Silicon 45° micromirrors fabricated by etching in alkaline solutions with organic additives

Abstract

The fabrication of 45°micromirrors by silicon anisotropic etching in potassium hydroxide (KOH) and tetramethylammonium hydroxide (TMAH) solutions containing organic additives is investigated in this paper. The reflective planes are formed by {110} sidewall planes inclined at 45°towards the Si (100) wafer. Isopropyl alcohol and Triton X-100 surfactant are used as additives, because they are supposed to provide the etch rate ratio R(100)/R(110) [ 1, which is necessary for {110} sidewalls development. The fabricated spatial microstructures with 45°sidewalls are examined in terms of the {110} surface roughness and the quality of the {110} sidewall profile. The KOH solution saturated with the alcohol gives the striped {110} surface, though the stripes almost disappear after addition of Triton surfactant to KOH and TMAH etchants. The 45°sidewall profiles fully defined by {110} planes are obtained in KOH as well as TMAH solutions containing additives. The measurements of micromirrors' reflectivity indicate that replacement of the alcohol by Triton surfactant in the KOH solution reduces the optical power loss caused by the reflection. The achieved reflectivity is comparable with the one obtained by etching in the TMAH solution with surfactant.

Influence of pyramid size on reflectivity of silicon surfaces textured using an alkaline etchant

“…Silicon substrates with various surface structures of different shapes and sizes are widely used in many research and industrial applications. Patterned silicon is popular and widely used, for example, to improve the efficiency of solar cells by increasing light trapping and minimizing light reflectivity of the textured silicon surfaces [1][2][3], for device fabrication of microelectromechanical system [4][5][6] and in many biological applications [7,8]. Since light surface reflections are among the major loss mechanisms in materials, different surface modifications were attempted by many research groups to control these losses [9].…”

Dynamic Wet Etching of Silicon through Isopropanol Alcohol Evaporation

“…From the solar cell industry [1,2] to MEMS (Microelectromechanical Systems) device fabrication [3][4][5] and biological applications [6,7], silicon wet etching profile has been studied and improved in order to address the specific requirements that each of these technological fields require.…”

Micromirror Angle Dependence with Etchant Choice on <100> Silicon Via Wet Etching

“…In addition these same etches are also integral to the manufacture of various integrated devices such as accelerometers [4], beam splitters [5], transistors [6] and comb structures [7]. The development of optics apparatus has recently been stimulated by the ability to use MEMS-micromachining to produce arrays of micromirrors which afford an optical 90° reflection of light [8]. The technique is both low-cost and scalable and is therefore suitable for large scale batch processing.…”