Failure analysis of tamper resistant materials for IC packaging

• Main Author: Siah, Yu Wen
• Other Authors: Gan Chee Lip
• Format: Theses and Dissertations
• Language: English
• Published: 2019
• Subjects: DRNTU::Engineering::Materials
• Online Access: https://hdl.handle.net/10356/104717; http://hdl.handle.net/10220/48618
• Institution: Nanyang Technological University

In recent years, the surge in counterfeit products in the microelectronics industry has escalated to problems such as losses and damages of companies’ reputation and consumers’ safety and confidence. With the aim to protect products and devices from attackers to obtain their circuit design, intellectual property (IP) or even secured data, anti-tampering (security) features have been gaining great interest in companies as well as government bodies. With equipment technology advancement, attackers may utilize them to tamper with the devices to retrieve information in an unorthodox manner. Therefore in this report, the motivation for tamper resistant material for IC packaging is first elaborated, follow by literature review conducted from types of integrated circuits (IC) packaging available on the market to the packaging materials, steps taken to produce counterfeit IC and analysis of the internal structure by removal of packaging materials with different techniques (e.g. laser decapsulation). In addition, the rationale of focusing on laser utilization will be mentioned and lastly, the fundamentals of laser and the laser applications in microelectronics will be elaborated. Experiments are conducted on commercial packages and in-house formulated epoxy resin, Glycidyl-POSS (GP), either with or without carbon black/surface treatment on fillers. The components that formed GP, sample preparation processes, laser parameters and the characterization tools utilized will be described. Different types of GP samples prepared are characterized. Images of these GP samples after laser ablation are captured and step profiler is used to quantify the etch depth for analysis. The resistance to laser ablation is obtained, analyzed and discussed. From the data, it is postulated that due to the strong light absorptivity of carbon black, GP samples which do not contain carbon black but with fillers show better resistance to laser ablation in contrast to samples that contain both carbon black and fillers. In addition, the relationship between adhesion of the matrix and fillers to improve stress transfer and its effect on the extent of laser ablation is also studied. Amino silane treated fillers added into GP matrix were used to fabricate good matrix-filler adhesion samples while Glycidyl silane treated fillers added into GP matrix produced samples with poor adhesion. More details of the results and analysis will be explained in this report. Overall, samples without carbon black showed superior performance, being almost laser resistant. This indicates that the carbon black plays the key role as the light absorber and if the material is designed to not absorb any of the laser light, the damage incurred will be very minimal. In the case where colour pigment such as carbon black cannot be omitted (for blocking light transmission) in the device encapsulating process, it is important to reduce air gaps due to poor adhesion between matrix and fillers or pores/voids as all these defects act as the point of weakness which hinder stress transfer, or to find alternative colour pigments which would absorb the laser light less efficiently.