Jill Becker

Diffusion barrier properties of tungsten nitride films grown by atomic layer deposition from bis(tert-butylimido)bis(dimethylamido)tungsten and ammonia

Highly uniform, smooth, and conformal coatings of tungsten nitride (WN) were synthesized by atomic layer deposition (ALD) from vapors of bis(tert-butylimido)bis(dimethylamido)tungsten and ammonia. The films are shiny, silver colored, and electrically conducting. The films were amorphous as deposited. 100% step coverage was obtained inside holes with aspect ratios greater than 40:1. WN films as thin as 1.5 nm proved to be good barriers to diffusion of copper for temperatures up to 600 °C. Annealing for 30 min at temperatures above 725 °C converted the WN to pure, polycrystalline tungsten metal. ALD of copper onto the surface of the WN produced strongly adherent copper films that could be used as “seed” layers for chemical vapor deposition or electrodeposition of thicker copper coatings.

Low-temperature atomic-layer-deposition lift-off method for microelectronic and nanoelectronic applications

We report a method for depositing patterned dielectric layers with submicron features using atomic layer deposition. The patterned films are superior to sputtered or evaporated films in continuity, smoothness, conformality, and minimum feature size. Films were deposited at 100–150 °C using several different precursors and patterned using either electron-beam or photoresist. The low deposition temperature permits uniform film growth without significant outgassing or hardbaking of resist layers. A lift-off technique presented here gives sharp step edges with edge roughness as low as ∼10 nm. We also measure dielectric constants (κ) and breakdown fields for the high-κ materials aluminum oxide (κ∼8–9), hafnium oxide (κ∼16–19), and zirconium oxide (κ∼20–29), grown under similar low temperature conditions.

ALTERNATING LAYER CHEMICAL VAPOR DEPOSITION (ALD) OF METAL SILICATES AND OXIDES FOR GATE INSULATORS

A new process was developed for deposition of the silicates and oxides of metals such as zirconium and hafnium at low substrate temperatures (100-300 o C). The silicon and oxygen source is tris(tert-butoxy)silanol, ( t BuO)3SiOH, and the metal precursors are metal amides. A typical reaction is ZrL4 +2 ( t BuO)3SiOH ZrSi2O6 +4 HL +6 H 2C=C(CH3)2 +2 H 2O in which the ligand L is ethylmethylamide, -NEtMe. The precursor vapors were alternately pulsed into a heated reactor, yielding about 0.3 to 0.7 nm of metal silicate film for each cycle. Replacing the silanol pulses with water pulses yields pure metal oxides with a thickness of about 0.1 to 0.15 nm per cycle. The silicon content of the films can be adjusted to any desired value by replacing some of the silanol pulses by water pulses. This new process has a number of advantages over previous methods for depositing metal silicates. Uniformity of thickness and stoichiometry are readily achieved. The deposition atmosphere is non-oxidizing, so that formation of low-k interfacial oxides between the deposited layer and a silicon substrate is minimized. The new halogen-free precursors avoid halogen contamination of films and corrosion of deposition systems. This process is a promising method for forming the next generation of ultra-thin high-k gate dielectrics in silicon-based microelectronics.