Multimodal backside imaging of a microcontroller using confocal laser scanning and optical-beam-induced current imaging

Microscopy imaging with a single technology is usually restricted to a single contrast mechanism. Multimodal imaging is a promising technique to improve the structural information that could be obtained about a device under test (DUT). Due to the different contrast mechanisms of laser scanning microscopy (LSM), confocal laser scanning microscopy (CLSM) and optical beam induced current microscopy (OBICM), a combination could improve the detection of structures in integrated circuits (ICs) and helps to reveal their layout. While OBIC imaging is sensitive to the changes between differently doped areas and to semiconductor-metal transitions, CLSM imaging is mostly sensitive to changes in absorption and reflection. In this work we present the implementation of OBIC imaging into a CLSM. We show first results using industry standard Atmel microcontrollers (MCUs) with a feature size of about 250nm as DUTs. Analyzing these types of microcontrollers helps to improve in the field of side-channel attacks to find hardware Trojans, possible spots for laser fault attacks and for reverse engineering. For the experimental results the DUT is placed on a custom circuit board that allows us to measure the current while imaging it in our in-house built stage scanning microscope using a near infrared (NIR) laser diode as light source. The DUT is thinned and polished, allowing backside imaging through the Si-substrate. We demonstrate the possibilities using this optical setup by evaluating OBIC, LSM and CLSM images above and below the threshold of the laser source.

[1]  T. Angot,et al.  Silicene: silicon conquers the 2D world , 2016 .

[2]  R. Soref,et al.  Electrooptical effects in silicon , 1987 .

[3]  P. Echlin,et al.  Scanning Electron Microscopy , 2014 .

[4]  Assia Tria,et al.  A high efficiency Hardware Trojan detection technique based on fast SEM imaging , 2015, 2015 Design, Automation & Test in Europe Conference & Exhibition (DATE).

[5]  Assia Tria,et al.  SEMBA: A SEM based acquisition technique for fast invasive Hardware Trojan detection , 2015, 2015 European Conference on Circuit Theory and Design (ECCTD).

[6]  Luis Martí-Bonmatí,et al.  Multimodality imaging techniques. , 2010, Contrast media & molecular imaging.

[7]  R. Webb.  Confocal optical microscopy , 1996 .

[8]  Gerber,et al.  Atomic Force Microscope , 2020, Definitions.

[9]  F. H. Köklü,et al.  Widefield Subsurface Microscopy of Integrated Circuits , 2008 .

[10]  Mark Y. Liu,et al.  A 14nm logic technology featuring 2nd-generation FinFET, air-gapped interconnects, self-aligned double patterning and a 0.0588 µm2 SRAM cell size , 2014, 2014 IEEE International Electron Devices Meeting.

[11]  M. Hofmann,et al.  Axial scanning in confocal microscopy employing adaptive lenses (CAL). , 2014, Optics express.

[12]  Dick James,et al.  The State-of-the-Art in IC Reverse Engineering , 2009, CHES.

[13]  Christof Paar,et al.  Large laser spots and fault sensitivity analysis , 2016, 2016 IEEE International Symposium on Hardware Oriented Security and Trust (HOST).

[14]  W. Denk,et al.  Comparison of one- and two-photon optical beam-induced current imaging , 1999 .

[15]  Markus Finkeldey,et al.  Common-path digital holography microscopy of buried semiconductor specimen , 2016 .

[16]  Angelique Louie,et al.  Multimodality imaging probes: design and challenges. , 2010, Chemical reviews.

[17]  Christof Paar,et al.  On the Complexity Reduction of Laser Fault Injection Campaigns Using OBIC Measurements , 2015, 2015 Workshop on Fault Diagnosis and Tolerance in Cryptography (FDTC).

[18]  Jeyavijayan Rajendran,et al.  Security analysis of integrated circuit camouflaging , 2013, CCS.

[19]  Masatsugu Yamashita,et al.  Imaging of large-scale integrated circuits using laser-terahertz emission microscopy. , 2005, Optics express.

[20]  Masatsugu Yamashita,et al.  Noncontact inspection technique for electrical failures in semiconductor devices using a laser terahertz emission microscope , 2008 .

[21]  J. Pawley,et al.  Handbook of Biological Confocal Microscopy , 1990, Springer US.

[22]  Christof Paar,et al.  Common-path depth-filtered digital holography for high resolution imaging of buried semiconductor structures , 2016, SPIE OPTO.