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ELECTRONIC DEVICE FAILURE ANALYSIS | VOLUME 20 NO. 4 24 EDFAAO (2018) 4:24-29

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ADVANCED PACKAGING FAULT ISOLATION CASE STUDIES AND ADVANCEMENT OF EOTPR Jesse Alton 1

Thomas White 1 Martin Igarashi 2

1 TeraView Ltd., Cambridge, U.K. 2 TeraView Ltd., Portland, Ore. jesse.alton@teraview.com

device-under-test (DUT) via a high frequency circuit probe. Portions of thepulseare reflectedas it encounters changes in impedance, such as dead opens, resistive opens, and

INTRODUCTION Electro optical terahertz pulse reflectometry (EOTPR) is a well-established, nondestructive fault isolation tool for advanced integrated circuit (IC) devices. This article provides examples of how EOTPR has been implemented to investigate a wide range of advanced package types, including 2.5D and 3D packages, wafer level fanout packages, and microelectromechanical systems (MEMS) devices. In addition, it presents recent improvements to the EOTPR instrument and results froma novel modeling approach (currently under development) that has the potential to vastly accelerate fault localization analysis. HARDWARE EOTPR is an implementationof the timedomain reflec- tometry (TDR) technique at terahertz frequencies, proven toenhance fault isolationaccuracy tobetter than10µm. [1-7] As in conventional TDR, the fault detection accuracy of EOTPR is a function of the rise time of the incident pulse, the time-based jitter, and signal-to-noise ratio (SNR). The EOTPR instrument generates a terahertz pulse using an ultrafast laser and a pair of photoconductive switches for signal generation and detection, resulting in a system with (i) high measurement bandwidth, (ii) low time-base jitter, and (iii) a high time-base resolution. Compared to conventional TDR, EOTPR generates signals with faster rise time, has greater SNR, and amuch reduced time base jitter-system properties that offer the potential for a sig- nificantly increased distance-to-defect accuracy. A schematic diagram of the EOTPR system is shown in Fig. 1a. During operation, pulses are launched into a

(a)

Fig. 1 (a) Schematic diagram of an EOTPR system. (b) Typical raw EOTPR waveform from the open end of a circuit probe. (b)

Author’s note: Portions of this article were presented at ISTFA 2013, ISTFA 2017, and IPFA 2018.

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