The Use Of Deep Reactive Ion Etching In The Fabrication Of High-Efficiency High-Resolution Crystal X-Ray Analyzers

摘要

Spherically bent silicon crystal x-ray analyzers have been employed in high-resolution inelastic x-ray scattering experiments to increase counting efficiency. To release the strain caused by the bending, the silicon wafers were diced using diamond saws into an array of ～1 x 1-mm~2 blocks, and then acid etched to remove saw damage, leaving blocks of ～0.6x0.6 mm~2 glued to a spherical concave substrate. With this method, meV energy resolution has been demonstrated. We seek to optimize the dicing process using the technique of deep reactive ion etching (DRIE) to develop efficient crystal analyzers. Ideally, each individual block subtends an angle that matches the Darwin width of the silicon reflection. This requires block sizes of about 500 μm~2. DRIE offers the flexibility of selecting the block size, with finely controlled groove widths (i.e., minimal loss of material), and hence the possibility of controlling the energy resolution of the analyzer. We have made a prototype analyzer using DRIE with blocks of 470 μm~2, groove widths of 30 μm, and about 500 μm deep. The wafer was bent and glued to a glass substrate with 2-m radius. Tests showed encouraging results, with the DRIE analyzer performing at the 200-meV level. Details of the process are discussed.