Micromachined hetero-core anti-scatter grid for a digital X-ray image sensor

A micromachined hetero-core anti-scatter grid is proposed with the aim of realizing a large field-of-view (FOV) for a digital X-ray image sensor. A theoretical anti-scattering ability was designed by deriving the rocking curve of the anti-scatter grid. The hetero-pattern, comprised of a silicon line and an air space, formed on either side of every septum, acts as the core of a linear grid. Large width silicon cores, one of the cores in a hetero-core design, play the role of a skeletal structure in the electroplating process. A large FOV was thus achieved owing to the high flexural rigidity of the skeletal structure. The hetero-cores were fabricated using photolithography and crystalline wet etching of (1 1 0) silicon, and the nickel septa were electroplated. Although the estimated theoretical limitation of the FOV was more than 100 mm × 100 mm, the FOV demonstrated from the experimental results was only 40 mm × 40 mm due to the constraint of the wafer size. The rocking curves of the fabricated grids were experimentally measured and compared with the theoretical calculations.