Analysis of terabit/second-class inter-chip parallel optoelectronic transceiver

Thesis (M. Eng.)--Massachusetts Institute of Technology, Dept. of Materials Science and Engineering, 2010.Cataloged from student submitted PDF version of thesis.Includes bibliographical references (p. 89-92).Electrical copper-based interconnect has been suffering from fundamental physical loss mechanism and its current infrastructure will not be able to meet the increasing demand for data rates due to reaching the limit of the transmission bandwidth-distance product. Optical interconnect has been known as the candidate for taking over the obsolete electrical counterpart owing to the capability of transmitting data at high rates with low loss and the feasibility for parallel integration. Optoelectronic transceiver is one of the essential elements in optical interconnect system. This thesis scrutinizes a complete set of constituent technologies developed for a novel inter-chip parallel optoelectronic (OE) transceiver (known as Terabus transceiver) which is able to communicate data at the speed in the range of Terabit/second. A novel packaging hierarchy and a creative design for an optical coupling mechanism devised to bring high-level integration and high-speed performance to a final package have been analyzed: Two 4x12 arrays (each < 9 mm2) of CMOS transmitter and receiver ICs have been flip-chip bonded to a silicon carrier interposer of 1.2-cm2 size. Other two 4x12 arrays of OE devices (VCSELs and photodiodes) with comparable size are then flip-chip bonded to the corresponding CMOS arrays attached to the silicon carrier, forming the Optochip assembly. The Optochip is in interface with an Optocard by the flip-chip bonding process between the silicon carrier and an organic card patterned with 48 integrated waveguides at density of 16-channel/mm and total length of 30 cm. The 985-nm operating wavelength of the lasers allows a simple optical design with emission and illumination through arrays of relay lenses directly etched into the backside of the OE Ill-V substrate. A novel design of 45*-tilted and Au-coated mirrors fabricated in 125-ptmpitch acrylate waveguides is to perpendicularly couple the light in and out of the core of these Optocard waveguides. Per-channel performance of up to 20 Gb/s for transmitter and of up to 14 Gb/s for receiver have been realized. Lastly, the thesis has analyzed the market opportunity of the transceiver by reviewing the market situation, identifying contemporary competing technologies, assessing the market prospect and predicting the cost.by Nguyen Hoang Nguyen.M.Eng

A novel scanned mask imaging system for high resolution solid state laser ablation

A technology gap has emerged between the sub-micron semiconductor manufacturing technologies used in the manufacture of integrated circuits and the semi-additive processes used to manufacture advanced chip packages which are currently limited to feature sizes greater than 10 µm. Embedding conductors in laser ablated circuit features is one of the proposed solutions to address this technology gap in the advanced chip packaging industry. Excimer laser systems are currently the only available production tools capable of the high throughput laser ablation of circuit features down to 2 µm. In this thesis I have developed an ablative, solid state laser, mask imaging system for the high volume 3D structuring of organic dielectrics. This system enables the ablation of circuit features down to 2 µm which are of comparable quality to excimer laser ablation. The system architecture has a throughput exceeding that of an excimer laser production system. I have developed an illumination system, which I have tested at both a feasibility stage and at a prototype stage, with custom designed optical components. The illumination system consists of a galvanometer scan head which is used to raster scan a solid state laser beam across a binary mask, the image of which is then projected onto the substrate. The system I present enables the use of multimode, UV, solid state lasers in well-developed and high resolution mask imaging optical systems. Through the use of a less expensive laser technology, the system I have developed has a cost of ownership estimated to be less than 50% of that of an excimer production system, thus reducing the cost of high resolution, high throughput laser ablation

Metodología para la Simulación y Fabricación de Circuitos Impresos en Radiofrecuencia

Proyecto de Graduación (Licenciatura en Ingeniería Electrónica) Instituto Tecnológico de Costa Rica, Escuela de Ingeniería Electrónica, 2018This thesis proposes a methodology for design, simulation and fabrication of printed circuits in radiofrequency for the new laboratory of Electronics Department at TEC. The approach to analyze electronic platforms designed in CAD environments and CAE environments is detailed. Prototype multilayer printed circuits are discussed and for this reason, an analysis of the plate profile is performed to define the variation range of the stackup for a nominal impedance of 50Ω. The proposed methodology is validated through the case of impedance control for striplines, microstriplines and lines with vias operating at frequency up to 5 GHz. Optimizations are made of all the elements present in the printed circuit (lines, pads, antipads, insulations, tracks, through hole and surface mount connectors), to ensure that the entire process is controlled. The manufactured results are correlated against the simulated ones and are analyzed in terms of electrical performance

Photo-definable dielectrics with improved lithographic, mechanical, and electrical properties

Permanent dielectric materials are integral to the fabrication of microelectronic devices and packaging. Dielectrics are used throughout devices to electrically and mechanically isolate conductive components. As such, they are required to have low electrical permittivity and robust mechanical properties. For packaging applications, dielectrics can be directly photo-definable. Dielectrics need to have excellent lithographic properties. These properties are pivotal for enabling high yield and low cost fabrication of reliable, energy efficient devices. The aim of this work was to develop new positive tone dielectrics which have improved or application-specific lithographic, mechanical, and electrical properties. To this end, several new dielectric polymers and chemistries were evaluated and characterized. Initially, it was desired to develop a positive tone, polynorbornene (PNB) dielectric that utilizes diazonaphthoquinone (DNQ) photochemistry. Cross-linking was achieved with epoxy cross-linkers during a thermal cure. Several DNQ-containing compounds were evaluated, but only one had good miscibility with PNB. The dissolution characteristics of PNB were measured with respect to polymer composition, DNQ loading, and cross-linker loading. PNB films exhibited unique dissolution properties, and these measurements allowed for an optimum formulation to be developed. A formulation with 20 pphr DNQ and 10 pphr epoxy cross-linker had sufficient inhibition in unexposed regions and fast dissolution in exposed regions. The resulting dielectric was the first positive tone, DNQ-based PNB dielectric. After achieving photo-definability, the cross-linking of the cured dielectric was evaluated by characterizing the mechanical properties. It was discovered that DNQ acted as a cross-linker in these films, and this insight was key to achieving good curing of the dielectric. Several experiments were performed to support this conclusions, and the reaction kinetics of this cross-linking reaction were evaluated. This effort produced a functional, positive tone dielectric with a sensitivity of 408 mJ cm-2 and contrast of 2.3. The modulus was 2.0 to 2.6 GPa and the dielectric constant of 3.7 to 3.9, depending on the curing conditions. The DNQ cross-linking results led to the investigation of other cross-linking chemistries for positive tone dielectrics. A chemically amplified (CA) photochemistry was utilized along with a Fischer esterification cross-linking reaction. Patterning and cross-linking were demonstrated with a methacrylate polymer. Successful positive tone lithography was demonstrated at a high sensitivity of 32.4 mJ cm-2 and contrast of 5.2. Cross-linking was achieved at 120°C as shown by residual stress and solubility measurements. The CA photochemistry and Fischer esterification cross-linking were also demonstrated using a PNB dielectric, which was shown to have improved lithographic properties: a sensitivity of 8.09 mJ cm-2 and contrast of ≥ 14.2. Work was performed to evaluate the effect of the polymer composition on the mechanical and electrical properties. A polymer with 60 mol% hexafluoroisopropanol norbornene and 40 mol% tert-butyl ester norbornene exhibited a dielectric constant of 2.78, which is lower than existing positive tone dielectrics. It also outperformed existing dielectrics in several other categories, including dark erosion, volume change, cure temperature, and in-plane coefficient of thermal expansion. However, a limitation of this dielectric was cracking in thick films. The final study was to improve the mechanical properties of this CA PNB dielectric specifically to enable 5 µm thick films. First, a terpolymer was tested that included a non-functional third monomer. The dielectric constant increased to 3.48 with 24 mol% of the third monomer. Second, low molecular weight additives were used to lower the modulus. Only one of the five tested additives enabled high quality, thick films. This additive did not significantly affect the dielectric constant at low loadings. An optimized formulation was made, and processing parameters were studied. The additive decreased the lithographic properties, lowering the sensitivity to 175 mJ cm-2 and lowering the contrast to 4.36. In all, this work produced three functional dielectrics with positive tone photo-definability and good lithographic properties. Each dielectric can serve a variety of purposes in microelectronics packaging.Ph.D

Directly-patternable benzocyclobutene dielectric materials

Silicon Valley, America’s bastion of innovation is named for the tiny pieces finely patterned silicon transistors that are the “brains” of all modern computational devices. However, without the ability to protect these valuable chips and translate their electrical signals to other hardware, silicon transistors are useless to the world. The demand for these microelectronic packages to perform better, cost less and be made in high yield is perhaps the next great challenge in the microelectronics industry. This dissertation covers several approaches to next generation packaging materials. In chapter two, the design, synthesis and characterization of long wavelength photobase generators for patterning polyimides is discussed. The rest of the dissertation focuses understanding and applying benzocyclobutene (BCB) thermosets to a packaging application. BCB materials have been combined with polyhedralsilsesquioxane (POSS), ring opening metathesis polymerization (ROMP) norbornenes, and addition polymer norbornenes to produce several original resins with interesting and attractive properties. New chemistry has been employed to understand the relationship of the BCB electrocyclic ring opening and Diels Alder crosslink.Chemistr

Design and development of base-catalyzed materials for microelectronics applications

Most lithographic processes in the microelectronics industry rely on the use of processes catalyzed by photochemically generated acids. The generation of organic bases photochemically is much less common, but allows for design of new resolution enhancement techniques and packaging materials. The microelectronics industry has been able to continue its path toward smaller transistors for several decades, but recently 157 nm and EUV lithography processes have faced delays. Alternative strategies such as double patterning are now required to keep the pace of scaling and they greatly increase manufacturing costs. This dissertation discusses a resolution enhancement technique termed pitchdivision designed to extend 193 nm lithography. This process depends on addition of a photobase generator (PBG) to commercial photoresists that enables printing of both positive and negative features, effectively doubling resolution. Using PBGs that require two separate photochemical events to generate base allows for improved image quality over standard PBGs. The use of PBGs in photosensitive polyimide packaging materials is also detailed. In packaging of integrated circuits, there is a need for an insulating material having low dielectric constant that provides support for the wires connecting the silicon chip to the circuit board. Aromatic polyimides meet many of the integration requirements, and can be patterned using PBGs in a base-catalyzed process. However, the UV absorbance of such materials is too high for thick films. The fluorinated polyimide pyromellitic dianhydride-co-2,2’-bis(trifluoromethyl)benzidine (PMDA-TFMB) was therefore auditioned for this use. PMDA-TFMB was printed using 365 nm lithography using near-UV PBGs and achieved resolution as small as 2.5 μm. This material was found to have a dielectric constant around 3.0, and a coefficient of thermal expansion of 6 ppm/K. Further work on the system sought to improve both material properties and lithographic patterning. The use of alternative monomers was explored. New PBGs capable of producing stronger amidine bases were also synthesized and used to cure PMDA-TFMB. Finally, the discovery of new catalysts for low temperature curing of polyimides is described. These materials include organic and inorganic salts that allow for the complete curing of polyimides below 200°C. The material properties of films cured with these catalysts are described.Chemical Engineerin