Fabrication of 45 degrees mirrors together with well-defined V-grooves using wet anisotropic etching of silicon

The most commonly used microstructure for passive fiber alignment is the ordinary upsilon-groove, defined by (111) planes on a (100) silicon wafer, The plane at the end of the groove, having a 54.7 degrees angle to the surface, can be used as a reflecting mirror, For single-mode fiber applications, a 45 degrees mirror is advantageous together with high accuracy in the position of the fiber, i,e, a smooth mirror and good control of the groove geometry is needed. Two techniques are presented to form 45 degrees mirrors along with well-defined grooves in silicon, using the wet anisotropic etchants EDP and KOH, These techniques are used: 1) to reveal (110) planes on (100) silicon and 2) to make (111) mirrors on wafers that are cut 9.7 degrees off the [100] axis, On (100) silicon, EDP without pyrazine gave the best result. The best mirror and groove reproducibility was found on off-axis cut silicon, using 36 wt.% KOH, with isopropyl alcohol added [145].