Mechanical and chemical investigation of the interface between tungsten-based metallizations and annealed borophosphosilicate glass

Annealing effects on the film stress and adhesion of tungsten-titanium barrier layers

“…The adhesion energy of the as-deposited film was 2.7 J/m² and increased continuously to 4.7 J/m² after two hours of annealing at 400°C. The adhesion energy for the as-deposited WTi film is similar to that of pure tungsten on glasslike substrates, which is know from literature to be in the range of 2.5-3 J/m² [9,13,15,22]. This indicates that the Ti content in the alloy does not significantly contribute to the adhesion of the system in the asdeposited state.…”

“…This indicates that the Ti content in the alloy does not significantly contribute to the adhesion of the system in the asdeposited state. The annealing treatment increased the adhesion of the system most likely due to the segregation of Ti from the WTi solid solution towards the interface, creating a titanium film that is only a few atom layers thick and promotes adhesion [6,9]. This process takes more than 30 minutes since a significant increase in adhesion was not detected within the margin of error.…”

“…The mixed mode adhesion energy calculated for the 1 and 2 hour annealing times compare well to the values measured from other methods for similar samples. For instance, 4PB performed by Völker et al [6,9] calculated an adhesion energy of 4.9-6 J/m² and microcantilever experiments by Matoy et al [13] which resulted in adhesion energies of 4.3 J/m². Fugger et al [5] detected a further increase of Ti segregation towards the copper above the WTi layer up to 16 hours of annealing at 600°C.…”

“…Several adhesion testing methods have been successful in quantitatively measuring the adhesion of thin films [7,8]. Common techniques include four point bending (4PB) [6,[9][10][11][12], microcantilever tests [13,14], nanoindentation [15][16][17][18] and scratch tests [19][20][21][22]. Four point bending and microcantilever tests require very elaborate sample preparation and testing procedures which may also change the properties of the interface in question.…”

“…The adhesion of WTi to commonly used substrates like silicon or silicon oxides and its dependence on several parameters such as composition or film thickness, have also been investigated using several different methods [6,9,23,24]. In order to quantitatively measure the adhesion of the WTi film the scratch test has been utilized.…”