High-density Interconnect Structures Research Articles

A Finite-Element Domain-Decomposition Methodology for Electromagnetic Modeling of Multilayer High-Speed Interconnects

The complicated geometry of high-density interconnect structures in multilayer, planar substrates is one of the major hurdles in the application of finite element methods for their multigigahertz electromagnetic analysis. In addition to compounding the complexity in the generation of the finite element grid, the multilayer nature of the structures and their multiscale attributes result in finite element systems of very large dimension which, more often than not, are not well conditioned. This paper presents a domain decomposition methodology for overcoming these hurdles. More specifically, the proposed methodology utilizes the multiple power and ground planes used in such structures as natural physical boundaries for their decomposition into a set of subdomains, each one of which is meshed and discretized separately from the rest. The electromagnetic interaction between the domains is effected through the enforcement of tangential field continuity conditions at the voids and via holes present at the power and ground planes. In particular, a Krylov subspace model order reduction approach is used to facilitate the broadband solution of the multilayer interconnect structure. The proposed modeling methodology is demonstrated through its application to the electromagnetic analysis of several multilayer interconnect structures.

2D Detectors for particle physics and for imaging applications

The demands on detectors for particle detection as well as for medical and astronomical X-ray imaging are continuously pushing the development of novel pixel detectors. The state of the art in pixel detector technology to date are hybrid pixel detectors in which sensor and read-out integrated circuits are processed on different substrates and connected via high density interconnect structures. While these detectors are technologically mastered such that large scale particle detectors can be and are being built, the demands for improved performance for the next generation particle detectors ask for the development of monolithic or semi-monolithic approaches. Given the fact that the demands for medical imaging are different in some key aspects, developments for these applications, which started as particle physics spin-off, are becoming rather independent. New approaches are leading to novel signal processing concepts and interconnect technologies to satisfy the need for very high dynamic range and large area detectors. The present state in hybrid and (semi-)monolithic pixel detector development and their different approaches for particle physics and imaging application is reviewed.

Two-dimensional, electrostatic finite element study of tip–substrate interactions in electric force microscopy of high density interconnect structures

Two-dimensional electrostatic finite element modeling is used to estimate the variation of tip force as a function of potential, dielectric film thickness, and tip–substrate spacing when imaging using electric force microscopy. Blanket dielectric films and ∼1000 nm thick interconnect structures were studied. We conclude that sidewall damage regions can be detected but will require special processing to make an unambiguous measurement.

High-temperature, low-modulus adhesive attach for large-area thin-film processing on silicon and alumina tiles

The fabrication of high-density interconnect structures typically involves sequential processing of alternate layers of thin organic dielectric materials and conducting copper lines. With the continued push toward low-cost fabrication, large-area processing of thin-film materials is being aggressively pursued by the electronic packaging industry. The objective of the ongoing work at Georgia Tech is to develop innovative materials, models, and processing techniques to facilitate large-area processing of alumina and silicon tiles. As the alumina and silicon tiles are commercially available in smaller dimensions, a palletization approach has been developed to facilitate large-area processing. In the palletization approach, alumina and silicon tiles are attached to re-usable glass pallets with an in-house developed thermally-stable, reworkable, and highly-compliant adhesive.

Epoxy-based aqueous-processable photodielectric dry film and conductive ViaPlug for PCB build-up and IC packaging

DuPont formulated a new generation of photoimageable permanent resists and conductive ViaPlug polymer to be used as building blocks for sequential build-up of printed circuit boards (PCB's), multichip module-laminates (MCM-Ls), and plastic integrated circuit (IC) packages. The buzzwords for these structures are high density interconnection structures (HDIS) and microvias. The conventional method of making PCB's and MCM-Ls is a sequential lamination of innerlayer cores or interplanes, followed by at least one mechanical drilling. In this paper we will discuss a new approach of using semi-additive plating which means starting with a multilayer core, mechanically drilling for through hole connection, filling the through-hole with conductive ViaPlug, then adding layers of dielectric to make blind or buried vias for interconnection and routing of circuits, and heat dissipation. The paper will discuss the challenges in each application, relevant industry specifications for each application, and the dielectric and conductor materials properties to meet the challenges. From the viewpoint of technology choices, we will compare photoimaging versus laser ablation and plasma etching. Lastly, we will discuss our reliability data developed internally and in conjunction with several consortia.

Electrostatic Printing of Parmod™ Electrical Conductors

A new family of liquid toners has been developed to print conductive traces on printed circuit boards by a digital printing technology. The new toners are based on Parmod™ technology which has been developed to enable low cost production of printed circuits by a simple print-and-heat process. The novel feature of these printable materials is that they cure to pure metallic conductors in seconds at a temperature low enough to be compatible with polymer-based printed circuit substrates. The resulting circuit traces have high electrical conductivity and are solderable. The use of conventional printed circuit substrates and the speed of the process permit high-production, low-cost roll to roll processing.The extension of Parmod™ technology to liquid toners provides two major additional benefits: 1) It provides a major increase in resolution for production of advanced technology high density interconnect structures, and 2) It permits direct digital printing of circuits from CAD files with no intermediate tooling requirements. The latter capability realizes the goal of total CAD/CAM integration and the ultimate in manufacturing flexibility. This paper discusses the characteristics of Parmod™ technology, the performance of the liquid toners based on it and some applications of the technology which can be foreseen.

PE-MOCVD of Dielectric Thin Films: Challenges and Opportunities

The current trend in electronic-systems technology is to produce compact, lighter, low-power-dissipating, affordable, reliable, and mobile information systems. These factors favor the augmentation of interface systems that sense, source, store, display, and actuate with artificial-intelligence strategies. Herein lies the opportunity to introduce novel technologies based on integrated multi-component oxide (e.g., titanates, niobates, and tantalates) films into usable systems. In particular the oxygen octahedra class of materials (e.g., (Ba,Sr)TiO3 or BST, Pb(Zr,Ti)O3 or PZT, layered SrBi2Ta2O9 or SBT, and polytitanates) that exhibit high permittivities; large electromechanical-coupling coefficients; and pyroelectric, electro-optic, and ferroelectric effects are of interest. They are being evaluated, due to growing demand for compatibility with integrated-circuit (IC) technology, for a variety of applications. These include nonvolatile memories, ultralargescale-integration (ULSI) dynamic random-access memories (DRAMs), decoupling capacitors, piezoelectric sensors and actuators, pyroelectric detectors, and neural network components. Moreover in high-performance multichip-module (MCM) technology, there remains a vital need for the replacement of discrete passive devices, which occupy valuable real estate, by embedded ones. These high-density interconnect structures will play a significant role in nondigital electronic modules including mixed-mode circuits, power conversion and conditioning, microwave transmit/receive (T/R), and optoelectronics. Table I specifically illustrates some electronic applications along with their estimated requirements.

Electron beam processing of interconnection structures in multi-layer ceramic modules

An electron beam is used as a source of energy directly on green Al2O3 to form patterns of holes and channels for subsequent conductive filling. Holes of 0.003 to 0.006 in. diam, and channels of 0.001 to 0.006 in. width and controlled depth were formed in 0.008 in. thick green A12O3 sheets. A channel forming speed of 200 in. per sec was achieved. The mechanism of material removal is discussed. This process is capable of high density interconnection structures needed for high performance module fabrication, and it is adaptable to automation.