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Title: Amorphorized tantalum-nickel binary films for metal gate applications

Amorphous metal gates have the potential to eliminate the work function variation due to grain orientation for poly-crystalline metal gate materials, which is a leading contributor to threshold voltage variation for small transistors. Structural and electrical properties of TaNi alloys using co-sputtering with different compositions and multilayer structures with different thicknesses are investigated in this work. It is found that TaNi films are amorphous for a wide range of compositions as deposited, and the films stay amorphous after annealing at 400 °C in RTA for 1 min and up to at least 700 °C depending on the composition. The amorphous films eventually crystallize into Ni, Ta, and TaNi{sub 3} phases at high enough temperature. For multilayer Ta/Ni structures, samples with individual layer thickness of 0.12 nm and 1.2 nm are amorphous as deposited due to intermixing during deposition, and stay amorphous until annealed at 500 °C. The resistivity of the films as-deposited are around 200 μΩ·cm. The work function of the alloy is fixed at close to the Ta work function of 4.6 eV for a wide range of compositions. This is attributed to the segregation of Ta at the metal-oxide interface, which is confirmed by XPS depth profile. Overall, the excellent thermal stability and low resistivitymore » makes this alloy system a promising candidate for eliminating work function variation for gate last applications, as compared to crystalline Ta or TiN gates.« less
Authors:
; ;  [1] ; ;  [2]
  1. Department of Materials Science and Engineering, Stanford University, Stanford, California 94305 (United States)
  2. Department of Electrical Engineering, Stanford University, Stanford, California 94305 (United States)
Publication Date:
OSTI Identifier:
22398891
Resource Type:
Journal Article
Resource Relation:
Journal Name: Applied Physics Letters; Journal Volume: 106; Journal Issue: 15; Other Information: (c) 2015 AIP Publishing LLC; Country of input: International Atomic Energy Agency (IAEA)
Country of Publication:
United States
Language:
English
Subject:
75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND SUPERFLUIDITY; ANNEALING; COMPARATIVE EVALUATIONS; DEPOSITION; ELECTRIC CONDUCTIVITY; ELECTRIC POTENTIAL; EV RANGE; FILMS; GRAIN ORIENTATION; INTERFACES; LAYERS; NICKEL; OXIDES; SPUTTERING; TANTALUM; THICKNESS; TITANIUM NITRIDES; TRANSISTORS; VARIATIONS; WORK FUNCTIONS; X-RAY PHOTOELECTRON SPECTROSCOPY