Dry Etching Process Research Articles

Assessment Of Cl 2 /CHF 3 Mixture For Plasma Etching Process On Barc And Tin Layer For 0.21 µm Metal Line: Silterra Case Study

In wafer fabrication manufacturing, aluminum etching process is a dry plasma etching process used as main process for construction of aluminum (Al) interconnects structures. As customer requirement changed for faster, more reliable and lower cost chips, chip manufacturers have learned to reduce the size of component on a chip in order to achieve those requirements(Ibrahim, Chik, & Hashim, 2016). As the geometry of the chip getting smaller, the width of Al line wiring specification also shrinking. To print the smaller geometry pattern requirement, the thickness in masking process also has to be reduced for better resolution. Such a thinner resist will create a challenge during plasma etching to ensure a minimal resist loss process which required new type of equipment but this research insist to sustain similar equipment. The use of oxide film as a hard mask has been evaluated by other researchers but alternative approach still needed to suit specific requirement of semiconductor factory installation base. This approach does require a process integration change and require a full technology qualification and easily take a lengthy qualification procedures especially when to qualify the existing products. It is worth trying at the situation of no other solution available. The challenge of insufficient margin for the metal line etching process for 0.2 µm width has caused the deformed metal pattern formation. This chemistry study of Cl2/CHF3 as a replacement gas to existing Cl2/O2 to address Organic backside anti refractive coating (OBARC) was evaluated and proven novelty where detail discussed in the following content.

Fabrication of freestanding Pt nanowires for use as thermal anemometry probes in turbulence measurements

We report a robust fabrication method for patterning freestanding Pt nanowires for use as thermal anemometry probes for small-scale turbulence measurements. Using e-beam lithography, high aspect ratio Pt nanowires (~300 nm width, ~70 µm length, ~100 nm thickness) were patterned on the surface of oxidized silicon (Si) wafers. Combining wet etching processes with dry etching processes, these Pt nanowires were successfully released, rendering them freestanding between two silicon dioxide (SiO2) beams supported on Si cantilevers. Moreover, the unique design of the bridge holding the device allowed gentle release of the device without damaging the Pt nanowires. The total fabrication time was minimized by restricting the use of e-beam lithography to the patterning of the Pt nanowires, while standard photolithography was employed for other parts of the devices. We demonstrate that the fabricated sensors are suitable for turbulence measurements when operated in constant-current mode. A robust calibration between the output voltage and the fluid velocity was established over the velocity range from 0.5 to 5 m s−1 in a SF6 atmosphere at a pressure of 2 bar and a temperature of 21 °C. The sensing signal from the nanowires showed negligible drift over a period of several hours. Moreover, we confirmed that the nanowires can withstand high dynamic pressures by testing them in air at room temperature for velocities up to 55 m s−1.

Highly durable organic photodetector for complementary metal oxide semiconductor image sensors

Utilizing organic electronics compatible with conventional semiconductor fabrication processes is extremely difficult because of their low chemical resistivity and poor environmental durability. To preserve the intrinsic functionality of organic materials, only a few fabrication processes can be used. Moreover, it is essential to achieve process expandability and silicon-process compatibility to develop high-resolution electronics suitable for mass production. Therefore, we developed wet-process-compatible organic photodetectors by replacing the conventional shadow-mask process with photolithography. This suppresses particle deposition during the serial fabrication processes, providing high operational stability. The fabricated green organic photodiodes exhibit a low dark current (1.0 × 10−11 A/cm2) with high photon–electron conversion efficiency (EQE = 65%). The charge collection and charge separation efficiencies are stable (ηcc = 84.6% and ηcs = 97.7%, respectively). Moreover, the organic semiconductors are compatible with conventional wet- and dry-etching processes owing to thin-film encapsulation layers. Finally, the novel organic image sensor can withstand 500 h under 85 °C/85% relative humidity and 1000 thermal cycles (−55–125 °C). Because of its robustness and strong barrier properties, the novel process architecture reported herein can be extended to any organic electronic devices, including widely commercialized organic light-emitting diodes and organic photovoltaic devices.

Anti-icing efficiency on bio-inspired slippery elastomer surface

In this study, we conducted a facile method to fabricate an anti-icing surface on elastomer thin film by combining the PDMS nanostructure with the low surface tension lubricant. PDMS solution was mixed with slippery lubricant Krytox 1506 in a rational concentration and followed by a plasma dry etching process to promote the anti-icing performance in terms of shear stress and water repellency ability. Experimental results were compared with the reference substrates and demonstrated the advantages of the slippery surface in all mentioned scenarios. In addition, the functionalized surfaces also present high durability and good transparency, demonstrating a new facile method and design for outdoor anti-icing devices.

The Display Week 2021 Symposium Preview

The Display Week 2021 Symposium Preview

Dry Phosphorus silicate glass etching and surface conditioning and cleaning for multi-crystalline silicon solar cell processing

As an alternative to the wet chemical etching method, dry chemical etching processes for Phosphorus silicate glass [PSG} layer rel11ova] using Tri?uormethane/Sulfur Hexafluoride (CHF3/ SF6) gas mixture in commercial silicon-nitride plasma enhanced chemical vapour deposition (SiN-PECVD) system is applied. The dependence of the solar cell performance on the etching temperature is investigated and optimized. It is found that the SiN-PECVD system temperature variation has a signi?cant impact on the whole solar cell characteristics. A dry plasma cleaning treatment of the Si wafer surface after the PSG removal step is also investigated and developed. The cleaning step is used to remove the polymer ?lm which is formed during the PSG etching using both oxygen and hydrogen gases. By applying an additional cleaning step, the polymer ?lm deposited on the silicon wafer surface after PSG etching is eliminated. The effect of different plasma cleaning conditions on solar cell performance is investigated. After optimization of the plasma operating conditions, the performance of the solar cell is improved and the overall gain in ef?ciency of 0.6 % absolute is yielded compared to a cell without any further cleaning step. On the other hand, the best solar cell characteristics can reach values close to that achieved by the conventional wet chemical etching processes demonstrating the effectiveness of the additional O2/H2 post cleaning treatment.

Increasing the Hot‐Electron Driven Hydrogen Evolution Reaction Rate on a Metal‐Free Graphene Electrode

AbstractRecently, it has been shown that a semiconductor–insulator–graphene device can drive the hydrogen evolution reaction (HER) at the graphene surface with a reduced onset potential by injecting hot electrons into graphene. However, the catalytic properties of graphene are limited by the large hydrogen adsorption energy and lack of electrochemically active sites. To address these limitations, a n‐silicon/insulator/plasma etched graphene device is investigated, where a dry etch process is used to increase the number of active sites on the graphene by creating a greater number of active edge sites, increasing hydrogen adsorption at a given potential. This has been shown to improve the properties of devices with cold electrons. However, here it is shown that this approach can improve the HER rate with hot electrons. The electrons injected into the graphene from the silicon shift the onset potential of HER by as high as ≈0.8 V reaching a current density of 90 mA cm−2 at an overpotential of ‐0.5 V versus RHE. Furthermore, the comparison between device with pristine graphene shows a ≈2X improvement in current density at high overpotentials. This result shows that hot‐electron devices can be improved by modifying the catalytically active sites without metal catalysts.

Fluorine-based Inductively Coupled Plasma Etching of α-Ga2O3 Epitaxy Film

α-Ga2O3 has the largest bandgap (~5.3 eV) among the five polymorphs of Ga2O3 and is a promising candidate for high power electronic and optoelectronic devices. To fabricate various device structures, it is important to establish an effective dry etch process which can provide practical etch rate, smooth surface morphology and low ion-induced damage. Here, the etch characteristics of α-Ga2O3 epitaxy film were examined in two fluorine-based (CF4/Ar and SF6/Ar) inductively coupled plasmas. Under the same source power, rf chuck power and process pressure, an Ar-rich composition of CF4/Ar and an SF6-rich composition of SF6/Ar produced the highest etch rates. Monotonic increase in the etch rate was observed as the source power and rf chuck power increased in the 2CF4/13Ar discharges, and a maximum etch rate of ~855 Å/min was obtained at a 500 W source power, 250 W rf chuck power, and 2 mTorr pressure. A smooth surface morphology with normalized roughness of less than ~1.38 was achieved in the 2CF4/13Ar and 13SF6/2Ar discharges under most of the conditions examined. The features etched into the α-Ga2O3 layer using a 2CF4/13Ar discharge with 2 mTorr pressure showed good anisotropy with a vertical sidewall profile.

P‐6.2: A Defect Defense Approach of Integrated Database Based on Over‐Etched Defect

The aluminum line overetched defect might be called as undercut PR Hole, etc by different manufacturers. The defect of this case study mainly shows a hole found on the aluminum line after stripper process but there is no any tracable symptom before the ending of dry etch process. That is, it seems no means to prevent or to found the root cause.A defect defense approach via cleanroom air quality database based integrated with TFT manufacturing processes air sampling characteristics of manufacturing chemicals cleanroom circulation and air flow pattern is proposed to demostrate how to figure out the root cause of aluminum line overetched defect, which found after stripper.Via the aid of proposed approach, the analysis shows the defect arises from the cross contamination between photo PVD and stripper process and the cross contamination comes from manufacturing layout cleanroom circulation and air flow pattern.

Removal of Post Etch Residue on BEOL Low-K with Nanolift

Particle removal from BEOL low-k structures is studied using a novel particle removal technique, called Nanolift which removes particles from the substrate by forming a thin polymer film on the surface and removing the polymer film together with the particles. It was confirmed that Nanolift is capable to remove TiFx particles successfully which are generated during the low-k dry etch process for dual damascene structure formation for BEOL interconnect fabrication. Pattern collapse of the fragile low-k structure was confirmed to be prevented by Nanolift in comparison with conventional dual fluid spray cleaning method. FTIR results show that Nanolift leaves no residual polymer remain in low-k films and K-value shift by the Nanolift process was negligible and comparable with the conventional formulated chemistry cleaning process. From these results, Nanolift can be concluded as a suitable cleaning process for advanced BEOL fabrication process.

Wide band UV/Vis/NIR blazed-binary reflective gratings: two lithographic techniques investigation

We report on subwavelength reflective gratings for hyperspectral applications operating in the 340 nm-1040 nm spectral range. The blazed grating period is 30 μm and is composed of 2D subwavelength binary structures with sizes in-between 120 nm and 350 nm. We demonstrate the manufacturing of gratings on 3” wafers by two lithography technologies (e-beam or nanoimprint) followed by dry etching process. These subwavelength gratings enable broadband efficiency which is in average 15%-20% above the efficiency requirement for next generation of spectro-imagers for Earth observation missions and a wavefront error that is much smaller than the 100 nm requirement for space application.

High-Q lithium niobate microring resonators using lift-off metallic masks [Invited

High-Q lithium niobate (LN) optical micro-resonators are an excellent platform for future applications in optical communications, nonlinear optics, and quantum optics. To date, high-Q factors are typically achieved in LN using either dielectric masks or femtosecond laser ablation, while the more standard and commonly available lift-off metallic masks are often believed to lead to rough sidewalls and lowered Q factors. Here, we show that LN microring resonators with strong light confinement and intrinsic Q factors over 1 million can be fabricated using optimized lift-off metallic masks and dry etching processes, corresponding to a waveguide propagation loss of ∼0.3 dB/cm. The entire process is fully compatible with wafer-scale production and could be transferred to other photonic materials.

Near-zero surface pressure assembly of rectangular lattices of microgels at fluid interfaces for colloidal lithography.

Understanding and engineering the self-assembly of soft colloidal particles (microgels) at liquid-liquid interfaces is broadening their use in colloidal lithography. Here, we present a new route to assemble rectangular lattices of microgels at near zero surface pressure relying on the balance between attractive quadrupolar capillary interactions and steric repulsion among the particles at water/oil interfaces. These self-assembled rectangular lattices are obtained for a broad range of particles and, after deposition, can be used as lithography masks to obtain regular arrays of vertically aligned nanowires via wet and dry etching processes.

Optimization on Dry-Etching Process for High-Density STT-MRAM

STT-MRAM (Spin-Transfer-Torque Magnetic Random-Access-Memory) with high-density is considered as one of the most promising storage candidates with potential applications. Considering the fabrication process of STT-MRAM, the patterning process has an obvious influence on the density and the quality of the storage cells. In the paper, optimization on the plasma etching process is conducted for the improvement of the pattern density. By the adjustment of the process and the introduction of the amorphous carbon as the sacrificial hard mask, the density of the patterned cells is improved, in which the bottom electrode spacing is optimized. In this way, the etching process is suitable for higher density STT-MRAM integration, while providing an practical approach for the high-density MTJ arrays. The simulation results demonstrate that the density of STT-MRAM can be improved by the proposed etching process. The optimization would be useful for future high-density STT-MRAM fabrication.

A novel Deal–Grove‐inspired model for fluorine‐based plasma jet etching of borosilicate crown optical glass

AbstractThe Deal–Grove model is a state‐of‐the‐art approach proposed for describing the thermal oxidation of silicon and the oxide thickness over time. In this study, the Deal–Grove concept provided the inspiration for a mathematical model for simulating plasma jet‐based dry etching process of borosilicate crown glass (N‐BK7®). The whole process is contained in two so‐called Deal–Grove parameters, which are extracted from experimental data including local etching depth and surface temperature distribution. The proposed model is extended for the evolution of dynamic etch profiles, and the obtained results are validated experimentally. By establishing such a model, it is possible to predict the effect of the residual layer and surface temperature on the evolution of local etching depths over dwell time.

Optimizing etching process recipe based on Kernel Ridge Regression

Abstract Exploring optimal recipes to reduce dimensional variations is critical in etching processes. Variations in critical dimensions that were acceptable previously can become problematic because of smaller node sizes and more complex structures. Dry etch can be a major source of variations and will be the focus of this research. Advanced Process Control (APC) has been widely studied in semiconductor manufacturing. Even though different APC methods have been developed to adjust recipes, it is challenging to explore an optimal recipe to achieve multiple critical dimensions. In this paper, a learning method based on Kernel Ridge Regression (KRR) is proposed to generate optimal recipes for multi-input multi-output (MIMO) systems. A KRR parameter optimization method is developed. To improve the recipe optimization process, a feedback fine tuning method is proposed. Experimental data in a dry etch process were collected and processed for model construction and recipe optimization. The results demonstrate the effectiveness of the proposed method in exploring optimal recipes for MIMO systems.

Optimizing Process Recipe for Critical Dimensions in Dry Etching Process

Reducing variations of fabrication processes is a primary focus for improvement in etching process. One powerful tool employed towards this goal is Advanced Process Control (APC). APC adjusts recipes to compensate for measured variations. Systemic variations that were acceptable previously can become problematic as node sizes get smaller and structures become more complex. Dry etch can be a major source of variations and will be the focus of this research. Different APC methods have been developed to adjust recipes. However it is challenging to determine an optimal recipe to achieve multiple critical dimensions. In this article, an optimization method is proposed to generate optimal recipes for multiple input and multiple output (MIMO) systems. Models are constructed by applying Gaussian Process Regression and the optimal recipe is predicted using the proposed optimization method. Experimental data in dry etch process were collected and processed for model construction and recipe prediction. The results demonstrate the effectiveness of the proposed method in exploring optimal recipes for MIMO systems.

Integration and characterization of micron-sized YIG structures with very low Gilbert damping on arbitrary substrates

We present a process that allows the transfer of monocrystalline yttrium-iron-garnet microstructures onto virtually any kind of substrate. The process is based on a recently developed method that allows the fabrication of freestanding monocrystalline YIG bridges on gadolinium-gallium-garnet. Here, the bridges' spans are detached from the substrate by a dry etching process and immersed in a watery solution. Using drop-casting, the immersed YIG platelets can be transferred onto the substrate of choice, where the structures finally can be reattached and, thus, be integrated into complex devices or experimental geometries. Using time-resolved scanning Kerr microscopy and inductively measured ferromagnetic resonance, we can demonstrate that the structures retain their excellent magnetic quality. At room temperature, we find a ferromagnetic resonance linewidth of μ0ΔHHWHM≈195 μT and we were even able to inductively measure magnon spectra on a single micrometer-sized yttrium-iron-garnet platelet at a temperature of 5 K. The process is flexible in terms of substrate material and shape of the structure. In the future, this approach will allow for types of spin dynamics experiments until now unthinkable.

Creation of Curved Nanostructures Using Soft-Materials-Derived Lithography.

In this study, curved nanostructures, which are difficult to obtain, were created on an Si substrate through the bonding, swelling, and breaking processes of the polymer and silicone substrate. This method can be utilized to obtain convex nanostructures over large areas. The method is simpler than typical semiconductor processing with photolithography or compared to wet- or vacuum-based dry etching processes. The polymer bonding, swelling (or no swelling), and breaking processes that are performed in this process were theoretically analyzed through a numerical analysis of permeability and modeling. Through this process, we designed a convex nanostructure that can be produced experimentally in an accurate manner.

Examination of Reducing Agents Used for Aluminum Electroless Deposition

1. Introduction Because of its properties such as low electrical resistance, simple to structure in dry etch processes, aluminum is widely used for wiring material in the field of semiconductors. However, it is necessary to use large instruments such as sputtering and glow plasma methods to deposit aluminum on the silicon substrate. If the technique of electroless plating of aluminum is established, it will be able to obtain the thin film on the silicon substrate easily without electricity. We reported an electroless plating of aluminum on the glass by using a room-temperature ionic liquid composed of aluminum chloride (AlCl3) and 1-ethyl-3-methylimidazolium chloride (EMIC) with lithium hydride (LiH) or di-isobutyl aluminum hydride (DIBAH) as reducing agents1). In this research, we tried electroless plating of aluminum on silicon substrate coated with tungsten (W) or with titanium nitride (TiN) which has not been reported so far. And the possibility of shortening the time of electroless plating was investigated by dissolving various new reducing agents in the plating solution.2. ExperimentalTo perform the electroless aluminum plating experiment, the silicon substrate coated with W or with TiN were degreased, pickled, and catalyzed. Thereafter, reducing agents (DIBAH or various new reducing agents) were added to a plating solution of 66.7 mol% AlCl3 + 33.3 mol% EMIC ionic liquid heated to 70 ℃, and the substrate was immersed in the solution to perform electroless aluminum plating. The linear sweep voltammetry measurements were employed, a three-electrode cell consisting of a tungsten working electrode, an aluminum counter electrode, and an aluminum reference electrode by the scan rate was 5 mV/s. An aluminum wire (99.99%, φ:2mm) immersed in a 66.7 mol% AlCl3 – 33.3 mol% EMIC melt in a Pyrex tube separated by a G4 glass frit was used as the reference electrode. The electrochemical behavior of reducing agents in 50mol% AlCl₃ + 50mol%EMIC ionic liquid was investigated. All experimental operations were performed inside a glove box under an inert gas atmosphere.3. Results and DiscussionA plating film was provided on silicon substrate coated with W and with TiN from the 66.7 mol% AlCl₃ + 33.3 mol% EMIC ionic liquid with the DIBAH reducing agent. The characteristics of the plated films were investigated by X-ray diffraction (XRD), scanning electron microscopy (SEM). The observed X-ray diffraction peaks of the plated film agreed with those of aluminum in the literatures. However, it took more than 6 hours to get few ㎛ thickness of aluminum plating. We tried to find other reducing agent to shorten the time of electroless plating. The self-potential of reducing agents in the 50mol% AlCl₃ + 50mol% EMIC ionic liquid were measured. Some reducing agents showed less-novel potential, indicating that they can be used as a reducing agent as well as DIBAH for electroless Al plating. It was confirmed that electroless plating was performed by using those reducing agents. Especially, reducing agent A shortens the plating time to about 1-2 minutes to get few ㎛ thickness. Also, it was found that when the concentration of the reducing agent E was high, the reactivity became too strong, and the liquid decomposition occurred rapidly, so that plating could not be performed. From these results, we could say that the reducing agent A was very useful, but it was important to control the reactivity by adjusting the concentration.The electroless plating mechanism was studied by the polarization curves of a tungsten electrode in room-temperature ionic liquids. It was concluded that the electroless plating reaction consisted of anodic oxidation reaction of reducing agent and cathodic reduction of Al2Cl7-.4. ConclusionElectroless Al plating is possible for W-coated silicon substrate and TiN-coated silicon substrate from 66.7 mol% AlCl₃ + 33.3mol% EMIC ionic liquid with DIBAH reducing agent. The results of self-potential measurement showed that reducing agents with less-novel potential could be used as reducing agents for Al electroless plating. The results of electroless plating experiments suggested that the use of reducing agent A could shorten the plating time significantly.5. References1) Setsuko Koura, Souta Ooshima, Daiki Kudo, Electroless deposition of Aluminum from a Room Temperature Ionic Liquid Electrolyte, 2016 / 230th ECS Meeting Electrochemical Society (USA and Japan) (2016)