Jw. Klaus et al., Atomically controlled growth of tungsten and tungsten nitride using sequential surface reactions, APPL SURF S, 162, 2000, pp. 479-491
Thin films of tungsten (W) and tungsten nitride (W2N) were grown with atomi
c layer control using sequential surface reactions. Tungsten atomic layer d
eposition was accomplished by separating the reaction WF6 + Si2H6 --> W + 2
SiHF(3) + 2H(2) into two half-reactions. The tungsten nitride atomic layer
growth was performed by dividing the reaction 2WF(6) + NH3 --> W2N + 3HF 9/2F(2) into two half-reactions. Successive exposure to WF6 and Si2H6 (NH,)
in an ABAB... reaction sequence produced W (W2N) deposition at substrate t
emperatures between 425-600 K (600-800 K). The W deposition rate was 2.5 An
gstrom/AB cycle for WF6 and Si2H6 reactant exposures > 800 and 3000 L, resp
ectively. The W2N deposition rate was also 2.5 Angstrom/AB cycle for WF6 an
d NH3 reactant exposures > 3000 and 10,000 L, respectively. Atomic force mi
crographs of the deposited films on Si(100) were remarkably flat indicating
smooth deposition. X-ray diffraction investigations revealed that the depo
sited tungsten and tungsten nitride films were either amorphous or composed
of very small crystalline grains. X-ray photoelectron spectroscopy demonst
rated that the films contained very low impurity concentrations. The result
s for tungsten represent the first demonstration of atomic layer deposition
(ALD) of smooth single-element films using sequential surface reactions. (
C) 2000 Elsevier Science B.V. All rights reserved.