Terahertz confocal imaging: Polarization and sectioning characteristics

Wan, Min; Yuan, Hui; Healy, John J.; Sheridan, John T.

doi:10.1016/j.optlaseng.2020.106182

Cited by 13 publications

(9 citation statements)

References 36 publications

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“…The postprocessing of the experimental data, given for example a priori knowledge of the system 3D PSF applying computational imaging techniques, will also increase resolution. 184 Many THz inspection systems such as those used for NDR are focused on deriving accurate 3D volumes without noise, and a common issue is a slow imaging time or scanning rate. Advanced methods require lengthy processing time per pixel and perform raster scanning to collect high-resolution THz data from across a sample.…”

Section: Image Enhancementmentioning

confidence: 99%

Review of THz-based semiconductor assurance

True

Jessurun

et al. 2021

Opt. Eng.

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Terahertz radiation for inspection and fault detection has been of interest for the semiconductor industry since the first generation and detection of THz signals. Until recent hardware advances, THz systems lacked the signal quality and reliability for use as an effective nondestructive testing (NDT) method. Incremental advances in THz sources, detectors, and signal processing resulted in the successful applied-industrial use of THz NDT techniques on carbon fiber laminates, automotive coatings, and for detection of counterfeit pharmaceutical tablets. Semiconductor inspection and verification methods ensure the functionality and thereby safety of vital electronics for several critical industries. For this reason, the reliability and verification of a THz NDT method must exceed currently used inspection systems. With recent laboratory access to THz radiation, THz inspection methods are often compared with existing optical, electrical, and volumetric semiconductor verification techniques for their production monitoring and failure analysis viability. This review will cover THz techniques and their applications at the printed circuit board (PCB), integrated circuit (IC), and transistor/gate scales. The THz radiation gap spans between optical and electronic ranges with a millimeter-sized wavelength allowing for adequate penetration of plastic and ceramic and semiconductor materials. THz radiation can be used to determine structural features, electrical signatures in the THz range, and chemical information simultaneously. Cost and environmental limitations restricted the ability for THz NDT semiconductor inspection methods to escape the lab and succeed in the dynamic environment of a semiconductor fabrication environment. Hybridized metrology methods incorporating information from multiple inspection tools are a regime where THz spectral and structural data can be combined with existing methods such as optical, x-ray, or E-beam. THz can be used initially to offer support to the complex failure analysis and verification requirements of the semiconductor industry from nanoscale to macroscale features and components. For THz systems to become independent inspection tools used for semiconductor production monitoring, in the lab or fab, this will require a confident level of statistical process control for THz signal generation, detection, or processing. Applied industrial semiconductor device inspection will likely be a result of a combination of research into THz hardware, reconstruction techniques, and the widespread application of machine learning techniques. Many breakthroughs occurred over the years to enable successful nondestructive characterization and inspection of semiconductor devices from the nanoscale transistors to fully packaged integrated circuits and assembled PCBs.

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Section: Image Enhancementmentioning

confidence: 99%

Review of THz-based semiconductor assurance

True

Jessurun

et al. 2021

Opt. Eng.

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“…For continuous-wave full-field imaging, e.g., THz digital holography and THz ptychography, efforts have been made to mechanically or numerically expand the aperture of the array detectors in squeezed recording distance [4][5][6][7] . For other imaging geometries using more sensitive cell detectors, their lateral resolution mainly depends on the diameter of the focusing spot of the illumination beam [8][9][10][11][12] , which is usually converged to ∼2 mm at minimum by off-axis parabolic mirrors or homogeneous transmissive convex lenses (TCLs) [13,14] . The Abbe limit can be overcome by using composite lens made of highly resistive silicon and high-density polyethylene, so that the resolution is enhanced from 0.85λ to 0.35λ at 0.5 THz [15] .…”

Section: Introductionmentioning

confidence: 99%

Binary diffractive lens with subwavelength focusing for terahertz imaging

et al. 2023

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The converging lens is one of the key components in high-resolution terahertz imaging. In this Letter, a binary diffractive lens is proposed for the scanning imaging system working at 278.6 GHz, in which a convergent beam with a waist diameter of 0.65 mm is generated, and 1 mm lateral imaging resolution is realized. This low-cost terahertz lens, constituted by concentric rings with different radii, is optimized by stimulated annealing algorithm and fabricated by three-dimensional printing. Compared with the conventional transmissive convex lens, higher resolution and enhanced imaging quality are achieved via smaller focal spot of the illumination beam. This type of lens would promote terahertz imaging closer to practical applications such as nondestructive testing and other scenarios.

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“…In 2020, Wan et al built a transmission THz confocal imaging system using a 300 GHz source and a Golay cell detector. The polarization characteristics and slice characteristics of high contrast amplitude and low contrast phase objects are studied, which effectively improves the resolution characteristics of the system [13]. THz confocal imaging can be combined with THz light field modulation elements, especially to form a modulation device with short focal depth and low sidelobe energy, or to generate a smaller focal spot to scan the object point by point.…”

Section: Introductionmentioning

confidence: 99%

Terahertz confocal microscopy based on Fibonacci super-oscillatory lens

Yang,

Rong,

Zhang

et al. 2023

Fourteenth International Conference on Information Optics and Photonics (CIOP 2023)

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Terahertz confocal imaging: Polarization and sectioning characteristics

Cited by 13 publications

References 36 publications

Review of THz-based semiconductor assurance

Review of THz-based semiconductor assurance

Binary diffractive lens with subwavelength focusing for terahertz imaging

Terahertz confocal microscopy based on Fibonacci super-oscillatory lens

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