Adhesion analysis for on-chip interconnect structures by beam bending techniques with optical crack length determination

• Published in: Microelectronic engineering Vol. 106; pp. 172 - 176
• Main Authors: Hentschel, R.L., Hecker, M., Hensel, M., Lehr, M.U., Breuer, D.
• Format: Journal Article Conference Proceeding
• Language: English
• Published: Amsterdam Elsevier B.V 01.06.2013; Elsevier
• Subjects: Adhesion tests; Applied sciences; Beams (radiation); Chips; Condensed matter: structure, mechanical and thermal properties; Crack-stop characterization; Density; Design. Technologies. Operation analysis. Testing; Double cantilever beam; Elasticity. Plasticity; Electronics; Exact sciences and technology; Fatigue, brittleness, fracture, and cracks; Four-point bending; Fracture mechanics; Fractures; Integrated circuits; Interconnections; Mechanical and acoustical properties of condensed matter; Mechanical properties; Mechanical properties and methods of testing. Rheology. Fracture mechanics. Tribology; Mechanical properties of solids; Metallizing; Metals. Metallurgy; On-chip interconnect structures; Physics; Semiconductor electronics. Microelectronics. Optoelectronics. Solid state devices; On-chip interconnect structures; Crack-stop characterization; Double cantilever beam; Four-point bending; Stacking; Metallizing; Porous material; Cantilever beam; Crack propagation; Microelectronic fabrication; Back end of line technology; Bending; Material testing; Copper; Low k dielectric; Die; Stacking sequence; Integrated circuit design; Mechanical properties; Adhesion; Fracture toughness; Four point probe; Signal delay; Interconnection; Measurement technique; Integrated circuit; Crack length; Adhesion test; Measurement method; Reliability; Bending test; Crack
• ISSN: 0167-9317; 1873-5568
• DOI: 10.1016/j.mee.2012.12.029

Crack propagation in BEoL (back-end of line) interconnect structures is a concern in terms of chip reliability. Due to the application of porous ultra low-k (ULK) materials, a careful trade-off is necessary between reducing signal delays and also decreasing mechanical properties of the interconnect structures. Therefore, fast and reliable measurement techniques for characterizing mechanical properties as film adhesion and fracture toughness are needed. In the present investigation, a camera assisted double-cantilever beam (DCB) technique has been used to obtain locally resolved adhesion measurements within the die. Two chip designs, produced in leading-edge technology nodes with two different ULK materials, were tested. The Gc values measured within the die show a correlation to density and arrangement of the Cu structures. ULK containing metallization levels with lowest k values have been identified as preferred crack paths. The measurements are compared with results of the four-point bending (4PB) test not having the local resolution of DCB but typically used for unpatterned film stacks and possessing a mode I/II load mixity. The DCB tests yield reduced Gc values compared to the 4PB tests, which can be understood as result of the different loading modes of both techniques.