PARTICLE CONTAMINATION DURING SPUTTER DEPOSITION OF W-TI FILMS

Particle contamination during sputter deposition of W-Ti films depends upon the target density, the amount of Ti rich beta(Ti,W) in the target, the target impurity content, and the film compressive stress. Particle contamination densities decrease from approximately 1.5 cm-2 to less than 0.1 cm-2 as the sputtering target microstructure is changed from a 76% dense multiphase mixture of Ti rich beta(Ti,W) and beta-W to a 99% dense two phase combination of beta-W and alpha-Ti. A process map is provided to guide the selection of optimum powder compaction process for W-Ti targets. We propose that particle emission from the Ti rich beta(W-Ti) phase in W-Ti sputtering targets occurs by argon bombardment induced compressive stress fracture of the Ti rich beta(Ti,W) phase. Particle contamination density increases at a rate of 1.5 X 10(-4) particles/cm2 for each (parts per million by weight) of target impurity. An inverse relationship between the total deposited film thickness and the film compressive strain was found. Increasing the W-Ti film compressive strain reduces the film thickness at which stress fracture (flaking) of the film deposited on the system shields occurs. A reduced stress fracture thickness means that particle emission from the system shielding will occur at an early stage as film accumulates on the exposed shielding.