For most micro-mechanical devices, a high precision alignment of mask pattern to crystal orientation is preferred. Such alignment even becomes critical for devices that simultaneously require a smooth sidewall and minimal undercut. In this article, we present an innovative pre-etching pattern to determine the crystal orientation on [100] silicon wafers. This pattern etched on the wafer allows us to determine the crystal orientation within an accuracy of. Such a pre-etching pattern can be used as a valuable reference for all subsequent mask patterns.