Systematic study of the etching characteristics of Si{111} in modified TMAH

Swarnalatha, Veerla; Pal, Prem; Pandey, Ashok Kumar; Rao, Avvaru Venkata Narasimha; Xing, Yan; Tanaka, Hiroshi; Sato, Kazuo

doi:10.1049/mnl.2019.0443

Cited by 5 publications

(3 citation statements)

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“…Though a smooth surface can be obtained by the addition of surfactant, it impedes the etch rate, consequently inhibiting the commercial scale fabrication. Different methods such as ultrasonic agitations, microwave irradiation, and by adding additives in wet anisotropic etching have been employed to increase the etch rate [41][42][43][44][45][46][47][48][49][50][51][52][53][54][55]. However, each method has its pros and cons.…”

Section: Introductionmentioning

confidence: 99%

“…Other way of increasing the etch rate is etching at (or near) the boiling point of the etchant [11,56]. Recently, NH 2 OH-added TMAH and KOH solutions, which provide very high etch rate in comparison to pure KOH and TMAH, are explored for applications in wet bulk micromachining for the formation of MEMS structures [49][50][51][52][53][54]. Although NH 2 OH-added KOH/TMAH provides very high etch rate, the etch rate is reduced with the age of etchant [54,55].…”

Section: Introductionmentioning

confidence: 99%

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Enhanced etching characteristics of Si{100} in NaOH-based two-component solution

Swarnalatha

Purohit

Pal

et al. 2022

Micro and Nano Syst Lett

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Silicon wet bulk micromachining is the most widely used technique for the fabrication of diverse microstructures such as cantilevers, cavities, etc. in laboratory as well as in industry for micro-electromechanical system (MEMS) application. Although, increasing the throughput remains inevitable, and can be done by increasing the etching rate. Furthermore, freestanding structure release time can be reduced by the improved undercutting rate at convex corners. In this work, we have investigated the etching characteristics of a non-conventional etchant in the form of hydroxylamine (NH2OH) added sodium hydroxide (NaOH) solution. This research is focused on Si{100} wafer as this orientation is largely used in the fabrication of planer devices (e.g., complementary metal-oxide semiconductors) and microelectromechanical systems (e.g., inertial sensors). We have performed a systematic and parametric analysis without and with 12% NH2OH in 10 M NaOH for improved etching characteristics such as etch rate, undercutting at convex corners, and etched surface morphology. 3D scanning laser microscope is used to measure average surface roughness (Ra), etch depth (d), and undercutting length (l). Morphology of the etched Si{100} surface is examined using optical and scanning electron microscopes. The addition of NH2OH in NaOH solution remarkably exhibited a two-fold increment in the etching rate of a Si{100} surface. Furthermore, the addition of NH2OH significantly improves the etched surface morphology and undercutting at convex corners. Undercutting at convex corners is highly prudent for the quick release of microstructures from the substrate. In addition, we have studied the effect of etchant age on etching characteristics. Results presented in this article are of large significance for engineering applications in both academic and industrial laboratories.

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Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Enhanced etching characteristics of Si{100} in NaOH-based two-component solution

Swarnalatha

Purohit

Pal

et al. 2022

Micro and Nano Syst Lett

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“…The salient factors that control the etching characteristics are etching time, etching temperature, agitation during etching, and the presence of an additive in the etchant. Lately, the influence of hydroxylamine (NH 2 OH) on the etching properties of KOH and TMAH is reported [37][38][39][40][41][42][43].…”

Section: Introductionmentioning

confidence: 99%

Wet anisotropic etching characteristics of Si{111} in NaOH-based solution for silicon bulk micromachining

Purohit

Swarnalatha

Pandey

et al. 2022

Micro and Nano Syst Lett

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Silicon bulk micromachining is extensively employed method in microelectromechanical systems (MEMS) for the formation of freestanding (e.g., cantilevers) and fixed (e.g., cavities) microstructures. Wet anisotropic etching is a popular technique to perform silicon micromachining as it is low-cost, scalable, and suitable for large scale batch processing, which are the major factors considered in the industry to reduce the cost of the product. In this work, we report the wet anisotropic etching characteristics of Si{111} in sodium hydroxide (NaOH) without and with addition of hydroxylamine (NH2OH). 10M NaOH and 12% NH2OH are used for this study. The effect of NH2OH is investigated on the etch rate, etched surface roughness and morphology, and the undercutting at mask edges aligned along < 112 > direction. These are the major etching characteristics, which should be studied in a wet anisotropic etchant. A 3D laser scanning microscope is utilized to measure the surface roughness, etch depth, and undercutting length, while the etched surface morphology is examined using a scanning electron microscope (SEM). The incorporation of NH2OH in NaOH significantly enhances the etch rate and the undercutting at the mask edges that do not consist of {111} planes. To fabricate freestanding structure (e.g., microcantilever) on Si{111} wafer, high undercutting at < 112 > mask edges is desirable to reduce the release time. Moreover, the effect of etchant age on the abovementioned etching characteristics are investigated. The etch rate and undercutting reduce significantly with the age of the modified NaOH. The present paper reports very interesting results for the applications in wet bulk micromachining of Si{111}.

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