Crystallization and failure behavior of Ta-TM (TM=Fe, Co) nanostructured/amorphous diffusion barriers for copper metallization

Abstract

This work examined the thin-film properties and diffusion barrier behavior of sputtered Ta-TM (TM ‫ס‬ Fe, Co) films, aiming at depositing a highly crystallization-resistant and conductive diffusion barrier film for Cu metallization. Four-point probe measurement, x-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), and a secondary ion mass spectrometer (SIMS) were used to examine the barrier properties. Structural examination indicated that intermetallic-compound-free amorphous Ta-TM films were obtained by magnetron sputtering, thus giving a resistivity of 146.82 ⍀-cm and 247.01 ⍀-cm for Ta 0.5 Fe 0.5 and Ta 0.5 Co 0.5 films, respectively. The Si/Ta 0.5 Fe 0.5 /Cu and Si/Ta 0.5 Co 0.5 /Cu stacked samples were observed to fail completely at temperature above 650°C and 700°C because of the formation of Cu 3 Si protrusions between silicon and the Ta-TM interface. Ta 0.5 Co 0.5 is thus superior to Ta 0.5 Fe 0.5 in preventing copper from diffusion. Highly thermally stabilized amorphous Ta-TM thin film can thus be potentially adopted as a diffusion barrier for Cu metallization.

Diffusion Barriers

“…(1) polycrystalline and amorphous Me-N, Me-C, Me-O and Me-B compounds, such as TiN x [25], VN x [26], ZrN x [27], NbN x [28], MoN x [21], HfN x [29], WN x [30], TaN x [31], WC x [32], TaC x [33], MoO x [34], TaO x [35] and TiB 2 [36], (2) polycrystalline and amorphous Me-Si compounds, such as MoSi x [37], WSi x [38] and TaSi x [39], (3) polycrystalline and amorphous Me alloys, such as TiW x [40], TaCo x and TaFe x [41], TaW x [42], NiNb x [43] and CuZr x [44].…”

Atomic-scale structural evolution of Ta–Ni–Si amorphous metal thin films

“…However, these improvements come at the expense of increased electrical resistivity that limits their widespread use. [5] Amorphous Ta-based alloys such as Ta-Ni [6], Ta-Co [7] and Ta-Fe [7] have reduced electrical resistivity but also suffer from depressed crystallization temperatures ranging from <700 °C to <800 °C.…”

Electrodeposition of Cu on CoTa Barrier in the Alkaline CuSO4-Ethylenediamine Solution

“…6 In this case, people search for a single layer barrier that can serve as both liner and barrier. 7,8 Co-based alloy barriers have exhibited good properties and have been widely investigated, such as CoW, 8,9 CoMo, 10,11 CoTi, 12,13 CoTa 14,15 and CoRu. 16 Alloying changes the film microstructure from polycrystalline to nanocrystalline or amorphous, reducing the fast diffusion of Cu through grain boundaries and providing better Cu diffusion barrier properties.…”