Characterization of Ti diffusion in PVD deposited WTi/AlCu metallization on monocrystalline Si by means of secondary ion mass spectroscopy

Thermal and oxidation stability of TixW1−x diffusion barriers investigated by soft and hard x-ray photoelectron spectroscopy

“…Several studies have also reported interdiffusion phenomena experienced during high-temperature annealing for multi-layered systems containing titanium or titanium-based alloys. 19,23,24,[67][68][69][70] These studies highlight that the diffusion mechanism of titanium through a polycrystalline metal over-layer largely proceeds via grain boundary diffusion through the metallization and then finally accumulation at the free surface. Moreover, the work by Baeri et al suggests that residual oxygen in the deposition chamber may act as the driving force for titanium to diffuse upward toward the free surface, owing to the very strong chemical affinity of titanium to oxygen.…”

“…During such events, titanium exhibits the ability to segregate out of the barrier layer, diffusing through the metallization, and accumulating at the surface. 19,21,23,24 These past investigations have shown that the addition of titanium to tungsten in the range of 10-30 at. % Ti improves the diffusion barrier performance, increasing its adhesion to the surrounding layers, 17,25 enhancing its corrosion resistance, 6 and increasing the barrier failure temperature relative to a single tungsten barrier.…”

“…Research into TiW has since seen a resurgence in response to these limitations, but also due to the development of wide bandgap materials for power semiconductor devices and the increasingly higher temperatures experienced in high-power applications. [19][20][21][22] Despite the effectiveness of TiW as a diffusion barrier, when subjected to high temperatures for a prolonged duration, whether experienced during the many thermal treatments in the fabrication route or during operation, the barrier is susceptible to degradation. During such events, titanium exhibits the ability to segregate out of the barrier layer, diffusing through the metallization, and accumulating at the surface.…”

Evaluation of the thermal stability of TiW/Cu heterojunctions using a combined SXPS and HAXPES approach

“…400 C was selected as the target annealing temperature as it is a common temperature experienced by a device during the manufacturing stages. 28 Synchrotron-based SXPS and HAXPES measurements were conducted at beamline I09 at the Diamond Light Source, UK, employing 1587.4 eV (1.6 keV) and 5927.4 eV (5.9 keV) photon excitation energies, respectively. 35 The maximum inelastic mean free path (λ) for copper at 1.6 and 5.9 keV is 2.2 and 6.4 nm, respectively (calculated using QUASES 36 ).…”

“…11,12 Since the introduction of TiW and its associated benefits, TiW has been applied between various metal contacts and metallization layers, all with moderate to good success. [13][14][15][16][17][18][19][20][21][22][23][24][25][26][27][28][29] However, these studies predominately focus on determining the conditions that are required for the barrier to fail (i.e., temperature and duration), with less emphasis on defining the mechanism that promotes the failure or studying the chemical states across the critical diffusion barrier/metallization interface.…”