Silver layer instability in a SnO2/Ag/SnO2 trilayer on silicon

• Published in: Thin solid films Vol. 520; no. 19; pp. 6189 - 6195
• Main Authors: Kim, Suk Jun, Stach, Eric A., Handwerker, Carol A.
• Format: Journal Article
• Language: English
• Published: Elsevier B.V 31-07-2012
• Subjects: Grain boundaries; Instability; Interface dewetting; Interface instability; Multilayers; Silicon substrates; Silver; Stability; Stress; Thermal expansion; Thermal expansion mismatch; Thin film stress; Tin dioxide; Tin oxides; Transmission electron microscopy; Whiskers; Multilayers; Transmission electron microscopy; Interface dewetting; Whiskers; Thermal expansion mismatch; Thin film stress; Interface instability; Stress
• ISSN: 0040-6090; 1879-2731
• DOI: 10.1016/j.tsf.2012.05.033

Trilayers of SnO2/Ag/SnO2 deposited on oxidized Si (100) substrates at room temperature become unstable after annealing at 100°C and 200°C, exhibiting five phenomena – formation of internal Ag hillocks, cracking of the top SnO2 layer above internal Ag hillocks, penetration of Ag/Ag grain boundaries by SnO2 leading to grain pinch-off, formation of Ag whiskers and islands on the free surface of the SnO2 through the cracked top layer, and void formation in the Ag layer. The possible driving forces and evolution path for the observed instabilities resulting from thermal expansion mismatch stresses and the reduction in interfacial energy are discussed.
► Interfacial instability phenomena of SnO2/Ag/SnO2 trilayers were observed. ► At 200°C, internal hillock, whiskers and islands of Ag were produced. ► Thermal stresses are not high enough to lead to the observed defect densities. ► Dewetting of internal Ag interfaces must be driving whisker and island formation.