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edfas.org ELECTRONIC DEV ICE FA I LURE ANALYSIS | VOLUME 24 NO . 2 18 A STRATEGIC REVIEW OF A NOVEL SAMPLE PREPARATION METHOD FOR DOPANT PROFILING OF ADVANCED NODE FinFET DEVICES WITH SCANNING CAPACITANCE MICROSCOPY Nirmal Adhikari, Phil Kaszuba, FASM, Gaitan Mathieu, and Daminda Dahanayaka GlobalFoundries, Essex Junction, Vermont daminda.dahanayaka@globalfoundries.com EDFAAO (2022) 2:18-23 1537-0755/$19.00 ©ASM International ® INTRODUCTION Scanning capacitance microscopy (SCM), scanning spreading-resistance microscopy (SSRM) and scanning microwave impedance microscopy (sMIM) are the three main scanning probe microscopy (SPM) techniques that are used to study electrically active, dopant-related anomalies in electronic devices. [1-3] Performance of fin field-effect transistors (FinFET) devices relies on correct formation of junctions within the device with precisely controlled dopant distributions. Unintentional varia- tion in dopant distribution can affect device electrical parameters such as threshold voltage (V th ), off current (I off ), gain, subthreshold swing (SS), and carrier mobil- ity. [4,5] There is no routine sample-preparation process available for cross-sectional and plan view dopant profil- ing of nanometer-scale FinFET devices. Sample preparation is a critical step for dopant profiling of FinFET devices in advanced-node technolo- gies. Cross-section samples for SCM, SSRM, and sMIM analysis are prepared by either cleaving silicon for bigger devices built in older technologies or by mechanical polishing, depending on the size of the targeted devices. Conventional sample preparation using mechanical pol- ishing can have a long turnaround time and requires very highly skilled and experienced personnel. To understand the dopant-related anomalies from the drain to source and through the channel region of FinFET devices, cross- sectional sample preparation by mechanical polishing for SCM in advanced-node technologies requires very controllable material removal with less than 2 nm per iteration. Therefore, it has very high risk of damage in analysis. Localization of root-cause failure mechanisms within FinFET devices is very challenging due to device complexity and the use of various complex materials in the fabrication process. [6] A routine sample-preparation technique that enables mapping of the doping distribu- tion in 3D structures is critical for device parameter and fabrication process optimization. Sample preparation for SCM analysis is especially challenging when a single, specific fin is the target structure. Kaszubaet al. have successfullyusedSCMandscanning capacitance spectroscopy (SCS) to find a dopant-related failuremechanismonan individual, location-specific14nm FinFET using mechanical polishing. [1] Jarausch et al. pre- pared location-specific SCM samples using a focused ion beam (FIB) and then cleaved or mechanically ground the cross-section surface to remove the FIB induceddamage. [7] In another work, Wang et al. used FIB and mechanical polishing to mill navigation marks which are optically visible to identify the area of interest for site-specific SCM sample preparation. [8] Subramanian et al. discussed a FIB lift-out-based approach for site-specific, cross-section sample preparation, in combination with a directional mechanical polishing procedure, to produce a smooth damage-free surface for dopant profiling. [9] Most of these sample preparation techniques combine FIB and mechanical polishing, and it is very difficult to control the rate of material removal of less than 2 nm per iteration for advanced-node technologies. This review describes a novel sample-preparation technique based on low- energy and low-angle ion milling to target an individual location-specific fin for dopant related analyses. This approachprovides a robust sample-preparation technique to enable routine SCManalysis of targeted FinFET devices in advanced-node technologies. [7,10]