Ming-Shiann Feng

Investigations of effects of bias polarization and chemical parameters on morphology and filling capability of 130 nm damascene electroplated copper

Through elucidating the effects of current density, cupric ion concentration, bath temperature, and air agitation on plating uniformity and filling capability of copper electroplating, the deposition of copper in an acid copper electrolyte will be illustrated to scale down to the sub-0.13 μm features with uniform plating, which is required by chemical mechanical polishing in current damascene techniques. In order to achieve the defect-free filling in sub-0.13 μm vias and trenches, the electrolyte must be composed of proper amounts of cupric ions, sulfuric acid, chloride ions, wetting agent, and filling promoter. The supplied current controlled at a lower current density, agitation acceded to the electroplating process were found as further keys. In the electrolyte, the filling promoter was consisted essentially of thiazole derivatives with benzyl groups and amino-group (−NH2) offering sufficient inhibition on copper depositing and selective inhibition gradient. Moreover, a lower resistivity film and highe...

Characterization of additive systems for damascene Cu electroplating by the superfilling profile monitor

Gap-filling dynamics of several different species of additives for copper electrodeposition was investigated by monitoring the cross section of a partially filled copper profile on the scanning electron microscopy photo. The filling ration Δy/Δx between “bottom-up” with “sidewall shift” was found to be proportional to the filling power of additives. The adsorption-diffusion model combined with cathode polarization and cyclic voltammetric stripping measurements was employed to explain the attribution of additives in superfilling phenomena. The superfilling dynamics was achieved under behavior of additives providing selective inhibition gradient within the damascene feature. By means of those analyses, we have optimized the appropriate amount of additives and achieved the superfilling performance for 0.15 μm vias with aspect ratio 6 by an acid-copper electrolyte with polyethylene glycol, C1−, and 2-mercaptopyridine (2-MP). Due to the additive of 2-MP, chelate formed which enhanced adsorption ability on Cu0 ...

Pattern Effects on Planarization Efficiency of Cu Electropolishing.

Cu electropolishing has recently been introduced to replace Cu-chemical mechanical polishing (CMP). In this work, we found that when the space width is fixed, the planarization efficiency (PE) decreases with increasing line width. When line width is fixed, the PE value decreases as space width increases. Furthermore, the average roughness (Ra) of blanket Cu films decreases as polishing time increases. After electropolishing, the resistivity of polished films is not obviously changed.

Chemical-mechanical polishing of low-dielectric-constant spin-on-glasses: film chemistries, slurry formulation and polish selectivity

Abstract Alkyl siloxane-based low-dielectric-constant (low-k) spin-on-glass (SOG) thin films with varying amounts of organic content were subjected to polishing experiments using silica- and ZrO 2 -based slurries with a variety of additives. As the amount of organic content in SOG increases, the chemical-mechanical polishing (CMP) removal rate decreases with silica-based potassium hydroxide-added slurry. On the other hand, zirconia-based slurry resulted in higher removal rates for both SOG (>400 nm/min) and thermal oxide and an adjustment in polish selectivity (related to thermal oxide) ranging from 1.2 to 9.1 can be achieved by adding various amounts of tetra-alkyl substituted ammonium hydroxide. Post-CMP materials characterization by Fourier transform infrared spectroscopy (FTIR) and atomic force microscopy (AFM) shows the chemical stability and CMP compatibility of SOG thin films.

Wetting effect on gap filling submicron damascene by an electrolyte free of levelers

By using an acid–copper electrolyte without levelers and brighteners, we achieved defect-free filling of 0.13 μm vias with aspect ratio 8:1. This novel electrolyte consisted of copper sulfate (CuSO4⋅5H2O), sulfuric acid (H2SO4), chloride ions (Cl−), and two different average molecular weights of polyethylene glycols (PEG). The smaller-molecular-weight PEG200, with higher diffusion ability, was identified to enhance cupric ions transporting into deep features and was treated as a bottom-up filling promoter. The larger-molecular-weight PEG2000, with higher polarization resistance, provided enough inhibition effect on cupric ion reduction to obtain denser and small-grained deposits in a lower-current-density region, which benefits the filling capability in submicron features. In addition, adding PEG2000 could reduce the interfacial energy between the electrolyte and the opening of trenches/vias to enhance the filling capability.

A ULSI shallow trench isolation process through the integration of multilayered dielectric process and chemical-mechanical planarization

Abstract A multilayer thin film structure (SiO2/SiNx/SiO2) with a one-step chemical–mechanical polish (CMP) process is developed for shallow trench filling and planarization for ULSI devices in the quarter micron regime. By fine-tuning the plasma-enhanced chemical vapor deposition (PECVD) conditions we successfully modified the stoichiometry and other characteristics of the as-deposited SiNx and oxide films. As these film characteristics are changed, the CMP removal rate selectivity between sacrificial oxide and nitride stopper layer can also be adjusted. Correspondingly, the CMP process latitude for shallow trench isolation in 0.25 μm memory devices can be broadened by sequentially depositing multilayered oxide and nitride films with adjustable characteristics and CMP removal rates. Dishing-free wide trench areas with excellent planarity can be achieved through the integration of the proposed multilayered PECVD oxide/nitride scheme and the one-step CMP process.

Microleveling mechanisms and applications of electropolishing on planarization of copper metallization

The optimization of Cu electropolishing processes was explored to be in the mass-transfer-limited plateau with a stable limiting current density and in concentrated phosphoric acid by elucidating surface morphologies and potentiodynamic polarization. After electropolishing, the average roughness of polished surfaces achieved to 1.1 nm. Both the x-ray photoelectron spectroscopy and the electrochemical impedance spectroscopy suggest that the existence of a passivation film on the polished surface contributed to the microleveling effect of Cu electropolishing. Moreover, this passivation layer also induces an application of end point in electropolishing.

Investigations of pulse current electrodeposition for damascene copper metals

The influence of current density, duty cycle, and frequency of the applied pulse current on film qualities of electroplated copper was discussed. With various filled damascene structures, the corresponding filling power was optimized in a range of pulse current frequency. The optimized pulse current plating in conjunction with a leveler-free electrolyte resulted in a defect-free filling in approximate 100 nm damascenes and reduced the resistivity of Cu deposits.

Palladium seeding on the tantalum-insulated silicon oxide film by plasma immersion ion implantation for the growth of electroless copper

Abstract The major aim of this study was to combine the techniques of using plasma immersion ion implantation (PIII) and electroless plating to implant Pd onto a Ta diffusion barrier layer as catalyst for the electroless Cu plating in order to accomplish the ULSI interconnection metallization. In our study, it has been demonstrated that the accelerating Pd + ions by 2 kV pulsed negative bias voltages produce an amorphous Pd layer on β-Ta. The outermost Pd forms an oxide to the chemisorption of oxygen on Pd in air, while innermost Pd does not react with β-Ta, but instead remains in the form of metallic Pd. The Pd doses in the range of 5.7×10 14 and 8.6×10 14 cm −2 invokes an excellent catalytic effect on the electroless Cu plating. This results in an extraordinary ability for filling the submicron holes for gaining high quality electroless plated Cu interconnects, and thus qualifies for the traditional wet activation by SnCl 2 and PdCl 2 solutions.

EFFECTS OF O2- AND N2O-PLASMA TREATMENTS ON PROPERTIES OF PLASMA-ENHANCED-CHEMICAL-VAPOR-DEPOSITION TETRAETHYLORTHOSILICATE OXIDE

The high quality silicon oxide films were prepared by plasma-enhanced chemical vapor deposition (PECVD) using tetraethylorthosilicate (TEOS)-oxygen based chemistry. The O2- or N2O-plasma treatments were performed on the as-deposited films as an attempt to improve the properties of the TEOS oxide films. TEOS oxide film deposited at lower pressure had lower Si–OH content, less carbon impurity, and flatter surface, and hence had better electrical properties. Both O2- and N2O-plasma would decrease the oxygen content of the oxide film, which led the composition of the film to deviate from the stoichiometric SiO2. The O2-plasma treatment did not show the encouraging effect on the chemical structure and electrical properties of the TEOS oxide films. In contrast, the N2O-plasma treatment could be a promising means to improve the breakdown field and leakage current density of the TEOS oxide films, which was accomplished by the N2O-plasma effect to facilitate the passivation of dangling bonds, linking reaction of Si–OH bonds, nitridation reaction and densification of the amorphous silicon oxide network.