Atomic layer deposition of tungsten using sequential surface chemistry with a sacrificial stripping reaction

Tungsten (W) films were grown with atomic layer control using a novel seque nce of self-limiting surface reactions. The tungsten film growth was achiev ed by dividing the binary reaction WF6 + Si2H6 --> W + 2SiHF(3) + 2H(2) int o two separate half-reactions. Alternating exposures to WF6 and Si2H6 in an ABAB... sequence produced tungsten deposition at temperatures between 425 and 600 K. The Si2H6, reactant served only a sacrificial role to strip fluo rine from tungsten without incorporating into the film. FTIR spectroscopic investigations demonstrated that the WF6 and Si2H6 half-reactions were comp lete and self-limiting at T > 400 K, In situ spectroscopic ellipsometry mea surements determined a tungsten growth rate of 2.5 Angstrom/AB cycle with W F6 and Si2H6 reactant exposures sufficient for complete half-reactions. The surface topography of the deposited tungsten films was flat indicating smo oth film growth. The tungsten films were either amorphous or composed of ve ry small crystalline grains and contained no measurable silicon or fluorine . These results represent the first. demonstration of atomic layer depositi on of smooth single-element metal films using sequential surface chemistry. (C) 2000 Elsevier Science S.A. All rights reserved.