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We demonstrated a micro-chemoresistive gas sensing device using mesoporous carbon as the sensitive film and immobilized by dielectrophoresis (DEP) process. The mesoporous materials were characterized by X-ray diffraction (XRD) patterns, N2 adsorption–desorption isotherms, scanning electron microscopy (SEM), and transmission electron microscopy (TEM). N2 adsorption–desorption isotherms shows the specific surface area of 1200 m2/g, total pore volume is 1.2 cm3/g of the mesoporous carbon, and the pore size distribution of mesoporous carbon yields an average pore size of 3 nm. SEM images show a rod-like morphology and TEM images show a highly ordered pore channel with linear arrays. CO gas sensor properties were measured and the resulting sensitivities were 5.7, 6.8, 8.8, 11.6, and 37.6% for concentrations of 30, 45, 60, 75, and 90 ppm, respectively. Additionally, this sensor also exhibited high sensitivity and fast response times for CO gas.

This article reports a new class of silicon-based microgas sensors utilizing hexagonally-ordered mesoporous carbon powders (MCPs) as the sensitive film. The mesoporous carbon powders featuring high-specific surface area are replicated by the SBA-15 silica template and immobilized between Cr electrodes on a 9 × 9 cm silicon chip by using a.c. dielectrophoresis (DEP) process at room temperature. The silicon sensor platform comprises Cr microheaters embedded in a dielectric thin membrane manufactured by microelectromechanical systems back-etching techniques. It is shown that MCPs can be satisfactorily aligned along electric fields and accumulated to the electrode area. Investigations into CO detection are carried out to verify gas-sensitive characteristics of the MCP nanofilm. Our experimental results disclose the mesoporous carbon powders are successfully chemoresistive to CO , and demonstrate distinct resistance change with respect to ppm-level variation. In addition, response time, recovery time, and reproducible sensing behavior are experimentally obtained.

Poly-crystalline ZnO films with high oriented columnar grains were deposited on ZnO-coated seed layers by chemical bath deposition (CBD) in an aqueous-solution bath containing zinc nitrate [Zn(NO 3 ) 2 ·6H 2 O], and dimethylamineborane (DMAB) at 60 °C without pre-activation especially. Sol–gel ZnO films on glass substrates were used as the seed layers which the mean size of the crystals in seed layer increased from several to approximately 80 nm at temperature from 150 °C to 550 °C. The deposited ZnO films on the ZnO-coated seed surfaces are preferentially on the (0 0 2) plane and exhibit increased from several 10 nm to 150 nm with increasing seed layer grain size.

A mesostructured cobalt oxide microsensor was fabricated using a template replication method under different hydrothermal treatments, and attempts were made to enhance the response of this gas sensor. To evaluate the sensing performance, the sensing materials were deposited via the dielectrophoresis (DEP) process, on micro-hot-plate platforms with interdigitated electrodes. The resistance changed when the carbon monoxide target gas was injected at the optimum temperature. The mesostructured cobalt oxide material with high hydrothermal treatment revealed the well-ordered domains, whereas with low hydrothermal treatment it did not contain ordered domains. Moreover, the cobalt oxide high hydrothermal material had 1.5 times the response to 70 ppm carbon monoxide as the low hydrothermal treatment sample. The unobstructed interconnectivity promotes gas diffusion and increases the active surface areas.

A solid-first scheme was employed for making ultra low-k materials (k < 2.5) based on methylsilsesquioxane (MSQ) and high-temperature porogens in order to circumvent the reliability issues related to as-deposited porous dielectric. Based on thermal stability data, the MSQ/poly(styrene-b-4- vinylpyridine) material system was recommended to be cured at 300 {degree sign}C for subsequent backend processes, and the porogen to be removed at 400 {degree sign}C for 2 hours after CMP step. The mechanical properties of ultra-low-k films used in different integration schemes were further investigated using nano-indentation and FT-IR for various porogen loading. The moduli of 2-phase films were higher than their porous films, and even better than dense MSQ, for porogen loading below a critical level (~50%), which could be attributed to their enhanced degree of crosslinking in MSQ. In addition, MSQ/porogen films cured at 300 {degree sign}C possessed good elastic modulus (> 4.0 GPa) to pass CMP test.

The present study investigated the effect of passivation on the kinetics of interfacial mass transport by measuring stress relaxation in electroplated Cu films with four different cap layers: SiN, SiC, SiCN, and a Co metal cap. Stress curves measured under thermal cycling showed different behaviors for the unpassivated and passivated Cu films, but were essentially indifferent for the films passivated with different cap layers. On the other hand, stress relaxation measured under an isothermal condition revealed clearly the effect of passivation, indicating that interface diffusion controls the kinetics of stress relaxation. The relaxation rates in the passivated Cu films were found to decrease in the order of SiC, SiCN, SiN, and metal caps. This correlates well with previous studies on the relationship between interfacial adhesion and electromigration. A kinetic model based on coupling of interface and grain-boundary diffusion was used to deduce the interface diffusivities and the corresponding activation energies.

Field emission of electrons from single crystal gallium phosphide (GaP) nanotips has been investigated. GaP nanotip arrays were fabricated using silane-methane-argon-hydrogen based plasma using the self-masking dry etching technique in an electron-cyclotron-resonance microwave plasma enhanced chemical vapor deposition system. These nanotips have an average of 2 and 80 nm in apex and bottom diameters, respectively. They are 900 nm in height, which makes them the perfect electron emission source for their high aspect ratio topography. A nanosized silicon carbide (SiC) cap on each GaP nanotip in the array has been found. The SiC core has a heterointerface with GaP crystal that was observed using a high resolution transmission electron microscope. Field emission analysis shows low turn-on fields of 8.5–9 V/μm. Cold electron emissions in Fowler–Nordheim type current-voltage were observed from such GaP nanotip arrays.

Continuing improvement in device density and performance has significantly affected the dimensions and complexity of the wiring structure for on-chip interconnects. These enhancements have led to a reduction in the wiring pitch and an increase in the number of wiring levels to fulfill demands for density and performance improvements. As device dimensions shrink to less than 0.25 μm, the propagation delay, crosstalk noise, and power dissipation due to resistance-capacitance (RC) coupling become significant. Accordingly the interconnect delay now constitutes a major fraction of the total delay limiting the overall chip performance. Equally important is the processing complexity due to an increase in the number of wiring levels. This inevitably drives cost up by lowering the manufacturing yield due to an increase in defects and processing complexity.To address these problems, new materials for use as metal lines and interlayer dielectrics (ILDs) and alternative architectures have surfaced to replace the current Al(Cu)/SiO2 interconnect technology. These alternative architectures will require the introduction of low-dielectric-constant k materials as the interlayer dielectrics and/or low-resistivity conductors such as copper. The electrical and thermomechanical properties of SiO2 are ideal for ILD applications, and a change to material with different properties has important process-integration implications. To facilitate the choice of an alternative ILD, it is necessary to establish general criterion for evaluating thin-film properties of candidate low-k materials, which can be later correlated with process-integration problems.

N,N'-Di-(4-anilino)-1,2,4,5-benzene bis(dicarboximide) was prepared in a three-step synthesis and purified by heating the resulting solid to 200°C. Condensation of the diamino-diimide with several dianhydrides (BPDA, BTDA, and 6-FDA) yielded polyamic acid-imides that could be either thermally or chemically cured to the corresponding alternating copolyimides. Imidization of the polyamic acid-imide to the final polyimide was monitored by FTIR for samples coated on silicon wafers before being thermally cured. Polyimides prepared by chemical imidization were found by thermogravimetric analysis to be stable to temperatures of 600°C.

The fracture characteristics of metal/polymer line structures formed by depositing Au/Cr lines on a semiflexible polyimide, pyromellitic dianhydride‐oxydianiline (PMDA‐ODA), substrate have been investigated using a stretch deformation technique. The delamination behavior, fracture morphology, fracture energy, and energy dissipation rate have been determined as a function of line width and thickness. The metal dimension was found to influence the crack formation mode and morphology. The experimental studies were supplemented by finite‐element analysis to evaluate the stress distribution and deformation energetics of the line structure, which takes into account the plastic deformation of the metal and the polymer. Results from this analysis show that the observed fracture characteristics can be attributed to the edge and thickness effects induced by metal confinement. Essentially, the deformation behavior is determined by the mechanical environment induced by metal confinement at the interface. Plastic deformation of both metal and polymer plays an important role in controlling the stress distributions as well as the deformation energetics. The fracture energy of the metal‐polyimide interface determined by an overall energy balance method was consistent with that obtained from energy dissipation rate. The average value is 25 J/m2 for the Au/Cr/PMDA‐ODA line structure.

The fracture behavior of the Au/Cr line structures formed on a rigid‐rodlike polyimide, biphenylenetetracarboxylic dianhydride‐phenylenediamine (BPDA‐PDA), film substrate has been investigated using a stretch deformation technique and compared with that of the Au/Cr line structures formed on a semiflexible polyimide, pyromellitic dianhydride‐oxydianiline. In general, the effects of metal line dimensions on the deformation behavior can be attributed to the changes in the mechanical environment induced by metal confinement at the line interface. This gives rise to a fracture behavior and geometrical dependence of these two polyimide structures which are qualitatively similar in most aspects. However, the fracture energy and crack propagation rate of these two polyimide line structures are quantitatively different, with values about twice higher for the BPDA‐PDA line structures. This cannot be accounted for solely by the different chemical bonding; instead, the high fracture toughness of the BPDA‐PDA structu...

In this paper, the adhesion strength between Cu metal and Benzocyclobutene (BCB) polymer dielectric was investigated and reported. The relation between the adhesion strength and thickness of metal layer and the relation between the adhesion strength and stacking order of copper and BCB polymer layer are discussed as well. Finally, the concept of an extra layer between Cu metal and BCB polymer layer to improve the adhesion strength was evaluated. The results of this research can provide important guidelines of hybrid bonding and underfill for 3D integration applications.

X‐ray photoelectron spectroscopy has been used to investigate the interaction between Cr and BPDA‐PDA polyimide for Cr coverages up to 18 A. Detailed core level analysis reveals that the spectral changes induced by Cr deposition are a consequence of both the chemistry and the redistribution of reaction products in the overlayer. Two distinct N bonding configurations are readily resolved; one formed at lowest coverage remains localized at the buried interface, whereas the second becomes intermixed in the overlayer. Uniform overlayer growth is observed above ∼3.5 A. The data for low Cr coverages are compared to molecular orbital calculations for two model bonding configurations. Agreement between theory and experiment for the C 1s core level is better for a model compound with an O atom removed from the polymer backbone than for one where Cr is bound to a benzene ring. However, the quantitative differences suggest that a model should be considered where Cr interacts with carbonyl groups and additional reaction sites.

Label free optical sensing of adenine and thymine oligonucleotides has been achieved at the sub-picomole level using self assembled silver nanoparticles (AgNPs) decorated gold nanotip (AuNT) arrays. The platform consisting of the AuNTs not only aids in efficient bio-immobilization, but also packs AgNPs in a three dimensional high surface area workspace, assisting in surface enhanced Raman scattering (SERS). The use of sub-10 nm AgNPs with optimum inter-particle distance ensures amplification of the chemically specific Raman signals of the adsorbed adenine, thymine, cytosine and guanine molecules in SERS experiments. High temporal stability of the Raman signals ensured reliable and repeatable DNA detection even after three weeks of ambient desk-top conservation. This facile architecture, being three dimensional and non-lithographic, differs from conventional SERS platforms.

Underfill materials, consisting of organic resin and inorganic filler, have been widely employed in flip-chip technology for preventing the failure of solder joints during packaging process. In order to meet the requirements of high frequency device applications, low-dielectric-constant underill is highly desired to alleviate the power consumption issue. However, it is disadvantageous to introduce low-k into organic resin because of its high cost and low volume fraction. Alternative approach is to use highly porous silica filler with appropriate pore sealing prior to mixing with epoxy. In this paper, a siloxane compound, polymerized vinyl-trimethoxysilane (poly-VSQ), was synthesized and applied to an ordered, porous silica structure, SBA-15 to study its effectiveness in pore sealing and interaction with SBA-15 matrix for low-k underfill applications. We have developed a convenient pore sealing treatment using poly-VSQ to achieve a 10.9% reduction (from 3.2 to 2.85) in dielectric constant of underfill material with 15% filler content by fully retaining the high porosity (61%) of SBA15. Moreover, excellent mechanical strength could be maintained as 3.0GPa without any interfacial delamination.

The change in chemical structure of the top surface layer of thin poly(methylmethacrylate) (PMMA) and polyimide (PI) films (200–1500 A) during downstream microwave NF3/CF4/O2 plasma etching are investigated by in situ Fourier transform infrared (FTIR) reflection–absorption spectroscopy. Plasma fluorination of PI by either NF3 or CF4 leads to significant surface fluorination characterized by the formation of aliphatic fluorine compounds (CFx), acyl fluoride, benzoyl fluoride, acyl hypofluorite, and polyfluorinated benzene. The surface fluorination process is found to be controlled by diffusion in the product layer and the depth of fluorination is estimated from infrared absorbance to be approximately 500 A. Addition of oxygen leads to a reduction in the fluoride species and the development of broad absorption bands representing oxygenated surface species. The FTIR data are supplemented by ex situ x‐ray photoelectron spectroscopy observations and mechanisms for the observed modifications of the polymer surf...

Low-k materials have been introduced in the backend interconnects since 90 nm node for advanced microelectronic products in order to reduce the RC delay. However, the fragile low-k layer is very sensitive to the thermal stress induced by the CTE (coefficient of thermal expansion) mismatch at metal/dielectric level as well as at die/package level. In the die/package interaction, the transition to lead-free solders from conventional SnPb eutectic solder degrades the reliability of flip-chip ball grid array (FC-BGA) packages due to its higher reflow temperature. As a result, the underfill layer becomes more critical in protecting both low-K layer and solder bumps from delaminations and cracks. In this study, regular and high resolution Moire interferometry were first employed to measure thermal strains of FC-BGA assemblies with CuSn solder and 2 latest underfill materials, which in turn validate our 3D FEA model. Besides, six kinds of FC-BGA assemblies with different solder alloys and underfill materials were also evaluated by thermal cycling test (TCT). A 3D simulation model using ANSYS™ was created to predict and analyze the fracture susceptibility of the assemblies. The simulation results showed good agreement with TCT experiments. The underfill material with low CTE, moderate modulus, and high Tg (glass transition temperature) is recommended for low-k/FC-BGA packages.

Underfill materials had been widely employed in the flip-chip packaging to fill the gaps of solder bumps connecting IC chip and organic substrate in order to prevent failure of the solder joints. For radio-frequency (RF) device applications, underfill materials should possess low dielectric constant to alleviate power loss at high-frequency, in addition to good thermal and mechanical properties. In this study, a novel approach of incorporating porosity through porous silica filler was attempted to develop low-k underfill materials. An inorganic, sacrificial material, hexamethylcyclotrisiloxane (D 3 ), was used to temporarily seal the interconnected pores in the porous silica at temperature ≪ 95 °C by thermal and solvent pretreatment methods, and was later removed thermally at 125–165 °C during the crosslinking reaction of underfill materials. For underfill materials with 15% filler content, a 7.8% reduction in dielectric constant has been successfully demonstrated and achieved by pore sealing of porous silica (60% porosity) using solvent pretreatment, while maintaining the mechanical strength of porous silica, 2.6 GPa. Moreover, the adhesion between epoxy and porous silica in the underfull materials was found to critical in preserving its mechanical strength when pore sealing pretreatment was applied.

In this paper, we present static thermal analysis of stress and strain on a thin-film transistor liquid-crystal display (TFT-LCD) panel and their correlation with light leakage phenomena under high-temperature durability test. Three-dimensional (3D) finite element analysis (FEA) is coupled with experimental parameters of key components of the TFT-LCD panel for the analysis. A strong correlation exists between light leakage and retardation difference induced by stress on triacetyl cellulose (TAC) films. Moreover, shrinkage in stretched poly(vinyl alcohol) (PVA) film and modulus of the adhesive layer are key factors affecting stress distribution and displacement of polarizer stack. An increase in Young's modulus (E) of the adhesive layer effectively reduces polarizer shrinkage and light leakage at the center of the panel. A TAC film with lower Young's modulus and/or coefficient of thermal expansion (CTE) is also an effective solution.

200-nm-thick organosilicate films deposited by mixture of tetraethyl orthosilicate (TEOS) and methyltrimethoxysilane (MTMS) dissolving in different cetrimonium bromide (CTAB)/ethanol ratios were characterized in terms of pore size determination and its distribution. Under the toluene ambient, the pores would adsorb the gas hence elevating the whole film density. The X-ray reflectivity (XRR) equipped with mass flow control was utilized to detect the film density increasing. By fitting with Gaussian function and conversing with Kelvin's equation, the pore size was increased from 6.2 to 10.8 A as the CTAB/ethanol ratio increasing to 0.075. It was attributed to the ethanol and CTAB enhanced the TEOS hollow droplets stability and dissolvability. As the CTAB/ethanol ratio is further increased, the pore size is reversely decreased, owing to the formation of solid microspheres. The non-destructive XRR measurement can evaluate the sub-nano pore sizes and its size distribution, which would fascinate the development and characterization of back-end of line process.

The bending curvature, stresses, and stress relaxation of various multi-layered structures with different adhesive layers pertaining to the polarizer in a thin-film transistor liquid-crystal display (TFT-LCD) have been successfully characterized by using bending beam technique under reliability test. To be more specific, three different types of pressure-sensitive adhesive (hard-, middle-, and soft-type) and various poly(vinyl alcohol) (PVA) stretched directions are devised to examine to key stress contributors and correlations with light leakage. The shrinkage stress in stretched PVA film and stress relaxation ability of pressure-sensitive adhesives (PSA) layers are found to be the key factors determining the stress distribution and out-of-plane displacement of a polarizer stack. For hard-type PSA, its polarizer stack generates the highest bending curvature with maximum out-of-plane displacement but minimum in-plane displacement, leading to anisotropic stress distribution with high stress around the edges. On the other hand, polarizer stack with soft-type PSA yields the maximum in-plane displacement but the minimum out-of-plane displacement, resulting in isotropic stress distribution.

The interfacial adhesion of lithographically patterned thin film structures has been measured. Fracture mechanics techniques, modified for thin-film geometries, were employed to quantify the interfacial adhesion of patterned arrays containing low-k and Cu metal lines with varying channel length scales, aspect ratios and orientations. The results indicate that interfacial adhesion may be affected by the line structures and their orientation. In addition, the fracture resistance of debonded interface was dependent on the specific low-k material employed in the structure.

We unveil an innovative and manufacturable process technique to pattern dual damascene structures in polymer interlayer dielectric (ILD) without the need for either a permanent hardmask or an embedded etch stop (ES) layer. We introduce a sacrificial hardmask (SAM) and a sacrificial via fill (SAVIL) material to enable the patterning process. Since the hardmask is sacrificial, it is removed at the end of the patterning process without compromising the overall dielectric value of the ILD. The utilization of the SAVIL material provided the trench lithography step with a hole-free, and planar substrate. We demonstrate patterning of dual damascene structures using SAM/SAVIL in a via-first integration scheme through a comparative patterning performance between the SAM/SAVIL-assisted dual damascene patterning and the dual hardmask approach used most in the industry.

In this study, we investigate the effect of passivation layer on mass transport by measuring stress relaxation in Cu damascene line structures. SiC and SiN/sub x/ passivation layers are investigated and compared with no passivation to examine the bonding effect on mass transport. The observed stress relaxation behavior is analyzed by a kinetic model considering the contribution to mass transport via various diffusion paths including the passivation interface. Results of this study show a significant effect due to the passivation layer that can be attributed to the interfacial chemistry.

Three‐dimensional finite element simulations were used to model stress relaxation due to diffusion along interfaces in a damascene copper interconnect structure. By fitting the predicted stress relaxation rates to the available experimental results, we have identified the interfaces that contribute to stress relaxation in the structure, and have estimated values for their diffusion coefficients.

Recent studies have shown that the Cu/cap layer interface is the dominant diffusion path for electromigration (EM) in Cu interconnects, making it important to develop effective methods to evaluate the effect of passivation layer on interfacial mass transport and EM lifetime for Cu interconnects. This work shows that a set of isothermal stress relaxation tests together with appropriate modeling analysis can be used to evaluate the kinetics of interface and grain boundary diffusion and the effects of passivation layer. Thermal stresses in electroplated Cu films with and without passivation were measured using a bending beam technique, subjected to thermal cycling and isothermal annealing at selected conditions. Thermal cycling experiments provide information to select the initial stresses and temperatures for isothermal stress measurements. A kinetic model coupling grain boundary diffusion with surface and interface diffusion was developed and found to account well for the isothermal stress relaxation exper...

1 Overview on Low Dielectric Constant Materials for IC Applications.- 1.1 Introduction.- 1.2 Dielectric Constant and Bonding Characteristics.- 1.3 Material Properties and Integration Requirements.- 1.4 Characterization of Low-? Dielectrics.- 1.5 Porous Low-? Materials.- 1.6 Conclusion.- References.- 2 Materials Issues and Characterization of Low-? Dielectric Materials.- 2.1 Introduction.- 2.2 Thin-Film Material Characterization.- 2.3 General Structure-Property Relationships.- 2.3.1 Dielectric Constant.- 2.3.2 Thermal Properties.- 2.3.3 Moisture Uptake.- 2.3.4 Thermomechanical and Thermal Stress Properties.- 2.4 Fluorinated Polyimide: Effect of Chemical-Structure Modifications on Film Properties.- 2.5 Crosslinked and Thermosetting Materials.- 2.6 Parylene Polymers: Effect of Thermal History on Film Properties.- 2.7 Future Challenges.- References.- 3 Structure and Property Characterization of Low-? Dielectric Porous Thin Films Determined by X-Ray Reflectivity and Small-Angle Neutron Scattering.- 3.1 Introduction.- 3.2 Two-Phase Methodology.- 3.2.1 Experimental.- 3.2.2 Two-Phase Analysis Using the Debye Model.- 3.2.3 Results and Discussion.- 3.3 Three-Phase Methodology.- 3.4 Films with Ordered Porous Structure.- 3.5 Limits of SANS Characterization Methods.- 3.6 Future Developments.- 3.6.1 Contrast Variation SXR.- 3.6.2 Inhomogeneous Wall Composition.- 3.7 Conclusion.- References.- 4 Vapor Deposition of Low-? Polymeric Dielectrics.- 4.1 Introduction.- 4.2 Vapor-Phase Deposition and Polymerization on Substrates.- 4.3 Parylenes.- 4.3.1 Synthesis Review.- 4.3.2 Properties of Parylene-N.- 4.3.3 Mechanisms and Models of Parylene Polymerization.- 4.3.4 Integration Issues with Parylene-N.- 4.3.5 Synthesis and Properties of Parylene-F.- 4.3.6 Integration Issues with Parylene-F.- 4.4 Polynaphthalene and Its Derivatives.- 4.4.1 Experimental System for Polynaphthalene Synthesis.- 4.4.2 Properties of Polynaphthalene and Fluorinated Polynaphthalene.- 4.5 Teflon and Its Derivatives.- 4.5.1 Synthesis of Teflon-AF.- 4.5.2 Properties of Teflon-AF.- 4.5.3 Integration Issues with Teflon.- 4.6 Vapor-Deposited Polyimides.- 4.7 Prospects for Vapor-Depositable Low-? Polymers.- References.- 5 Plasma-Enhanced Chemical Vapor Deposition of FSG and a-C:F Low-? Materials.- 5.1 Introduction.- 5.2 FSG Films.- 5.2.1 Introduction.- 5.2.2 General Characteristics.- 5.2.3 HDP-CVD FSG Film.- 5.3 a-C:F Films.- 5.3.1 Introduction.- 5.3.2 Deposition of a-C:F by PE-CVD and Controlling Fluorine Concentration.- 5.3.3 Control of F/C Ratio by Helicon-Wave HDP-CVD.- 5.3.4 Mechanism of the Reduction of the Dielectric Constant of a-C:F.- 5.3.5 Signal-Delay Measurements of CMOS Circuits.- 5.3.6 Conclusion.- References.- 6 Porous Organosilicates for On-Chip Applications: Dielectric Generational Extendibility by the Introduction of Porosity.- 6.1 Introduction.- 6.2 Porous Silica.- 6.3 Organosilicates.- 6.4 Porogens.- 6.5 Porous Organosilicate Matrix Resins.- 6.6 Formation of Nanohybrids.- 6.7 Porous Organosilicates.- 6.8 Characterization of Porous Organosilicates.- 6.9 Conclusion.- References.- 7 Metal/Polymer Interfacial Interactions.- 7.1 Introduction.- 7.2 Experimental Methods.- 7.2.1 XPS and AES Analysis.- 7.2.2 XPS for Nucleation Modes.- 7.2.3 Other Surface-Science Techniques.- 7.2.4 Metal-Deposition Techniques.- 7.3 Metallization of Fluoropolymers.- 7.3.1 Metal Evaporation.- 7.3.2 Sputter Deposition.- 7.3.3 Aluminum MOCVD.- 7.3.4 Copper MOCVD.- 7.4 Polymers on Metals: Adhesion to Cu.- 7.4.1 Introduction to SiC films.- 7.4.2 Vinyl Silane-Derived Films on Cu.- 7.5 Conclusion.- References.- 8 Diffusion of Metals in Polymers and During Metal/Polymer Interface Formation.- 8.1 Introduction.- 8.2 Thermodynamic Considerations.- 8.3 Effect of Metal-Polymer Interaction on the Mobility of Metal Atoms.- 8.4 Surface Diffusion, Nucleation, and Growth of Metal Films.- 8.5 Diffusion and Aggregation.- 8.6 Atomic Diffusion.- 8.7 Conclusion.- References.- 9 Plasma Etching of Low Dielectric Constant Materials.- 9.1 Introduction.- 9.2 Technological Requirements and Patterning Approaches.- 9.2.1 Damascene Processing.- 9.2.2 Plasma Etching.- 9.2.3 Important Low Dielectric Constant Materials.- 9.3 Fluorocarbon-Based Etching Processes.- 9.3.1 Fluorine-Doped SiO2(SiOF), Hydrogen Silsequioxane (HSQ) and Methyl Silsequioxane (MSQ).- 9.3.2 Porous Silica Films.- 9.4 Directional Etching of Organic Low-? Materials.- 9.4.1 Hydrocarbon-Based Organic Materials: Etching of Olyarylene Ether (PAE-2) in Ar/O2/N2Gas Mixtures..- 9.4.2 Fluorocarbon-Based Organic Materials: Polytetrafluoroethylene.- 9.4.3 Hybrid Materials.- 9.5 Postetch Mask-Stripping and Via-Cleaning Processes.- 9.6 Conclusion.- References.- 10 Integration of SiLK Semiconductor Dielectric.- 10.1 Introduction.- 10.2 SiLK Semiconductor Dielectric.- 10.3 Subtractive Technologies.- 10.3.1 Introduction.- 10.3.2 Integration Flow for Subtractive Interconnects.- 10.3.3 Integration Unit Steps.- 10.3.4 Electrical Results.- 10.3.5 Conclusion.- 10.4 Damascene Technologies.- 10.4.1 Introduction.- 10.4.2 Embedded-Hardmask Approach for Dual Damascene.- 10.4.3 Dual Damascene Schemes with Multilayered Hardmasks.- 10.5 Cost-of-Ownership.- 10.6 Conclusion.- References.

As the industry moves towards using low k dielectrics in advanced interconnects, interfacial adhesion and film mechanical properties play increasingly important roles in yield and reliability. Improving these mechanical properties requires a better understanding of the surface, interface and film chemistry. Time‐of‐Flight Secondary Ion Mass Spectrometry (TOF‐SIMS) was used to examine the surface molecular structure of organosilicate and organic polymer based low k interlayer dielectrics (ILDs). Strong correlations were established between surface group functionality, reactivity of the TiN precursors with the ILDs during Atomic Layer Deposition (ALD), and adhesion between the copper barrier and the ILDs. Hydrogen plasma treatment significantly changed the surface chemical structure of the polymer ILD through hydrogenation. Correspondingly, degradation of barrier/polymer adhesion and thermal stability was observed. For the organosilicate ILD, the modulation of film chemistry, primarily the siloxane structur...

This paper describes the collaboration between university and industry in the evaluation of low dielectric materials for on-chip interconnect applications. The collaboration has established selection criteria and characterization methodologies for materials evaluation of dielectric thin films in the micron range. A review on the concerted efforts of semiconductor industry, materials suppliers, university and consortium in materials and processing evaluation and in improving the interlayer dielectrics (ILD) materials in alignment of SIA Technology Roadmap are described. The characterization techniques of thin films and results of materials evaluation are discussed.

A process control system is composed of a variety of elements, from measurement technologies and techniques, through sampling strategies and analysis algorithms, to data-driven action plans. All components are required to ensure a stable process, however, effective control is founded upon a set of easily measured, yield-relevant parameters. In this work, we describe the use of a toolset and methodology to provide such parameters, and explore sampling and analysis components for the evaluation, development, and control of low-/spl kappa/ dielectric processes. In comparison to historically-employed interline dielectric (ILD) materials such as SiO/sub 2/, these low-/spl kappa/ materials and processes present significant integration, reliability, and stability concerns. A particularly sensitive parameter is the dielectric constant itself. Damage from high-power ultraviolet inspection techniques may also present challenges. As these relatively immature processes migrate into volume production, these same tools and parameters can be used to monitor the low-/spl kappa/ process module, improve baseline yield, and control excursions.

This study comprehensively investigates the effect of ultraviolet (UV) curing time on the physical, electrical, and reliability characteristics of porous low-k materials. Following UV irradiation for various periods, the depth profiles of the chemical composition in the low-k dielectrics were homogeneous. Initially, the UV curing process preferentially removed porogen-related CHx groups and then modified Si-CH3 and cage Si-O bonds to form network Si-O bonds. The lowest dielectric constant (k value) was thus obtained at a UV curing time of 300 s. Additionally, UV irradiation made porogen-based low-k materials hydrophobic and to an extent that increased with UV curing time. With a short curing time ( 300 s) was associated with improved mechanical strength, electrical performance, and reliability of the low-k materials, but none of these increased linearly with UV curing time. Therefore, UV curing is necessary, but the process time must be optimized for porous low-k materials on back-end of line integration in 45 nm or below technology nodes.

This study investigates the effect of the NH3/N2 ratio in plasma treatment on the physical and electrical properties as well as the reliability characteristics of porous low-k films. All of the plasma treatments resulted in the formation of a thin and modified layer on the surface of porous low-k films, and the properties of this modified layer were influenced by the NH3/N2 ratio in the plasma. Experimental results indicated that pure N2 gas plasma treatment formed an amide-like/ nitride-like layer on the surface, which apparently leads to a higher increase in the dielectric constant. Plasma treatment with a mixture of NH3/N2 gas induced more moisture uptake on the surface of the low-k dielectric, degrading the electrical performance and reliability. Among all plasma treatment with NH3/N2 mixed gas, that with pure NH3 gas yielded low-k dielectrics with the worse electrical and reliability characteristics.

Two types of periodic nanostructures, self-organized nanodots and nanolines, were fabricated on the surfaces of indium-tin-oxide (ITO) films using femtosecond laser pulse irradiation. Multiple periodicities (approximately 800 nm and 400 nm) were clearly observed on the ITO films with nanodot and nanoline structures and were identified using two-dimensional Fourier transformation patterns. Both nanostructures show the anisotropic transmission characteristics in the visible range, which are strongly correlated with the geometry and the metallic content of the laser-induced nanostructures.

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— Mura defects become visible in a 13.3-in. TFT-LCD using chip-on-glass (COG) packaging when the thickness of the glass substrate is decreased from 0.5 to 0.3 mm. Mura, the non-uniform brightness in LCDs, is caused by COG packaging due to the mismatch of the coefficient of thermal expansion (CTE) and Young's modulus between the glass substrate and the IC-driver Si chips. In this paper, a 3-D finite-element-analysis (FEA) model, coupled with transient thermal analysis is first established to examine the warpage and stress behavior in the upper-glass-plate post-COG-package processing for identifying the root causes of the light-leakage phenomenon. Prior to that, the simulated warpage results are validated by surface-contour measurement. Data and modeling results show that a low bonding temperature together with a low modulus in novel ACF materials can effectively eliminate Mura. Besides, thinner silicon or a shorter length of Si chips as drivers offers enhanced reduction in the localized warpage, and thus can be a practical and low-cost solution for eliminating mura defects.

Large-area surface ripple structures of indium-tin-oxide films, composed of self-organized nanodots, were induced by femtosecond laser pulses, without scanning. The multi-periodic spacing (~800 nm, ~400 nm and ~200 nm) was observed in the laser-induced ripple of ITO films. The local conductivity of ITO films is significantly higher, by approximately 30 times, than that of the as-deposited ITO films, due to the formation of these nanodots. Such a significant change can be ascribed to the formation of indium metal-like clusters, which appear as budges of ~5 nm height, due to an effective volume increase after breaking the In-O to form In-In bonding.

The evolution of microstructure and composition of titanium dioxide (Ti0 2 ) nanotube arrays fabricated with hydrofluoric acid (HF) and NH 4 F electrolytes as a function of annealing temperature up to 400°C was investigated and compared using X-ray diffraction, scanning electron microscopy, and X-ray absorption near-edge structure spectroscopy. Results showed that TiO 2 nanotube arrays grown in HF electrolyte contained 90% amorphous Ti0 2 and 10% lower oxidation states of titanium from Ti 2+ (TiO) and Ti 3+ (Ti 2 O 3 ) cations. After annealing at 400°C, TiO 2 nanotube arrays underwent charge transfer and phase transformation to 93% anatase phase, 6% amorphous Ti0 2 , and 1% suboxides. In contrast, as-grown Ti0 2 nanotube arrays using NH 4 F electrolyte possessed less amorphous TiO 2 (82%) but more suboxides (18%) due to lower oxygen ion formation from scanty 3 wt % of H 2 0 addition. Its onset temperature of phase transformation was found to be higher than Ti0 2 nanotube arrays prepared by HF solution. Moreover, when annealed to 400°C, the crystallinity of TiO 2 nanotube arrays increased only by 86% for the anatase phase. The lower anatase phase could be attributed to the formation of (NH 4 ) 2 TiF 6 type compounds presumably formed by the reaction of TiF 2― 6 and NH + 4 ions dissociated from NH 4 F.

The interaction between a polystyrene-b-polybutadiene-b-polystyrene (SBS) porogen and a low-k methylsilsesquioxane (MSQ) matrix under different curing profiles and their impact on porogen size were studied by grazing incidence small-angle X-ray scattering, viscosity measurement, and Fourier transform infrared analysis. For slow curing, significant porogen diffusion and aggregation occurred between 100 and 170°C, at which the porogen size increased from 12 to 32 nm. The interaction mechanism between porogen and the MSQ matrix and its correlation with porogen size during the thermal cure process were elucidated. The aggregation of the SBS porogen was greatly influenced by the microstructure of the MSQ matrix at three controlling temperatures; namely, (1) glass transition temperature, Tg ( ∼ 100°C), (2) onset temperature (160°C) for transforming cage to network structure, and (3) immobilization temperature (170°C). In contrast, a rapid curing rate enabled the formation of small porogen size ( ∼ 12 nm) in the hybrid films and yielded better mechanical strength. .

We have carried out a comparative study on the thermomechanical properties and interfacial fracture for two polyimides, a rigid-rod like BPDA-PDA and a flexible-chain PMDA-ODA. This study is focused on the correlation between material strength and polymeric chain morphology. A strong correlation was observed, with high chain packing order giving rise to strong material strength. Quantitatively, the mechanical strength of PMDA-ODA thin films along the direction tangential to the film plane is about 1/3 of that of BPDA-PDA, and its thermal expansivity 1.5 to 5 times larger. For fracture, the mechanical strength of the polyimide plays a different role. A softer polyimide such as PMDA-ODA will strengthen the confinement exerted by the metal lines with smaller interfacial strain, thereby decreasing the amount of deformation transmitted through the interface into the metal, and shifting the onset of delamination to a higher strain on the entire structure. However, the same softer polyimide layer also induces a larger amount of plastic deformation, leading to fracture of the film at a smaller strain. For a strong metal/polymer interface, the strength of the interfacial bonds is sufficient to hold the interface intact while the polymer near the interface deforms plastically because it is much softer mechanically than the metal. This continues until the deformation energy accumulated in the polymer is sufficient to delaminate the interface. Under this condition, the locus of failure will be determined by the relative fracture toughness of the polymer compared with the interface, which may very well occur in the polymer very close to the interface.

The effect of the heating rate during curing on the thermal expansivity and mechanical properties of poly(p-phenylene biphenyltetracarboximide) (BPDA-PDA) polyimide thin films has been investigated in the range from 3 to 40 μm, which is commonly used for packaging application. Structural characterization was carried out using birefringence and wide-angle x-ray diffraction (WAXD) techniques. The morphology and packing order are found to be strongly influenced by the heating rate and, to a lesser extent, by the film thickness. The themomechanical properties of the polyimide films show an overall variation consistent with the changes in the molecular packing, thus demonstrating a close structure-property correlation. For slow-cure films, the variation of the molecular order is almost independent of film thickness. In contrast, the molecular order for the fast-cured films strongly depends on the thickness. The in-plane chain orientation decreases, but crystallinity increases with increasing film thickness. The heating rate gives rise to an opposite effect on the morphology for thin (∼ 5 μm) and thick films (∼ 38 μm). For thin films, high heating rate yields a high degree of crystallinity and in-plane chain orientation of the polymeric chains, leading to low thermal expansion coefficient (TEC) and high mechanical strength. In contrast, high heating rate for the thicker film gives a low in-plane chain orientation, leading to high TEC and low mechanical strength. The close correlation between morphology and the thermomechanical properties such as Young's modulus, stress-strain relationship, and lateral TEC is demonstrated.

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The paper presents a method for mesostructured cobalt oxide sensor fabrication by the template replication method and immobilization using dielectrophoresis process. The method consists of enriching the mesostructured cobalt oxide particles in a microelectrode gap that drove mesostructured cobalt oxide particles to a high electric field region and then exposed to CO gas. The cobalt oxide sensor has improved sensing performance in carbon monoxide (CO) detection at concentration as low as 10 ppm and a very short recovering time, due to the higher surface area.

This study presents the synthesis of mesostructured ZnO using a template replication method and the fabrication of a carbon monoxide sensor using the synthesized ZnO using the dielectrophoresis process. The mesoporous carbon, CMK-3, was employed for the template and zinc nitrite was used as the precursor for synthesizing the ordered porous ZnO. The mesostructured ZnO was analyzed using X-ray diffraction XRD patterns, scanning electron microscopy, transmission electron microscopy, selected area electron diffraction, and N2 adsorption–desorption isotherms. The XRD patterns indicated that the ZnO exhibited a highly ordered structure after the template was removed. The morphology of the ZnO was randomly oriented and the structure was polycrystalline. The surface area, pore volume, and pore size of the porous ZnO were 61.3 m2 g−1, 0.31 cm3 g−1, and 5.3 nm, respectively. When CO gas was injected, the optimum sensitivities at 250°C were 12.1, 14.6, 18.4, 26.0, and 60% when the CO concentrations were 10, 20, 30, 50, and 70 ppm, respectively. © 2008 The Electrochemical Society. DOI: 10.1149/1.3021044 All rights reserved.

Recent studies on Cu interconnects have shown that interface diffusion between Cu and the cap layer dominates mass transport for electromigration. The kinetics of mass transport by interface diffusion strongly depends on the material and processing of the cap layer. In this series of two papers, we report in Part I the interface and grain-boundary mass transport measured from isothermal stress relaxation in electroplated Cu thin films with and without a passivation layer and in Part II a kinetic model developed to analyze the stress relaxation based on the coupling of grain boundary and interface diffusion. We show that a set of isothermal stress relaxation experiments together with appropriate modeling analysis can be used to evaluate the kinetics of interface and grain-boundary diffusion that correlate to electromigration reliability of Cu interconnects. Thermal stresses in electroplated Cu films with and without passivation, subjected to thermal cycling and isothermal annealing at selected temperatures...

We describe a series of experiments and numerical simulations that were designed to determine the rate of stress-driven diffusion along interfaces in a damascene copper interconnect structure. Wafer curvature experiments were used to measure the rate of stress relaxation in an array of parallel damascene copper lines, which were encapsulated in a dielectric, and passivated with an overlayer of silicon nitride or silicon carbide. The stress relaxation was found to depend strongly on the choice of passivation. Three-dimensional finite element simulations were used to model the experiments, and showed that this behavior is caused by changes in the diffusivity of the interface between the copper lines and the passivation. By fitting the predicted stress relaxation rates to experimental measurements, we have identified the interfaces that contribute to stress relaxation in the structure, and have estimated values for their diffusion coefficients.