Persons

During the formation of the structures using the deep anisotropic plasma etching of the silicon method with small and ultra-small aspect ratios (much less than 0.5), a number of difficulties, related to the geometry of the structures and the quality etching has been observed. In particular, this is due to large areas, 30% or more of the total area of the substrate, which qualitatively distinguishes the process from the formation of deep trenches with aspect ratios of more than 100. In the work the characteristics of the process of the deep anisotropic plasma etching of silicon depending on the operating parameters for structures with small aspect ratio (less than 0.5) have been investigated. The following aspects of the process have been considered: etching profile, radius of bottom curvature and the absence of microdefects (black silicon effect) on the bottom surface of the structure after etching, uniformity of the etching depth across the substrate, selectivity of silicon etching with respect to the photoresist mask. The use of an integrated approach in planning and analyzing the data of the Taguchi experiment has permitted a qualitative assessment of the influence of operational parameters on the output characteristics of the process. Out of 13 observed parameters 7 the most significant ones have been identified, which have the maximum effect on the process output characteristics. This has made possible to significantly reduce the number of experiments with further optimization of the etching modes and to achieve a significant improvement of the process characteristics. The processes with optimal modes allow obtaining maximally vertical etching profiles and the etching unevenness at the same time reaches the values less than ±3 % at a depth of 300 μm and the total etching area of about 50 % of the plate area.

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