Optimization of the Hydrazine‐Water Solution for Anisotropic Etching of Silicon in Integrated Circuit Technology

Abstract

Anisotropic etching of silicon with the hydrazine‐water mixture is studied and characterized for its practical use in integrated circuit technology. The solution is applied to {100} wafers where the etch presents a v‐shaped cross section limited at the side‐walls by {111} planes and at the bottom by a {100} plane. The etching process is evaluated in terms of the etch rate of the {100} plane, quality of side‐walls and bottom surface, and corner rounding. It is shown that the results are both concentration and temperature dependent. The optimal temperature for the etching process is found to be 100°C for both simple temperature control and high quality etching. It is also shown that the optimal mixture concentration must be choesn according to the particular use of the anisotropic etching. The optimal volume concentrations of hydrazine for the various applications are: 65% for VMOS devices and for v‐groove isolation rings, 70–80% for two‐level structures with flat bottom surface, and for electrode and sensor fabrication.

Investigation of texturization for monocrystalline silicon solar cells with different kinds of alkaline

“…Many investigators have put forward their explanations to the texturization [8,10,11]. These explanations can be generalized as following: (a) pyramid formed from the defects in the surface; (b) contamination being the initiator of pyramid; (c) pyramid formation due to the slow dissolution rate of hydrous silca; (d) IPA and carbonic ion being the initiator of pyramid.…”

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

“…The anisotropic etchants etch materials much faster in one direction than in another, exposing the slowest etching crystal planes over time [1,2,4,10,[23][24][25][26][27]. Several kinds of aqueous alkaline solutions such as potassium hydroxide solution (KOH) [23][24][25][26][28][29][30][31][32][33][34][35], tetramethylammonium hydroxide (TMAH) [27,[36][37][38][39][40][41][42][43][44][45], ethylenediamine pyrocatechol water (EDP or EPW) [26,35,46,47], hydrazine [23,48,49], ammonium hydroxide [50], and cesium hydroxide (CsOH) [51] are employed for silicon wet anisotropic etching. Among these etchants, potassium hydroxide (KOH) and tetramethylammonium hydroxide (TMAH) are most frequently used.…”

Light Capture

“…45,46 The isopropanol is used to ensure good uniformity of pyramids by reducing the interfacial energy and so improving the wettability of the surface, 47 and by acting as a complexing agent to dissolve the hydrous silica formed during the etch reaction. 48 In an effort to reduce chemical costs, other etchants have been investigated including hydrazine monohydrate (N 2 H 4 $H 2 O), 47 K 2 CO 3 49 or Na 2 CO 3 . 50…”