Linewidth Control Research Articles

Linewidth Control and the Improved Adhesion of Inkjet-Printed Ag on Polyimide Substrate, Textured Using Near-Atmospheric Pressure Plasmas

In this paper, the effect of polyimide surface modification – using near-atmospheric pressure plasmas – on the line width and adhesion of inkjet-printed Ag was investigated by texturing and modifying the chemical composition of the polyimide surface. The polyimide surface was textured with He/O2, to increase the surface area of the polyimide substrate and it increased the water contact angle from 57 to 137°, when the textured polyimide surface was treated with a SF6 plasma after the texturing process. The textured polyimide surface also exhibited the increased adhesion strength of Ag film (by about two times), due to the increase in the contact area, as expected, according to the Wenzel model. The linewidth of the inkjet-printed Ag line decreased by about ten times from 330 µm (for the flat polyimide surface) to 23 µm (for the textured polyimide surface) in addition to having smoother line edges.

Roughening of Polyimide Surface for Inkjet Printing by Plasma Etching Using the Polyimide Masked with Polystyrene Nanosphere Array.

Two key conditions are required for the application of fine-line inkjet printing onto a flexible substrate such as polyimide (PI): linewidth control during the inkjetting process, and a strong adhesion of the polyimide surface to the ink after the ink solidifies. In this study, the properties of a polyimide surface that was roughened through etching in a He/SF6 plasma, using a polystyrene nanosphere array as the etch mask, were investigated. The near-atmospheric-pressure plasma system of the He/SF6 plasma that was used exhibits two notable properties in this context: similar to an atmospheric-pressure plasma system, it can easily handle inline substrate processing; and, similar to a vacuum system, it can control the process gas environment. Through the use of plasma etching, the polyimide surface masked the 120-nm-diameter polystyrene nanospheres, thereby forming a roughened nanoscale polyimide surface. This surface exhibited not only a greater hydrophobicity--with a contact angle of about 150° for water and about 30° for silver ink, indicating better silver linewidth control during the silver inkjetting process--but also a stronger adhesion to the silver ink sprayed onto it when compared with the flat polyimide surface.

The effect of hydrophilic photoacid generator on acid diffusion in chemical amplification resists.

A photoacid generator (PAG) is a component of chemical amplification photoresists (CAR). The most widely used PAG in CAR system is triphenyl onium salt which is well known to one of the best leaving groups from various radiation. Acid diffusion influences resist characteristics in area such as resolution and linewidth control. The structure of the hydrophilic PAG was designed to restrict acid diffusion within the photoresist. Acid amplification was suppressed by the hydroxyl group-acid interaction. Novel PAGs with functional groups were synthesized and characterized. Poly(GMA-co-MMA) was synthesized with a combination of crosslinkable glycidyl methacrylate (GMA) and highly refractive methyl methacrylate (MMA). The synthesized polymers were confirmed by NMR and FT-IR, and their thermal properties were studied using TGA and DSC. The resists were evaluated as a positive type resist for ArF lithography. PAGs exhibited good acid generation efficiency with controlled acid diffusion. We found that the energy latitude property of the photoresist was improved with hydroxyl-PAG.

Tunneling control of cavity linewidth narrowing via quantum interference in triangular quantum dot molecules

A scheme for tunneling control of cavity linewidth narrowing by quantum interference in triangular-type triple quantum dots (TQDs) is proposed. In such system, quantum interference induced by tunneling between the TQDs can result in the appearance of two transparency windows and a steep dispersion. Furthermore, when the sample is embedded in a ring cavity, an ultranarrow transmission peak is obtained within the narrowed transparency windows. And by varying the tunneling, the linewidth and the position of the ultranarrow transmission peak can be engineered. Because no coupling laser is required, the scheme proposed here is more convenient for future experiments and applications in optics, and may be useful in designing novel optoelectronic devices.

Design and Experimental Study of 4H-SiC Trenched Junction Barrier Schottky Diodes

This paper presents the design, fabrication, and experimental analysis of 1200 V 4H-SiC trenched junction barrier Schottky (TJBS) diodes. Design considerations and device performances of the TJBS devices are compared with those of the conventional planar JBS diodes via numerical simulation, analytical modeling, and experiments. It was found that, for conventional planar JBS diodes, due to its limited P <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">+</sup> implantation depth, there is a tight tradeoff between forward ON-resistance and blocking voltage. This does not only put stringent requirement on obtaining a narrow photolithography line width ( <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="TeX">\(\sim 1.5\) </tex-math></inline-formula> <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="TeX">\(\mu \) </tex-math></inline-formula> m), but also makes the device design window narrow. The TJBS diodes can substantially alleviate such tradeoff and obtain a larger design window that enables good reverse blocking and forward conduction capabilities at the same time. As a result, this structure demands less restriction on line width control (2.2–3.2 <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="TeX">\(\mu \) </tex-math></inline-formula> m) of the fabrication process and hence can improve the device yield.

A novel approach to hedge and compensate the critical dimension variation of the developed-and-etched circuit patterns for yield enhancement in semiconductor manufacturing

Linewidth control is critical for yield enhancement in semiconductor manufacturing. As wafer fabrication reaching nano-technology nodes, existing approaches on advanced equipment control and advanced process control (AEC/APC) for variation control of individual processes are increasingly difficult to achieve desired process control due to shrinking process windows. This study aims to propose a novel approach to determine tool affinity to hedge the variation between the photolithography for pattern development and the etching process to effectively reduce the etching bias caused by tool misalignment. In particular, the proposed approach integrates a feed-forward run-to-run (R2R) controller and the proposed mini-max regret tool dispatching rules in light of the tool characteristics of the photolithography and etching processes. To validate the proposed approach, an empirical study was conducted in a leading semiconductor company in Taiwan and the results showed practical viability of the approach.

Advanced warpage characterization for FOWLP

Current standards for silicon wafers shape characterization use simple metrics. Warpage and bow are computed as the mean surface wafer height range or the mean surface wafer center height, respectively [1]. These metrics are valid for silicon wafers because of their homogenous and linear thermomechanical properties [2]. In fan-out wafer level package (FO-WLP), embedded Wafer Level Ball Grid Array in specific (eWLB), the use of epoxy mold compound that works both as the physical carrier of the dies and as the base of second level connections has a major impact on the overall macroscopic behavior of the wafer, inducing shapes that do not follow a simple bended or bowed wafer, impacting wafer processability [3]. Warped wafers can affect device performance, reliability, and linewidth control in various processing steps [3]. Early detection will minimize cost and processing time. In our research, we present a solution for wafer characterization in FO-WLP by increasing the information vector that one obtains from standard automated non-contact scanning equipment. For this, we defined wafer shape and wafer ratio as the two new metrics besides warpage, creating a three dimensional vector that can be used to compare and evaluate wafers in high volume production or even single wafer analysis. This is a major improvement over previously used approaches, in which only the average warpage is considered. These metrics were determined by the developed numeric algorithm and their validity was demonstrated through the use of different production conditions, wafer constructions and production monitoring. The proposed approach requires no extra processing steps and time, as compared to conventional off-line methods. Experimental results demonstrate its feasibility and repeatability. This methodology was successfully used in the field and proved to be of high value when evaluating wafer geometrical requirements for both product development and process monitoring.

基于F-P标准具的固体激光可调线宽控制技术

基于F-P标准具的固体激光可调线宽控制技术

Bioprinting of a mechanically enhanced three-dimensional dual cell-laden construct for osteochondral tissue engineering using a multi-head tissue/organ building system

The aim of this study was to build a mechanically enhanced three-dimensional (3D) bioprinted construct containing two different cell types for osteochondral tissue regeneration. Recently, the production of 3D cell-laden structures using various scaffold-free cell printing technologies has opened up new possibilities. However, ideal 3D complex tissues or organs have not yet been printed because gel-state hydrogels have been used as the principal material and are unable to maintain the desired 3D structure due to their poor mechanical strength. In this study, thermoplastic biomaterial polycaprolactone (PCL), which shows relatively high mechanical properties as compared with hydrogel, was used as a framework for enhancing the mechanical stability of the bioprinted construct. Two different alginate solutions were then infused into the previously prepared framework consisting of PCL to create the 3D construct for osteochondral printing. For this work, a multi-head tissue/organ building system (MtoBS), which was particularly designed to dispense thermoplastic biomaterial and hydrogel having completely different rheology properties, was newly developed and used to bioprint osteochondral tissue. It was confirmed that the line width, position and volume control of PCL and alginate solutions were adjustable in the MtoBS. Most importantly, dual cell-laden 3D constructs consisting of osteoblasts and chondrocytes were successfully fabricated. Further, the separately dispensed osteoblasts and chondrocytes not only retained their initial position and viability, but also proliferated up to 7 days after being dispensed.

Frequency-selective control of ferromagnetic resonance linewidth in magnetic multilayers

We report on a frequency-specific linewidth broadening of the ferromagnetic resonance (FMR) mode of a NiFe free layer within a magnetic multilayer stack. The FMR studies reveal a significant broadening of the FMR linewidth of the free layer at frequencies where this resonance is degenerate with FMR modes stemming from other layers within the multilayer stack. By pinning part of the magnetic multilayer to an antiferromagnet, we tailor a ferromagnetic linewidth behavior that is anisotropic for a specific frequency.

Fabrication of highly ordered multi-segment line pattern over a large-area

We report on the fabrication of well-aligned multi-segment line patterns over large areas featuring dimensional and compositional exquisite tunability using a combination of photolithography and soft-lithography techniques. We show that thus this new top-down approach has great advantages and that it is beneficial by increasing the control of the multi-segment line width and pattern feature dimensions ranging from microns to a few hundred nanometres. Various combinations of multi-segment materials with full control over the periodic alignment, which include Au–Ni, Au–Cu and Au–Ag, were prepared by simply changing the metals evaporated before the lift-off process. Au–Ni multi-segment metal line patterns showed a linear current–voltage response, identical with that of a line pattern from a single material. Thus, one can take advantage of the simple electrical properties of the 1-dimensional nanostructure. Our approach provides great potential in practical fabrication of well-integrated multi-metal component devices for electrical and optical detection.

Nanostructuring of Ultra-Thin HfO&lt;SUB&gt;2&lt;/SUB&gt; Layers for High-&lt;I&gt;k&lt;/I&gt;/III–V Device Application

We report on the nanopatterning by electron beam lithography (EBL) and reactive ion etching (RIE) in a SF6/Ar+ plasma of ultra-thin HfO2 films deposited on GaAs (001) substrates for gate oxide application in next generation III-V metal-oxide-semiconductor field effect transistors (MOSFETs). Characterization of the HfO2/GaAs nanostructured samples by atomic force microscopy (AFM), high-resolution scanning electron microscopy (HRSEM), energy-dispersive X-ray spectroscopy microanalysis (EDX) and transmission electron microscopy (TEM) has shown the formation of well defined HfO2 patterns with nanometre-scale linewidth control and anisotropic profiles. In addition, atomically smooth, stoichiometric and residue-free bottom GaAs etched lines with a lateral dimension of approximately 50 nm have been demonstrated.

High aspect ratio nanostructuring by high energy electrons and electroplating

Due to the ability of 100keV electrons to penetrate deep into resist with little scattering, we were able to directly write various dense and high aspect ratio nanostructures in up to 1.65μm thick layers of poly(methyl methacrylate) (PMMA) resist. The PMMA molds produced by electron beam lithography were developed using a high contrast developer. The molds were used to transfer the pattern into metallic nanostructures by filling the developed trenches with Au by electroplating. By exposing lines narrower than the target width, we observed improved process latitude and line width control. The obtained aspect ratios of the dense structures are nearly 17 in 1.1μm PMMA layers and >13 for structures electroplated into these PMMA molds. The fabrication method was successfully applied to produce Au diffractive X-ray Fresnel zone plates of exceptionally good quality with 70nm outermost zones using 1.1μm thick PMMA mold. In addition, we also produced regular arrays of high aspect ratio and dense Au nanorods and high aspect ratio split ring resonators with line widths down to 65nm and with heights up to 1.5μm.

Direct e-beam writing of dense and high aspect ratio nanostructures in thick layers ofPMMA for electroplating

Due to the ability of 100 keV electrons to penetrate deep into resist with little scattering, we wereable to directly write various dense and high aspect ratio nanostructures in 540 nm and 1.1 µm thick layers of poly(methyl methacrylate) (PMMA) resist. The PMMA molds produced byelectron beam lithography were developed using a high contrast developer. Themolds were used to transfer the pattern into metallic nanostructures by fillingthe developed trenches with Au by electroplating. By exposing lines narrowerthan the target width, we observed improved process latitude and line widthcontrol. The obtained aspect ratios of the dense structures are nearly 20 in 1.1 µm PMMAlayers and > 16 for structures electroplated into this PMMA mold. The fabrication method wassuccessfully applied to produce Au diffractive x-ray Fresnel zone plates ofexceptionally good quality with 50 and 70 nm outermost zones using 540 nm and 1.1 µm thick PMMA molds. In addition, we also produced regular arrays of high aspect ratio anddense Au nanorods with periods down to 100 nm and high aspect ratio split-ring resonators.

Collimated Aerosol Beam Deposition: Sub-5-$\mu$m Resolution of Printed Actives and Passives

Materials deposition based upon directed aerosol flow has the potential of finding application in the field of flexible electronics where a low-temperature route to printed transistors with high mobilities remains elusive. NDSU has been actively engaged in addressing this opportunity from the following two perspectives: 1) developing an appreciation of the basic physics that dominate aerosol beam deposition toward engineering a robust method that allows the realization of deposited features with sub-5 μm resolution; and, 2) developing an understanding of the mechanistic transformations of silane-based precursor inks toward the formation of electronic materials at atmospheric-pressure. In this paper, we will briefly discuss the genesis of a new materials deposition method termed collimated aerosol beam direct-write (CAB-DW) where precision linewidth control has been realized using a combined theoretical/experimental approach. Next, we will discuss progress using Si <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">6</sub> H <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">12</sub> (cyclohexasilane-a liquid silane) as a precursor for solution-processed diodes and transistors. Finally, we demonstrate the ability to CAB-DW Si <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">6</sub> H <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">12</sub> -based precursor inks for printing Si-based semiconductors.

Remediation of Line Edge Roughness in Chemical Nanopatterns by the Directed Assembly of Overlying Block Copolymer Films

Block copolymer structures have been directed to assemble on chemically patterned surfaces with the domain interfaces oriented perpendicular to the substrate. Such methods have been pursued for lithographic applications to achieve long-range order in the assembled structures and, potentially more important, provide nanometer-level control over the interfaces between structures. The chemically striped surfaces used for the directed assembly of lamellae are patterned by top-down lithographic techniques and thus often have rough edges between the regions of different chemistry. Here we quantitatively characterize, using experiments and molecular-level simulations, the propagation of line edge roughness from the chemically patterned surfaces into the interfaces between domains of block copolymer lamellae as a function of the wavelength, amplitude, and geometry of the roughness. Two geometries of surface pattern roughness are considered with oscillatory neighboring interfaces that are either in-phase or out-of-phase. Block copolymer lamellae of poly(styrene-block-methyl methacrylate) effectively self-corrected surface patterns with small wavelength in-phase and out-of-phase roughness such that little or no memory of the substrate pattern roughness could be observed at the top surface of a 40 nm thin film. Larger wavelength in-phase roughness, and to a lesser extent larger wavelength out-of-phase roughness, propagated farther from the surface pattern such that the domain interfaces between block copolymer lamellae maintained the roughness throughout the film. These self-healing capabilities of block copolymers will be essential for lithographic applications with tight tolerances on line edge roughness and line width control, e.g., in patterning transistor gates.

Degradation-resistant lasing at 980 nm in a Yb/Ce/Al-doped silica fiber

In this work we measure how photodarkening affects the optical efficiency for three different Yb/Al-doped silica fibers operating at 980 nm, one of which is codoped with cerium. A volume Bragg grating is used for linewidth control and added rejection of amplified spontaneous emission. Several hours of degradation-resistant operation is obtained with the Ce-codoped fiber, while for the Yb/Al doped fibers a large drop in efficiency is observed within the first hour of operation. Our results show that Yb/Ce/Al-doped fibers could be excellent candidates for high-power 980 nm fiber laser sources.

Subnanometer Linewidth Uniformity in Silicon Nanophotonic Waveguide Devices Using CMOS Fabrication Technology

We report subnanometer linewidth uniformity in silicon nanophotonics devices fabricated using high-volume CMOS fabrication tools. We use wavelength-selective devices such as ring resonators, Mach-Zehnder interferometers, and arrayed waveguide gratings to assess the device nonuniformity within and between chips. The devices were fabricated using 193 or 248 nm optical lithography and dry etching in silicon-on-insulator wafer technology. Using 193 nm optical lithography, we have achieved a linewidth uniformity of 2 nm (after lithography) and 2.6 nm (after dry etch) over 200 mm wafer. Furthermore, with the developed fabrication process, using wavelength-selective devices, we have demonstrated a linewidth control better than 0.6 nm within chip and better than 2 nm chip-to-chip. The necessity for high-resolution optical lithography is demonstrated by comparing device nonuniformity between the 248 and 193 nm optical lithography processes.

Injection-seeded intracavity terahertz optical parametric oscillator

We report a terahertz (THz) source continuously tunable over ~20 GHz with a linewidth &lt;100 MHz (close to the transform limit of 1-10 ns pulses) and settable anywhere in the range of 1-3 THz. The source consists of an injection-seeded intracavity THz optical parametric oscillator, which exhibits the benefits of lower threshold and enhanced efficiency and power over a similar extracavity device. Linewidth control was achieved with &lt;1 mW of seed laser power and THz pulse energies of &gt;5 nJ observed with up to 68% downconversion of the pump wave. Spectroscopy of the 1.4969 THz carbon monoxide absorption line was performed to verify linewidth and demonstrate tuning capability.

Design Space for Low Sensitivity to Size Variations in [110] PMOS Nanowire Devices: The Implications of Anisotropy in the Quantization Mass

A 20-band sp(3)d(5)s* spin-orbit-coupled, semiempirical, atomistic tight-binding model is used with a semiclassical, ballistic, field effect transistor (FET) model, to examine the ON-current variations to size variations of [110]-oriented PMOS nanowire devices. Infinitely long, uniform, rectangular nanowires of side dimensions from 3 to 12 nm are examined and significantly different behavior in width versus height variations are identified and explained. Design regions are identified, which show minor ON-current variations to significant width variations that might occur due to lack of line width control. Regions which show large ON-current variations to small height variations are also identified. The considerations of the full band model here show that ON-current doubling can be observed in the ON-state at the onset of volume inversion to surface inversion transport caused by structural side size variations. Strain engineering can smooth out or tune such sensitivities to size variations. The cause of variations described is the structural quantization behavior of the nanowires, which provide an additional variation mechanism to any other ON-current variations such as surface roughness, phonon scattering, etc.