Indentation damage evaluation on metal-coated thin-films stacked structure
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Indentation damage evaluation on metal-coated thin-films stacked structure Alfred Yeo Operation Backend Development, Infineon Technologies Asia Pacific Pte Ltd, Singapore 349253; and School of Mechanical and Aerospace Engineering, Nanyang Technological University, Singapore 639798
Mao Liu and Kun Zhoua) School of Mechanical and Aerospace Engineering, Nanyang Technological University, Singapore 639798 (Received 27 May 2015; accepted 26 August 2015)
A micro-indentation system integrated with an acoustic emission (AE) sensor is used as a damage test method for crack detection of the specimen during the indentation loading–unloading cycle. The specimens investigated are the Si die, and various stacked structures of metallization (Al or Cu) deposited over the dielectric layers (SiO2 or Si3N4) on the Si substrate. The 1st AE event detected during the loading stage corresponded to the ‘pop-in’ observation in the force–displacement curve, which was related to the brittle cracking in the dielectric or Si substrate. However, during unloading, a 2nd AE event was detected, but no “pop-out” was observed, which was mainly due to the delamination between the dielectric and Si substrate. It was also found that for Si die, “pop-out” was observed without any AE event during the unloading stage, which was related to the Si phase transformation. This observation is unique to sharp indenter tip but not for a blunt indenter tip. I. INTRODUCTION
An instrumented indentation equipment, also known as the depth-sensing indentation, has been increasingly being used to probe the mechanical response of materials from metals and ceramics to polymeric engineering materials.1–39 Due to the ease and speed of the indentation testing, this method has gained popularity in assessing the mechanical properties of thin films and small volume specimens, as motivated by their modern applications in microelectronics, microelectromechanical systems (MEMSs), biomaterials, etc.3–7,15–18,22–25,29–35 The most fundamental measures made by an instrumental indentation system are force and displacement, which describe the mechanical behavior of the material during the indentation process. The two measurements are typically coupled in the system through support springs. The additional levels of control, sensitivity, and data acquisition offered by depth-sensing indentation systems have resulted in numerous advances in materials science, particularly on fundamental mechanisms of mechanical behavior at the micrometer and even submicrometer length scales. As such, it can be used to determine not only the hardness but also the elastic modulus E, yield strength Y, strain-hardening exponent, fracture toughness, energy absorption, and other timedependent properties.1–39 All these material properties
Contributing Editor: Sam Zhang a) Address all correspondence to this author. e-mail: [email protected] DOI: 10.1557/jmr.2015.278 J. Mater. Res., Vol. 30, No. 20, Oct 28, 2015
depend on the interpretation and analysis of the force– displacement F–d results, coupled with the analyt
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