Comparison of low-pressure and plasma-enhanced chemical vapor deposited tungsten thin films

Abstract
Tungsten thin films deposited by low-pressure and plasma-enhanced chemical vapor deposition are characterized to detail the effect of plasma-surface interactions on nucleation and growth. Transition from α- to β-W is observed as the H2/WF6 flow ratio is decreased from 10/1 to 1/1 in plasma-enhanced deposition; transition from α-W to amorphous W is observed under the same conditions in low-pressure chemical vapor deposition. The temperature coefficient of resistivity varies from 4.9 to 2.0 ppthou/K as the plasma-deposited films switch from α to β phase; the temperature coefficient of resistivity varies from 3.2 to −0.5 ppthou/K as the low-pressure chemically vapor deposited films become amorphous. The increased crystallinity and metastable phase formation in plasma environments are attributable to higher effective surface temperature resulting in enhanced surface mobility and grain growth.

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