Non-integral depth measurement of high-aspect-ratio multi-layer microstructures using numerical-aperture shaped beams

Advancements in metrology for advanced semiconductor packaging

“…OCD is in fact a general term for a group of optical systems in which optical signatures generated from the light-matter interaction of the sample were measured and compared with the simulated optical signatures based on physical modeling (e.g., RCWA or FDTD) of the test structure. Typical OCD configurations include spectral reflectometry [32], spectroscopic ellipsometry [33], Mueller-matrix ellipsometry [34], and pupil-plane scatterometry [35], each with its distinct advantages for measuring certain CD parameters. Due to the strengths of OCD being a non-contact, non-destructive, and high throughput metrology tool, it has been the workhorse for in-line CD and profile measurements in the fab.…”

Non-integral model-based scatterometry for single-structure OCD metrology

“…Founded on the concept of the conservation of Etendue, the maximization of the light efficiency for the measurement of a single HAR structure with a small opening size (i.e., small Etendue) is achieved by applying a spatially coherent supercontinuum laser with a small source size and a small divergence angle [16,17]. The system design concept is shown in Fig.…”

“…As shown in the figure, to achieve a collimated illumination, the objective focuses the laser beam into a small spot with the beam waist positioned at the structure's top surface. Additionally, in the illumination path, a beam shaping setup for controlling the NA is implemented to shape the illumination to the optimal NA and spot size [17]. In the beam shaping setup, the diameter of the laser beam incident to the objective is controlled with an aperture.…”