Micromachined anti-scatter grid fabricated using crystalline wet etching of (110) silicon and metal electroplating for X-ray imaging

摘要

Two-dimensional micromachined anti-scatter grids were fabricated using MEMS technology, including crystalline wet etching of (110) silicon and metal electroplating for X-ray imaging. The core sizes of the square grids were 100, 200, and 300 μm with 2.2 mm height and 50 urn septa thickness. To prepare the etch mask for crystalline wet etching, silicon nitride was deposited using low pressure chemical vapor deposition (LPCVD). The grid patterns, which are aligned parallel to the vertical (111) plane of the (110) silicon, were transferred from the photomask onto the photoresist using deep ultraviolet (DUV) photolithography, and consecutively onto the silicon nitride using reactive ion etching (RIE). A (110) silicon substrate was then etched in a tetramethyl ammonium hydroxide (TMAH) solution to form a skeleton for the septa structure. Chrome was sputtered to provide a seed layer for nickel electroplating, where nickel grows on the sidewalls of the skeleton of the septa structure. Finally, two-dimensional septa with various grid ratios were constructed by cross-stacking several layers of the patterned (110) silicon wafer. Anti-scattering ability was experimentally characterized in terms of X-ray transmission by one-dimensional scanning of incident angle.