Mechanical properties and fracture mechanism of porous SiOCH low-k dielectrics

Abstract

A series of low-k dielectric films with various mechanical properties were prepared for a 32-nm back-end-of-line technology node. Various precursors were used, and the porogen removal treatment was performed using the H(2) or E-beam-assisted method. This study presents a novel approach for determining the loss of materials during treatment. This approach includes determining yield strength, fracture toughness, bonding structure, and fracture mechanism of a series of low-k silica films. The results show that a low-k film formed using the precursor trimethylsilane has higher yield strength and fracture toughness than the low-k films formed using the precursor tetramethylsilane or octamethylcyclotetrasiloxane. The residual gas analysis was conducted to determine the loss of materials and predict the bonding structure: the results show that the E-beam treatment rearranges the structure more effectively than the H(2) treatment by using the H radial to decompose the methyl group. Finally, the fracture mechanism of these low-k films was determined by relating the crack patterns of the indents on these films to their indentation load-displacement curves. (C) 2011 Elsevier B.V. All rights reserved.