Investigation on the security of stored data in emerging non-volatile memory devices using AFM- based techniques

Abstract

Nowadays, non-volatile memory (NVM) devices are extensively used for information storage in artificial intelligence, communication, transportation, mobile and many other applications. With their intended use in these applications, it is important to evaluate the security of stored data in these devices against extraction or modification. Hardware security analysis includes physical attacks and software attacks. Prior studies have been conducted on NVMs such as Flash and EEPROM devices using Atomic Force Microscopy (AFM) based techniques. AFM is a versatile tool that can measure different material properties along with topography and morphology information. This makes it suitable for the investigation on the emerging NVMs such as magnetic random-access memory (MRAM), ferroelectric random-access memory (FeRAM), phase-change memory (PCM), and resistive random-access memory (RRAM) in the market.In this study, RRAM and MRAM devices that are available in the market will first be analyzed through the use of failure analysis techniques such as chemical deprocessing, Xray imaging and scanning electron microscopy (SEM) with focused ion beam (FIB) to understand its device architecture. Next, deprocessing steps such as chemical etching and reactive ion etching will be developed to access the data storage layer of the RRAM/MRAM where the devices store their data depending on the resistance state, which corresponds to the binary bit of '1' or '0'. Then, the AFM technique such as conductive probe AFM (CP-AFM), using a constant dc bias, will be used to scan across the sample's surface and directly probe on the data storage layer to measure the current and thus its resistance. The collected results from the current scans will be validated with the input data in order to assess the accuracy of the technique. Precaution measures adopted to prevent the loss of data during the sample preparation process will also be discussed. The first ever successful readout of data in RRAM samples using CP-AFM has been achieved and block level data organization of the memory is also presented in this study, thus demonstrating the vulnerability of RRAM devices to security attacks, and potentially MRAM technology as well.