Engineering Materials and Processes phần 4 pptx

Diffusion Barriers and Self-encapsulation 33

The XRD spectra obtained from the TaN films, deposited on Si using different

nitrogen flow ratios, are shown in Figure 3.10. The variations in position, intensity

and shape of the peaks indicate changes in the phase of the TaN films. From Figure

3.10, the phases present in the films were identified by comparing the observed

peak positions (2θ) in the XRD spectra with data from JCPDS cards. The

diffraction peaks of the films deposited with 15% nitrogen flow (Figure 3.10a) can

be indexed as belonging to a mixture of β-Ta and Ta-rich nitride (Ta2N). When the

nitrogen partial flow rate is increased to 25% (Figure 3.10b), a small fraction of the

phases observed at 15% are still present, but the dominant phase is stoichiometric

TaN. Upon increasing the flow rate from 30–40%, only peaks at 2θ = 35°, 41, 60,

and 72°, which correspond to TaN, are observed (Figure 3.10c–d). As the nitrogen

flow ratio is increased to 30%, the diffraction peak at 2θ ≈ 35° shifts to a lower

angle, and the shift becomes even more evident for the 40% spectrum. The shift of

the peaks to lower angles confirmed that a new phase is formed with increasing

nitrogen. In the range of 30–40% N2 flow rate, the diffraction peaks become

increasingly broader and peak intensities drop.

20 40 60 80 100



  

Ta2 † N

†

„ „

†

„ β-Ta TaN

†



„

(d)

(c)

(b)

(a)

Intensity (Arb. unit)

2θ (degree)

Figure 3.10. XRD spectra obtained from TaN films as-deposited using various N2/Ar flow

ratios, (a) 15% N2, (b) 25% N2, (c) 30% N2 and (d) 40% N2 [5]