A model explaining mask-corner undercut phenomena in anisotropic silicon etching: a saddle point in the etching-rate diagram

Shikida, Mitsuhiro; Nanbara, Ken-ichi; Koizumi, Tohru; Sasaki, Hikaru; Odagaki, Michiaki; Sato, Kazuo; Ando, Masaki; Furuta, Shinji; Asaumi, Kazuo

doi:10.1016/s0924-4247(02)00017-1

Cited by 63 publications

(56 citation statements)

References 19 publications

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“…The shape of the exterior corners is more complicated, but Shikida, et al, have identified the faces that emerge during etching: two {311} faces and two smaller {110} faces, as shown in Figure 3(a). 10 These etch rapidly. If the DPO is held in the etch bath after it has been released, the corners will continue to etch while the {111} edges remain mostly fixed.…”

Section: Etching Geometrymentioning

confidence: 99%

Annealing and Extended Etching Improve a Torsional Resonator for Thin Film Internal Friction Measurements

2018

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We evaluate two methods to improve the background internal friction of the Double Paddle Oscillator (DPO), which has a nominal low temperature value of Q -1 ≈ 2×10-8. We find that annealing the DPO in vacuum at 300°C for 3 hours systematically reduced Q -1 at all temperatures and revealed a 100K internal friction peak by permanently removing it. We also find a striking decrease of low temperature Q -1 as the DPO geometry is altered through extended etching. This decrease is evaluated via Finite Element Method modeling in terms of mode mixing and attachment loss.

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Section: Etching Geometrymentioning

confidence: 99%

Annealing and Extended Etching Improve a Torsional Resonator for Thin Film Internal Friction Measurements

2018

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“…In general, these facets in the case of {100} surface are typically {311}, {211}, {331}, {411}, {212}, {772}, etc. are {311}, {772} and {411}, respectively [83,84,92]. Hence, there is some disagreement in the literature about the exact orientation of planes that emerge at the convex corners during etching process.…”

Section: Figure 19mentioning

confidence: 99%

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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“…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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A model explaining mask-corner undercut phenomena in anisotropic silicon etching: a saddle point in the etching-rate diagram

Cited by 63 publications

References 19 publications

Annealing and Extended Etching Improve a Torsional Resonator for Thin Film Internal Friction Measurements

Annealing and Extended Etching Improve a Torsional Resonator for Thin Film Internal Friction Measurements

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

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A model explaining mask-corner undercut phenomena in anisotropic silicon etching: a saddle point in the etching-rate diagram

Cited by 63 publications

References 19 publications

Annealing and Extended Etching Improve a Torsional Resonator for Thin Film Internal Friction Measurements

Annealing and Extended Etching Improve a Torsional Resonator for Thin Film Internal Friction Measurements

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

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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