Experimental study and computer simulation of collimated sputtering of titanium thin films over topographical features

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Abstract
An experimental study and computer simulation of collimated sputtering of titanium (Ti) thin films onto submicrometer trenches is presented. The effect of square grid collimators with aspect ratios varying from 0.5 to 2 has been studied. Simulation of collimated sputtering involves the combination of the simulation of sputter distributions vapor transport model and the simulation by ballistic deposition film growth model. This combination is able to simulate the effect of collimation on the spatial and angular distributions of deposited atoms, and is able to predict the film coverage, deposition rate change, and microstructure of the deposited films. Both experimental and simulation results show that bottom coverage in trenches of aspect ratio 1.2 can be significantly improved from 50% to more than 80% using collimation. However, a penalty is paid by a corresponding decrease in deposition rate down to 15% of the uncollimated value. Additionally, the microstructure (grain size and orientation) is altered by collimation. The good agreement between the simulation and experimental results indicates that the model will be very useful for predicting and optimizing the properties of films deposited by collimated sputtering over topographical features.

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