Review of THz-based semiconductor assurance

Abstract

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.

Terahertz Barcodes Enabled by All‐Silicon Metasurfaces for Process Control and Monitoring Applications

“…Terahertz imaging and spectroscopy are considered as promising candidates for PCM applications due to the considerable penetration depth and high temporal and spatial resolution of terahertz wave. [18] Besides quality control in food and water security, [19] architectural art, [20] and pharmaceutical and clinical applications, [21] terahertz non-contact detection has been employed in semiconductor product assurance [22,23] based on the optical properties of related materials, for example, silicon. [24,25] The development of portable terahertz sources enables high-efficiency PCM in semiconductor industries.…”

High-resolution imaging enabled by 100-kW-peak-power parametric source at 5.7 THz

“…As a result, THz imaging has become a powerful means to reveal hidden objects with high contrast in some materials 1 , 2 . This has been exploited in applications, such as security checking 3 , 4 , semiconductor quality assurance 5 , and others. Especially, tunable THz radiation is useful for wavelength-sensitive applications such as spectrally resolved imaging for illicit drugs 6 and biomedical materials 7 , 8 .…”

“…High source power is important to achieving enough signal-to-noise ratio, whereas the resolution of an image is scaled by the wavelength of the source illuminating the object. Currently, most THz imaging is performed with a source frequency below 2 THz 3 , 5 , 6 , 8 , where commercial microbolometer sensors, Schottky diodes, or photoconductive antennas are available for detection and image construction 9 – 11 . Although high-frequency THz radiation is advantageous for high-resolution imaging, low-cost image sensor arrays are not widely available in the 5–10 THz frequency range.…”

Lightwave‐Driven Long‐Wavelength Photomultipliers

“…[1][2][3][4][5][6] Several applications are branching out of the laboratories into real-world environments with hopes and promises of a significant impact on our future society. THz spectroscopy proves to be a strong tool for quality control of various processes such as in the semiconductor industry, [7] for environmental control by monitoring gases, [8] or for food product safety. [9] The transparency of many materials to and non-ionizing properties of THz radiation is also engendering the development of several non-destructive in-situ tools to monitor industrial processes, pharmaceutics, or to detect hidden objects in security applications, [10] as well as cultural heritage studies [11] and THz-imaging.…”