Copper electrodeposition processes for filling metallized through-hole (TH) and through-silicon v... more Copper electrodeposition processes for filling metallized through-hole (TH) and through-silicon vias (TSV) depend on spatially selective breakdown of a co-adsorbed polyether-chloride adlayer within the recessed surface features. In this work, a co-adsorption-dependent suppression model that has previously captured experimental observations of localized Cu deposition in TSV is used to explore filling of TH features. Simulations of potentiodynamic and galvanostatic TH filling are presented. An appropriate applied potential or current localizes deposition to the middle of the TH. Subsequent deposition proceeds most rapidly in the radial direction leading to sidewall impingement at the via center creating two blind vias. The growth front then evolves primarily toward the two via openings to completely fill the TH in a manner analogous to TSV filling. Applied potentials, or currents, that are overly reducing result in metal ion depletion within the via and void formation. Simulations in larger TH features (i.e., diameter = 85 μm instead of 10 μm) indicate that lateral diffusional gradients within the via can lead to fluctuations between active and passive deposition along the metal/electrolyte interface.
The manufacturing of semiconductor devices involves electrodeposition of copper interconnects fro... more The manufacturing of semiconductor devices involves electrodeposition of copper interconnects from additive containing electrolytes. The process depends on additives that affect the local deposition rate to yield void-free superconformal or bottom–up filling of trenches and vias. Useful quantitative surfactant conservation models are available for describing the filling of high aspect ratio features ranging from nanometers (on-chip wiring) to micrometers (through-silicon-vias) to millimeters (printed circuit boards). This includes the curvature enhanced adsorbate coverage (CEAC) model as well as the additive derived S-shaped negative differential resistance (S-NDR) description of film growth and feature filling. Nonetheless, much remains to be known about the operational limits of these constructs as well as the molecular nature of the competitive, co-adsorption dynamics of the additives and their impact on metal deposition. This lecture will detail recent experiments that reveal th...
This work demonstrates void-free cobalt filling of 56 μm tall, annular Through Silicon Vias (TSVs... more This work demonstrates void-free cobalt filling of 56 μm tall, annular Through Silicon Vias (TSVs) using a mechanism that couples suppression breakdown and surface topography to achieve controlled bottom-up deposition. The chemistry, a Watts electrolyte containing a dilute suppressing additive, and processes are described. This work extends understanding and application of the additive-derived S-shaped Negative Differential Resistance (S-NDR) mechanism, including previous demonstrations of superconformal filling of TSVs with nickel, copper, zinc and gold.
Superconformal Au deposition is demonstrated in a Na 3 Au(SO 3) 2 + Na 2 SO 3 electrolyte using B... more Superconformal Au deposition is demonstrated in a Na 3 Au(SO 3) 2 + Na 2 SO 3 electrolyte using Bi species to catalyze the reduction of Au(SO 3) 2 3−. Micromolar additions of Bi 3+ to the sulfite-based electrolyte accelerate the reduction of Au(SO 3) 2 3− as shown by hysteretic voltammetry and rising chronoamperometric transients. Superconformal feature filling is observed over a defined range of Bi 3+ concentration, potential and hydrodynamics. Over a more limited parameter range, approximately −0.9 V to −0.95 V, void-free, bottom-up filling of Damascene trenches is achieved. Furthermore, in the presence of significant convection the bottom-up filling is accompanied by passivation of the free surface. Bottom-up feature filling is characterized by a counterintuitive dependence of the free surface reactivity on the available flux of the Bi 3+ accelerator species suggestive of an unusual coupling between hydrodynamic transport, shear and interfacial chemistry.
Bottom-up metal deposition arising from variation of adsorbate coverage can be strongly impacted ... more Bottom-up metal deposition arising from variation of adsorbate coverage can be strongly impacted by modest variation of local concentrations and potential associated with deposition in other features. As a result, bottom-up copper filling of fully metallized features in suppressor-based electrolytes can be made to occur in all, none, or only a subset of recessed features on a substrate. Furthermore, and to the greater detriment of uniformity, localized deposition can continue over filled features, further retarding deposition in still unfilled features. In contrast, accelerator-based bottom-up gold deposition, as well as copper filling using different concentrations of the suppressing additives that yielded inhomogeneity, exhibit not only excellent uniformity during feature filling but also self-termination of deposition at a controllable depth within the filling features. This presentation will discuss the origins of these different behaviors in light of the underlying filling mech...
Superconformal electrodeposition processes enable void- and seam-free metal filling of high aspec... more Superconformal electrodeposition processes enable void- and seam-free metal filling of high aspect ratio features from tens of nanometers to hundreds of micrometers in size. There are two known mechanisms underlying such processes: Curvature Enhanced Accelerator Coverage (CEAC) and S-shaped Negative Differential Resistance (S-NDR). Voltammetric measurements on planar substrates can quantify kinetics in models based on both mechanisms, enabling accurate, a-priori prediction of filling from a particular electrolyte in a particular size and aspect ratio feature. I will summarize the chemistries and associated mechanisms for superconformal Cu, Ag, Au, Co, and Ni feature filling, including experiment and model predictions, for processes that are drop-in compatible with those presently used for fabrication of Cu damascene and through silicon via interconnects.
Superconformal electrodeposition processes enable void- and seam-free metal filling of high aspec... more Superconformal electrodeposition processes enable void- and seam-free metal filling of high aspect ratio features from tens of nanometers to hundreds of micrometers in size. There are two known mechanisms underlying such processes: Curvature Enhanced Accelerator Coverage (CEAC) and S-shaped Negative Differential Resistance (S-NDR). Voltammetric measurements on planar substrates can quantify kinetics in models based on both mechanisms, enabling accurate, a-priori prediction of filling from a particular electrolyte in a particular size and aspect ratio feature. I will summarize the chemistries and associated mechanisms for superconformal Cu, Ag, Au, Co, and Ni feature filling, including experiment and model predictions, for processes that are drop-in compatible with those presently used for fabrication of Cu damascene and through silicon via interconnects.
D. JOSELL, L. BENDERSKY, NIST-To enhance the maximum energy product of exchanged coupled hard/sof... more D. JOSELL, L. BENDERSKY, NIST-To enhance the maximum energy product of exchanged coupled hard/soft phase nanocomposite, we need to establish the parameters that govern the exchange coupling interaction (ECI). To this end, on single chips, up to a hundred thin film bilayer samples were grown by e-beam evaporation varying composition and soft layer thicknesses (t s). Magnetic hysteresis loops were taken by magneto-optical Kerr effect measurements. The simultaneous analysis of the samples allows us to delineate subtle variations of the exchange coupling behavior. We will show examples of studies of CoPt/(Fe, Co or Ni) and SmCo/(Fe, Co or Ni) libraries. We characterized ECI by measuring the variations of the coupling length (λ) and the nucleation field (H N) on various magnetic parameters, t s , and interface conditions. The trend indicates that the dominant factors determining λ and H N are the hard layer magnetic constants and the saturation magnetization of the soft layer. We will also discuss the role played by other magnetic parameters. The results allow us to predict the behavior of coupled hard/soft magnetic layers in general. Supported by ONR MURI N00014-05-1-0497.
This paper details the use of scanning photocurrent microscopy to examine localized current colle... more This paper details the use of scanning photocurrent microscopy to examine localized current collection efficiency of thin-film photovoltaic devices with in-plane patterning at a submicrometer length scale. The devices are based upon two interdigitated comb electrodes at the micrometer length scale prepatterned on a substrate, with CdSe electrodeposited on one electrode and CdTe deposited over the entire surface of the resulting structure by pulsed laser deposition. Photocurrent maps provide information on what limits the performance of the windowless CdSe/CdTe thin-film photovoltaic devices, revealing "dead zones" particularly above the electrodes contacting the CdTe which is interpreted as recombination over the back contact. Additionally, the impact of ammonium sulfide passivation is examined, which enables device efficiency to reach 4.3% under simulated air mass 1.5 illumination.
Adsorbates based on a number of P-block elements are known to accelerate Au deposition from sulfi... more Adsorbates based on a number of P-block elements are known to accelerate Au deposition from sulfite as well as cyanide electrolytes. However, the nature of deposits from an electrolyte-additive system, and from the different electrolyte-additive systems, varies substantially. Optically smooth planar deposits coupled with superconformal filling of patterned features such as trenches and vias can be obtained from sulfite-Pb (and cyanide-Pb) electrolytes. With other additives superconformal feature filling is also observed, but it manifests with a geometry more akin to the extreme bottom-up filling seen during Cu filling of through silicon vias. Perhaps most interesting, deposits ranging from optically smooth surfaces to dense arrays of uniformly oriented nanowires can be obtained from sulfite-Tl electrolytes through adjustment of only the applied potential. I will discuss how electroanalytical measurements, coupled with mechanistic models, can help us understand, and in some cases pre...
Gold electrodeposition was studied in a sulfite electrolyte to which micromolar concentrations of... more Gold electrodeposition was studied in a sulfite electrolyte to which micromolar concentrations of Tl 2 SO 4 were added. Hysteresis and a regime of negative differential resistance (NDR) evident in electroanalytical measurements are correlated with deposit morphology and interpreted through measurements of thallium underpotential deposition (upd). Deposit morphologies range from specular surfaces to highly faceted dendrite-like grains of moderate aspect ratio and, for potentials within the NDR region, sub-50 nm diameter, high aspect ratio 110 oriented single crystal nanowires. The nanowires exhibit an epitaxial relationship to the substrate that permits one step fabrication of surfaces densely covered with high aspect ratio nanowires having controlled orientations. The NDR and nanowires are a consequence of the non-monotonic relationship between Tl coverage and growth velocity; at low coverage Tl accelerates Au deposition while at higher coverage it inhibits deposition. Immiscibility of the Tl and Au supports ongoing surface segregation during area expansion that accompanies nanowire growth leading to greater dilution of the additive coverage and more rapid growth at the nanowire tips, while the sidewalls remain passivated by a saturated Tl coverage.
Copper electrodeposition processes for filling metallized through-hole (TH) and through-silicon v... more Copper electrodeposition processes for filling metallized through-hole (TH) and through-silicon vias (TSV) depend on spatially selective breakdown of a co-adsorbed polyether-chloride adlayer within the recessed surface features. In this work, a co-adsorption-dependent suppression model that has previously captured experimental observations of localized Cu deposition in TSV is used to explore filling of TH features. Simulations of potentiodynamic and galvanostatic TH filling are presented. An appropriate applied potential or current localizes deposition to the middle of the TH. Subsequent deposition proceeds most rapidly in the radial direction leading to sidewall impingement at the via center creating two blind vias. The growth front then evolves primarily toward the two via openings to completely fill the TH in a manner analogous to TSV filling. Applied potentials, or currents, that are overly reducing result in metal ion depletion within the via and void formation. Simulations in larger TH features (i.e., diameter = 85 μm instead of 10 μm) indicate that lateral diffusional gradients within the via can lead to fluctuations between active and passive deposition along the metal/electrolyte interface.
The manufacturing of semiconductor devices involves electrodeposition of copper interconnects fro... more The manufacturing of semiconductor devices involves electrodeposition of copper interconnects from additive containing electrolytes. The process depends on additives that affect the local deposition rate to yield void-free superconformal or bottom–up filling of trenches and vias. Useful quantitative surfactant conservation models are available for describing the filling of high aspect ratio features ranging from nanometers (on-chip wiring) to micrometers (through-silicon-vias) to millimeters (printed circuit boards). This includes the curvature enhanced adsorbate coverage (CEAC) model as well as the additive derived S-shaped negative differential resistance (S-NDR) description of film growth and feature filling. Nonetheless, much remains to be known about the operational limits of these constructs as well as the molecular nature of the competitive, co-adsorption dynamics of the additives and their impact on metal deposition. This lecture will detail recent experiments that reveal th...
This work demonstrates void-free cobalt filling of 56 μm tall, annular Through Silicon Vias (TSVs... more This work demonstrates void-free cobalt filling of 56 μm tall, annular Through Silicon Vias (TSVs) using a mechanism that couples suppression breakdown and surface topography to achieve controlled bottom-up deposition. The chemistry, a Watts electrolyte containing a dilute suppressing additive, and processes are described. This work extends understanding and application of the additive-derived S-shaped Negative Differential Resistance (S-NDR) mechanism, including previous demonstrations of superconformal filling of TSVs with nickel, copper, zinc and gold.
Superconformal Au deposition is demonstrated in a Na 3 Au(SO 3) 2 + Na 2 SO 3 electrolyte using B... more Superconformal Au deposition is demonstrated in a Na 3 Au(SO 3) 2 + Na 2 SO 3 electrolyte using Bi species to catalyze the reduction of Au(SO 3) 2 3−. Micromolar additions of Bi 3+ to the sulfite-based electrolyte accelerate the reduction of Au(SO 3) 2 3− as shown by hysteretic voltammetry and rising chronoamperometric transients. Superconformal feature filling is observed over a defined range of Bi 3+ concentration, potential and hydrodynamics. Over a more limited parameter range, approximately −0.9 V to −0.95 V, void-free, bottom-up filling of Damascene trenches is achieved. Furthermore, in the presence of significant convection the bottom-up filling is accompanied by passivation of the free surface. Bottom-up feature filling is characterized by a counterintuitive dependence of the free surface reactivity on the available flux of the Bi 3+ accelerator species suggestive of an unusual coupling between hydrodynamic transport, shear and interfacial chemistry.
Bottom-up metal deposition arising from variation of adsorbate coverage can be strongly impacted ... more Bottom-up metal deposition arising from variation of adsorbate coverage can be strongly impacted by modest variation of local concentrations and potential associated with deposition in other features. As a result, bottom-up copper filling of fully metallized features in suppressor-based electrolytes can be made to occur in all, none, or only a subset of recessed features on a substrate. Furthermore, and to the greater detriment of uniformity, localized deposition can continue over filled features, further retarding deposition in still unfilled features. In contrast, accelerator-based bottom-up gold deposition, as well as copper filling using different concentrations of the suppressing additives that yielded inhomogeneity, exhibit not only excellent uniformity during feature filling but also self-termination of deposition at a controllable depth within the filling features. This presentation will discuss the origins of these different behaviors in light of the underlying filling mech...
Superconformal electrodeposition processes enable void- and seam-free metal filling of high aspec... more Superconformal electrodeposition processes enable void- and seam-free metal filling of high aspect ratio features from tens of nanometers to hundreds of micrometers in size. There are two known mechanisms underlying such processes: Curvature Enhanced Accelerator Coverage (CEAC) and S-shaped Negative Differential Resistance (S-NDR). Voltammetric measurements on planar substrates can quantify kinetics in models based on both mechanisms, enabling accurate, a-priori prediction of filling from a particular electrolyte in a particular size and aspect ratio feature. I will summarize the chemistries and associated mechanisms for superconformal Cu, Ag, Au, Co, and Ni feature filling, including experiment and model predictions, for processes that are drop-in compatible with those presently used for fabrication of Cu damascene and through silicon via interconnects.
Superconformal electrodeposition processes enable void- and seam-free metal filling of high aspec... more Superconformal electrodeposition processes enable void- and seam-free metal filling of high aspect ratio features from tens of nanometers to hundreds of micrometers in size. There are two known mechanisms underlying such processes: Curvature Enhanced Accelerator Coverage (CEAC) and S-shaped Negative Differential Resistance (S-NDR). Voltammetric measurements on planar substrates can quantify kinetics in models based on both mechanisms, enabling accurate, a-priori prediction of filling from a particular electrolyte in a particular size and aspect ratio feature. I will summarize the chemistries and associated mechanisms for superconformal Cu, Ag, Au, Co, and Ni feature filling, including experiment and model predictions, for processes that are drop-in compatible with those presently used for fabrication of Cu damascene and through silicon via interconnects.
D. JOSELL, L. BENDERSKY, NIST-To enhance the maximum energy product of exchanged coupled hard/sof... more D. JOSELL, L. BENDERSKY, NIST-To enhance the maximum energy product of exchanged coupled hard/soft phase nanocomposite, we need to establish the parameters that govern the exchange coupling interaction (ECI). To this end, on single chips, up to a hundred thin film bilayer samples were grown by e-beam evaporation varying composition and soft layer thicknesses (t s). Magnetic hysteresis loops were taken by magneto-optical Kerr effect measurements. The simultaneous analysis of the samples allows us to delineate subtle variations of the exchange coupling behavior. We will show examples of studies of CoPt/(Fe, Co or Ni) and SmCo/(Fe, Co or Ni) libraries. We characterized ECI by measuring the variations of the coupling length (λ) and the nucleation field (H N) on various magnetic parameters, t s , and interface conditions. The trend indicates that the dominant factors determining λ and H N are the hard layer magnetic constants and the saturation magnetization of the soft layer. We will also discuss the role played by other magnetic parameters. The results allow us to predict the behavior of coupled hard/soft magnetic layers in general. Supported by ONR MURI N00014-05-1-0497.
This paper details the use of scanning photocurrent microscopy to examine localized current colle... more This paper details the use of scanning photocurrent microscopy to examine localized current collection efficiency of thin-film photovoltaic devices with in-plane patterning at a submicrometer length scale. The devices are based upon two interdigitated comb electrodes at the micrometer length scale prepatterned on a substrate, with CdSe electrodeposited on one electrode and CdTe deposited over the entire surface of the resulting structure by pulsed laser deposition. Photocurrent maps provide information on what limits the performance of the windowless CdSe/CdTe thin-film photovoltaic devices, revealing "dead zones" particularly above the electrodes contacting the CdTe which is interpreted as recombination over the back contact. Additionally, the impact of ammonium sulfide passivation is examined, which enables device efficiency to reach 4.3% under simulated air mass 1.5 illumination.
Adsorbates based on a number of P-block elements are known to accelerate Au deposition from sulfi... more Adsorbates based on a number of P-block elements are known to accelerate Au deposition from sulfite as well as cyanide electrolytes. However, the nature of deposits from an electrolyte-additive system, and from the different electrolyte-additive systems, varies substantially. Optically smooth planar deposits coupled with superconformal filling of patterned features such as trenches and vias can be obtained from sulfite-Pb (and cyanide-Pb) electrolytes. With other additives superconformal feature filling is also observed, but it manifests with a geometry more akin to the extreme bottom-up filling seen during Cu filling of through silicon vias. Perhaps most interesting, deposits ranging from optically smooth surfaces to dense arrays of uniformly oriented nanowires can be obtained from sulfite-Tl electrolytes through adjustment of only the applied potential. I will discuss how electroanalytical measurements, coupled with mechanistic models, can help us understand, and in some cases pre...
Gold electrodeposition was studied in a sulfite electrolyte to which micromolar concentrations of... more Gold electrodeposition was studied in a sulfite electrolyte to which micromolar concentrations of Tl 2 SO 4 were added. Hysteresis and a regime of negative differential resistance (NDR) evident in electroanalytical measurements are correlated with deposit morphology and interpreted through measurements of thallium underpotential deposition (upd). Deposit morphologies range from specular surfaces to highly faceted dendrite-like grains of moderate aspect ratio and, for potentials within the NDR region, sub-50 nm diameter, high aspect ratio 110 oriented single crystal nanowires. The nanowires exhibit an epitaxial relationship to the substrate that permits one step fabrication of surfaces densely covered with high aspect ratio nanowires having controlled orientations. The NDR and nanowires are a consequence of the non-monotonic relationship between Tl coverage and growth velocity; at low coverage Tl accelerates Au deposition while at higher coverage it inhibits deposition. Immiscibility of the Tl and Au supports ongoing surface segregation during area expansion that accompanies nanowire growth leading to greater dilution of the additive coverage and more rapid growth at the nanowire tips, while the sidewalls remain passivated by a saturated Tl coverage.
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Papers by Daniel Josell