Crystallization and failure behavior of Ta-Ni nanostructured/amorphous diffusion barriers for copper metallization

Hsu

2007

Highly thermally stable amorphous Ta x Ni 1-x (x = 0.25 and 0.75) thin films were deposited on Si and Si/SiO 2 substrate by magnetron dc sputtering, and the performance of films (20-nm thick) as barriers for copper (Cu) interconnection was evaluated. The failure behaviors of the films were elucidated using a four-point probe, x-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), and Auger emission spectrometry (AES). A highly (111) textured Cu film could be obtained when Cu was deposited on Si/Ta 0.25 Ni 0.75 and Si/SiO 2 /Ta 0.25 Ni 0.75 substrates. The failure temperatures of Si/Ta 0.25 Ni 0.75 /Cu-and Si/Ta 0.75 Ni 0.25 /Cu-stacked films were 550°C and 600°C, respectively. Failure of the studied films initiated the penetration of Cu into the Si/Ta x Ni 1-x interface and triggered the partial dissociation of the Ta x Ni 1-x barrier layer, forming Cu 3 Si precipitates, Ni-silicide and Ta-silicide. Increasing the Ta content enhanced the microstructural and thermal stability of the stacked films, markedly improving barrier properties. The experimental findings demonstrated that the barrier characteristic of Ta 0.75 Ni 0.25 was substantially superior to that of Ta 0.25 Ni 0.75 .

Section: Resultsmentioning

confidence: 55%

“…The diffraction spectra revealed that the as-deposited Ta-Ni thin film indeed had an amorphous structure (not shown). 13 In addition, the microstructure of Ta 0.75 Ni 0.25 thin film remained amorphous at an elevated temperature of 750°C for 5 min, as shown in Fig. 2.…”

Section: Resultsmentioning

confidence: 87%

Barrier Properties of Amorphous Binary Ta-Ni Thin Films for Cu Interconnection

Hsu

2007

“…13 Our previous study has also shown that electron-gun-evaporated Ta-Co and sputtered Ta-Ni thin films indeed have an amorphous structure, and are free from intermetallic compounds up to 500°C and 700°C. 14 A superior barrier characteristic for evaporated Ta-Co and sputtered Ta-Ni thin films in preventing Cu diffusion can also be found up to annealing temperatures of 500°C and 700°C. Thin-film crystallization and Ta-Co and Ta-Fe thin films have not yet been reported.…”

Section: Introductionmentioning

confidence: 94%

“…The resistivity for as-deposited films showed the same level with that of our previous study on sputtered Si/Ta-Ni film. 14 The films were subsequently annealed at an elevated temperature to evaluate the variation in resistivity dependence of annealing temperature. The tiny variation in resistivity of the film was found (range 140-165 ⍀-cm) at an annealing temperature range from 300°C to 700°C for the Si/ Ta 0.5 Fe 0.5 film, as shown in Fig.…”

Section: Crystallization Characteristics Of Deposited Filmsmentioning

confidence: 99%

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

Hsu

2006

Self Cite

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.

“…6,7 Crystalline Ta and TaN thin films are the most promising diffusion barriers for preventing the highly diffusive copper from the penetrating the barrier to react with silicon. [8][9][10][11] Sputter-deposited TaN is most commonly used as the diffusion barrier, owing to its good thermal stability at a high temperature and limited solid solubility in Cu.…”

Section: Introductionmentioning

confidence: 99%

Evaluation of DC-sputtered Glassy TaCoN Thin Film for Copper Metallization

2007

The failure mechanism of the TaCoN barrier for copper metallization was examined using films by direct current (dc) magnetron reactive sputtering at various nitrogen flow rates. The as-deposited TaCoN films had a glassy structure and were free from intermetallic compounds. Optimizing the nitrogen flow rate during sputtering maximized the thermal stability of the Si/Ta 66.8 Co 11.4 N 21.8 /Cu metallization system up to an annealing temperature of 750°C when the film was deposited using a nitrogen flow rate of 1 sccm, as revealed by using X-ray diffraction, a scanning electron microscope, a fourpoint probe and a transmission electron microscope. Structural analysis indicated that the failure mechanisms of the studied Si/TaCoN/Cu stacked films involved the initial dissociation of the barrier layer that was annealed at a specific temperature, and the subsequent formation of diffusion paths along which the copper penetrates through the TaCoN barrier layer to react with underlying Si. The high formation temperature of the Cu 3 Si phase demonstrated that the studied film was highly stable, indicating that the TaCoN thin film is highly promising for use as a diffusion barrier for Cu metallization.