Plasmonic Waveguide Lithography for Patterning Nanostructures with High Aspect-Ratio and Large-Area Uniformity

The rapid development of the semiconductor industry in the past decades has driven advances in nano-manufacturing technologies towards higher resolution, higher throughput, better large-area uniformity, and lower manufacturing cost. Along with these advancements, as the size of the devices approaches tens of nanometers, challenges in patterning technology due to limitations in physics, equipment and cost have quickly arisen. To solve these problems, unconventional lithography systems have attracted considerable interest as promising candidates to overcome the diffraction limit. One recently evolved technology, plasmonic lithography, can generate subwavelength features utilizing surface plasmon polaritons (SPPs). Evanescent waves generated by the subwavelength features can be transmitted to the photoresist (PR) using plasmonic materials. Another approach of plasmonic lithography involves the use of hyperbolic metamaterial (HMM) structures, which have been studied intensively because of their unique electromagnetic properties. Specifically, epsilon near zero (ENZ) HMMs offer the potential to produce extremely small features due to their high optical anisotropy. Despite the advancements in plasmonic lithography, several key issues impede progress towards more practical application, which includes shallow pattern depth (due to the evanescent nature of SPPs), non-uniformity over a large area (due to the interference of multiple diffraction orders) and high sensitivity of the roughness on the films and defects on the mask. The light intensity in the PR is very weak which results in an extremely long exposure time. To this end, this dissertation is dedicated to plasmonic lithography systems based on SPP waveguides and ENZ HMMs for patterning nanostructures with high aspect-ratio and large-area uniformity. New schemes are exploited in this thesis to address these challenges. Lithography systems based on a specially designed waveguide and an ENZ HMM are demonstrated. By employing the spatial filtering properties of the waveguide and the ENZ HMM, the period, linewidth and height of the patterns can be well controlled according to various design purposes. Periodic structures were achieved in both systems with a half-pitch of approximately 50 ~ 60 nm, which is 1/6 of the exposure wavelength of 405 nm. The thickness of the PR layer is around 100 ~ 250 nm, which gives an aspect-ratio higher than 2:1. The subwavelength patterns are uniform in cm2 areas. In addition to the design principle, various numerical simulations, fabrication conditions and corresponding results are discussed. The design principle can be generalized to other materials, structures and wavelengths. The real-world performance of the lithography system considering non-idealities such as line edge roughness and single point defect is analyzed. Comparisons between the plasmonic systems based on different design rules are also carried out, and the advantages of the spatial frequency selection principle is verified. The plasmonic waveguide lithography systems developed in this dissertation provide a technique to make deep subwavelength features with high aspect-ratio, large-area uniformity, high light intensity distribution, and low line-edge-roughness for practical applications. Compared with the previously reported results, the performance of plasmonic lithography is drastically improved. A plasmonic roller system combining the photo-roller system and plasmonic lithography is also developed. This plasmonic roller system can support a continuous patterning with a high throughput for cost sensitive applications. Several potential applications of the plasmonic materials including near field spin Hall effects and a particle based Lidar design are explored. Other advances towards plasmonic functional devices including silicon (Si) nanowire (NW) arrays, light-thermal converters and plasmonic lasers are also reported.PHDApplied PhysicsUniversity of Michigan, Horace H. Rackham School of Graduate Studieshttps://deepblue.lib.umich.edu/bitstream/2027.42/144126/1/sxichen_1.pd

Organisation of Innovation in High-Tech Industries: Acquisitions as Means for Technology Sourcing.

Innovation activities in the semiconductor industry provide considerable challenges for technology and innovation management. In particular, firms frequently face make-or-buy decisions and such decisions have considerable management implications. The semiconductor industry has a long history of radical innovations which are taking place through distinct industry cycles of high and low demand. The paper investigates these issues for the Electronic Design Automation industry which is a specific sub-segment of the semiconductor industry. Based on database searches and structured interviews, the paper analyses empirically the reasons for make or buy decisions with regard to innovation and the level of acquisition activities of innovative small firms in the Electronic Design Automation industry. This analysis is supported by an analysis of the SEC filings of large firms in the Electronic Design Automation industry.

Impact of Interoperability on CAD-IP Reuse: An Academic Viewpoint

Mind-boggling complexity of EDA tools necessitates reuse of intellectual property in any large-scale commercial or academic operation. However, due to the nature of software, a tool component remains an ill-defined concept, in contrast to a hardware component (core) with its formally specified functions and interfaces. Furthermore, EDA tasks often evolve rapidly to fit new manufacturing contexts or new design approaches created by circuit designers; this leads to moving targets for CAD software developers. Yet, it is uneconomical to write off tool reuse as simply an endemic “software problem”. Our main message is that CAD tools should be planned and designed in terms of reusable components and glue code. This implies that industrial and academic research should focus on (1) formulating practical tool components in terms of common interfaces, (2) implementing such components, and (3) performing detailed evaluations of such components. While this is reminiscent of hardware reuse, most existing EDA tools are designed as stand-alone programs and interface through files. 1

Open-access silicon photonics: current status and emerging initiatives

Silicon photonics is widely acknowledged as a game-changing technology driven by the needs of datacom and telecom. Silicon photonics builds on highly capital-intensive manufacturing infrastructure, and mature open-access silicon photonics platforms are translating the technology from research fabs to industrial manufacturing levels. To meet the current market demands for silicon photonics manufacturing, a variety of open-access platforms is offered by CMOS pilot lines, R&D institutes, and commercial foundries. This paper presents an overview of existing and upcoming commercial and noncommercial open-access silicon photonics technology platforms. We also discuss the diversity in these open-access platforms and their key differentiators

Spectroscopy and Biosensing with Optically Resonant Dielectric Nanostructures

Resonant dielectric nanoparticles (RDNs) made of materials with large positive dielectric permittivity, such as Si, GaP, GaAs, have become a powerful platform for modern light science, enabling various fascinating applications in nanophotonics and quantum optics. In addition to light localization at the nanoscale, dielectric nanostructures provide electric and magnetic resonant responses throughout the visible and infrared spectrum, low dissipative losses and optical heating, low doping effect and absence of quenching, which are interesting for spectroscopy and biosensing applications. In this review, we present state-of-the-art applications of optically resonant high-index dielectric nanostructures as a multifunctional platform for light-matter interactions. Nanoscale control of quantum emitters and applications for enhanced spectroscopy including fluorescence spectroscopy, surface-enhanced Raman scattering (SERS), biosensing, and lab-on-a-chip technology are surveyed. We describe the theoretical background underlying these effects, overview realizations of specific resonant dielectric nanostructures and hybrid excitonic systems, and outlook the challenges in this field, which remain open to future research

Towards Faster Data Transfer by Spoof Plasmonics

With the emergence of complex architectures in modern electronics such as multi-chip modules, the increasing electromagnetic cross-talk in the circuitry causes a serious issue for high-speed, reliable data transfer among the chips. This thesis aims at developing a cross-talk resilient communication technology by utilizing a special form of electromagnetic mode, called spoof surface plasmon polariton for information transfer. The technique is based on the fact that a metal wire with periodic sub-wavelength patterns can support the propagation of confined electromagnetic mode, which can suppress cross-talk noise among the adjacent channels; and thus outperform conventional electrical interconnects in a parallel, high channel density data-bus. My developed model shows that, with 1 THz carrier frequency, the optimal design of cross-talk resilient spoof plasmon data-bus would allow each channel to support as high as 300 Gbps data, the bandwidth density can reach 1 Tbps per millimeter width of data-bus, and the digital pulse modulated carrier can travel more than 5 mm distance on the substrate. I have demonstrated that spoof plasmonic interconnects, comprised of patterned metallic conductors, can simultaneously accommodate electronic TEM mode, which is superior in cross-talk suppression at low-frequencies; and spoof plasmon mode, which is superior at high-frequencies. The research work is divided into two complementary parts: developing a theory for electromagnetic property analysis of spoof plasmon waveguide, and manipulating these properties for high-speed data transfer. Based on the theory developed, I investigated the complex interplay among various figure-of-merits of data transfer in spoof plasmonics, such as bandwidth density, propagation loss, thermal noise, speed of modulation, etc. My developed model predicts that with the availability of 1 THz carrier, the bit-error-rate of spoof plasmon data bus, subject to thermal noise would be $sim10^{-8}$ while the Shannon information capacity of the bus would be $10$ Tbps/mm. The model also predicts that, by proper designing of the modulator, it can be possible to alter the transmission property of the waveguide over one-fifth ($1/5$) of the spoof plasmon band which spans from DC frequency to the frequency of spoof plasmon resonance. To exemplify, if the spoof plasmon resonance is set at $1$ THz, then we can achieve more than $200$ Gbps speed of modulation with a very high extinction ratio, assuming the switching latency of the transistors at our disposal is negligible to the time-resolution of interest. We envision spoof plasmonic interconnects to constitute the next generation communication technology that will be transferring data at hundreds of Gigabit per second (Gbps) speed among different chips on a multi-chip module (MCM) carrier or system-on-chip (SoC) packaging.PHDElectrical EngineeringUniversity of Michigan, Horace H. Rackham School of Graduate Studieshttp://deepblue.lib.umich.edu/bitstream/2027.42/163041/1/srjoy_1.pd

Infrared Energy Conversion in Plasmonic Fields at Two-Dimensional Semiconductors

Conversion of infrared energy within plasmonic fields at two-dimensional, semiconductive transition metal dichalcogenides (TMD) through plasmonic hot electron transport and nonlinear frequency mixing has important implications in next-generation optoelectronics. Drude-Lorentz theory and approximate discrete dipole (DDA) solutions to Maxwell’s equations guided metal nanoantenna design towards strong infrared localized surface plasmon resonance (LSPR). Excitation and damping dynamics of LSPR in heterostructures of noble metal nanoantennas and molybdenum- or tungsten-disulfide (MoS2; WS2) monolayers were examined by parallel synthesis of (i) DDA electrodynamic simulations and (ii) near-field electron energy loss (EELS) and far-field optical transmission UV-vis spectroscopic measurements. Susceptibility to second-order nonlinear frequency conversion processes, X(2), for monolayer MoS2 and WS2 were measured to be 660±130 pm V-1 and 280±18 pm V-1, respectively, by Hyper Rayleigh Scattering. Femtosecond conversion of resonant irradiation to injection of plasmonic hot electrons into the TMD were measured in EELS at a maximum of 11±5% quantum efficiency for an optimized physicochemical Au-WS2 junction. Measured nonlinear second harmonic generation (SHG) from a ca. 1 μm MoS2 monolayer was enhanced 17-84% by local electric field augmentation from a single 150 nm Au nanoshell to a conversion efficiency of up to 0.023% W-1. Capacitive coupling between nanoshells arranged into dimers further augmented SHG activity from MoS2. New theoretical and experimental insights into energy conversion interactions between coupled plasmonic and excitonic materials spanning the linear and nonlinear optical regimes were established towards their implementation as an optoelectronic platform

Interfacial Contact with Noble Metal - Noble Metal and Noble Metal - 2D Semiconductor Nanostructures Enhance Optical Activity

Noble metal nanoparticles and two-dimensional (2D) transition metal dichalcogenide (TMD) crystals offer unique optical and electronic properties that include strong exciton binding, spin-orbital coupling, and localized surface plasmon resonance. Controlling these properties at high spatiotemporal resolution can support emerging optoelectronic coupling and enhanced optical features. Excitation dynamics of these optical properties on physicochemically bonded mono- and few-layer TMD crystals with metal nanocrystals and two overlapping spherical metal nanocrystals were examined by concurrently (i) DDA simulations and (ii) far-field optical transmission UV-vis spectroscopic measurements. Initially, a novel and scalable method to unsettle van der Waals bonds in bulk TMDs to prepare mono- and few-layer crystals was performed. Examination of the solution-based and electrochemical deposition of metal nanocrystals on 2D TMD crystals, comparing their optical, electronic, and optoelectronic characteristics was accomplished via characterization methods. Subsequently, DDA simulations for noble metal - semiconductor nanocrystal and noble metal - noble metal nanocrystal heterostructures analyzed the effects of metal type, geometry, and orientation for the predefined nanoantennae parameters. Results from these computational and experimental optical spectra demonstrate promising percent error difference, in which distinguished quantitative effects of 2D TMDs crystals - metal nanocrystals and metal nanocrystals - metal nanocrystals facilitated optoelectronic activity in the UV-Vis-NIR region. New experimental and theoretical insights into energy conversion interactions between coupled plasmonic and excitonic materials spanning the optical regimes were established towards their applications in optoelectronic and biological engineering platforms

Analog layout design automation: ILP-based analog routers

The shrinking design window and high parasitic sensitivity in the advanced technology have imposed special challenges on the analog and radio frequency (RF) integrated circuit design. In this thesis, we propose a new methodology to address such a deficiency based on integer linear programming (ILP) but without compromising the capability of handling any special constraints for the analog routing problems. Distinct from the conventional methods, our algorithm utilizes adaptive resolutions for various routing regions. For a more congested region, a routing grid with higher resolution is employed, whereas a lower-resolution grid is adopted to a less crowded routing region. Moreover, we strengthen its speciality in handling interconnect width control so as to route the electrical nets based on analog constraints while considering proper interconnect width to address the acute interconnect parasitics, mismatch minimization, and electromigration effects simultaneously. In addition, to tackle the performance degradation due to layout dependent effects (LDEs) and take advantage of optical proximity correction (OPC) for resolution enhancement of subwavelength lithography, in this thesis we have also proposed an innovative LDE-aware analog layout migration scheme, which is equipped with our special routing methodology. The LDE constraints are first identified with aid of a special sensitivity analysis and then satisfied during the layout migration process. Afterwards the electrical nets are routed by an extended OPC-inclusive ILP-based analog router to improve the final layout image fidelity while the routability and analog constraints are respected in the meantime. The experimental results demonstrate the effectiveness and efficiency of our proposed methods in terms of both circuit performance and image quality compared to the previous works

Uniquely Identifiable Tamper-Evident Device Using Coupling between Subwavelength Gratings

Reliability and sensitive information protection are critical aspects of integrated circuits. A novel technique using near-field evanescent wave coupling from two subwavelength gratings (SWGs), with the input laser source delivered through an optical fiber is presented for tamper evidence of electronic components. The first grating of the pair of coupled subwavelength gratings (CSWGs) was milled directly on the output facet of the silica fiber using focused ion beam (FIB) etching. The second grating was patterned using e-beam lithography and etched into a glass substrate using reactive ion etching (RIE). The slightest intrusion attempt would separate the CSWGs and eliminate near-field coupling between the gratings. Tampering, therefore, would become evident. Computer simulations guided the design for optimal operation of the security solution. The physical dimensions of the SWGs, i.e. period and thickness, were optimized, for a 650 nm illuminating wavelength. The optimal dimensions resulted in a 560 nm grating period for the first grating etched in the silica optical fiber and 420 nm for the second grating etched in borosilicate glass. The incident light beam had a half-width at half-maximum (HWHM) of at least 7 µm to allow discernible higher transmission orders, and a HWHM of 28 µm for minimum noise. The minimum number of individual grating lines present on the optical fiber facet was identified as 15 lines. Grating rotation due to the cylindrical geometry of the fiber resulted in a rotation of the far-field pattern, corresponding to the rotation angle of moiré fringes. With the goal of later adding authentication to tamper evidence, the concept of CSWGs signature was also modeled by introducing random and planned variations in the glass grating. The fiber was placed on a stage supported by a nanomanipulator, which permitted three-dimensional displacement while maintaining the fiber tip normal to the surface of the glass substrate. A 650 nm diode laser was fixed to a translation mount that transmitted the light source through the optical fiber, and the output intensity was measured using a silicon photodiode. The evanescent wave coupling output results for the CSWGs were measured and compared to the simulation results