A method of determining crystal orientation in a wafer is described in the publication "A latching accelerometer fabricated by the anisotropic etching of (110)-oriented silicon wafers" by Dino R. Ciarlo in the journal "Micromech. Microeng.," 2, 1992, pages 10-13. According to the method described therein, rectangular mask openings such as circular scale marks are arranged one next to the other. The angle between two adjacent rectangular mask openings is 0.1.degree.. Each rectangular mask opening is 8 .mu.m wide and 3 mm long. During anisotropic etching of the wafer surface to which the etching mask has been applied, undercut zones, which are bounded by (111) planes, develop at the sides of the mask openings. The dimensions of the undercut zone will vary depending on the orientation of the mask opening relative to the crystal orientation which is to be found. The dimensions of a particular undercut zone are determined optically, and the location of the mask opening at the side of which the undercut zone is smallest is utilized for determining the crystal orientation. The dimension of the smallest undercut zone must be larger than the wavelength of the light used for measuring in order for it to be perceived; thus it must be larger than around 0.5 .mu.m. This is ensured according to this method, among other things, by the dimensions selected for the rectangular mask openings. The achievable angle precision in determining crystal orientation using this method depends on the angle between two adjacent mask openings. For reasons related to the manufacture of masks, this angle cannot be made smaller than 0.1.degree.. The best precision achievable in determining crystal orientation is thus 0.05.degree.. The required etching time in the known method is around 30 hours, depending on the length of the rectangular mask openings. While a reduction of the length of the rectangular mask openings would result in a reduction in etching time, it would also affect the dimensions of the undercut zones causing them no longer to be measurable.