Critical Step In Fabrication Research Articles

Advancements in Flexible Electronics Fabrication: Film Formation, Patterning, and Interface Optimization for Cutting-Edge Healthcare Monitoring Devices.

Flexible electronics can seamlessly adhere to human skin or internal tissues, enabling the collection of physiological data and real-time vital sign monitoring in home settings, which give it the potential to revolutionize chronic disease management and mitigate mortality rates associated with sudden illnesses, thereby transforming current medical practices. However, the development of flexible electronic devices still faces several challenges, including issues pertaining to material selection, limited functionality, and performance instability. Among these challenges, the choice of appropriate materials, as well as their methods for film formation and patterning, lays the groundwork for versatile device development. Establishing stable interfaces, both internally within the device and in human-machine interactions, is essential for ensuring efficient, accurate, and long-term monitoring in health electronics. This review aims to provide an overview of critical fabrication steps and interface optimization strategies in the realm of flexible health electronics. Specifically, we discuss common thin film processing methods, patterning techniques for functional layers, interface challenges, and potential adjustment strategies. The objective is to synthesize recent advancements and serve as a reference for the development of innovative flexible health monitoring devices.

Effect of Structure to Promote Organic Residue Removal during Cu Post-Chemical Mechanical Planarization (p-CMP) Cleaning

The extension of Moore’s law remains a focal point as semiconductor manufacturers drive to advance Integrated Circuit (IC) technology by implementing new materials. Chemical Mechanical Planarization (CMP) has emerged as a critical processing step in device fabrication to keep up with these demands. However, one drawback to this process is the generation of killer defects that result from residual contamination (i.e., organic residues, abrasive particles, pad remnants, etc.) that are reliant on post-CMP (p-CMP) cleaning methods. Current Cu p-CMP cleaning methods implement the use of an industry standard polymer brush coupled with cleaning chemistries to remove residual contamination. It has been well established that shear and compressive forces coupled with surface active cleaning chemistries have proven to be efficient albeit with the potential for secondary defectivity (i.e., pitting, etching, scratching). Additionally, current cleaning formulations rely on additives that promote aggressive redox conditions to remove residues through an undercutting mechanism, which leads to the propagation of the aforementioned defect modes. This work focuses on the development of a “softer” approach to Cu p-CMP cleaning by surveying various additives (i.e., -unsaturated carboxylic acids, carboxylic acids, and unsaturated benzaldehydes) to exploit an “overcutting” mode of organic residue removal. By implementing additional modes of interaction (i.e., p-stacking, H-bonding, conformational relationships, etc.), the mode of residue removal can be finely tuned to achieve desired surface-active conditions. This work employs a suite of techniques (i.e., Tafel analysis, OCP vs. time, time-resolved contact angle, shear force analysis) to correlate structure-activity to organic residue removal efficiency and the effects on the coefficient of friction (COF), particle removal efficiency, and the generation of secondary defectivity. Initial results have shown that implementing an “overcutting” mechanism will decrease the overall shear force and significantly reduce the proliferation of p-CMP cleaning defects. Furthermore, adding ancillary structure activity aids in additional modes of residue interaction to alter removal at the liquid-brush interface. Additionally, increased structure-activity has promoted residue-chemistry interactions to form a second passivation layer. Moreover, conformational changes that result in limited accessibility to the a,b-unsaturated double bond promote an “undercutting” mode of removal to become the predominant mode of organic residue mediation.

Comparative evaulation of condylar guidance obtained by digital panoramic radiographic images with that of obtained during jaw relation and try-in using two different interocclusal record material in completely edentulous patients: an in vivo study

Background: In completely edentulous patients, maintaining the patient's TMJ health and intraoral components is very important. This can be achieved by an accurate interocclusal record, which can we taken by various materials and also at various stages. Simulation of the temparomandibular joint anatomy and mandibular movements is possible on a semi adjustable articulator which is use widely in prosthodontics. Transferring the record on articulator is a critical step in fabrication of complete dentures so it should be done precisely to reduce chair side time and also to avoid complications for patients. This study examines which material is more accurate and also records which stage gives more precision, by comparing the Condylar guidance on radiographs. This is because it has consistent bony landmarks and is comparable to clinical methods in terms of standardisation. The objective will be to determine the inter occlusal records created during Jaw Relation stage and Try-in using reinforced wax and Polyvinyl siloxane and compare these values to the condylar guidance obtained by OPG. Methods: Recording the Condylar Guidance value on OPG, obtained with tracing Glenoid fossa, Articular eminence and the Frankfurt Horizontal Plane. Followed with conventional steps in making complete dentures, at jaw relation and try-in stage. we will record values of condylar guidance with the two different Interocclusal record materials. Expected result: It will help the clinicians to get knowledge about obtaining precise condylar inclination angle by using right interocclusal record materials. Conclusions: This study will help us to obtain condylar inclination which inturn helps the patients satisfaction as it maintains the patient's TMJ health and intraoral components.

Comparative evaulation of condylar guidance obtained by digital panoramic radiographic images with that of obtained during jaw relation and try-in using two different interocclusal record material in completely edentulous patients: an in vivo study

Background: In completely edentulous patients, maintaining the patient's TMJ health and intraoral components is very important. This can be achieved by an accurate interocclusal record, which can we taken by various materials and also at various stages. Simulation of the temparomandibular joint anatomy and mandibular movements is possible on a semi adjustable articulator which is use widely in prosthodontics. Transferring the record on articulator is a critical step in fabrication of complete dentures so it should be done precisely to reduce chair side time and also to avoid complications for patients. This study examines which material is more accurate and also records which stage gives more precision, by comparing the Condylar guidance on radiographs. This is because it has consistent bony landmarks and is comparable to clinical methods in terms of standardisation. The objective will be to determine the inter occlusal records created during Jaw Relation stage and Try-in using reinforced wax and Polyvinyl siloxane and compare these values to the condylar guidance obtained by OPG. Methods: Recording the Condylar Guidance value on OPG, obtained with tracing Glenoid fossa, Articular eminence and the Frankfurt Horizontal Plane. Followed with conventional steps in making complete dentures, at jaw relation and try-in stage. we will record values of condylar guidance with the two different Interocclusal record materials. Expected result: It will help the clinicians to get knowledge about obtaining precise condylar inclination angle by using right interocclusal record materials. Conclusions: This study will help us to obtain condylar inclination which inturn helps the patients satisfaction as it maintains the patient's TMJ health and intraoral components.

Impact of plasma induced damage on the fabrication of 3D NAND flash memory

A physical process model for dry plasma etching is presented and applied to simulate vertical channel hole etching, a critical fabrication step in modern three-dimensional (3D) NAND flash memory. The presence of physical etching with high energy ions is shown to induce damage in the underlying silicon, which results in the formation of voids during the subsequent selective epitaxial growth (SEG) step. In this manuscript, we present a model for ion induced damage by storing it as a surface property during the plasma etching simulation. A specialized advection algorithm is subsequently applied to simulate silicon SEG on the bottom source line. The model clearly shows the damage caused by the high energy particles, on the crystal nature of silicon, resulting in poor coverage during the SEG step. The removal of this damaged layer using lower energy plasmas results in highly crystalline epitaxially grown silicon. The simulation results show excellent agreement with experiments in the formation of undesired voids without the low-energy pre-epitaxial plasma treatment.

Delamination of polyimide in hydrofluoric acid

Wet etching is a critical fabrication step for the mass production of micro and nanoelectronic devices. However, when an extremely corrosive acid such as hydrofluoric (HF) acid are used during etching, an undesirable damage might occur if the device includes a material that is not compatible with the acid. Polyimide thin films can serve as sacrificial/structural layers to fabricate freestanding or flexible devices. The importance of polyimide in microelectronics is due to its relatively low stress and compatibility with standard micromachining processes. In this work, a fast delamination process of a 4-μm-thin film of polyimide from a silicon substrate has been demonstrated. The films’ detachment has been performed using a wet-based etchant of HF acid. Specifically, the effect of HF concentration on the delamination time required to detach the polyimide film from the substrate has been investigated. This study is intended to provide the information on the compatibility of using polyimide films with HF, which can help in the design and fabrication of polyimide-based devices.

Low-Cost, Volume-Controlled Dipstick Urinalysis for Home-Testing.

Dipstick urinalysis provides quick and affordable estimations of multiple physiological conditions but requires good technique and training to use accurately. Manual performance of dipstick urinalysis relies on good human color vision, proper lighting control, and error-prone, time-sensitive comparisons to chart colors. By automating the key steps in the dipstick urinalysis test, potential sources of error can be eliminated, allowing self-testing at home. We describe the steps necessary to create a customizable device to perform automated urinalysis testing in any environment. The device is cheap to manufacture and simple to assemble. We describe the key steps involved in customizing it for the dipstick of choice and for customizing a mobile phone app to analyze the results. We demonstrate its use to perform urinalysis and discuss the critical measurements and fabrication steps necessary to ensure robust operation. We then compare the proposed method to the dip-and-wipe method, the gold standard technique for dipstick urinalysis.

On miniaturisation of spirally wound tubular heat exchanger

Spirally coiled multilayer, Giauque-Hampson type heat exchangers, the classical examples of early generation cryogenic heat transfer devices, are best known for their unique and favourable features. These exchangers are capable of handling multiple fluid streams in different phases in a single unit, typically meant for high Ntu applications, operational over a wide range of temperature and pressure with minimum thermal stress development. On the negative part, they belong to the non-compact class of heat exchangers. As the trend of miniaturisation is gradually diffusing into almost every engineering discipline, the development of a compact system is the call of the present era. While probing the prospect of miniaturising multilayer spirally wound tubular (Giauque-Hampson) heat exchangers satisfying the compactness criteria, this article presents the design, fabrication, and testing of a miniature, compact, laboratory-scale prototype. Initially, the pros and cons of miniaturisation have been studied based on the ‘goodness factors’. Subsequently, a step-by-step methodology is proposed to design a compact and miniature heat exchanger geometry, subjected to design constraints. Description of critical fabrication steps is followed by the experimental performance evaluation of the prototype. The heat exchanger effectiveness is calculated based on the steady-state experimental data. Performance degradation is linked to the prevailing non-ideal operating conditions causing external heat ingress. The analysis including heat leak shows good agreement between the experimental results and theoretical predictions.

Nondestructive characterization of nanoscale subsurface features fabricated by selective etching of multilayered nanowire test structures using Mueller matrix spectroscopic ellipsometry based scatterometry

Nondestructive measurement of three-dimensional subsurface features remains one of the most difficult and unmet challenges faced during the fabrication of three-dimensional transistor architectures, especially nanosheet and nanowire based field effect transistors. The most critical fabrication step is the selective etching of silicon-germanium subsurface layers. The resulting shape and dimensions of the remaining Si(1 − x)Gex structure strongly impacts further processing steps and ultimately the electrical performance of gate-all-around transistors, thus creating the need for accurate inline metrology. In order to demonstrate the ability to characterize this etch, nanowire test structures made from Si(1 − x)Gex/Si/Si(1 − x)Gex/Si/Si(1 − x)Gex/Si multilayers have been characterized using Mueller matrix spectroscopic ellipsometry based scatterometry. Transmission electron microscopy images were used to corroborate the authors’ scatterometry measurements. Here, they successfully demonstrate the ability to measure the Si(1 − x)Gex etch, providing an industrially viable technique for inline three-dimensional metrology.

Research Toward a Heterogeneously Integrated InGaN Laser on Silicon

A heterogeneously integrated InGaN laser diode (LD) on Si is proposed as a path toward visible wavelength photonic integrated circuits (PICs) on Si. Herein, InGaN films are vertically stacked on a TiO2 waveguide (WG) fabricated on a Si wafer by bonding. In the light propagation direction, it is composed of a hybrid InGaN/TiO2 section, a TiO2 WG, an adiabatic taper, and mirrors that can form a cavity. As the refractive index of GaN is well matched with that of TiO2, the optical transverse mode extends to both the GaN and TiO2 in a hybrid mode. Modes between a hybrid InGaN/TiO2 and a pure TiO2 WG can transfer with an adiabatic taper structure. The coupling loss is calculated to be less than 0.5 dB with fairly short taper length of 78 μm and tip width of 200 nm. GaN substrate removal and bonding are critical fabrication steps of this LD and PIC. The substrate removal is successfully done by photoelectrochemical etching. Although direct bonding of GaN wafers with thermal oxide on Si is successful, GaN epitaxial wafers are more difficult. An implication and remedy of this is discussed in terms of surface roughness of GaN epitaxial film.

Relation of fovea palatine and vibrating line in different soft palatal forms

Background: The posterior palatal seal (PPS) area plays a major role in retention of a maxillary denture. Many dentures have failed due to faulty recording of posterior palatal seal area. Hence, locating posterior palatal seal area is a critical step in complete denture fabrication. Various techniques have been described in the literature for locating the posterior border of maxillary complete denture. One of the most commonly used methods is the one that uses anatomical landmark like fovea palatine for locating the palatal seal area. However, many studies show a wide range of variation regarding position of fovea palatine with the vibrating line.
 Materials and Methods: A total of 200 subjects were selected for the study and clinical examination carried out to mark the vibrating line and fovea palatine. The location of vibrating line whether it is anterior to fovea palatine, on the fovea palatine or posterior to the fovea palatine in the different soft palate type(Class I, II or III) was recorded using the phonation method.
 Results: The vibrating line was located interiorly to the fovea palatine in 70%, 54% and 60% of the subjects with Class I, II and III soft palate. The vibrating line was located on the fovea palatine in22%, 40% and 36% of the subjects with Class I, II and III soft palate and posteriorly to the fovea palatine in 23%, 5% and 3% of the subjects with Class I, II and III soft palate respectively.
 Conclusion: The vibrating line was predominantly found to be anterior to the fovea palatine in all the soft palatal forms.

Direct Fabrication of Stretchable Electronics on a Polymer Substrate with Process‐Integrated Programmable Rigidity

AbstractDespite the increasingly important role of stretchable electronics for use as the human–machine interface, their manufacturing in a commercially realistic manner remains an unresolved challenge. The bottleneck lies in the efficiency and scalability of transfer printing that is typically employed in the fabrication process to enable device stretchability via strain isolation. Here, the use of a polymer substrate with programmable rigidity for direct manufacturing of stretchable electronics is reported, forgoing the need for transfer printing while significantly enhancing strain isolation. The process starts with a stretchable elastomeric substrate synthesized via the thiol‐acrylate click chemistry. Designable rigid islands can be introduced via spatially confined oxidation of the elastomer. Strain‐sensitive microdevices can then be directly fabricated onto the rigid islands without transfer printing. Following this manufacturing scheme, a fast‐responding stretchable temperature sensor is demonstrated, with unusual accuracy and real‐time temperature monitoring capability suitable for use in a highly dynamic environment. Importantly, the critical fabrication step that introduces the programmable substrate rigidity is fully integrated into a well‐established lithographic process. Therefore, the methodology not only reduces greatly the complexity in fabricating prototype devices but also points to a highly effective way for potential manufacturing in a commercial setting.

Experimental Analysis of Fabrication Parameters in the Development of Microfluidic Paper-Based Analytical Devices (µPADs)

Microfluidic paper-based analytical devices (µPADs) have emerged as viable multiplexable platforms with the potential to transcend existing analytical techniques in resource-limited settings. µPADs are fabricated by patterning hydrophobic materials on hydrophilic paper. Reproducibility in fabrication is essential in a myriad of applications and particularly, in the development of point-of-care (POC) diagnostic devices that utilize paper-based platforms. A critical step in fabrication involves the wax heating process that determines the channel dimensions and the depth at which hydrophobic wax material permeates paper to create barriers. In this paper, we assess µPAD viability by examining two fabrication parameters that affect wax ink spreading and permeation using a commercial heat press: temperature and time of heating. Analysis of the µPADs revealed that functional chips could be fabricated at temperatures between 143 and 215 °C and time of heating between 50 and 135 s, while non-functioning chips were obtained at temperatures between 76 and 140 °C and time of heating between 5 and 45 s. Wax ink spread and permeated paper consistently between 143 and 215 °C. Also shown is a simple three dimensional (3D) microfluidic channel fabricated in a single sheet of cellulose paper utilizing the fabrication conditions described herein. This work demonstrates that controlling the extent of wax printing in the fabrication process of a µPAD can yield versatile and interesting devices for use in both resource-rich and -limited settings.

Effect of metallization on the strength and fracture behaviour of functional co-fired multilayer ceramics

Functional components are commonly fabricated combining a ceramic substrate with external and/or internal metallization. Different layers are printed and fired onto the ceramic part to provide the component with a functionality. As a result of the combination of materials with different coefficients of thermal expansion, internal stresses during the fabrication steps may lead to cracks and/or reduce the strength. In this work, several architectures combining metal and glass layers on the surface of ZnO substrates were analyzed to identify critical fabrication steps in functional co-fired multilayer ceramics. Three-point bending tests were performed on samples taken after different process steps. Experimental results showed a strong effect of the layered architecture on the strength distributions: details of geometrical designs can have a dramatic impact on the strength. Fractographic analyses and ex-situ Focused Ion Beam experiments in pre-loaded samples were the key to assess the location of failure and predict critical configurations.

In-situ doped junctionless polysilicon nanowires field effect transistors for low-cost biosensors

Silicon nanowire (SiNW) field effect transistor based biosensors have already been proven to be a promising tool to detect biomolecules. However, the most commonly used fabrication techniques involve expensive Silicon-On-Insulator (SOI) wafers, E-beam lithography and ion-implantation steps. In the work presented here, a top down approach to fabricate SiNW junctionless field effect biosensors using novel in-situ doped polysilicon is demonstrated. The p-type polysilicon is grown with an optimum boron concentration that gives a good metal-silicon electrical contact while maintaining the doping level at a low enough level to provide a good sensitivity for the biosensor. The silicon nanowires are patterned using standard photolithography and a wet etch method. The metal contacts are made from magnetron sputtered TiW and e-beam evaporation of gold. The passivation of electrodes has been done by sputtered Si3N4 which is patterned by a lift-off process. The characterization of the critical fabrication steps is done by Secondary Ion Mass Spectroscopy (SIMS) and by statistical analysis of the measurements made on the width of the SiNWs. The electrical characterization of the SiNW in air is done by sweeping the back gate voltage while keeping the source drain potential to a constant value and surface characterization is done by applying liquid gate in phosphate buffered saline (PBS) solution. The fabricated SiNWs sensors functionalized with (3-aminopropyl)triethoxysilane (APTES) have demonstrated good sensitivity in detecting different pH buffer solutions.

Integration and fabrication of high-performance Sb-based heterostructure backward diodes with submicron-scale airbridges for terahertz detection

In this work, the authors report integration and fabrication of high-performance Sb-based heterostructure backward diodes (HBDs) with planar folded dipole antennas (FDAs) using submicron-scale airbridges for terahertz (THz) detection. By integrating HBDs into FDAs, high detector responsivity of 20 000 V/W at 200 GHz and 9500 V/W at 585 GHz could be potentially achieved due to the optimized impedance matching between the antenna and HBD detector. In order to minimize interconnect parasitics, the HBD integration is accomplished using submicron-scale airbridges. Electromagnetic simulations coupled to device models show that by introducing submicron-scale airbridges and optimizing the device layout, parasitic capacitance and spreading resistance can be significantly reduced. This allows performance nearly equal to the intrinsic device performance to be obtained. To achieve this level of performance, a novel fabrication and integration process has been developed. The process includes mix-and-match electron beam and optical lithography to span the size scales required for both the FDA and small-area HBDs, and offers high accuracy and reproducibility while requiring fewer critical fabrication steps compared to conventional hybrid integration techniques. Devices fabricated using this process have obtained a record-high device curvature coefficient of −58 V−1, indicating the quality of the devices that can be achieved. The process is scalable—in terms of device size, frequency range, and array size—enabling the development of THz focal plane arrays in a wide frequency range (100 GHz to beyond 1 THz).

Monitoring the formation of oxide apertures in micropillar cavities

An imaging technique is presented that enables monitoring of the wet thermal oxidation of a thin AlAs layer embedded between two distributed Bragg reflector (DBR) mirrors in a micropillar. After oxidation we confirm by white light reflection spectroscopy that high quality optical modes confined to a small volume have been formed. The combination of these two optical techniques provides a reliable and efficient way of producing oxide apertured micropillar cavities for which the wet thermal oxidation is a critical fabrication step.

Better, Faster and Cheaper Precision Cleaning: Advanced CO2 Cleaning Technology

Precision cleaning of microelectronic substrates is a requirement prior to critical fabrication steps such as wire bonding and adhesive bonding, and following processes such as laser machining and soldering. With respect to adhesive bonding, difficult-to-bond materials such as thermoplastics, metals, glasses, ceramics and composites of same present special challenges. Important surface preparation steps include surface cleaning, microscopic etching, and functionalization. This is especially true for materials which exhibit low surface energy or heterogeneous surface contamination and chemistry. Surface treatment challenges are amplified when bonding adherent surfaces with dissimilar cohesive energy densities, for example metal-to-polymer and metal-to-ceramic. Post-laser processing of organic substrates leaves carbon char and particles on or near the laser kerf and surrounding area. These residues must be removed prior to the follow-on fabrication steps such as plating, adhesive bonding, wire bonding, and precision assembly operations. In this regard, conventional precision cleaning processes typically require multiple steps, chemistries, and equipment to accomplish the decontamination and surface modification if required. Moreover, conventional cleaning methods are sometimes non-selective for both contaminant and contaminated surface. For example, conventional vacuum plasma using Ar/O2 is typically used to remove post-laser char on organic films such as Kapton flexible circuits. Vacuum plasma is usually performed off-line, taking up to 30 minutes to complete, and is generally non-selective for the organic contamination. The entire organic substrate is etched away during the cleaning process to remove laser char. In another example, surfaces are prepared for adhesive bonding using multiple steps involving vacuum plasma, organic solvents, chemical etchants or primers. Advanced carbon dioxide (CO2) cleaning technology uniquely and consistently achieves precision clean (and functional surfaces if needed), including 2D and 3D surface geometries, for a variety of critical cleaning applications using one process chemistry – CO2. Numerous possible hybrid combinations of CO2 are possible including centrifugal CO2 immersion, supercritical CO2 extraction, CO2 composite spray, and atmospheric CO2 plasma cleaning and treatment. Besides addressing a broad spectrum of surface treatment requirements, CO2 cleaning technology can adapt to existing or new manufacturing tools or processes to improve production flow, increase equipment utilization, and decrease floor space. Measurable benefits derived from utilizing this technology include more productive processes with reduced labor and material inputs, improved worker safety and environmental quality, and cleaner parts – faster and with a lower cost-per-clean.

Improved performance of top-emitting oxide-confined polyimide-planarized 980 nm VCSELs with copper-plated heat sinks

Top-emitting, oxide-confined, copper-plated 980 nm vertical-cavity surface-emitting lasers (VCSELs) with improved performance were fabricated and characterized. Annular copper-plated heat sinks reduced the device's thermal resistance and increased the output optical power and the bias current density at which the output optical power saturates. Increasing the plated heat sink radii from 0 to 8 µm greater than the mesa diameter for VCSELs with 26 µm mesa diameter and 8 µm active area diameter reduced the measured thermal resistance by 65% and increased the bias current density at which the output optical power saturates by 62%, which increased the maximum output optical power achieved by 162%. VCSELs with active area diameter and heat sink overlap of 8 µm demonstrated ∼64% decrease in active region temperature at the maximum output optical power compared with devices with no heat sink overlap. A 29% improvement in the devices' modulation bandwidth was calculated due to reduced temperature and increased power. Devices with identical mesa diameters of 26 µm and different heat sink overlaps exhibited a threshold current density and a total series resistance of (1.25 ± 4%) kA cm−2 and ∼95 Ω, respectively. Simple VCSEL L–I and thermal models were used to simulate the VCSEL's L–I performance at elevated ambient temperatures. Good agreement between measured and simulated characteristics was obtained. Detailed protocols for critical fabrication steps are presented.

Bulk FinFET fabrication with new approaches for oxide topography control using dry removal techniques

This work presents a process to fabricate Bulk FinFETs with advancements in critical fabrication steps such as the shallow trench oxide recess and the adjustment of the fin height. These steps are accomplished with the adoption of Siconi™ Selective Material Removal (SMR™) in the fabrication flow. FinFETs obtained with this new integration scheme were tested in a co-fabrication process flow proposed to integrate planar CMOS and Bulk FinFETs on the same wafer. Morphological and electrical results indicate perfectly filled trenches, a better fin height control and a Bulk FinFET static performance similar to planar CMOS. The 20nm wide fins are fabricated using 193nm illumination lithography followed by a series of trimming steps during the trench etching, the filling and a fin re-oxidation during the steam densification of the trench filling oxide. Trench depth is 300nm and the electrically active fin height is 40nm.