Etching simulation of convex and mixed InP and Si structures

Chahoud, M.; Wehmann, H.-H.; Schlachetzki, A.

doi:10.1016/s0924-4247(98)00090-9

Cited by 10 publications

(11 citation statements)

References 18 publications

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“…Hence the fabrication of structures with protected convex corner is a tedious task for both {100} and {110} silicon wafers. The mechanism of undercutting [79][80][81][82][83][84][85][86][87] and the fabrication of convex corners [24, are widely investigated. Although we have published a review article in 2007 on the fabrication of convex corners, it covers the techniques reported upto 2005 for Si{100} wafers only [109].…”

Section: Classification Of Micromachining For the Realization Of Micrmentioning

confidence: 99%

“…Moreover, why the undercutting is suppressed when the etching is done in alcohol-added KOH (or surfactant-added TMAH) as shown in Figures 11 and 12. Several models have been developed to explain the mechanism behind the undercutting at convex corner [80][81][82][83][84][85][86]. Most of the models talk about Si{100} wafers as this orientation is most widely employed in microfabrication.…”

Section: Why Does Undercutting Starts At Convex Corners?mentioning

confidence: 99%

“…Most of the models talk about Si{100} wafers as this orientation is most widely employed in microfabrication. In general, they explain that the undercutting occur due to the appearance of high etch rate planes during etching process [80][81][82][83][84][85]. At the atomistic scale, the convex corner exposes low coordination atoms with high removal rates, hence inducing the emergence of fast etching planes as the sloping facets or bevels [164].…”

Section: Why Does Undercutting Starts At Convex Corners?mentioning

confidence: 99%

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

Pal¹,

Sato²

2016

Nano Online

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Wet anisotropic etching based silicon micromachining is an important technique to fabricate freestanding (e.g. cantilever) and fixed (e.g. cavity) structures on different orientation silicon wafers for various applications in microelectromechanical systems (MEMS). {111} planes are the slowest etch rate plane in all kinds of anisotropic etchants and therefore, a prolonged etching always leads to the appearance of {111} facets at the sidewalls of the fabricated structures. In wet anisotropic etching, undercutting occurs at the extruded corners and the curved edges of the mask patterns on the wafer surface. The rate of undercutting depends upon the type of etchant and the shape of mask edges and corners. Furthermore, the undercutting takes place at the straight edges if they do not contain {111} planes. {100} and {110} silicon wafers are most widely used in MEMS as well as microelectronics fabrication. This paper reviews the fabrication techniques of convex corner on {100} and {110} silicon wafers using anisotropic wet chemical etching. Fabrication methods are classified mainly into two major categories: corner compensation method and two-steps etching technique . In corner compensation method, extra mask pattern is added at the corner. Due to extra geometry, etching is delayed at the convex corner and hence the technique relies on time delayed etching. The shape and size of the compensating design strongly depends on the type of etchant, etching depth and the orientation of wafer surface. In this paper, various kinds of compensating designs published so far are discussed. Two-step etching method is employed for the fabrication of perfect convex corners. Since the perfectly sharp convex corner is formed by the intersection of {111} planes, each step of etching defines one of the facets of convex corners. In this method, two different ways are employed to perform the etching process and therefore can be subdivided into two parts. In one case, lithography step is performed after the first step of etching, while in the second case, all lithography steps are carried out before the etching process, but local oxidation of silicon (LOCOS) process is done after the first step of etching. The pros and cons of all techniques are discussed.

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Section: Classification Of Micromachining For the Realization Of Micrmentioning

confidence: 99%

Section: Why Does Undercutting Starts At Convex Corners?mentioning

confidence: 99%

Section: Why Does Undercutting Starts At Convex Corners?mentioning

confidence: 99%

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

Pal¹,

Sato²

2016

Nano Online

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“…Hence the fabrication of structures with protected convex corner is a tedious task. The mechanisms of undercutting for {100}-oriented silicon wafer are widely investigated [11][12][13][14][15][16]. However, very less is reported for {110}Si wafers [17][18][19][20].…”

Section: Introductionmentioning

confidence: 99%

A New Model for the Etching Characteristics of Corners Formed by Si<sub>{111}</sub> Planes on Si<sub>{110}</sub> Wafer Surface

Pal¹,

Singh²

2013

ENG

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The etching characteristics of concave and convex corners formed in a microstructure by the intersection of {111} planes in wet anisotropic etchant are exactly opposite to each other. The convex corners are severely attacked by anisotropic etchant, while the concave corners remain unaffected. In this paper, we present a new model which explains the root cause of the initiation and advancement of undercutting phenomenon at convex corners and its absence at concave corners on {110} silicon wafers. This contrary etching characteristics of convex and concave corners is explained by utilizing the role of dangling bond in etching process and the etching behavior of the tangent plane at the convex corner. The silicon atoms at the convex edge/ridge belong to a high etch rate tangent plane as compared to {111} sidewalls, which leads to the initiation of undercutting at the convex corner. On the other hand, all the bonds of silicon atoms pertaining to concave edges/ridge are engaged with neighboring atoms and consequently contain no dangling bond, thus resulting in no-undercutting at concave edges/corners.

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“…is added in the etchant [16][17][18][19][20][21][22][23]. In order to explain the mechanism behind the corner undercutting, several models have been proposed [12,[24][25][26][27]. They explain that the appearance of high index planes during etching is the main cause of the undercutting.…”

Section: Introductionmentioning

confidence: 99%

A simple and robust model to explain convex corner undercutting in wet bulk micromachining

Pal

Singh

2013

Micro Nano Syst Lett

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In this paper, a simple and robust model is presented to explain the main reason behind undercutting at convex corners and no-undercutting at concave corners. The etch rate of the tangent plane at convex corner and the role of dangling bond in etching process are utilized to explain the undercutting at convex corner and the no-undercutting at concave corner, respectively. The present model shows that {110} is the tangent plane at convex corner which exhibits higher etch rate than the neighboring {111} plane in all types of anisotropic etchants; consequently the undercutting occurs at convex corners. The absence of dangling bonds at concave corner prevents the undercutting there. Moreover, the same model explains the reason of very less undercutting when the etching is carried out in surfactant-added tetramethylammonium hydroxide (TMAH).

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Etching simulation of convex and mixed InP and Si structures

Cited by 10 publications

References 18 publications

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

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

A New Model for the Etching Characteristics of Corners Formed by Si<sub>{111}</sub> Planes on Si<sub>{110}</sub> Wafer Surface

A simple and robust model to explain convex corner undercutting in wet bulk micromachining

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Etching simulation of convex and mixed InP and Si structures

Cited by 10 publications

References 18 publications

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

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

A New Model for the Etching Characteristics of Corners Formed by Si&lt;sub&gt;{111}&lt;/sub&gt; Planes on Si&lt;sub&gt;{110}&lt;/sub&gt; Wafer Surface

A simple and robust model to explain convex corner undercutting in wet bulk micromachining

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A New Model for the Etching Characteristics of Corners Formed by Si<sub>{111}</sub> Planes on Si<sub>{110}</sub> Wafer Surface