Platinum metallization for MEMS application. Focus on coating adhesion for biomedical applications

Area of Science:

• Materials Science
• Thin Film Technology
• Surface Engineering

Background:

• Adhesion of Platinum (Pt) thin films is critical for high-temperature MEMS and biomedical devices.
• Challenges exist in maintaining Pt film adhesion to substrates in demanding industrial and health applications.
• Investigating interlayer materials is essential for improving Pt film performance.

Purpose of the Study:

• To evaluate Chromium (Cr), Titanium (Ti), and Alumina (Al2O3) as interlayers for Platinum (Pt) thin film adhesion on Si/SiO2 wafers.
• To introduce Al2O3 as a novel ceramic interlayer for enhanced high-temperature performance of Pt films.
• To assess the electrical properties and adhesion of Cr/Pt, Ti/Pt, and Al2O3/Pt films in gas sensor applications.

Main Methods:

• Electron beam deposition of Cr, Ti, and Al2O3 thin films on Si/SiO2 wafers.
• Deposition of Platinum (Pt) thin films onto the prepared interlayers.
• Annealing experiments at various temperatures to evaluate film adhesion and electrical properties.
• Testing of metallic film performance in gas sensor applications.

Main Results:

• All investigated interlayers (Cr, Ti, Al2O3) exhibited good adhesion to Si/SiO2 and Au wire bondability at room temperature.
• Cr/Pt and Ti/Pt films showed poor adhesion above 400 °C due to atomic inter-diffusion between Pt and the metal interlayers.
• Al2O3/Pt ceramic-metal layers demonstrated significantly improved adherence at elevated temperatures.

Conclusions:

• Alumina (Al2O3) serves as a superior interlayer for Platinum (Pt) thin films compared to Chromium (Cr) and Titanium (Ti) at high temperatures.
• The inter-diffusion of atoms at the interface is a key factor limiting the high-temperature adhesion of traditional metal interlayers.
• Alumina interlayers offer a promising solution for enhancing the reliability and performance of Pt-based devices operating under thermal stress.