Ultra thin ultrafine-pitch chip-package interconnections for embedded chip last approach

Ever growing demands for portability and functionality have always governed the electronic technology innovations. IC downscaling with Moore s law and system miniaturization with System-On-Package (SOP) paradigm has resulted and will continue to result in ultraminiaturized systems with unprecedented functionality at reduced cost. The trend towards 3D silicon system integration is expected to downscale IC I/O pad pitches from 40µm to 1- 5 µm in future. Device- to- system board interconnections are typically accomplished today with either wire bonding or solders. Both of these are incremental and run into either electrical or mechanical barriers as they are extended to higher density of interconnections. Alternate interconnection approaches such as compliant interconnects typically require lengthy connections and are therefore limited in terms of electrical properties, although expected to meet the mechanical requirements. As supply currents will increase upto 220 A by 2012, the current density will exceed the maximum allowable current density of solders. The intrinsic delay and electromigration in solders are other daunting issues that become critical at nanometer size technology nodes. In addition, formation of intermetallics is also a bottleneck that poses significant mechanical issues. Recently, many research groups have investigated various techniques for copper-copper direct bonding. Typically, bonding is carried out at 400oC for 30 min followed by annealing for 30 min. High thermal budget in such process makes it less attractive for integrated systems because of the associated process incompatibilities. In the present study, copper-copper bonding at ultra fine-pitch using advanced nano-conductive and non-conductive adhesives is evaluated. The proposed copper-copper based interconnects using advanced conductive and non-conductive adhesives will be a new fundamental and comprehensive paradigm to solve all the four barriers: 1) I/O pitch 2) Electrical performance 3) Reliability and 4) Cost. This thesis investigates the mechanical integrity and reliability of copper-copper bonding using advanced adhesives through test vehicle fabrication and reliability testing. Test vehicles were fabricated using low cost electro-deposition techniques and assembled onto glass carrier. Experimental results show that proposed copper-copper bonding using advanced adhesives could potentially meet all the system performance requirements for the emerging micro/nano-systems.M.S.Committee Chair: Prof. Rao R Tummala; Committee Member: Dr. Jack Moon; Committee Member: Dr. P M Ra

Advances in panel glass packaging of mems and sensors for low stress and near hermetic reliability

MEMS based sensing is gaining widespread adoption in consumer electronics as well as the next generation Internet of Things (IoT) market. Such applications serve as primary drivers towards miniaturization for increased component density, multi-chip integration, lower cost and better reliability. Traditional approaches like System-on-Chip (SoC) and System on Board (SoB) are not ideal to address these challenges and there is a need to find solutions at package level, through heterogeneous package integration (HPI). However, existing MEMS packaging techniques like laminate/ceramic substrate packaging and silicon wafer level packaging face challenges like standardization, heterogeneous package integration and form factor miniaturization. Besides, application specific packages take up the largest fraction of the total manufacturing cost. Therefore, advanced packaging of MEMS sensors for HPI plays a critical role in the short and long run towards the SOP vision. This dissertation demonstrates a low stress, reliable, near-hermetic ultra-thin glass cavity MEMS packages as a solution that combines the advantages of LTCC/laminate substrates and silicon wafer level packaging while also addressing their limitations. These glass based cavity packages can be scaled down to 2x smaller form factors (<500μm) and are fabricated out of large panel fabrication processes thereby addressing the cost and form factor requirements of MEMS packaging. Flexible cavity design, advances in through-glass via technologies and dimensional stability of thin glass also enable die stacking and 3D assembly for sensor-processor integration towards sensor fusion. The following building block technologies were explored: (a) reliable cavity formation in thin glass panels (b) low stress glass-glass bonding, and (c) high throughput, fully filled through-package-via metallization in glass. Three main technical challenges were overcome to realize the objectives: (a) glass cracking, side wall taper, side wall roughness and defects, (b) interfacial voids at glass-polymer-glass interface and (c) electrical opens and high frequency performance of copper paste filled through-package-vias in glass.M.S

Methodology For Performing Whole Body Pmhs Underbody Blast Impact Testing, And The Corresponding Response Of The Hybrid Iii Dummy And The Finite Element Dummy Model Under Similar Loading Condition

In recent wars, the use of improvised explosive devices and landmines has dramatically increased as a tactical measure to counter armored vehicles. These weapons not only deform and damage the vehicle structure but also produce serious vertical deceleration injuries to mounted occupants. The reported injury patterns largely differ from those in an automotive crash and are often more severe than those in other vertical loading scenarios such as pilot seat ejection, helicopter crash, parachute landing and fall from height. High kinetic energy predominately along the principal vertical (Z-axis) over a short duration makes the underbody blast (UBB) loading conditions unique compared to other vertical and blunt impacts. With the lack of biomechanical response corridors (BRCs), the non-biofidelic nature of the automotive dummies to Z-axis loading and the lack of a finite element dummy model designed for vertical loading make it difficult to evaluate occupant response and develop mitigation strategies for UBB impact conditions. An introduction to the development of the BRCs this study provides a detailed methodology to perform whole body cadaver testing under a laboratory setup. Two whole body PMHS UBB impact tests were conducted using a sled system. An overview of pre-impact parameters such as bone mineral density, instrumentation technique, and vertical impulse generation is presented. Post-test CT scans, response data, and possible injury mechanisms were investigated. In addition, to PMHS testing, the responses of the Hybrid III dummy to short-duration large magnitude vertical acceleration in a laboratory setup were analyzed. Two unique test conditions were investigated using a horizontal sled system to simulate the UBB loading conditions. The biomechanical response in terms of the pelvis acceleration, chest acceleration, lumbar spine force, head accelerations and neck forces were measured during the tests. Subsequently, a series of finite element analyses (FEA) were performed to simulate the physical tests. The material parameters of various components as well as the mesh size were updated based on the high strain rate loading conditions obtained from Zhu et.al (2015) study. The correlation between the Hybrid III test and numerical model was evaluated using the CORA version 3.6.1. The Cora score for WSU FE model was determined to be 0.878 and 0.790 for loading conditions 1 and 2, respectively, in which 1.0 indicated a perfect correlation between the experiment and simulation response. The original LSTC model simulated under the current loading condition became numerically unstable after 12 ms. With repetitive vertical impacts, the Hybrid III dummy pelvis showed a significant increase in the peak acceleration accompanied by rupture of the pelvis foam and flesh. The revised WSU Hybrid III model indicated high stress concentrations at the same location where the pelvis foam and flesh in the actual ATD showed rupture. The stress contour under the ischial tuberosities in the finite element model provides a possible explanation for the material failure in the actual Hybrid III tests

Climate and Constructions : International Conference 24 and 25 October 2011, Karlsruhe, Germany / Competence Area "Earth and Environment" (KIT Scientific Reports ; 7618)

The two-day international conference "Climate and Constructions" covered the topics "Building Science", "Construction Chemistry", "Urban Climate" and "Materials Technology and Construction Techniques". Beside invited lectures and a workshop part about the interactions between climate and the construction sector, there was an open call to submit abstracts. The abstracts were assessed by an international advisory board

Wide Bandgap Based Devices: Design, Fabrication and Applications, Volume II

Wide bandgap (WBG) semiconductors are becoming a key enabling technology for several strategic fields, including power electronics, illumination, and sensors. This reprint collects the 23 papers covering the full spectrum of the above applications and providing contributions from the on-going research at different levels, from materials to devices and from circuits to systems

3D Hybrid Integration for Silicon Photonics

Silicon photonics (SiPh) has emerged as a photonic integrated circuit (PIC) platform, especially for high volume applications. Integrated laser sources, however, remain a challenge. SiPh foundries have existed for more than 10 years but still don’t offer a qualified process with integrated lasers. Direct heteroepitaxy of group III-V materials on silicon is still immature and suffers from reliability issues. Heterogeneous and hybrid integration techniques, however, have been pursued in research and by industry and present a practical near-term solution for laser integration. Heterogenous approaches based on wafer bonding involve the bonding of bare III-V epitaxial material to silicon on insulator (SOI), co-fabrication, and evanescent light coupling. The laser active medium is thermally isolated from the silicon substrate by the buried oxide layer limiting the laser efficiency at high temperature. Hybrid integration approaches, such as the butt coupling of fabricated III-V lasers to SOI waveguides, may address the thermal issue. However, the main limitation for butt coupling is the significant mode mismatch of the waveguides that imposes a strict alignment requirement.In this thesis the novel 3D hybrid integration technique for SiPh, addressing the aspects of thermal performance and alignment tolerance, was proposed and demonstrated for the first time. This approach is based on the flip-chip integration of indium phosphide (InP) reflective semiconductor optical amplifiers (RSOAs) containing total internal reflection turning mirrors for surface emission. Light is coupled to the SOI waveguides through surface grating couplers. This technique yields increased alignment tolerance compared to butt coupling. Flip-chip integration also allows the RSOA chip to be bonded P-side down directly to the silicon substrate. In this way, the heat generated in the active region can dissipate more efficiently in the silicon. 3D hybrid integration can be carried out at wafer level in a backend step for high throughput manufacturing, and also allow for the integration of InP PICs on silicon interposers for large-scale electronic-photonic integration.A tunable laser was demonstrated with 3D hybrid integration demonstrating a side-mode suppression ratio up to 43 dB. Greater than 4 mW of optical power was coupled into SiPh waveguide and more than 20 nm wavelength tuning range was achieved. A linewidth of 1.5 MHz and relative intensity noise of -132 dB/Hz were demonstrated. A low thermal impedance of 6.2 ℃/W was extracted experimentally from a 3D hybrid laser that was bonded to the silicon substrate, demonstrating a factor of three improvement over a laser that was bonded above the SOI layer. To improve coupling efficiency, various advanced silicon surface grating couplers as well as dilute waveguide RSOAs were investigated. Coupling efficiency up to 85\% can be achieved while also maintaining an alignment tolerant implementation

An investigation of nanoscale materials and their incorporation in patch antenna for high frequency applications

The rapid development in the polymer-based electronic contribute a strong determination for using these materials as substitute to the high-cost materials commonly used as medium substrate in the fabrication of Microstrip Patch Antenna (MPA). Antenna technology can strongly gain from the utilisation of low-cost, flexible, light weight with suitable fabrication techniques. The uniqueness of this work is the use of variety of common but unexplored different polymer materials such as Polyethylene (PE), Polypropylene (PP), Polyvinyl chloride, (PVC) Polystyrene (PS), Polystyrene fibre (PSF) as the substrates for the design and fabrication of different MPAs for communication and sensing applications in millimetre wave (MMW)region. Electrospinning (ES) technique is used to reconstruct PS and produced PSF material of low dielectric constant. A co-solvent vehicle(comprising 50:50 ratio) of Dichloromethane (DCM) and acetone was utilised with processing condition of solution infusion flow-rate of 60μL/min and an applied voltage of 12± kV yielded rigid PSF substrates. The PSF Produced has complex permittivity of 1.36±5% and a loss tangent of 2.4E-04±4.8E-04 which was measured using Spilt-Post Dielectric Resonators (SPDR) technique at National Physics Laboratory, Teddington, London. A diamond-shaped MPAs on RT Duriod material were simulated and fabricated using photo-lithography for different inner lengths to work in the frequencies range from (1-10 GHz). The resonant frequency is approximated as a function of inner length L1 in the form of a polynomial equation. The fabricated diamond-shaped MPA more compact (physical geometry) as compared with a traditional monopole antenna. This MPAs experimentally measured and have a good agreement with the simulated results. The coplanar waveguide (CPW) diamond-shaped MPA working in the MMW region was designed and fabricated with polymer materials as substrates using thermal evaporation technique and the RF measurement was carried out using Vector Network Analyser (VNA). The resonant frequencies of the CPW diamond shaped MPAs for (PE, PP, PVC, PS and PSF) were found to be 67.5 GHz, 72.36 GHz, 62.41 GHz, 63.25 GHz and 80.58 GHz, respectively. The antenna fabricated on PSF were resonating at higher frequency when compared to the other polymers materials. In adding an air-bridge to the CPW diamond-shaped MPA the resonating frequency increased from ≈55 GHz to≈ 62 GHz. Three different shaped nano-patch antennas (Diamond shaped, diamond shaped array and T-shaped) have been designed, simulated and fabricated on Silicon substrate with DLC deposition using focused Ion Beam (FIB) technique, these antennas were found to resonate at 1.42 THz with (-19 dB return loss), 2.42 THz with (-14 dB return loss) and 1.3 THz with (-45 dB return loss) respectively

Nanostructured porous materials form Micro- and nano-electronics applications

This thesis work presents new research on porous silicon technologies for the heterogeneous integration on silicon platforms, as a key enabling technology for future 3D integrated systems. Porous silicon can be obtained with CMOS compatible processes on localized area on silicon wafer and, due to its tunable electrical, mechanical and thermal characteristics is an effective buffer material. Moreover, macroporous morphologies of porous silicon can can be exploited for the realization of “bed-of-nails” type through wafer interconnects, paving the way to high density, low-cost, through silicon vias. This work is divided in three parts: the first part introduces porous silicon, summarizes the available literature and presents process characterization for the porous layers obtained in this work and their properties; the second part describes the layer transfer technology and the buried cavities technologies developed in this work using the porous layers presented in the previous part; the last part introduces two applications of the layer transfer technology: compliant contacts and integrated physically small antennas