A novel, high-refractive index, methacrylic monomer was produced by incorporating 1-diamantane-carboxylic acid (1-D2-CA) and glycidyl methacrylate (GMA). The resulting monomer was gently polymerized with organic peroxide, and was formed transparent polymer thin film. Physicochemical and optical properties were compared with isobornyl methacrylate (IBoMA) homo-polymer film. 1-D2-CA/GMA homo-polymer reveals that the refractive index is 1.56, and the softening temperature is 107.8 °C. High thermal stability and high-refractive index of 1-D2-CA/GMA homo-polymer indicate the potential use in optical applications.

Phosphor-concentration-dependent characteristics of white light-emitting diodes (LEDs) under different current regulation conditions were investigated. It is found that the phosphor conversion efficiency of white LEDs driven under constant current is lower than that under pulse current. In addition, white LEDs driven under constant current exhibit higher junction temperature than under pulse current, and the difference is phosphor concentration dependent. For both pulse and constant current modes, white LEDs show relatively stable optical characteristics at relatively higher drive currents, when relatively higher phosphor concentrations are used. At relatively higher phosphor concentrations, the correlated color temperature and the chromaticity coordinates have also been observed to be relatively stable for white LEDs in both constant and pulse current modes.

The refractive index of various diamondoid powders from adamantane to hexamantane is reported by Becke line method for the first time. The variation in refractive index with increasing polymantane order can be explained by two factors: molecular refractivity (Rm) and specific molecular volume (Vm) with increasing polymantane order. The dispersion properties with increasing polymantane order was investigated. They can be closely related to the Kitaigorodskii packaging coefficient and density as a function of polymantane order.

A new series of 0.4MgF2–0.4BaF2–0.1Al(PO3)3–0.1Ba(PO3)2 glasses doped with Yb3+ is introduced for fiber and waveguide laser applications. Spectroscopic properties including emission cross-section and lifetime and optical properties including refractive index, nonlinear refractive index, and Abbe number are reported as a function of Yb2O3 concentration. The refractive index nd is linearly dependent on Yb2O3 concentration, while the nonlinear refractive index, n2 = 1.42 × 10−13 esu, which is independent of Yb2O3 concentration, is extremely small. In addition, the Abbe number is remarkably high, >65, and is also independent of Yb2O3 concentration. To our knowledge, the emission cross-section σemi, which was found to be ∼0.87 pm2 at the lasing wavelength of 996 nm, is the highest one among fluorophosphate glasses. This glass exhibits an extremely high gain coefficient, G = 0.95 ms pm4, and high quantum efficiency of η = 94%. The combination of outstanding spectroscopic (high emission cross-section and gain coefficient) and optical (low dispersion and small nonlinear refractive index) properties demonstrates that the current Yb3+ activated fluorophosphate glass is an excellent candidate material for fiber and waveguide lasers.

The effect of deposition methods on dielectric breakdown strength of PECVD low-k dielectric carbon doped silicon dioxide films is investigated. I–V measurements were performed using metal-insulator semiconductor structures for carbon doped silicon dioxide thin films with various thicknesses by single deposition station and six sequential deposition systems. I–t measurements are also performed for films with the thickness of 32 nm prepared using both deposition methods. Comparison studies have been carried out for the thickness dependence, temperature dependence, conduction mechanism and time dependence of dielectric breakdown for carbon doped silicon dioxide with single layer and six sub-layers. Results demonstrated that both films follow the newly obtained relationship between dielectric strength EB and thickness d, i.e. EB∝(d−dc)−n, but with a lower exponential factor n and a larger thickness limit dc for films with six sub-layers. It is also demonstrated that films with six sub-layers have a higher dielectric strength in all the thickness and temperature ranges, a thickness independent thermal behavior and a longer lifetime under constant voltage stressing. This indicates that by tuning the deposition methods smaller thickness with desired dielectric properties can be achieved.

The experimental results obtained on the dielectric strength EB of carbon doped silicon dioxide thin films for various film thicknesses using I–V measurements with metal–insulator–semiconductor structures suggest a new relationship between the film thickness d and the dielectric strength EB, i.e. EB∝(d−dc)−n. This inverse power law relationship indicates the existence of a critical thickness dc which may correspond to an ultimate thickness limit below which the rate of detrapping of electron charges exceeds the rate of trapping and no dielectric breakdown can be observed. The newly obtained inverse power law relationship appears to be general since it is also supported by other published dielectric strength data for both amorphous and polycrystalline polymer thin films.

Physical vapor deposition (PVD) copper seeding and subsequent fill by electroplating have become the most attractive technique for the implementation of copper metallization. However, a PVD seed layer provided as a continuous thin film with low resistivity to carry current for the subsequent electroplating process might have limitations of poor step coverage, rough morphology, discontinuity, overhang, and coverage asymmetry. Hence, it is of importance to extend the capability of PVD seed-layer deposition process for future high performance devices. An ion chromatography (IC) method is shown to be capable for electrochemical copper seed layer enhancement (SLE) process metrology. Composition dynamics of fresh and aged SLE bath solutions with an electroplating time up to 66.5 min are measured and analyzed with an IC system. The solution dynamics are found to be significant for electroplated copper film properties, the resistivity and roughness, which are found to be crucial for filling by electroplating the sub-0.2 μm vias and trenches of high aspect ratio. A strong correlation between the ion chromatograms and the electroplated copper film properties is observed.

Increases in data transmission speeds of optoelectronic devices have consequently increased high-frequency requirements for optoelectronic packaging materials including substrate, EMC/EMI shielding, adhesive and encapsulant (molding and underfill) materials. Most of those materials are polymer/filler composites, and critical materials properties for the device design and packaging include the effective dielectric constant, dielectric loss and their frequency and filler concentration dependence. This work presents a systematic theoretical investigation of the effective dielectric constant of polymer/filler composite materials, and its dependence on the filler concentration, the filler/polymer interaction, and the size of fillers. Our results demonstrate that, in contrary to the prevailing views, the filler concentration dependence of the effective dielectric constant is non-monotonic. Depending on the dielectric constant ratio between filler and polymer matrix, and the degree of interaction between filler and matrix, the effective dielectric constant exhibits an extreme as a function of filler concentration. In addition, our model is demonstrated to contain the Maxwell–Wagner formulation as an asymptotic limit. The present results have significant implications to the targeted formulation of optoelectronic packaging materials.

Low-k dielectric carbon doped silicon dioxide films 105–1255 nm in thickness, prepared by plasma-enhanced chemical vapor deposition (PECVD) in a six-station sequential deposition system and in a single deposition station, have been investigated for their optical properties using an optical spectrometer coupled with a hot stage. A decrease in refractive index, n, for films with six sub-layers compared with films with a single layer of similar thickness has been observed. This decreased refractive index is thought to be caused by the different effect of crystallinity of the substrate, as a film interface effect is introduced due to the different deposition methods. Both types of PECVD thin films show an increasing refractive index with increasing thickness, which could be attributed to the increased effective density with the increased thickness indicated from Fourier transform infrared spectroscopy microstructure analysis. Cauchy dispersion function is found to be valid for films within all the thickness range and with different deposition methods from visible spectrum to IR spectrum. The refractive index is found to decrease as the temperature increases from 25 to 450 °C at a fixed wavelength for all the films.

Low-k dielectric carbon-doped silicon dioxide films created by Plasma Enhanced Chemical Vapor Deposition (PECVD) using a six-station sequential deposition system exhibit different glass transition behavior from films created by PECVD in a single deposition station. The enhanced glass transition temperature (Tg) for the PECVD thin films of a layer consisting of six sub-layer deposited in a six-station sequential deposition system to the Tg for films of a single layer deposited in a single deposition system is traced back to the introduced film interface effect inherent to the different deposition methods. Both types of PECVD thin films range in thickness from 50 to 1255 nm and show an increasing Tg with decreasing film thickness. The observed glass transition behavior for films with six sub-layers can be well explained by a theoretical model of thickness dependent Tg for multiple sub-layers obtained by modifying the currently existing theoretical model for the single layer thickness dependent Tg behavior, which explains the observed thickness dependent Tg for single layer PECVD thin films.

Thickness dependent dielectric soft-breakdown and corresponding activation energy in low dielectric constant (low-k) thin films with thickness ranging from 48 to 1141 nm are investigated to evaluate the reliability of polymer integration on device wafers for the first time. It is found that the strength against soft-breakdown decreases and the leakage current increases with the decrease in low-k film thickness. In the regions both before and after soft-breakdown, the conduction activation energy increases with the increase in low-k film thickness. The conduction activation energy before soft-breakdown is smaller than that after soft-breakdown.

The use of electrically conductive adhesives as interconnection materials in electronic assembly process is increasingly becoming a vital part of the electronics industry. Flip-chip joining technique using conductive adhesives has been identified as a key technology for future electronics assembly and manufacturing. The purpose of the present work is to investigate optimum conditions to achieve the best electrical performance in conductive adhesive joints. This study shows a comparison of electrical performance in conductive adhesive joints at various current densities with different curing conditions. Differential scanning calorimetry and resistance measurement were used to monitor curing condition in conductive adhesives. Accelerated life testing of conductive adhesive joints made of the selected conductive adhesive using different curing conditions was performed with various current densities. The current-induced degradation of conductive adhesive joints was investigated using optical microscopy and electrical resistance measurements. Results show a strong dependence of curing condition and current density on electrical performance of adhesive joints. Additionally, sample cured for less time exhibited better quality than sample cured for more time at high current densities. It is also found that conducting particles move with the current-induced aging, which shows that the migration of conducting particles can induce the failure of conductive adhesive joint during the current-induced resistance increase.

Polymeric composite based underfill materials, with well-controlled coefficient of thermal expansion (CTE) are critical to flip-chip and other advanced high-density integrated circuit packaging technologies. The use of underfills beneath the flip-chip integrated circuits leads to an increase in reliability by reducing the strain on the solder bumps during thermal cycling imposed by the CTE mismatch between the chip and substrate. A fundamental understanding of the composite CTE of underfill materials is critical to the manufacture of high performance underfill materials and is critical to market expansion of flip-chip technology for high density packaging applications. This work presents a novel model for predicting the effective CTE of underfills and other polymeric composite materials by considering the effect of an interphase zone surrounding the filler particles in a polymer matrix. A microscopic model is also introduced for the volume fraction of the interphase as a function of filler concentration as well as filler–filler overlapping. The CTE model resolves several conflicts regarding the effect of filler concentration, filler size and filler–polymer interaction on the effective CTE of underfill and other polymeric composite materials. The results are demonstrated to be critical for accurate flip-chip reliability predictions based on finite-element and other modeling techniques.

According to the SIA National Technology Roadmap for Semiconductors, interlevel dielectrics (ILDs) with a relative dielectric constant less than two will be needed for future integrated circuit devices beyond 0.1 μm generation. For possible low-dielectric constant (low-k) candidates with a relative dielectric constant less than two, polytetrafluoroethylene (PTFE) has the lowest dielectric constant among nonporous low-k materials, and thus is a strong future ILD candidate. As the feature size decreases, the ILD thickness is also expected to decrease. Thus needs exist for characterizing and understanding the possible thickness-induced thermal reliability of PTFE thin films for deep-submicron multilevel interconnection applications. The majority of low-dielectric constant candidates for ULSI ILD applications are amorphous polymers; techniques exist for characterizing the glass transition temperatures of amorphous polymers, which is the critical measure of their thermal stability. However, a simple but reliable method remained to be introduced for characterizing the thermal stability of submicron crystalline thin films such as PTFE. It is determined in the present work that the directly measured ellipsometric angles Δ and ψ can be used for detecting the solid↔liquid transition temperatures of on-wafer polycrystalline thin films. The novel approach is applied for investigating the solid↔liquid transitions of on-wafer PTFE thin films. The results show that the solid–liquid transitions depend on the film thickness as a result of film/surface, film/substrate interactions and the thickness-dependent crystal size. The results can be well described by modifying a previous model for size dependent solid–liquid transitions of nanocrystals.

Fiber-coupled laser diodes are indispensable for optical fiber communications. The design of laser–fiber coupling is often guided by maximizing the optical power coupled into fiber, and by relaxing the fiber–laser alignment tolerances. Many of those fiber-optic designs are susceptible to optical back-reflections from the fiber resulting in not only a reduced coupling efficiency but also an increased optical noise of the signal. For many optical fiber communications, the most important parameter is not necessarily the coupling efficiency, but the quality of optical signal coupled into the fiber characterized by the carrier-to-noise ratio (CNR). This paper reports a novel laser–fiber coupling design for the purpose of optimizing the CNR. This new design involves the use of an intentional offset between the lensed fiber and laser. Though such offset has been studied previously in the context of coupling optics, it is never studied in the context of RIN and CNR. The results enable one to optimize the design of any laser–fiber coupling with respect to CNR.

Automation of fiber-to-optic alignment is critical to the development of cost effective fiber-optic component manufacturing technologies. Key to the alignment automation is the angular alignment automation, which is now unavailable. But angular misalignments are unavoidable in practical fiber-optic aligning process. This work evaluates the effects of pitch, yaw, and roll angular misalignments for a butt coupling scheme involving the optical coupling between a single-mode fiber and a laser diode. It is demonstrated that the coupling efficiency and misalignment tolerance are more sensitive to tilt, i.e., pitch and yaw angular misalignments than lateral ones. It is further demonstrated that the time for locating the optimal coupling position using conventional hillclimbing automation searching algorithm is a strong function of angular misalignments.

For the first time, the effects of preexisting voids inside the flip chip solder bump and at the interface of bump/underbump metallization (UBM) are considered on electromigration-induced failures to provide a mechanistic understanding on solder bump electrical reliability. Local peaks of current density due to preexisting voids supported by high operating temperature and temperature gradients and gradients of mechanical stress result in inhomogeneous drift of metal atoms, which leads to the formation of hillocks and more microvoids or large voids in the bump or the bump interfaces. The voids decrease the cross-section of the solder contact, which increases local current density and local resistance. This expected positive feedback cycle can eventually lead to the so-called electromigration failure. In the meantime, the increased volume of the extruded hillocks under electromigration can lead to circuit shorts between neighboring bumps, where the distance becomes closer and closer. A stochastic approach is employed to quantify the effects of various preexisting voids. It is found that preexisting voids at the interface of solder bump/UBM is more prone to growth during electromigration and therefore, a much shorter lifetime of the bump. Voids inside the bump can also speed up the failure of the solder bump and their effects depend on their location, size and total volume fraction. The simulation results can be applied for the reliable design of flip chip solder bumps by modifying the design rule with the consideration of the effects of preexisting voids.

The curing reactions and optimal schedules of three promising flip-chip underfill materials under isothermal and nonisothermal treatments are reported. It is found that curing reactions for three-tested underfill materials are autocatalytic, and the cure rate can be well described by the corresponding model. The activation energy, the rate constants, as well as two reaction orders m and n are determined to describe the curing progress. The temperature dependence of the cure degree for each heating rate is also investigated. It is found that the extent of reactions at a given temperature is a function of the heating rate. The glass transition temperature for the underfill UF-II is determined as a function of cure degree. It is found that the glass transition temperature increases with the cure time.

The force–resistance relationship is investigated by considering for the first time the effect of size distribution of metallic filler particles in anisotropic conductive adhesives. It is shown, for both the elastic and plastic interactions between the metallic particle and the conducting plate, that the relationships between the applied force (F) and the resistance can be described as power–laws (i.e. ∝F−n). The universal power–law relationships are found to be independent of both the mean particle size and the standard deviation of the particle size distribution. However, the exponent constant n is much larger for a non-monosized filler particle distribution than that for a monosized one. Although the power–law relationships are independent of the standard deviation of the particle size distribution and the mean particle size, a large standard deviation of particle size distribution leads to a large resistance. The theoretical prediction of the power–law relationship is found to be supported by available experimental observations.

A general analytical expression for the size-dependent constriction (contact) resistance is obtained for non-quantum contacts of arbitrary size as a solution of Laplace’s equation with appropriate boundary conditions. The new analytical expression contains both the Holm resistance and the Sharvin resistance as the asymptotic limits for the respective large and small contact sizes relative to the mean free path of electrons. This first general theoretical result is fully supported by available experimental data on the pressure dependence of contact resistance.

A new theory is introduced for the onset of electrical conduction in isotropic conductive adhesives, based on the observation that conduction is a result of the creation of conducting contacts in metal–insulator composite adhesives. The present theory resolves several prevalently contradicting issues including the onset dependency of electrical conduction on the volume fraction of filler particles, the particle size, the pressure effect, and the type of insulator matrix of an adhesive. The theory also predicts the condition for the occurrence of two percolation thresholds.

The oxidation behavior of the nanocrystalline FeBSi alloy prepared using the crystallization method has been investigated. The results indicate that the microstructures of the materials have a strong effect on the oxidation behavior. Because of the unique nature of the microstructure, the nanocrystalline FeBSi alloy shows a significantly enhanced oxidation resistance over those of the amorphous and coarse-grained crystalline FeBSi alloys with the same composition.