Meaning
Metallic layers deposited between silicon contacts and copper or aluminum conducting tracks prevent the chemical interdiffusion of metal and silicon. The titanium barrier is widely used in semiconductor manufacturing because it provides both low contact resistance and strong adhesion to silicon and dielectric surfaces. This interface layer limits metal migration and is deposited via sputtering before the primary metallization steps are carried out, ensuring the longevity of sub-micron microprocessors.
Material Properties
Titanium possesses excellent chemical reactivity with silicon, forming a highly conductive disilicide during annealing. This reaction creates a stable contact with low electrical resistance while the titanium layer above acts as a diffusion block. The dual-functionality of the material makes it preferred in sub-micron interconnects.
Deposition Technique
Sputter deposition processes are used to apply the metal across the patterned wafer surface with high uniformity. This physical vapor deposition occurs in a high-vacuum chamber to prevent oxygen contamination, which would increase electrical resistance. The thickness must be precisely monitored to ensure continuous coverage.
Barrier Limitation
Metal atoms can still diffuse through the layer if the temperature rises too high. Once this thermal threshold is breached, the barrier undergoes chemical reaction with silicon and fails. This breakdown terminates the protective function of the metal layer.
