This review highlights various aspects of current palladium membrane research and serves as a comprehensive bibliography covering palladium membrane preparation methods and applications. There are many promising uses for palladium membranes, although widespread use of the available technologies is constrained primarily by the high cost of palladium, lack of durability due to hydrogen embrittlement, and susceptibility to fouling. Various researchers in the field are tackling these problems and fabricating thinner palladium alloy composite membranes that better withstand contaminantion and thermal cycling. What has been accomplished to address these issues and the directions presently being explored are discussed.

Innovations in palladium membrane research

Recent development and application of Li4Ti5O12 as anode material of lithium ion battery

A process for applying a metallization interconnect structure to a semiconductor workpiece having a barrier layer deposited on a surface thereof is set forth. The process includes the forming of an ultra-thin metal seed layer on the barrier layer. The ultra-thin seed layer having a thickness of less than or equal to about 500 Angstroms. The ultra-thin seed layer is then enhanced by depositing additional metal thereon to provide an enhanced seed layer. The enhanced seed layer has a thickness at all points on sidewalls of substantially all recessed features distributed within the workpiece that is equal to or greater than about 10% of the nominal seed layer thickness over an exteriorly disposed surface of the workpiece.

Apparatus and method for electrolytically depositing copper on a semiconductor workpiece

A process for metallization of a workpiece, such as a semiconductor workpiece. In an embodiment, an alkaline electrolytic copper bath is used to electroplate copper onto a seed layer, electroplate copper directly onto a barrier layer material, or enhance an ultra-thin copper seed layer which has been deposited on the barrier layer using a deposition process such as PVD. The resulting copper layer provides an excellent conformal copper coating that fills trenches, vias, and other microstructures in the workpiece. When used for seed layer enhancement, the resulting copper seed layer provide an excellent conformal copper coating that allows the microstructures to be filled with a copper layer having good uniformity using electrochemical deposition techniques. Further, copper layers that are electroplated in the disclosed manner exhibit low sheet resistance and are readily annealed at low temperatures.

Method for electrochemically depositing metal on a semiconductor workpiece

Embodiments of the invention generally provide methods of filling contact level features formed in a semiconductor device by depositing a barrier layer over the contact feature and then filing the layer using an PVD, CVD, ALD, electrochemical plating process (ECP) and/or electroless deposition processes. In one embodiment, the barrier layer has a catalytically active surface that will allow the electroless deposition of a metal on the barrier layer. In one aspect, the electrolessly deposited metal is copper or a copper alloy. In one aspect, the contact level feature is filled with a copper alloy by use of an electroless deposition process. In another aspect, a copper alloy is used to from a thin conductive copper layer that is used to subsequently fill features with a copper containing material by use of an ECP, PVD, CVD, and/or ALD deposition process. In one embodiment, a portion of the barrier layer is purposely allowed to react with traces of residual oxide at the silicon junction of the contact level feature to form a low resistance connection.

Contact metallization scheme using a barrier layer over a silicide layer

Electroless Cu thermodynamics, electrochemistry, mechanism, kinetics, and mass transport are reviewed. Electroless Cu deposition is a thermodynamically favorable and kinetically inhibited process, with two electrochemical reactions including anodic oxidation of a reducing agent and cathodic reduction of metal ions occurring simultaneously, with a multistep catalytic redox mechanism, an Arrhenius type of rate equation, and mass-transport limited reaction in narrow and deep features such as subhalf micron trenches and vias of high aspect ratios (>3). Selective and blanket electroless Cu deposition from formaldehyde-based solutions with ethylenediaminetetraacetic acid as a complexing agent was investigated for trench/via filling applications. A single-wafer electroless Cu deposition system with up to 8 in. wafer capability has been designed and manufactured. An electroless Cu deposition solution and operation conditions have been optimized to obtain electroless Cu films at high deposition rate (∼75 to 120 nm/min), with low resistivity (p < 2 μΩ cm), low surface roughness (R a ∼ 10 to 15 nm for ∼1.5 μm thick deposits) and good electrical uniformity (std dev <3% for 6 in. wafers and 5 to 7% for 8 in. wafers). A novel dry seeding method on sputtered Cu/Al bilayers has been developed to provide protection of Cu catalytic properties from passivation by using an Al sacrificial layer and to obtain uniform initiation and blanket growth of electroless Cu by in situ Al dissolution in the plating bath. Electroless Cu films blanket deposited on sputtered Cu/Al seed layer were conformal with 100% step coverage. A novel wet seeding method has been developed with Cu contact displacement deposition on a TiN diffusion barrier to provide selective and blanket electroless copper plating. Subhalf micron (down to 0.3 μm) trenches and vias of high aspect ratios (up to 5:1) were completely filled for both blanket and selective electroless deposition modes.

https://iopscience.iop.org/article/10.1149/1.1837505/pdf

P. K. Vasudev

Papers

Selective and Blanket Electroless Copper Deposition for Ultralarge Scale Integration

Selective and Blanket Electroless Copper Deposition for Ultralarge Scale Integration.