Residual stress study of thin films deposited by atomic layer deposition

Atomic layer deposition (ALD) has been widely used in microelectromechanical systems (MEMS) due to its unique advantages, e.g. precise film thickness control, high uniformity and superb conformality. The understanding of ALD film's mechanical properties is important for MEMS device design and fabrication. In this work, the studied thin films (Al
₂
O
₃
and Al
₂
O
₃
/TiO
₂
laminates) were deposited by thermal ALD (THALD) and plasma-enhanced ALD (PEALD). The film growth behavior was determined by ellipsometry, and the residual stress was analyzed by wafer curvature measurements. We extracted a low residual stress near 100 MPa for Al
₂
O
₃
and Al
₂
O
₃
/TiO
₂
laminates. A clear correlation was found between the film's process conditions (parameters and configurations) and residual stress.