Phase, Texture, Grain Size, Stress

Jordan Valley polycrystalline X-ray diffraction technology (XRD) provides an ideal metrology solution for thin film microstructure applications, including phase, texture, grain size and stress. Jordan Valley's XRD mode offers many advantages, including:

• Non- destructive method, no contact with samples to avoid contamination
• Unique information on the microstructure of polycrystalline materials
• Single and multiple layers can be investigated
• Penetration depth control (grazing incidence)

XRD Overview

Metal Barrier Phases: Ta or TaN

Requirement:

• Maintain low resistivity of the barrier layer
• Different Ta and TaN phases have different resistivity: Ta(α) = 35 Ω-cm and Ta(β) = 175 Ω-cm

In-line Monitor:

• Ratio of Ta(α) and Ta(β) phases

Taα also promotes growth of (111) texture in Cu
Phase issues with Ta/TaN barriers

PVD Ta Phase & Texture

Metal diffusion barrier properties depend on crystal structure and composition, not just thickness. Phase variations are a known problem in Ta/TaN barriers.

• Ta(α) (bcc) has a low resistivity so a good barrier choice - Ta(β) (tetragonal) is undesired
• Phase variation a root cause of some process problems
• XRD is already adopted at major semiconductor manufacturers as a means to identify phase variations

[1] C.C. Wang et al, Proc. Characterisation and Metrology for ULSI Tech. 2003, p.519
[2] D. Edelstein et al, Proc. IITC SF 2001, p.9-11
[3] H. Donohue et al, Proc. IITC, SF 2002 p.179

Mixed Ta/TaN Phases

Seed vs. electroplated Cu texture