Triton Surfactant as an Additive to KOH Silicon Etchant

Abstract

Anisotropic etching of Si (100) and (110) planes in alkaline solutions containing the nonionic surfactant is studied in this paper. Triton X-100 surfactant, normally used for the modification of TMAH (tetramethylammonium hydroxide) etchant, is added to KOH (potassium hydroxide) solution. As a result, the (100) and (110) etch rates are significantly reduced and the etch rate ratio R(100)/R(110) >1 is obtained. The influence of KOH concentration (at 10 and 100 ppm (v/v) of the surfactant) on the etching process is also investigated. Low roughness of (110) surface is achieved in the 2 M KOH solution containing Triton. The smooth {110} sidewall planes inclined at 45°toward the (100) substrate are fabricated by etching in the KOH + Triton solution. The 45°{110} sidewalls are potentially attractive as MEMS micromirrors for optical beam reflection at an angle of 90°. The low etch rate of (100) plane is kind of a disadvantage of the fabrication method, but it can be fairly overcome by elevating the process temperature and stirring the etching solution.[ 2012-0371]Index Terms-Anisotropic etching, potassium hydroxide (KOH), silicon, surfactant, Triton X-100.

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“…0.1% v/v) in TMAH [134][135][136][137][138][139][140][141][142][143][144][145][146][147] ensure a significant reduction in the etch rates of {110} and its vicinal planes (or the planes between {110} and {111} surfaces such as {441}, {331}, {221}, etc.). Recently, surfactant added KOH is characterized to alter the etching anisotropy and etched surface morphology [148,149]. The etch rates of principle orientations (i.e.…”

A comprehensive review on convex and concave corners in silicon bulk micromachining based on anisotropic wet chemical etching

“…0.1% v/v) in TMAH [134][135][136][137][138][139][140][141][142][143][144][145][146][147] ensure a significant reduction in the etch rates of {110} and its vicinal planes (or the planes between {110} and {111} surfaces such as {441}, {331}, {221}, etc.). Recently, surfactant added KOH is characterized to alter the etching anisotropy and etched surface morphology [148,149]. The etch rates of principle orientations (i.e.…”

Wet etching of deep trenches on silicon with three-dimensional (3D) controllability

“…In basic wet etching, the controllability of tapering angle originates from the different etch rate of crystalline plane in single crystal silicon substrate. Tapering angle of 90 o , 54.7 o and 45 o have been achieved from various combinations of etchant, additives [14] and silicon substrate. The trenches etched by basic wet etching have been widely used for MEMS [15], microfluidic system [16] and optical devices [17,18].…”