluated under 26°C and 60 % of relative humidity. The electrical impedance was measured by introducing the sensor into a glass vessel filled with a headspace vapor. Figure 1(c) shows the picture of the measurement configuration. The vessels contained 2 mL of pure chemical liquids and the sensor was placed at ≈3 cm above the liquid surface. It should be noted that the sensor was not immersed into the liquid. The exposure time under the vapor was 30 s.Figure 1(d) shows the response to the vapor from four pure butanol isomers. Colored region indicates the exposure time. Response times (t 90) of the curves are 10.6, 4.7, 7.5, and 2.4 s, in 1-butanol, 2-butanol, 2-methyl-1-propanol, and tert-butyl alcohol, respectively. On the contrary, recovery times (t 10) of the curves are less than 2 s (indicated by the arrow), which is not obviously dependent on the liquids. The quickness for saturation of the impedance is largely attributed to a high vapor pressure of the chemicals. The vapor pressure of the chemicals at 20°C are 0.9, 2.3, 1.5, and 5.4 kPa, in 1-butanol, 2-butanol, 2-methyl-1-propanol, and tert-butyl alcohol, respectively. The saturated minimum impedance of the response is related to the conductivity of the polar liquids. Figure 1(e) classifies the minimum impedance versus the response time in each curve. The advantage of the proposed noncontact method is a quick recovery without a heating element.Reference:1. X. Y. Bai et al., Cryst. Growth Des., 17, 423–427 (2017).2. N. J. Kybert, M. B. Lerner, J. S. Yodh, G. Preti, and A. T. C. Johnson, ACS Nano, 7, 2800–2807 (2013).3. F. Filsinger et al., Angew. Chemie - Int. Ed., 48, 6900–6902 (2009).4. H. Shiigi et al., Electrochem. Solid-State Lett., 6, 3–6 (2003).5. S. Kano and H. Mekaru, Nanotechnology, 33, 105702 (2022).6. L. R. Fisher, R. A. Gamble, and J. Middlehurst, Nature, 290, 575–576 (1981).Figure Caption: Figure 1 (a) Schematic of sensing mechanism. (b) Cross-section of nanoparticle film. (c) Sensor exposed to headspace vapor. (d) Impedance response under exposure to isomer vapor. (e) Two-dimensional plot of minimum impedance and response time of impedance response. A group of ethanol is shown as a reference. Figure 1

(Digital Presentation) Uniformity and Profile Improvement of Fin Etching Process at Wafer Extreme Edge for Finfet Mass Production

The plasma sheath bending effect is widely observed in the wafer edge where the transition area to the edge ring is located. It is due to the electrical discontinuity and results in the difference in Ion Electron Angle Distribution (IEAD) between wafer extreme edge and inner wafer. As the aspect ratio increases during semiconductor scaling, the profile of etching is getting progressively sensitive to the sheath bending effect, resulting in a tilting profile or abnormal CD at the wafer's extreme edge. In our work, we presented a novel approach to improve the process capability to control the uniformity and profile during a two-step Fin etching process, where Fin hard mask (HM) etching and Fin etching are implemented: 1) Fin HM etching is applied in a capacitively-coupled plasmas (CCP) etcher by fine-tuning the focus ring temperature and the by-zone temperature module for local non-uniformity improvement, with a uniformity of Fin Critical Dimension (CD) improved by 60%; 2) Fin etching is applied in an inductively-coupled plasma (ICP) etcher by fine-tuning the movable edge ring to improve the sheath bending effect, with a profile and uniformity meeting targets. The improvement of the dry etching process at the extreme wafer edge will be discussed in detail. Figure 1

P‐1.4: Analysis of the Hump Characteristics in Poly‐Si Thin Film Transistor & Process a method to suppress hump effect

In this study, we investigate the transfer characteristics of low‐temperature polycrystalline silicon(LTPS) thin film transistors(TFTs) often show a “hump” in subthreshold region. This effect can be attributed to the presence of an enhanced electrical field at edges of the active layer. To reduce the hump effect which is one of the critical issues in ploy‐Si TFT, we focus on crowding of gate fringing field at channel edge and suggest a modified structure of channel edge. Using dry etching process, change the polysilicon layer at the edge of the channel from a steep profile to a slightly flat profile. And we confirmed that the severity of the hump effect is directly related to the edge profile of the polysilicon.

Selective Wet and Dry Etching of NiO over β-Ga2O3

Patterning of NiO/Ga2O3 heterojunctions requires development of selective wet and dry etch processes. Solutions of 1:4 HNO3:H2O exhibited measurable etch rates for NiO above 40 °C and activation energy for wet etching of 172.9 kJ.mol−1 (41.3 kCal.mol−1, 1.8 eV atom−1), which is firmly in the reaction-limited regime. The selectivity over β-Ga2O3 was infinite for temperatures up to 55 °C. The strong negative enthalpy for producing the etch product Ga(OH)4 suggests HNO3-based wet etching of NiO occurs via formation and dissolution of hydroxides. For dry etching, Cl2/Ar Inductively Coupled Plasmas produced etch rates for NiO up to 800 Å.min−1, with maximum selectivities of <1 over β-Ga2O3. The ion energy threshold for initiation of etching of NiO was ∼55 eV and the etch mechanism was ion-driven, as determined the linear dependence of etch rate on the square root of ion energy incident on the surface.

The effect of powder particle size on the corrosion behavior of atmospheric plasma spray-Y2O3 coating: Unraveling the corrosion mechanism by fluorine-based plasma

The atmospheric plasma spray (APS) -Y2O3 coatings are widely used to minimize damage to internal parts of the chamber caused by the strong corrosive effect of fluorine-based plasma used in dry etching; however, the poor density of APS-Y2O3 coatings results in low plasma corrosion resistance. This is a major cause of the generation of contamination particles during CF4/O2 plasma etching. Hence, defects inside the coating must be eliminated to improve the plasma corrosion resistance of APS-Y2O3 coatings.The correlation between the decrease in the number of defects inside the APS-Y2O3 coatings according to the powder particle size and the surface corrosion process by CF4/O2 plasma etching was confirmed. We verified that the internal defects in APS-Y2O3 coatings can be controlled with small powder particles because the powder particles in the APS layer melt efficiently under the APS coating conditions; in addition, the fluorine content rate inside the coating is improved. After the focused ion beam (FIB) process, by examining YOxFy layer with a field emission scanning electron microscope (FE-SEM), energy dispersive X-ray spectroscopy (EDS), and X-ray photoelectron spectroscopy (XPS); we observed the formation of a thick YOxFy layer with decreasing number of defects inside the APS-Y2O3 coatings; thereby, the bonding strength among the Y2O3 powder particles was increased, and corrosion of YOxFy layer due to physical and chemical reactions decreased; as a result, the etch amount was significantly reduced.Therefore, it can be seen that the generation of contamination particles in the CF4/O2 plasma etching can be reduced by controlling the occurrence of defects inside the APS-Y2O3 coatings. The results of this study demonstrate the possibility of minimizing the effect of contamination particles generated in the dry etching process to remove YOxFy layer using chamber self-cleaning such as waferless step. This paper presents a new direction for controlling contamination particles in the inner coating parts of the plasma etching chamber.

The Impact of Manufacturing Imperfections on the Performance of Metalenses and a Manufacturing-Tolerant Design Method.

Metalenses play an important role in optoelectronic integrated devices, given their advantages in miniaturization and integration. Due to its high aspect ratio subwavelength structure, fabricating metalenses requires a high-level dry etching technology. Consequently, structure deformation of the metalens will exist if the etching process of the material is not mature enough, which will impair the metalens’ performance. In this paper, a polarization-independent InP dielectric metalens is designed to focus the incident light from air into the substrate, which is used for monolithically integrating with the InGaAs/InP photodetector in the future. Subsequently, with the simulation method, we investigated the impact of the structure deformation on the metalens’ performance, which was found in our InP dry etching process development. We have found that the sidewall slope and aspect ratio-dependent etching effect greatly impaired the focusing efficiency because of the phase modulation deviation. To solve this problem, we proposed a manufacturing-tolerant design method, which effectively improved the performance of the device with structural deformation. Our work is instructive for developing metalenses and can accelerate their integration application.

Analysis of formation mechanism of deposited film in a high-aspect-ratio hole during dry etching using fluorocarbon gas plasmas

In the dry etching process using fluorocarbon (FC) gas, deposited amorphous-CF x (a-CF x ) films in patterns, such as holes and trenches, strongly affect the etching performance. The influence of the FC gas molecular structures and their atomic compositions on the formation of a-CF x films at different positions in the holes were investigated. It was found that the deposition region and thickness of the a-CF x film strongly depend on the molecular structures of the FC gas, such as double bonds, benzene rings, and the atomic ratio of fluorine to carbon.

Improving detection of plasma etching end point using light compensation on optical emission spectra

When the high aspect ratio contact, called as HARC, hole dry etching process with a high degree of difficulty is carried out in the high performance memory manufacturing process, there is a problem that the sensitivity of the optical signal detection is low due to the small open ratio and the high aspect ratio of the hole when detecting the etching end point signal using the plasma light emission. In particular, due to the fluorocarbon polymer characteristics of fluorocarbon gas, such as C4F6, C4F8, C3F8, and CH2F2, which is mainly used in the HARC hole dry etching process, the viewport, which is a part to which the optical lens is connected to measure the plasma light emitting signal with optical emission spectroscopy, called as OES, can be contaminated with the fluorocarbon polymer coating. As a result of this viewport clogging phenomenon, the intensity of the optical signal collected gradually decreases during the process (∼4%), and thus the sensitivity of the etching end point signal indicating that the etching process is terminated gradually decreases. In this study, a xenon flashlamp for optical signal compensation was additionally applied to the existing OES structure to improve the detection of the etching end point during the HARC hole dry etching process. This can improve the detection sensitivity of the OES etching end point by monitoring the viewport clogging phenomenon in real time and compensating for the reduction of the collected OES signal. The pattern wafer for testing used to verify the effect of the etching end point consists of a structure in which a mold layer sequentially stacked with Si3N4, SiO2, and SiO2 are mixed as a single layer, and as a result of the experiment, it was confirmed that the detection sensitivity of the etching end point applied with the optical signal compensation method was 18% improved from the signal measured only by the existing OES. The method is expected to improve the detection sensitivity of etching end point during the next generation high difficulty HARC hole etching process to improve the plasma etching process control method.

Large-scale vivid metasurface color printing using advanced 12-in. immersion photolithography

Nanostructures exhibiting optical resonances (so-called nanoantennas) have strong potential for applications in color printing and filtering with sub-wavelength resolution. While small scale demonstrations of these systems are interesting as a proof-of-concept, their large scale and volume fabrication requires deeper analysis and further development for industrial adoption. Here, we evaluate the color quality produced by large size nanoantenna arrays fabricated on a 12-in. wafer using deep UV immersion photolithography and dry etching processes. The color reproduction and quality are analyzed in context of the CIE color diagram, showing that a vivid and vibrant color palette, almost fully covering the sRGB color space, can be obtained with this mass-manufacturing-ready fabrication process. The obtained results, thus, provide a solid foundation for the potential industrial adoption of this emerging technology and expose the limits and challenges of the process.

High‐Resolution Study of Changes in Morphology and Chemistry of Cylindrical PS‐b‐PMMA Block Copolymer Nanomasks during Mask Development

AbstractNanolithography with self‐assembled block copolymers (BCPs) is an emerging competitive alternative to conventional lithography, which is currently reaching its limits with regard to resolution and economic feasibility. For high‐resolution lithography, both the abruptness of BCP internal interfaces between self‐assembled polymer nanodomains and the processing steps used to selectively remove one of the polymers are crucial. This paper presents a detailed investigation of the chemistry, the mask wall morphology, and the line edge roughness (LER) of self‐assembled nanomasks from polystyrene‐b‐polymethylmethacrylate (PS‐b‐PMMA) before and after selective removal of the PMMA nanodomains. For the latter, either wet or plasma etching are employed and their impact on both the morphology and chemistry of resulting nanomasks is analysed using analytical (scanning) transmission electron microscopy (STEM), X‐ray photoelectron spectroscopy and polarization‐modulated infrared reflection‐absorption spectroscopy. Dedicated image analysis tools are developed to determine for the first time the LER of cylindrical openings in PS masks from STEM dark‐field images at sub‐nanometer resolution. Applying these tools prior to and after PMMA removal from the BCP films, the statistics of feature sizes, LERs, and interfacial widths are determined. In addition, the impact of wet and dry etching processes on PS‐co‐PMMA random copolymer brushes required for substrate functionalization is evaluated.