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Feasibility of Novel Wafer Scale Imaging Methods for Identification of Defects in Semiconductors for Net-Zero

Koutsourakis, G; Baltusis, A; Wood, S; Blakesley, J; Castro, F A (2022) Feasibility of Novel Wafer Scale Imaging Methods for Identification of Defects in Semiconductors for Net-Zero. NPL Report. TQE 21

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Semiconductor materials have a significant role to play towards the national Net Zero targets, through their roles in renewable energy generation, electricity distribution, and efficient energy consumption. Both established and emerging semiconductors have relevant net zero applications such as: power electronics for electric vehicles, grid infrastructure, and inverters for renewable energy generation, photovoltaics, as well as efficient telecommunications and lighting/display devices. Quality control is critical to the manufacturing industry for these semiconductor materials where defect-related yield and performance losses are widely recognised challenges.

This report describes research carried out by NPL within the NMS programme towards developing a new imaging approach for wafer-scale defect identification. We have explored the use of compressed sensing as a strategy for increasing the throughput and sensitivity of defect inspection for various semiconductor materials. In particular we consider the novel application of compressed sensing (CS) to time-resolved photoluminescence (TRPL) mapping, where the local photoluminescence lifetime of the semiconductor reveals the presence of defects and inhomogeneities. We evaluate the feasibility and the potential gains in performance compared with traditional point-by-point measurement strategies and evaluate the feasibility of applying the method to several semiconductor materials.

The developed system of this work is currently operating as a typical TRPL system, with single point and raster scanning capability. This has added a capability that did not previously exist at NPL. Simulations of the CS TRPL sampling process have showed that the methodology is feasible and can be applied to achieve TRPL mapping with high resolution for small areas of semiconductor wafers with the developed instrument. In addition, the simulations have provided the necessary insights into how the reconstruction process can be applied for the CS TRPL method.

Comparison of the instrument specifications with typical material parameters for ‘Net Zero’ materials indicates that the current system is well-suited for TRPL measurements of the vast majority of photovoltaic absorber materials. The current capabilities also apply to many organic semiconductors and transition metal dichalcogenides, which have various optoelectronic applications relevant to ‘Net Zero’ technologies. The potential upgrades of the system in regard to light sources, detectors, optical components or algorithms have been discussed.

Item Type: Report/Guide (NPL Report)
NPL Report No.: TQE 21
Keywords: Photoluminescence, imaging, semiconductors, net zero
Subjects: Advanced Materials > Non-Destructive Testing
Divisions: Electromagnetic & Electrochemical Technologies
Identification number/DOI: 10.47120/npl.TQE21
Last Modified: 13 Apr 2022 13:58
URI: http://eprintspublications.npl.co.uk/id/eprint/9415

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