Review of Recent
Progress in Atomic Layer Deposition (ALD)
ROY G. GORDON, JR.
DEPT. OF CHEMISTRY & CHEMICAL
BIOLOGY
HARVARD UNIVERSITY
I review processes discovered
recently for ALD of transition metals, metal nitrides and metal
oxides. Successful ALD requires pairs of precursors with high but
self-limiting reactivity with surfaces prepared by the complementary
co-reactant, along with high thermal stability, sufficient volatility
and non-etching behavior toward substrates and the deposited films.
New precursor pairs meeting all of these demanding requirements were
found for depositing the transition metals iron, cobalt, nickel,
copper and ruthenium, their oxides, tungsten nitride, silicon dioxide,
and oxides of hafnium, zirconium, lanthanum, praseodymium, vanadium,
tantalum, manganese, magnesium and bismuth. The silica deposition is
suitable for filling isolation trenches in microelectronics and
sealing pores in porous low-k dielectrics. The metal depositions may
be applicable to interconnects and to magnetic devices. Tungsten
nitride is an excellent diffusion barrier even at nanometer
thicknesses. Cobalt and ruthenium are excellent adhesion layers
between WN and ALD copper seed layers.