Roughness reduction of large-area high-quality thick Al films for echelle gratings by multi-step deposition method.

Generally, echelle grating ruling is performed on a thick Al film. Consequently, high-quality large-area thick Al films preparation becomes one of the most important factors to realize a high-performance large-size echelle grating. In this paper, we propose a novel multi-step deposition process to improve thick Al films quality. Compared with the traditional single-step deposition process, it is found that the multi-step deposition process can effectively suppress large-size grains growth resulting in a low surface roughness and high internal compactness of thick Al films. The differences between single- and multi-step deposition processes are discussed in detail. By using multi-step deposition process, we prepared high-quality large-area Al films with a thickness more than 10 µm on a 520 mm × 420 mm neoceramic glass substrate.