Abstract: An authentication article includes: a substrate including: a first surface; a second surface disposed laterally to the first surface and at a depth below the first surface; and a plurality of indentations including the depth at the second surface of the substrate; and an array disposed on the substrate and including a plurality of analytes, the analytes being disposed in the indentations at a depth below a first surface of the substrate and provided to emit an authentication signature in response to being subjected to a probe stimulus. A process for authenticating the authentication article includes: providing the authentication article; subjecting the analytes to a probe stimulus; acquiring a response from the plurality of analytes in response to being subjected to the probe stimulus; and determining whether the response is the authentication signature to authenticate the, wherein the authentication article is not authenticated if the response is not the authentication signature for the array.

Abstract: An authentication article includes: a substrate including: a first surface; a second surface disposed laterally to the first surface and at a depth below the first surface; and a plurality of indentations including the depth at the second surface of the substrate; and an array disposed on the substrate and including a plurality of analytes, the analytes being disposed in the indentations at a depth below a first surface of the substrate and provided to emit an authentication signature in response to being subjected to a probe stimulus. A process for authenticating the authentication article includes: providing the authentication article; subjecting the analytes to a probe stimulus; acquiring a response from the plurality of analytes in response to being subjected to the probe stimulus; and determining whether the response is the authentication signature to authenticate the, wherein the authentication article is not authenticated if the response is not the authentication signature for the array.

Abstract: Imaging instruments for inspecting products, such as semiconductor chips, are calibrated by providing a reference test structure having features which can be located by electrical measurements not subject to tool-induced shift and wafer-induced shift experienced by the imaging instrument. The reference test structure is first qualified using electrical measurements, and is then used to calibrate the imaging instrument. The electrical measurements may be made by forcing a current between a plurality of spaced reference features and an underlying conductor, or may be made by capacitive, conductive, magnetic, or impedance-measuring techniques. Capacitive techniques may also be used to detect features not susceptible of resistance measurement, such as dielectric or insulative materials, or metallic structures not accessible for forcing a current therethrough.