Motivation: Imaging of electronics circuits is an important technique used in failure analysis, qualification analysis, and process development. Because optical signals from the front side of integrated circuits (ICs) are degraded by multiple layers of wiring, backside imaging of the chip is used. Since silicon is opaque to visible light, infrared wavelengths of 1 micron or longer are required. Unfortunately, the “diffraction limit” to resolution is approximately ½λ, implying that about 500 nm resolution is achievable. This limit is decreased by the index of refraction, n = 3.6 for silicon, when employing a solid immersion lens (SIL). SiSIL Imaging: The SiSIL image captured by the LPS collaborator Microcosm, compares favorably to images taken by other researchers (S. B. Ippolito, B. B. Goldberg and M. S. Unlu, Appl. Phys. Lett. 78 (4071) for instance). Further improvement is planned by switching to a confocal laser scanning set-up.
Novel Feature: Unlike most academic and commercial SiSIL lenses, the SiSIL is embedded in the objective. This allows for easy focus and repositioning of the lens. Applications: Any IR optical failure analysis technique should be realizable with SiSIL. Examples include Optical Beam Induced Resistance Change (OBIRCH), Laser Voltage Probe (LVP), Time Resolved Emission (TRE), Light Induced Voltage Alteration
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