Thin-film characterization using a scanning laser acoustic microscope with surface acoustic waves

Area of Science:

• Materials Science
• Acoustics
• Surface Physics

Background:

• Characterizing thin films requires precise methods for evaluating mechanical and acoustic properties.
• Piezoelectric substrates are crucial for acoustic wave interactions.
• Limitations exist in conventional acoustic wave methods for thin film analysis.

Purpose of the Study:

• To demonstrate the utility of surface acoustic waves (SAWs) in a scanning laser acoustic microscope (SLAM) for thin film characterization.
• To quantitatively measure the mass loading effects of thin films on piezoelectric substrates.
• To explore the applicability of SAWs on non-piezoelectric materials.

Main Methods:

• Utilizing a scanning laser acoustic microscope (SLAM) with 100-MHz surface acoustic waves.
• Depositing 5000-angstrom tungsten films onto lithium niobate (a piezoelectric substrate).
• Comparing SAW measurements with compressional wave measurements.

Main Results:

• Quantitative measurements of mass loading effects were successfully obtained for tungsten films on lithium niobate using 100-MHz SAWs.
• 100-MHz compressional waves provided no discernible information about the tungsten film.
• The study confirmed the effectiveness of SAWs for thin film property evaluation.

Conclusions:

• Surface acoustic waves are highly effective for characterizing mechanical and acoustic properties of thin films on piezoelectric substrates.
• SLAM utilizing SAWs offers a quantitative approach for mass loading effect measurements.
• Further methods are discussed for extending SAW analysis to arbitrary (non-piezoelectric) substrates.