Rapid 3D-Imaging of Semiconductor Chips Using THz Time-of-Flight Technique

Yim, Ji Hye; Kim, Su-Yeon; Kim, Yiseob; Cho, Suyoung; Kim, Jangsun; Ahn, Y. H.

doi:10.3390/app11114770

Cited by 16 publications

(10 citation statements)

References 34 publications

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“…We used a delay-scan range of Δ T = 100 ps, which corresponds to a vertical range of 15 mm in the case of free-space propagation. Here, the time delay can be converted into depth information, in which 1 ps corresponds to 0.15/ n mm in the reflection geometry, where n is the refractive index of the materials [ 33 , 34 ]. The images were recorded as a single binary file, which can be reconstructed using home-built analyzing software.…”

Section: Methodsmentioning

confidence: 99%

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High-Speed THz Time-of-Flight Imaging with Reflective Optics

Yoo

Kim²,

Ahn

2023

Sensors

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In this study, we develop a 3D THz time-of-flight (TOF) imaging technique by using reflective optics to preserve the high-frequency components from a THz antenna. We use an Fe:InGaAs/InAlAs emitter containing relatively high-frequency components. THz-TOF imaging with asynchronous optical sampling (ASOPS) enables the rapid scanning of 100 Hz/scan with a time delay span of 100 ps. We characterize the transverse resolution using knife edge tests for a focal length of 5; the Rayleigh resolution has been measured at 1.0 mm at the focal plane. Conversely, the longitudinal resolution is determined by the temporal pulse width, confirmed with various gap structures enclosed by a quartz substrate. The phase analysis reveals that reflected waves from the top interface exhibit a phase shift when the gap is filled by high-indexed materials such as water but shows in-phase behavior when it is filled with air and low-indexed material. Our imaging tool was effective for inspecting the packaged chip with high lateral and longitudinal resolution. Importantly, the phase information in 2D and 3D images is shown to be a powerful tool in identifying the defect—in particular, delamination in the chip—which tends to be detrimental to the packaged chip’s stability.

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Section: Methodsmentioning

confidence: 99%

“…Recently, rapid THz-TOF imaging methods have been introduced for the inspection of packaged integrated circuits and defects in insulating materials [ 33 , 34 ]. An imaging rate of 100–200 Hz/pixels has been achieved based on the THz–TDS technique where fast time-delay scanning methods have been implemented.…”

Section: Introductionmentioning

confidence: 99%

High-Speed THz Time-of-Flight Imaging with Reflective Optics

Yoo

Kim²,

Ahn

2023

Sensors

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“…The presence of epoxy molding compounds (EMCs) in the package generally might affect the performance of encapsulated detectors, and this influence needs to be evaluated. Multiple studies of various EMCs in the THz range [ 29 , 30 , 31 ] indicated their very similar refractive index values of

, n = 1.897–1.940, and

, respectively. The obtained small variations of the refractive index were attributed to differences in the silica filler content [ 30 ].…”

Section: Methodsmentioning

confidence: 99%

Design and Performance of Extraordinary Low-Cost Compact Terahertz Imaging System Based on Electronic Components and Paraffin Wax Optics

Tamošiūnas

Minkevičius

Bučius

et al. 2022

Sensors

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Terahertz (THz) imaging is a powerful technique allowing us to explore non-conducting materials or their arrangements such as envelopes, packaging substances, and clothing materials in a nondestructive way. The direct implementation of THz imaging systems relies, on the one hand, on their convenience of use and compactness, minimized optical alignment, and low power consumption; on the other hand, an important issue remains the system cost and its figure of merit with respect to the image quality and recording parameters. In this paper, we report on the design and performance of an extraordinary low-cost THz imaging system relying on a InP Gunn diode emitter, paraffin wax optics, and commercially available GaAs high-electron-mobility transistors (HEMTs) with a gate length of 200 nm as the sensing elements in a room temperature environment. The design and imaging performance of the system at 94 GHz is presented, and the spatial resolution in the range of the illumination wavelength (∼3 mm) and contrast of nearly two orders of magnitude is determined. The operation of two models of the HEMTs of the same nominal 20 GHz cut-off frequency, but placed in different packages and printed circuit board layouts was evaluated at 94 GHz and 0.307 THz. The presence of two competing contributions—self-resistive mixing and radiation coupling through the antenna effects of the printed circuit boards—to the detected signal is revealed by the signal dependence on the gate-to-source voltage, resulting in a cross-sectional responsivity of 27 V/W and noise-equivalent power of 510 pW/Hz at 94 GHz. Further routes in the development of low-cost THz imaging systems in the range of EUR 100 are considered.

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“…Only one high-end laser is typically used for this technique, but it is of course limited by physically moving parts. To date, scan rates of a few hundred Hz have been demonstrated 9 , 10 . PHIRE (parallel heterodyne interferometry via rep-rate exchange), a conceptually similar single-laser technique, was demonstrated for use in dual-comb interferometry 11 , where kHz scan rates were achieved (164 kHz in the case of raw acquisitions, slowed to a few kHz when averaging was used to improve the signal quality).…”

Section: Introductionmentioning

confidence: 99%

Megahertz scan rates enabled by optical sampling by repetition-rate tuning

Bajek

Cataluna

2021

Sci Rep

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We demonstrate, for the first time, optical sampling by repetition-rate tuning (OSBERT) at record megahertz scan rates. A low-cost, tunable and extremely compact 2-section passively mode-locked laser diode (MLLD) is used as the pulsed laser source, whose repetition rate can be modulated electronically through biasing of the saturable absorber section. The pulsed output is split into two arms comparable to an imbalanced Michelson interferometer, where one arm is significantly longer than the other (a passive delay line, or PDL). The resulting electronic detuning of the repetition rate gives rise to a temporal delay between pulse pairs at a detector; the basis for time-resolved spectroscopy. Through impedance-matching, we developed a new system whereby a sinusoidal electrical bias could be applied to the absorber section of the MLLD via a signal generator, whose frequency could be instantly increased from sub-hertz through to megahertz modulation frequencies, corresponding to a ground-breaking megahertz optical sampling scan rate, which was experimentally demonstrated by the real-time acquisition of a cross-correlation trace of two ultrashort optical pulses within just 1 microsecond of real time. This represents scan rates which are three orders of magnitude greater than the recorded demonstrations of OSBERT to date, and paves the way for highly competitive scan rates across the field of time-resolved spectroscopy and applications therein which range from pump probe spectroscopy to metrology.

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Rapid 3D-Imaging of Semiconductor Chips Using THz Time-of-Flight Technique

Cited by 16 publications

References 34 publications

High-Speed THz Time-of-Flight Imaging with Reflective Optics

High-Speed THz Time-of-Flight Imaging with Reflective Optics

Design and Performance of Extraordinary Low-Cost Compact Terahertz Imaging System Based on Electronic Components and Paraffin Wax Optics

Megahertz scan rates enabled by optical sampling by repetition-rate tuning

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