Etching Quality Research Articles

High Quality of Color Etching in a Heat-Treated Copper

High Quality of Color Etching in a Heat-Treated Copper

Microwave hydrogen plasma etching on the laser-cut surface of single crystal diamond: Phases, etching morphology, stress evolution and the effect of etching on the subsequent homoepitaxial growth

In order to improve the pretreating efficiency of single crystal diamond (SCD) before its homoepitaxial growth, a strategy coupling laser cutting and microwave hydrogen plasma etching was proposed to replace the traditional pretreatment steps, which underwent laser cutting, mechanical polishing, acid cleaning, and microwave plasma etching in order. The feasibility of this idea has been studied by growing SCD after directly etching its laser-cut surface using microwave hydrogen plasma. The effect of the etching time on the SCD including surface phase, etching morphology, etching pit shape, residual stress, growth morphology, and quality of SCD are investigated and analyzed. The results show that microwave hydrogen plasma etching can quickly (within 10 min) remove the residual graphite carbon on the SCD surface caused by laser cutting. The extension of the etching time mainly affects the surface morphology and the internal stress of SCD. Etching pits with different shapes (square, trapezoid, inverted pyramid) and sizes can be found on the hydrogen plasma etched surface under different etching times. Fortunately, these etching pits do not introduce polycrystals on the SCD during subsequent homoepitaxial growth. All the hydrogen plasma etched laser cut SCD samples exhibit typical step-flow growth morphology after 20 h of homoepitaxial growth. Moreover, the step-flows are orderly and parallel, which is better than the disorderly step-flows on the polished SCD. Besides, a higher growth quality and a lower residual stress are obtained for the etched SCD. The above results indicate that replacing the traditional complex pretreatment steps with laser cutting and etching pretreatment is feasible. The new approach can effectively improve the pretreatment efficiency and result in superior quality of SCD after homoepitaxial growth.

Bubble detection in photoresist with small samples based on GAN augmentations and modified YOLO

Photoresist coating is a key procedure in semiconductor wafer surface processing, and bubbles in a photoresist dropper usually affect the uniformity of photoresist film, which seriously reduces the etching quality of semiconductor wafer surface. However, the problems of blurred edges of photoresist bubbles and complex corrugations in photoresist itself make the automatic detection of photoresist bubbles very challenging. To overcome this problem, a high-precision photoresist bubble detection method based on deep learning is proposed in this paper. First, aiming at the problem that the photoresist bubble samples are extremely lacking and cannot meet the requirement of deep learning model training, this paper proposes a sample automatic generator bubbleGAN based on the adversarial generative network, so as to effectively increase the number of photoresist bubble samples with better diversity of the target to be detected, thus improving the performance of the detection model; Second, aiming at the challenges of target detection caused by the blurred edges of photoresist bubbles and the complex ripples of photoresist itself, this paper proposes a novel bubble detection method mYOLO. Based on the recently developed high-performance target detection method YOLOX, we optimize its structure and activation function to reduce the difficulty of model training, solve the dead zone problem of activation function, and improve the accuracy of model detection. The experimental results on the dataset collected by the actual rotary coating machine prove the effectiveness of the proposed algorithm. In addition, we further compare the impact of different manual data augmentation methods on the detection model.

Inline metrology of high aspect ratio hole tilt and center line shift using small-angle x-ray scattering

High aspect ratio (HAR) structures found in three-dimensional nand memory structures have unique process control challenges. The etch used to fabricate channel holes several microns deep with aspect ratios beyond 50:1 is a particularly challenging process that requires exquisitely accurate and precise control. It is critical to carefully analyze multiple aspects of the etch process, such as hole profile, tilt, uniformity, and quality during development and production. X-ray critical dimension (XCD) metrology, which is also known as critical dimension small-angle x-ray scattering, is a powerful technique that can provide valuable insights on the arrangement, shape, and size of periodic arrays of HAR features. XCD is capable of fast, non-destructive measurements in the cell-area of production wafers, making XCD ideal for in-line metrology. Through several case studies, we will show that XCD can be used to accurately and precisely determine key properties of holes etched into hard mask, multilayer oxide/nitride film stacks and slit trenches. We show that the measurement of hole and slit tilt can be achieved without the aid of a structural model using a Fast Tilt methodology that provides sub-nanometer precision. Measurements were performed across several production wafers to determine the etch uniformity and quality. Particular attention was given at the edge of the wafers to account for large variations observed. In addition, we used a detailed physical model to characterize the HAR structures beyond linear tilt. This approach provides a more complete picture of the etch quality.

Roll-to-roll reactive ion etching of large-area nanostructure arrays in Si: Process development, characterization, and optimization

Roll-to-roll (R2R) nanofabrication processes are recognized as key enabling-technologies for many next-generation applications in flexible electronics, displays, energy generation, storage, as well as healthcare. However, R2R processing techniques reported in the literature currently lack a scalable method of performing high-throughput nanoscale pattern transfer of geometry requiring a high degree of fidelity in terms of critical dimension resolution, etch uniformity, and aspect ratio. Reactive ion etching (RIE) addresses the need for sub-10 nm pattern transfer with large-area uniformity in wafer-scale semiconductor manufacturing, but adapting plasma etch systems for use in R2R nanopatterning has proven to be nontrivial. Moreover, robust models for simulating R2R RIE do not exist, which is an obstacle to the creation of computational approaches to design, control, and scale-up of nanoscale R2R equipment and processes. To address these challenges, we demonstrate a process flow for fabricating Si nanopillar arrays utilizing a combination of nanoimprint lithography and RIE with all pattern transfer steps performed using a R2R plasma reactor system. Specifically discussed are process development details for etching imprint resist and Si including etch rates, cross-web etch uniformity, etch directionality, and etch selectivity at varying gas chemistries, powers, and pressures. 2k full-factorial Design of Experiments (DoEs) and ordinary least-squares regression analysis are also employed to study influence of process parameters on multiple outgoing etch quality characteristics and generate stochastic models of the R2R RIE pattern transfer process into Si. Utilizing these DOE-based models and desired targets for etch quality characteristics, we describe a bounded multivariate inverse-optimization scheme for automated etch process parameter tuning. The culmination of these efforts, to the best of the authors' knowledge, is the first reported RIE-based pattern transfer of 100 nm-scale features performed in continuous R2R fashion with control of feature geometry over large area. The methodology employed herein may be applied similarly to additional materials and geometries for future applications.

Study on Process and Quality of Dual Laser Etching and Cleaning Flexible Copper Clad Laminate

Study on Process and Quality of Dual Laser Etching and Cleaning Flexible Copper Clad Laminate

Fano-Resonant Metasurface with 92% Reflectivity Based on Lithium Niobate on Insulator.

Lithium niobate is an excellent optoelectronic and nonlinear material, which plays an important role in integrated optics. However, lithium niobate is difficult to etch due to its very stable chemical nature, and the microstructure of lithium niobate's metasurface is generally of subwavelength, which further increases its processing difficulty. Here, by using Ar+-based inductively coupled plasma etching and KOH wet etching, we improve the etching quality and fabricate a Fano-resonant metasurface based on lithium niobate on insulator, which has a very high reflectivity of 92% at near-infrared wavelength and the potential of becoming a high-reflectivity film. In addition, to evaluate the practical performance of the metasurface, we constructed a Fabry-Perot cavity by using it as a cavity mirror, whose reflection spectrum shows a finesse of 38. Our work paves the way for the development of functional metasurfaces and other advanced photonic devices based on lithium niobate on insulator.

Effect and mechanism analysis of sarcosine on the chemical mechanical polishing performance of copper film for GLSI

With the decrease of integrated circuits feature size, chemical mechanical polishing (CMP) of copper (Cu) film for multilayer wiring is faced with new challenges. In order to reduce the step height of Cu film for cobalt-based Cu interconnect during CMP process, the selection of additives in the slurry is crucial. In this paper, sarcosine was used as an important additive in Cu slurry to improve the planarization properties. Through the polarization curves, dynamic polishing, static etching experiments and scanning electron microscopy (SEM) measurement, it was identified sarcosine as a complexing agent and trace functional reagent could improve the Cu planarization properties. Meanwhile, the adsorption and complexation mechanisms of sarcosine on Cu film surface were analyzed by electrochemical tests and X-ray photoelectron spectroscopy (XPS). The improvement of static etching and surface quality of Cu patterned wafers by sarcosine was verified by laser scanning confocal microscopy (LSCM). Low static etch rate (SER) (1658 Å/min), high removal rate (RR) (5091 Å/min), RR/SER of 3.07 and effective correction of the step height on Cu patterned wafers were achieved by the synergistic effect of sarcosine and benzotriazole (BTA). In this study, a green functional reagent for Cu film CMP in low-tech node multilayer wiring was provided, which is good practical application prospects.

Thermoplasmonic laser-induced backside wet etching

The article is devoted to one of the effective technologies for processing solid transparent materials—thermoplasmonic laser-induced backside wet etching (TP LIBWE). This technology involves aqueous solutions of metal precursors as a working medium. The dependence of the efficiency of sapphire TP LIBWE micromachining on the parameters of laser action is studied with the aqueous solution of the AgNO3 precursor as a working media. The near-optimal range of laser intensities from the point of the etching speed and quality is found. Utilizing the optoacoustic methods, high-speed video, and an optical integrating sphere, the initial stage of the TP LIBWE process is studied in detail. A four-stage model of the TP LIBWE beginning process is proposed, which explains the effects from the beginning of Ag nanoparticle formation in the region of laser exposure to the transition of the TP LIBWE process to a stationary laser microstructuring mode. It is shown that effective microstructuring occurs due to the appearance on the sapphire surface of a thin modified layer in the region of laser action. This thin modified layer is an amorphous Al2O3 with numerous plasmonic Ag nanoparticles inside it and at the sapphire/liquid interface.

Effects of laser parameters on machining precision and quality of wave-permeable materials

Wave-permeable materials with certain metallic film patterns are of importance for electromagnetic wave transportation. Laser processing showed obvious advantages when fabricating such materials. The article studied the etching effects of key laser parameters on Al-coated composite materials. It is found that (1) a balance of etching quality and efficiency could be obtained when the operating laser energy density is about five to eight times that of the ablation threshold; (2) the effects of the laser focal spot size and the pulse overlap are interrelated to decide machining precision; and (3) the laser scanning trajectory affects the appearance of the etched surface, possibly due to the fiber bundle braided direction. The findings could benefit similar wave-permeable materials laser processing.

The quality of etched enamel in different regions and tooth types and its significance in bonding and the development of white spot lesions.

To quantify differences in the etch quality of enamel within and between human teeth, which has not previously been attempted. The buccal right and left halves of 27 extracted human teeth were randomly allocated to scanning electron microscopy (SEM) or micro-computed tomography (μCT) for evaluation. The buccal surfaces were pumiced, etched with 37% phosphoric acid gel etchant for 15 seconds, rinsed, and air dried. Each tooth was divided into three regions (incisal, middle, and cervical) and viewed after etching at 1200× magnification with SEM. The μCT scans were taken before and after etching to calculate apparent and material mineral densities. SEM showed greater aprismatic enamel and poorer etch quality (ie, significantly less percentage enamel) for the posterior than anterior teeth and for the cervical region than for the incisal and middle regions of all teeth. Although there were no density differences prior to etching, μCT demonstrated that etching increased material density significantly more for the anterior than posterior teeth. Prior to etching, the enamel in the cervical regions was significantly less dense than the enamel in the middle or incisal regions. Etching significantly increased the material density of all three regions, which decreased initial regional differences. After etching, the apparent density of the cervical region remained significantly lower than the densities of the other two regions. Based on SEM and μCT, there is greater aprismatic enamel and inferior etch quality in the cervical regions of all tooth types and is clinically significant in explaining the failure of sealant retention and the propensity for white spot lesions.

3.4-kV AlGaN/GaN Schottky Barrier Diode on Silicon Substrate With Engineered Anode Structure

In this letter, we demonstrate high-performance lateral AlGaN/GaN Schottky barrier diodes (SBD) on Si substrate with a recessed-anode structure. The optimized rapid etch process provides results in improving etching quality with a ~ 0.3 nm roughness of the 5 × 5 μm <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sup> anode recessed surface. Supported by the flat anode recess surface and optimized anode field plate design. When the anode-to-cathode spacing is 30 μm, the physical breakdown voltage (VBK) can reach 3.4 kV, with a specific on-resistance (R <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">on,sp</sub> ) of 3.7 mΩ·cm <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sup> , the power figure of merit (V <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">BK</sub> <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sup> /R <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">on,sp</sub> ) can be as high as 3.1 GW/cm <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sup> , demonstrating its great potential for the application in power electronics.

2.7-kV AlGaN/GaN Schottky barrier diode on silicon substrate with recessed-anode structure

In this paper, we demonstrate high-performance lateral AlGaN/GaN Schottky barrier diodes (SBD) on Si substrate with a recessed-anode structure. The optimized rapid etch process provides results in improving etching quality with a 0.26-nm roughness of the anode recessed surface. By using the high work function metal Pt as the Schottky electrode, a low turn-on voltage of 0.71 V is obtained with a high uniformity of ±0.023 V for 40 devices. Supported by the flat anode recess surface and related field plate design, the SBD device with the anode–cathode spacing of 15 μm show the specific on-resistance (Ron,sp) of 1.53 mΩ·cm2 only, the physical breakdown voltage can reach 1678 V with a high power figure-of-merit (P-FOM) of 1840 MW/cm2. For the SBD device with the anode–cathode spacing of 30 μm, the physical breakdown voltage can be as high as 2705 V and the power FOM is 2217 MW/cm2.

Nanosecond Laser Etching of Aluminum-Plated Composite Materials Applied to Frequency Selective Surfaces.

High-quality frequency selective surfaces (FSSs) are important for electromagnetic signal absorption/filtration. Usually, they are made from wave-transparent composite materials covered with a thin metal layer. Current machining methods show some disadvantages when performing fabrication on the structure. Based on its flexibility and uncontactable processing characteristics, nanosecond laser etching of aluminum-plated composite materials applied to FSSs was investigated. To observe the influence of the laser light incident angle, etching of a series of square areas with different incident angles was performed. Thereafter, an image processing method, named the image gray variance (IGV), was employed to perform etching quality evaluation analysis. The observed microscopic pictures of experimental samples were consistent with those of the IGV evaluation. The potential reasons that might affect the etching quality were analyzed. Following all the efforts above, an incident angle range of ±15° was recommended, and the best etching result was obtained at the incident angle of 10°. To observe the influence of the laser pulse overlap and focal spot size on the etched area border uniformity and on the potential damage to the base materials, a theoretical equation was given, and then its prediction of area border edge burrs fluctuation was compared with the experiments. Furthermore, SEM pictures of etched samples were examined. Based on the study, a processing window of the laser pulse overlap and focal spot size was recommended. To conclude, optimal etching results of the FSS materials could be guaranteed by using the right laser operating parameters with the nanosecond laser.

High speed and low roughness micromachining of silicon carbide by plasma etching aided femtosecond laser processing

Silicon carbide has a high hardness and corrosion resistance. Accordingly, high rate machining of this material is a big challenge to obtain good surface quality. In this work, plasma etching aided femtosecond laser micromachining was proposed to address this issue. A series of square and circular blind holes for forming SiC pressure sensor diaphragms were obtained by using a 50fs, 800 nm, 1000Hz Ti:Sapphire laser. Using the control variable method, the effects of laser machining power, scan line spacing and scanning rate on surface topography of the structure were investigated. As demonstrated by experimental results, surface roughness of the structure increases with the laser machining power within a certain range. While the scanning rate has negligible effects on surface quality of the structure. The maximum surface roughness after femtosecond laser micromachining is 2.867 μm measured by laser scanning confocal microscope, and this value is reduced to 2.143 μm after inductively coupled plasma etching. In addition, a Raman spectroscopy shows that this composite micromachining method can eliminate accumulation of amorphous carbon on SiC surface caused by the femtosecond laser processing. The reduction of surface roughness and removal of amorphous carbon can effectively decrease probability of crack failure of the sensor diaphragm and increase its deformation capability, thereby ensuring sensitivity of the sensor. The composite micromachining method fully combines the advantages of high efficiency of femtosecond laser machining and high surface quality of plasma etching, making it has high potential to be applied in precision machining of silicon carbide and fabrication of SiC sensors.

Ablation of piezoelectric polyvinylidene fluoride with a 193 nm excimer laser.

The unique flexible and piezoelectric properties of polyvinylidene fluoride (PVDF) films would allow for new applications for integrated bioelectronic devices. The use of these films has been precluded by the difficulty in machining them into small, discrete features without damaging the properties of the material. The etching of piezoelectric PVDF by means of a 193 nm excimer laser is explored and characterized. Etch rates are shown for common laser fluence values, along with images of the quality of the cuts to provide the reader with an understanding of the compromise between etch rate and edge roughness. The authors describe a novel method for the etching of piezoelectric, -phase PVDF. While PVDF is flexible, acoustically matched to biological tissue, and has a wide resonance bandwidth, it is often overlooked as a piezoelectric material for micro-electrical-mechanical-system devices because of the difficulty in fabrication. In this paper, the authors characterize the etch rate and quality while using a 193 nm argon fluoride excimer laser for patterning.

Reactive ion etching of Cr-doped Sb2Te3 phase change materials in CHF3/O2 gas

Cr doped Sb2Te3(CST) was considered to be a potential phase-change material mainly due to its fast phase transition and high thermal stability. To manufacture high-integration phase change memory devices, etching technology of CST films is indispensable. Herein we investigated the properties of reactive ion etching of CST thin films in CHF3/O2-based plasma. The etch parameters such as etch rate, selectivity and surface roughness were optimized by varying the CHF3/O2 gas mixture ratio to explore the effect of etching gas on etching quality. We observed that etching of CST films was optimized under the condition of CHF3/O2 gas ratio of 40/10, RF power of 200 W, and chamber pressure of 10 mTorr, i.e. the etch rate was up to 101.8 nm/min, the selectivity to photoresist was 0.78 and the surface was smooth. The etching mechanism and residual products in the etching process were also explored by X-ray photoelectron spectroscopy (XPS). Under the optimized conditions, a highly efficient and low-damage reactive ion etching method for CST materials is obtained.

Microchannel Fabrication in Fused Quartz by Backside Laser-Induced Plasma Ablation Using 248 nm KrF Excimer Laser

Laser-induced plasma ablation (LIPA) using a 248 nm KrF excimer laser was investigated for microchannel fabrication. Examination of the morphology in relation to ablation performance was emphasized, and a synthetic LIPA mechanism model was proposed based on the results. Backside LIPA with a metal target on the bottom can be attributed to a combination of two phenomena: laser-induced plasma vaporization thermal ablation from the metal target below and enhanced laser–glass direct interaction from the plasma residuum. The laser absorption enhancement of quartz substrate resulting from the metal residuum was validated clearly using absorption spectrum measurements. The influence of laser parameters on the etching quality during LIPA was also analyzed for processing optimization. Finally, fused quartz glass microchannels of outstanding surface quality and dimension uniformity were implemented. The channel depth was 28 μm, and the bottom surface roughness was better than several hundred nanometers.

Raman spectroscopic determination of the degree of dissociation of nitric acid in binary and ternary mixtures with HF and H2SiF6

AbstractThe oxidizing effect of nitric acid in aqueous solutions depends on the concentration of undissociated nitric acid. This makes the concentration of undissociated nitric acid an essential parameter to monitor and control the quality of silicon etching in the industrial manufacturing of solar cells. In the present study, a method known already is extended in such a way that the degree of dissociation of nitric acid can be determined by Raman spectroscopy in HF/HNO3/H2SiF6 acid mixtures over a broad concentration range for the first time and without using an internal or external standard to compensate the typical time‐dependent drift of a Raman spectrometer. The method developed requires the calculation of a peak area ratio from the areas of the unimpeded Raman signals assigned to nitrate (νN − O) at 1,048 cm−1 and to undissociated HNO3 (νN − OH) at 957 cm−1. The correlation between the peak ratio and the degree of dissociation of nitric acid revealed can be described by a simple empirical equation. Using this equation, the degree of dissociation of nitric acid can be determined over a broad concentration range in binary and ternary mixtures of HNO3 with HF and H2SiF6. The impact of the acids HF and H2SiF6 and the total water content in the degree of dissociation of nitric acid is discussed.

Investigation of etching optimization in capacitively coupled SF6–O2 plasma

The selective etching process is widely used for achieving the desired etch rate in semiconductor fabrication. Parameters such as input power, operating pressure, gas mixture, chamber geometry, and amplitude of the radio-frequency voltage govern the etch rate and etch quality in plasma. In this work, we experimentally investigated the optimum plasma etching conditions required to achieve an anisotropic etch profile and analyzed how the optimum etching can be carried out using an appropriate operating pressure and oxygen concentration. Optical emission spectroscopy was used to measure the concentrations of oxygen and fluorine, and Langmuir probe was used to measure the electron density in the plasma. The oxygen concentration was varied from zero to 100 vol. % for pressures in the range of 20–600 mTorr. The optimum etch conditions are used to study the ion energy distribution given by Kawamura et al., Plasma Sources Sci. Technol. 8, R45 (1999). The results suggest that in addition to O2% and pressure, the DC bias is another crucial parameter for achieving the optimum etch conditions.