Porous methylsilsesquioxane (p-MSQ) films (JSR LKD 5109) were treated withalkyldimethylmonochlorosilanes having chain lengths of one, four, and eightcarbon atoms dissolved in supercritical carbon dioxide at 150-300 atm and50-60°C to repair oxygen ashing damage. Fourier transform infrared (FTIR)spectroscopy showed that trimethylchlorosilane (TMCS),butyldimethylchlorosilane (BDMCS), and octyldimethylchlorosilane (ODMCS)reacted with silanol groups on the surfaces of the pores producing covalentSi-O-Si bonds. Selfcondensation between alkylsilanols produced a residue onthe surface, which was partially removed using a pure scCO2rinse. The hydrophobicity of the blanket p-MSQ surface was recovered aftersilylation treatment as shown by contact angles >85°. The initialdielectric constant of 2.4 ± 0.1 increased to 3.5 ± 0.1 after oxygen plasmaashing and was reduced to 2.6 ± 0.1 by TMCS, 2.8 ± 0.1 by BDMCS, and 3.2 byODMCS.

Optical waveguides for three-dimensionally stacked chip fabricationtechnologies, in which optical connection between layers plays a centralrole, are described. CMOS-compatible approaches to optical via and waveguidefabrication are addressed. Detailed modeling is used for design optimizationand also addresses how manufacturing variations from ideal design may affectdevice performance.

Textural evolution of Cu interconnects having a different line width wasinvestigated after annealing. Texture was measured on the surface of Cuinterconnects using EBSD (electron backscattered diffraction) techniquesincluding GBCD (grain boundary character distribution). To analyze arelationship between the stress distribution and textural evolution in thesamples investigated, the micro stresses were calculated for the differentline width at 200°C using FEM (finite element modeling). In thisinvestigation, it was found that the inhomogeneity of stress distribution inCu interconnects is an important factor is necessary for understandingtextural transformation after annealing. A new interpretation of texturalevolution in damascene interconnects lines after annealing is suggested,based on the state of stress and the growth mechanisms of Cuelectrodeposits.

The effect of moisture and aqueous solution chemistry on the rate of crackgrowth in lithographically patterned arrays of copper and low dielectricconstant (LKD) materials is reported. Crack growth in the directionorthogonal to the features is demonstrated to fail at significantlyincreased loads compared to parallel cracking. Decreasing feature width isalso shown to increase the structures resistance to fracture, particularlyat reduced loads. The chemical interactions and mechanisms of energydissipation are discussed.

In this work, the adhesion of CVD dielectric caps to ULK MSQ spin-ondielectric materials with k values of 2.2 and 2.0, and a ULK CVD materialwith a k value of 2.7 is presented. A substantial improvement in capadhesion to both the k2.2 ULK MSQ and the k2.7 ULK CVD material isdemonstrated. The improvement is obtained using a low-k CVD glue materialbetween the ULK dielectric and the subsequent cap material and/or byoptimizing the CVD cap film deposition. Four-point bend measurement ofadhesion strength is used to quantify the improvement in interface adhesion.The improvement in CVD cap adhesion is demonstrated to be strongly dependentupon both the glue layer film and the cap deposition conditions. Whileoptimization of the CVD cap materials results in adequate adhesion for thek2.2 ULK MSQ, these improvements are demonstrated not to extend to the k2.0ULK MSQ film.

This work is aimed at understanding the nature of the interactions betweenmetal interconnects and nanoporous dielectrics in integrated circuits.Electrical testing of MIS capacitors is used to assess Cu diffusion andcharge injection in the dielectric in the presence of an electric field. Wehave found that surface modification of nanoporous silica reveals theimportance of chemically bound or adsorbed water species in the dielectricand how they trigger metal diffusion. We propose that a combination ofmoisture-related species in the dielectric and interfacial oxygen oxidizeCu. The copper oxide acts as a source for Cu ions available for diffusion. Aquantitative analysis of Cu drift in nanoporous dielectrics that shows theimportance of surface chemistry is presented and the mechanism of metaldiffusion and charge injection in nanoporous dielectrics is discussed.

Numerical simulations of thermal stresses in copper interconnect and low-κdielectric systems are carried out. The analyses include two- andthree-dimensional finite element modeling of the interconnect structure.Various combinations of metal, oxide and polymer-based low-κ dielectricschemes are considered in the simulation. The evolution of stresses anddeformation pattern in copper, barrier layers, and the dielectrics arecritically assessed.

Cross-section nano-indentation is a technique that consists of cleaving awafer, indenting behind the stack on the side surface causing delamination,and measuring the delaminated area in an optical microscope. It is shown tobe a reliable rapid technique for adhesion evaluation and processoptimization of the SiO2/barrier/copper stack.

Ternary W-Si-N thin films have been reactively sputter-deposited from aW5Si3 target at different nitrogen partial pressures. The composition hasbeen determined by 2.2 MeV4He+ beam, the structure byx-ray diffraction and transmission electron microscope, the chemical bondsby Fourier transform - infrared spectroscopy and the surface morphology byscanning electron microscopy. Electrical resistivity was measured by fourpoint probe technique on the as grown films. The film as-deposited isamorphous with the Si/W ratio increasing from about 0.1 up to 0.55 with thenitrogen content going from 0 to 60 at%. The heat treatments up to 980 °Cinduce a loss of nitrogen in the nitrogen rich samples. Segregation ofmetallic tungsten occurs in the sample with low nitrogen content (W58Si21N21). Samples with high nitrogencontent preserve the amorphous structure, despite of the precipitation of amore ordered phase inferred by FT-IR absorbance spectrum of the layertreated at highest temperature. The surface morphology depends upon thenitrogen content; the loss of nitrogen induces the formation of blisteringand in the most nitrogen rich sample the formation of holes. Electricalresistivity preliminary results on the as grown layers range between 500 and4750 μωcm passing from the lowest to the highest N concentration.

A process oriented approach is demonstrated for modeling the stressevolution during the entire back end process flow. No ad hoc assumptions regarding stress states are made for layerdeposition and etching. Intrinsic stresses from material formation, thermalmismatch stresses from temperature ramps, stress relaxation due to viscousdeformation, and stress profile redistribution upon deposition and etchingare all considered at each process. Parametric studies are carried out toexamine the effects of viscous flow, material selection and layoutvariations. It is found that the viscous flow of the passivation anddielectric materials have large impact on stress evolution. A TCAD assisteddesign approach is suggested for lowering stress levels of critical stresscomponents. The implications of the stress modeling results on reliabilityissues like stress-triggered void formation are discussed.

The thermal stability and electrical resistivity of Ag(Al) alloy thin filmson SiO2 are investigated and compared to pure Ag thin films byperforming various analyses: Rutherford backscattering spectrometry (RBS),X-ray diffractometry (XRD), transmission electron microscopy (TEM), andfour-point probe. The susceptibility to agglomeration of Ag on SiO2 layer is a drawback of Ag metallization. Ag(Al) thinfilms show good thermal stability on SiO2 layer without anydiffusion barrier. The films are stable up to 600 °C for 1 hour in vacuum.Electrical resistivity of as-deposited Ag (5 at % Al) thin film is slightlyhigher than that of pure Ag thin film. However, the resistivity of Ag(Al)samples annealed at high temperatures (up to 600 °C for 1 hour in vacuum)remains constant due to the improvement of thermal stability (largereduction of agglomeration). This finding can impact metallization for thinfilm transistors (TFT) for displays, including flexible displays, andhigh-speed electronics due to lower resistivity value compared to Cu thinfilm.

Free-standing Cu- and Ni-line patterns with varying line dimensions in therange of a few micrometers were manufactured by means of electrodepositionthrough a lithographically prepared mask. XRD studies revealed for Cu-linesa pronounced influence of the pattern geometry on crystallographic textureand peak broadening. Information on the strain distribution withinindividual Cu-lines was obtained from FEM.

The interactions of sputter-deposited ruthenium with organosilicate glass(OSG) at 300 K have been studied by x-ray photoelectron spectroscopy (XPS)for Ru coverages from ∼ 0.1 monolayer to several monolayers, using in-situsample transfer between the deposition and analysis chambers. The resultsindicate Stranski-Krastanov (SK) type growth, with the completion of thefirst layer of Ru at an average thickness corresponding to 1 monolayeraverage coverage. Ru(0) is the only electronic state present. XPS core levelspectra indicate weak chemical interactions between Ru and the substrate. Aless pronounced tendency towards SK growth was observed for Ru deposition onparylene. Deposition of Ru on OSG followed by electroless deposition of Curesulted in the formation of a shiny copper film that failed the Scotch Tapetest. Results indicate failure mainly at the Ru/OSG interface.

The increasing demand for faster and more reliable integrated circuits (ICs)has promoted the integration of Copper-based metallization. Electroplated Cufilms demonstrate a microstructural transition at room temperature, known asself annealing. In this paper we intend to investigate the annealingbehavior of electroplated Cu films grown on a seed Cu layer on top of thebarrier layers over a single crystal silicon substrate. All the samples wereundergone through a multistep annealing process. Grazing incident x-raydiffraction pattern shows stronger x-ray reflections from Cu (111) and (220)planes but weaker reflections from (200), (311) and (222) planes in all theelectroplated Cu samples. Transmission electron microscopy was performed onthe cross section of the samples and the diffraction pattern showed thecrystalline behavior of both seed layer and electroplated Cu.Nanoindentation was performed on all the samples using the continuousstiffness measurement (CSM) technique and it was found that the elasticmodulus varies from 110 to 130 GPa while the hardness varies from 1 to 1.6GPa depending on the annealing conditions. The tribological properties ofall the copper films were also measured using the Bench Top CMP tester.Subsequently, Nanoindentation was performed on the samples after polishingthe top surface in order to investigate the work hardening and an increasein hardness and modulus was observed. Finite Element Modeling was performedin order to investigate the stress behavior during nanoindentation.

We have developed platinum (Pt) deposition and chlorine-based Reactive IonEtch (RIE) processes that are needed to deposit, pattern and embedelectrodes deep within a MEMS process flow. Various combinations ofchlorinebased gases were tested to find the optimum gas mixture for RIE. A1: 0.4 mixture ratio of pure chlorine to argon and 100-150 Watts of RFmicrowave power were found to be optimum conditions for the RIE of platinummetal. The addition of argon gas to chlorine was found to contribute to theanisotropic etching of platinum, obtaining vertical shaped sidewallpatterns. A simple model of the platinum etching mechanism is proposed.Following the plasma enhanced formation of platinum and chlorine ions,volatile products of platinum chlorides were formed and driven away atelevated temperature. As a demonstration of our RIE process, micron-sizedplatinum patterns with vertical sidewalls were fabricated. Etch chemistrywas investigated using ToF SIMS analysis. This etch technique will be usefulto device developers intending to use the unique properties of platinummetal as an electrode that is deeply embedded within a MEMS processflow.

Pulsed metalorganic chemical vapor deposition (MOCVD) of conformal copperseed layers, for the electrodeposition Cu films, has been achieved by analternating supply of a Cu(I) source and H2 reactant at thedeposition temperatures of 50 - 100°C. The Cu thickness increasedproportionally to the number of cycle, and the growth rate was in the rangeof 3.5 to 8.2 A /cycle, showing the ability to control the nano-scalethickness. As-deposited films show highly smooth surfaces even for more than100nm. In addition, about a 90% step coverage was obtained inside trenches,with an aspect ratio greater than 30:1. H2, introduced as areactant gas, can play an active role in achieving highly conformalcoatings, with increased grain sizes.

Copper films were prepared at room temperature under a Cu(hfac)2-Ar-H2 atmosphere in order toobtainmetallized plastics by using ECR-MOCVD (Electron Cyclotron Resonance MetalOrganicChemical Vapor Deposition) coupled with a DC bias system. Structuralanalysis of the films byECR showed that fine copper grains were embedded inan amorphous plastic matrix with goodadherence. Considering the AES resultof the film prepared by ECR-CVD, we construe that thecopper film ischemically bonded with a plastic substrate. The delamination forcedetermined bythe nano-scratch tester® showed in the range from 10 to20mN.

The application of porous low-k interlayer dielectrics is needed forreducing the parasitical capacitance, especially at 65-nm node and beyond.The understanding of process-induced modifications to material properties iscrucial for a successful integration of these low-k dielectrics. The dryetching processes of porous low-k materials are important modules in ULSIfabrication. In this study, the interaction between MSQ-based JSR LKD-5109films (shown by PALS to have interconnected 2.8 nm size pores) with CF4/O2 plasma has been investigated. Various ratios of O2 content were designed to characterize its effects on theetch rate, formation of polymerization layer, and properties of the LKD-5109film. Composition analysis was conducted by SIMS and FTIR. Moistureabsorption and fluorine diffusion into low-k films after etch process areobserved, along with carbon depletion near the surface region. The influenceof etching chemistries on the morphological characteristics of thin Tabarrier layers (8-nm in thickness) deposited on etched low-k films werefurther investigated by SEM, and it is found that oxygen concentration hassignificant influences on the morphological characteristics of thin Tabarriers.

Wafer-level three-dimensional (3D) integration as an emerging architecturefor future chips offers high interconnect performance by reducing delays ofglobal interconnects and high functionality with heterogeneous integrationof materials, devices, and signals. Various 3D technology platforms havebeen investigated, with different combinations of alternative alignment,bonding, thinning and inter-wafer interconnection technologies. Precisealignment on the wafer level is one of the key challenges affecting theperformance of the 3D interconnects. After a brief overview of thewafer-level 3D technology platforms, this paper focuses on waferto-waferalignment fundamentals. Various alignment methods are reviewed. A higheremphasis lies on the analysis of the alignment accuracy. In addition to thealignment accuracy achieved prior to bonding, the impacts of wafer bondingand subsequent wafer thinning will be discussed.

Increasing the elastic modulus and hardness of low K films is one of the keychallenges towards integration of these materials into future integratedcircuits. Several approaches are explored for increasing the hardness ofcarbon doped oxide (CDO) dielectrics. Several low K precursors and theirmixtures specifically chosen to enhance the hardness (H) and modulus (E) ofCDO films through chemically induced cross-linking. Composition and FTIRmeasurements suggest the presence of C-C and C-Si cross-linking withconcurrent observation of improved film hardness and modulus at relativelylow deposition temperatures. Films deposited at 373°C usingdiethoxy-methyl-oxiranyl have a hardness and modulus of 2.5 GPa and 18.1 GParespectively. Films deposited at 180°C using tetramethylcyclotetrasiloxane(TMCTS) and 25% hardener have hardness and modulus of 1.5 GPa and 9.4 GPa,respectively. These film properties are significantly higher than thoseobserved for TMCTS alone under similar deposition conditions. Based on theseresults a low temperature process with 25% hardener and 75% TMCTS combinedwith a porogen was used to produce a porous film with a k<2.5 and ahardness of 0.72GPa.