Formation of self-aligned holes in an arbitrary pattern in silicon substrate

Abstract
A self‐aligning etch method for silicon substrates is presented. A hole pattern is defined on the front side of the silicon substrate while etching of the hole takes place from the back side through the application of a current from the front side of the silicon substrate to a cathodeelectrode in a solution of HF, HNO3, and H2O. As the etching proceeds, the etched pattern in the back side gradually becomes self‐aligned with the front side pattern of the silicon substrate. Twenty five circular holes arranged in a 5×5 array are formed in a boron‐doped (100) silicon substrate. The etch method provides control over hole dimensions which are 520 μm in diameter and spaced 520 μm apart. The self‐aligning property of the etch method enables the formation of different shaped holes.

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