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Interfacial Electrochemistry of Metal Nanoparticles Formation on Diamond and Copper Electroplating on Ruthenium Surface

Description: An extremely facile and novel method called spontaneous deposition, to deposit noble metal nanoparticles on a most stable form of carbon (C) i.e. diamond is presented. Nanometer sized particles of such metals as platinum (Pt), palladium (Pd), gold (Au), copper (Cu) and silver (Ag) could be deposited on boron-doped (B-doped) polycrystalline diamond films grown on silicon (Si) substrates, by simply immersing the diamond/Si sample in hydrofluoric acid (HF) solution containing ions of the corresponding metal. The electrons for the reduction of metal ions came from the Si back substrate. The diamond/Si interfacial ohmic contact was of paramount importance to the observation of the spontaneous deposition process. The metal/diamond (M/C) surfaces were investigated using Raman spectroscopy, scanning electron microscopy (SEM), x-ray photoelectron spectroscopy (XPS) and x-ray diffractometry (XRD). The morphology (i.e. size and distribution) of metal nanoparticles deposits could be controlled by adjusting the metal ion concentration, HF concentration and deposition time. XRD data indicate the presence of textured and strained crystal lattices of Pd for different Pd/C morphologies, which seem to influence the electrocatalytic oxidation of formaldehyde (HCHO). The sensitivity of electrocatalytic reactions to surface crystal structure implies that M/C could be fabricated for specific electrocatalytic applications. The research also presents electroplating of Cu on ruthenium (Ru), which a priori is a promising barrier material for Cu interconnects in the sub 0.13 μm generation integrated circuits (ICs). Cu plates on Ru with over 90% efficiency. The electrochemical nucleation and growth studies using the potentiostatic current transient method showed a predominantly progressive nucleation of Cu on Ru. This was also supported by SEM imaging, which showed that continuous thin films of Cu (ca. 400 Å) with excellent conformity could be plated over Ru without dendrite formation. Scotch tape peel tests and SEM on Cu/Ru samples both at room temperature (RT) and ...
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Date: May 2003
Creator: Arunagiri, Tiruchirapalli Natarajan
Partner: UNT Libraries

Interfacial Electrochemistry of Copper and Spectro-Electrochemical Characterization of Oxygen Reduction Reaction

Description: The first part of this dissertation highlights the contents of the electrochemical characterization of Cu and its electroplating on Ru-based substrates. The growth of Ru native oxide does diminish the efficiency of Cu plating on Ru surface. However, the electrochemical formed irreversible Ru hydrate dioxide (RuOxHy) shows better coverage of Cu UPD. The conductive Ru oxides are directly plateable liner materials as potential diffusion barriers for the IC fabrication. The part II of this dissertation demonstrates the development of a new rapid corrosion screening methodology for effective characterization Cu bimetallic corrosion in CMP and post-CMP environments. The corrosion inhibitors and antioxidants were studied in this dissertation. In part III, a new SEC methodology was developed to study the ORR catalysts. This novel SEC cell can offer cheap, rapid optical screening results, which helps the efficient development of a better ORR catalyst. Also, the SEC method is capable for identifying the poisoning of electrocatalysts. Our data show that the RuOxHy processes several outstanding properties of ORR such as high tolerance of sulfation, high kinetic current limitation and low percentage of hydrogen peroxide.
Date: August 2011
Creator: Yu, Kyle Kai-Hung
Partner: UNT Libraries

Cu Electrodeposition on Ru-Ta and Corrosion of Plasma Treated Cu in Post Etch Cleaning Solution

Description: In this work, the possibility of Cu electrodeposition on Ru-Ta alloy thin films is explored. Ru and Ta were sputter deposited on Si substrate with different composition verified by RBS. Four point probe, XRD, TEM and AFM were used to study the properties of Ru-Ta thin films such as sheet resistance, crystallinity, grain size, etc. Cyclic voltammetry is used to study the Cu electrodeposition characteristics on Ru-Ta after various surface pretreatments. The results provide insights on the removal of Ta oxide such that it enables better Cu nucleation and adhesion. Bimetallic corrosion of Cu on modified Ru-Ta surface was studied in CMP related chemicals. In Cu interconnect fabrication process, the making of trenches and vias on low-k dielectric films involves the application of fluorocarbon plasma etch gases. Cu microdots deposited on Ru and Ta substrate were treated by fluorocarbon plasma etch gases such as CF4, CF4+O2, CH2F2, C4F8 and SF6 and investigated by using x-ray photoelectron spectroscopy, contact angle measurement and electrochemical techniques. Micropattern corrosion screening technique was used to measure the corrosion rate of plasma treated Cu. XPS results revealed different surface chemistry on Cu after treating with plasma etching. The fluorine/carbon ratio of the etching gases results in different extent of fluorocarbon polymer residues and affects the cleaning efficiency and Cu corrosion trends.
Date: August 2011
Creator: Sundararaju Meenakshiah Pillai, Karthikeyan
Partner: UNT Libraries

Process Evaluation and Characterization of Tungsten Nitride as a Diffusion Barrier for Copper Interconnect Technology

Description: The integration of copper (Cu) and dielectric materials has been outlined in the International Technology Roadmap for Semiconductors (ITRS) as a critical goal for future microelectronic devices. A necessity toward achieving this goal is the development of diffusion barriers that resolve the Cu and dielectric incompatibility. The focus of this research examines the potential use of tungsten nitride as a diffusion barrier by characterizing the interfacial properties with Cu and evaluating its process capability for industrial use. Tungsten nitride (β-W2N) development has been carried out using a plasma enhanced chemical vapor deposition (PECVD) technique that utilizes tungsten hexafluoride (WF6), nitrogen (N2), hydrogen (H2), and argon (Ar). Two design of experiments (DOE) were performed to optimize the process with respect to film stoichiometry, resistivity and uniformity across a 200 mm diameter Si wafer. Auger depth profiling showed a 2:1 W:N ratio. X-ray diffraction (XRD) showed a broad peak centered on the β-W2N phase. Film resistivity was 270 mohm-cm and film uniformity < 3 %. The step coverage (film thickness variance) across a structured etched dielectric (SiO2, 0.35 mm, 3:1 aspect ratio) was > 44 %. Secondary ion mass spectroscopy (SIMS) measurements showed good barrier performance for W2N between Cu and SiO2 with no intermixing of the Cu and silicon when annealed to 390o C for 3 hours. Cu nucleation behavior and thermal stability on clean and nitrided tungsten foil (WxN = δ-WN and β-W2N phases) have been characterized by Auger electron spectroscopy (AES) and thermal desorption spectroscopy (TDS) under controlled ultra high vacuum (UHV) conditions. At room temperature, the Auger intensity ratio vs. time plots demonstrates layer by layer Cu growth for the clean tungsten (W) surface and three-dimensional nucleation for the nitride overlayer. Auger intensity ratio vs. temperature measurements for the Cu/W system indicates a stable interface up to 1000 ...
Date: August 2005
Creator: Ekstrom, Bradley Mitsuharu
Partner: UNT Libraries

Study of Ruthenium and Ruthenium Oxide's Electrochemical Properties and Application as a Copper Diffusion Barrier

Description: As a very promising material of copper diffusion barrier for next generation microelectronics, Ru has already obtained a considerable attention recently. In this dissertation, we investigated ruthenium and ruthenium oxide electrochemical properties and the application as a copper diffusion barrier. Cu under potential deposition (UPD) on the RuOx formed electrochemically was first observed. Strong binding interaction, manifesting by the observed Cu UPD process, exists between Cu and Ru as well as its conductive ruthenium oxide. Since UPD can be conformally formed on the electrode surface, which enable Ru and RuOx has a potential application in the next generation anode. The [Cl-] and pH dependent experiment were conducted, both of them will affect UPD Cu on Ru oxide. We also found the Cu deposition is thermodynamically favored on RuOx formed electrochemically. We have studied the Ru thin film (5nm) as a copper diffusion barrier. It can successfully block Cu diffusion annealed at 300 oC for 10min under vacuum, and fail at 450 oC. We think the silicidation process at the interface between Ru and Si. PVD Cu/Ru/Si and ECP Cu/Ru/Si were compared each other during copper diffusion study. It was observed that ECP Cu is easy to diffuse through Ru barrier. The function of RuOx in diffusion study on Cu/Ru/Si stack was discussed. In pH 5 Cu2+ solution, Ru and Pt electrochemical behavior were investigated. A sharp difference was observed compared to low pH value. The mechanism in pH 5 Cu2+ solution was interpreted. An interesting compound (posnjakite) was obtained during the electrochemical process. An appropriate formation mechanism was proposed. Also Cu2O was formed in the process. We found oxygen reduction reaction is a key factor to cause this phenomenon.
Date: August 2005
Creator: Zhang, Yibin
Partner: UNT Libraries

Nano-crystallization Inhibition in 5 Nm Ru Film Diffusion Barriers for Advanced Cu-interconnect

Description: As the semiconductor industries are moving beyond 22 nm node technology, the currently used stacked Ta/TaN diffusion barrier including a copper seed will be unable to fulfill the requirements for the future technologies. Due to its low resistivity and ability to perform galvanic copper fill without a seed layer, ruthenium (Ru) has emerged as a potential copper diffusion barrier. However, its crystallization and columnar nanostructure have been the main cause of barrier failures even at low processing temperatures (300 oC -350 oC). In this study, we have proposed and evaluated three different strategies to improve the performance of the ultrathin Ru film as a diffusion barrier for copper. The first study focused on shallow surface plasma irradiation/amorphization and nitridation of 5 nm Ru films. Systematic studies of amorphization and nitrogen incorporation versus sample bias were performed. XPS, XRD and RBS were used to determine the physico-chemical, crystallization and barrier efficiency of the plasma modified Ru barrier. The nitrogen plasma surface irradiation of Ru films at substrate bias voltage of -350 V showed an improved barrier performance up to 400 oC annealing temperatures. The barrier barely started failing at 450 oC due mainly to nitrogen instability. The second study involved only amorphization of the Ru thin film without any nitrogen incorporation. A low energy ion beam irradiation/amorphization on Ru thin film was carried out by using 60 KeV carbon ions with different irradiation doses. The irradiation energy was chosen high enough so that the irradiation ions pass through the whole Ru thin film and stop in the SiO2/Si support substrate. The C-ion fluence of 5×1016 atoms/cm2 at 60 KeV made the Ru film near amorphous without changing its composition. XRD and RBS were used to determine the relationship between crystallization and barrier efficiency of the carbon irradiated Ru barrier. The amorphized ...
Date: December 2013
Creator: Sharma, Bed P.
Partner: UNT Libraries