Microstructure and composition of annealed Al/Ti-metallization layers

Area of Science:

• Materials Science
• Nanotechnology
• Thin Film Deposition

Background:

• Al/Ti multilayers are utilized in various electronic applications.
• Understanding their behavior under thermal stress is crucial for device reliability.
• Piezoelectric substrates like Lithium Niobate (LiNbO(3)) are sensitive to processing conditions.

Purpose of the Study:

• To investigate the microstructural and chemical changes in Al/Ti multilayers deposited on LiNbO(3) after annealing.
• To determine the effect of annealing on the Ti interlayer and surrounding Al matrix.
• To explore the stability of an underlying oxidized Ti layer.

Main Methods:

• Electron-beam evaporation for Al/Ti multilayer deposition.
• Annealing in air and vacuum.
• Conventional and analytical Transmission Electron Microscopy (TEM) for microstructural and chemical analysis.

Main Results:

• Complete dissolution of the Ti interlayer upon annealing.
• Formation of globular Aluminum-3-Titanium (Al(3)Ti) grains within an Aluminum (Al) matrix.
• Preservation of an underlying oxidized Ti layer and a thin Al layer below it, attributed to oxidation resistance.

Conclusions:

• The Ti interlayer in Al/Ti multilayers on LiNbO(3) is unstable under annealing conditions.
• Oxidation plays a key role in protecting underlying layers from interdiffusion.
• Microstructural evolution involves the formation of Al(3)Ti phases and changes in layer integrity.