Accessible determination of die-to-wafer bond strength with the Schwickerath test. (15th April 2020)

• Record Type: Journal Article
• Authors: Shao, Shuai; Niu, Yuling; Wang, Jing; Park, Seungbae; Lee, Bongsub
• Is Part Of: Engineering fracture mechanics. Volume 229(2020)
• Publication Date: 2020-04-15
• Subjects: Direct bonding -- Bond energy -- Fracture mechanics -- Beam theory -- Three-point bending test -- Finite element method; Fracture mechanics -- Periodicals; Rupture, Mécanique de la -- Périodiques; Fracture mechanics; Periodicals; 620.112605
• DOI: 10.1016/j.engfracmech.2020.106929
• Languages: English
• ISSNs: 0013-7944

Abstract

Highlights: A test method is proposed to evaluate die-to-wafer bond strength without pre-crack. This method is validated by simulation, analytical solution and experiment. Delamination mechanism in the Schwickerath test is investigated. Bond strength is improved greatly with wafer-to-wafer bonding after annealing. Abstract: Die-to-wafer or wafer-to-wafer direct bonding has been drawing significant attention and undergoing rapid development for its various applications in three-dimensional integrated circuits (3D-IC), such as image sensors, micro-electro-mechanical system (MEMS) sensors, and stacked memory products. The bond strength is one of the most considerable factors that affect the reliability of such stacked devices. Measurement of wafer-to-wafer bond strength is normally performed by the razor blade method, but there was no such well-established technique for die-to-wafer direct bond. To characterize the die-to-wafer bond strength accurately and conveniently, this work introduced the Schwickerath three-point bending test and derived an analytical solution of bond energy, which does not require initial crack preparation. To examine the correctness of applying this method in a novel area, finite element method (FEM) and razor blade experiments on equivalent samples were conducted. Furthermore, the annealing effect on die-to-wafer bond strength was studied. Top die thickness, loading rate in three-point bending test, and the compensation factor of analytical solution are discussed and summarized in this study.