Preparation and properties of tantalum thin films

Improvement of Ta Barrier Film Properties in Cu Interconnection by Using a Non-mass Separated Ion Beam Deposition Method

“…When the bias voltage was increased to −125 V, β-Ta (200) peak was weakened and the α-Ta (110) peak became the strongest. This result coincides with the fact that electrical resistivity measured on the film deposited at a bias voltage of −125 V was 360 n m, which corresponds to the resistivity value reported on α-Ta films of ∼ 500 n m. 17) These results make us suggesting that ion bombardment by applying a substrate bias voltage during the deposition process plays an important role in the growth of Ta films. By further increasing in the bias voltage, β-Ta (200) peak intensity again gradually increased and α-Ta (110) peak finally disappeared at a bias voltage of −200 V. This behavior is in a good correspondence with the results of the resistivity measurement as mentioned above.…”

“…In general, sputtered Ta films on silicon substrates prefer to have a metastable β-Ta structure, 17) whereas α-Ta structure can be obtained by served methods, such as applying a bias voltage to the substrate, deposition onto the titanium substrate, 19) annealing treatment, 20) and so on. In the present study, we tried to investigate the effect of the substrate bias voltage on the structure of Ta films, and found that it could control the phase of the deposited films, in which ion bombardment played an important role in the film growth.…”

“…Figure 1 shows resistivity change as a function of the bias voltage. A Ta film deposited at zero voltage shows the highest resistivity (2600 n m), which is considered as of reported β-Ta films of 1100-3000 n m. 17) When the bias voltage was applied to a substrate, the resistivity of the film sharply decreased and at a bias voltage of −125 V, the resistivitiy had a smallest value of 360 n m, which was roughly close to the bulk resistivity of 130 n m. 17) It is worth noting that the resistivity of Ta films deposited by IBD system with the high purity ion source has a value roughly equal to the bulk one, which is smaller than the reported value on α-Ta films of 250-500 n m. 17) Further increase of the bias voltage up to −200 V, results in gradually increasing the resistivity.…”

Theory of the structural phases of group 5B–6B metals and their transport properties

“…23,24,30,45,46,53 The β phase of tantalum has been reported to nucleate preferentially on certain kinds of substrates, [25][26][27][28][29] and may be stabilized by oxygen impurities. 7,25,26,[29][30][31] From work such as that of Tian et al, 1,2 and Marcus et al, 12 who have used total energy calculations to show that the bulk structure of a thin Ti film on an Al{001} substrate is strained fcc Ti, it is evident that the nature of the substrate on which a thin film is deposited can determine the kind of stress prevailing in the deposited film, and therefore the final structural form of the film. β-tantalum has been observed to form preferentially on certain substrates, so the nature of the substrate upon which thin tantalum films are deposited appears to play an important role in the subsequent formation of the β phase.…”

“…7,9,18,[23][24][25][26][27][28][29][30][31] The metastable phase, referred to as the β phase, is sometimes formed alongside the stable bcc phase, referred to as the α phase. The β phase of tantalum occurs mostly as a thin film and is not easily formed as bulk material.…”