Passivation mechanisms in cryogenic SF<sub>6</sub>/O<sub>2</sub>etching process

Dussart, Rémi; Boufnichel, Mohamed; Marcos, G.; Lefaucheux, Philippe; Basillais, Armelle; Benoit, Robert R.; Tillocher, Thomas; Mellhaoui, X.; Estrade‐Szwarckopf, H.; Ranson, P.

doi:10.1088/0960-1317/14/2/004

Cited by 99 publications

(87 citation statements)

References 25 publications

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“…10,11 The crystallographically anisotropic roughness observed here also seems to be related to ͕111͖ planes of silicon; however, the appearances differ, which indicates that a different mechanism might be involved.…”

mentioning

confidence: 64%

Study of the Roughness in a Photoresist Masked, Isotropic, SF[sub 6]-Based ICP Silicon Etch

Larsen¹,

Petersen²,

Hansen

2006

J. Electrochem. Soc.

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In this paper we study the etching behavior and the resulting roughness in photoresist-masked isotropic silicon plasma etch performed in an inductively coupled plasma ͑ICP͒ etcher using SF 6 . We report detailed observations of the resulting roughness for various etching parameters, covering: pressure from 2.5 to 70 mTorr, SF 6 flow rate from 50 to 300 sccm, platen power from 0 to 16 W, and ICP power from 1000 to 3000 W. Etch processes with a normalized roughness below 0.005 were found at low pressure, p = 10 mTorr, while larger normalized roughness, above 0.02, occurred at higher pressures, p = 40-70 mTorr. Here the normalized roughness is the ratio of the roughness amplitude to the etch depth. The rough etching processes showed characteristic high-aspect-ratio and crystal-orientation-dependent surface morphology. The temporal evolution of this roughness was studied, and observations suggest a gradual buildup of surface contamination ͑redeposits͒ originating from the photoresist mask. A model was used to analyze the etched profiles with respect the internal etching conditions. The almost isotropic etching profiles, obtained in both rough and smooth etching processes, are generally highly radical-dependent; however, the surface roughness itself can be reduced dramatically using an ion energy above a certain threshold value. The roughness causing mechanism is discussed.

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mentioning

confidence: 64%

Study of the Roughness in a Photoresist Masked, Isotropic, SF[sub 6]-Based ICP Silicon Etch

Larsen¹,

Petersen²,

Hansen

2006

J. Electrochem. Soc.

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“…As a result, the etch rate is now mainly dependent on the number of F atoms that reach the wafer surface, which gradually decreases with O 2 content, and on the amount of sputtering. As is clear from Figure 10 ions are electron impact dissociative ionization of SF 6 ( Table 2; label 9; threshold = 15.9 eV) and electron impact ionization of SF 5 (Table 2; label 18; threshold = 11.8 eV). Both processes are almost equally important.…”

Section: Additional Effects Of Bias Voltage In Combination With Wafmentioning

confidence: 98%

“…[3] During SF 6 /O 2 cryogenic deep reactive ion etching (DRIE), first proposed in 1988 by Tachi et al, [4] a SiF x O y passivation layer is formed, which desorbs naturally when the wafer is brought back to room temperature, leaving a clean trench with no scalloping. [5] However, the underlying mechanisms of how the SiF x O y passivation layer is formed and automatically desorbs afterwards are not yet fully understood. [6] A topical review by Dussart et al [6] covers the latest advances in cryoetching, ranging from the origin of cryoetching to today's technologies.…”

Section: Introductionmentioning

confidence: 99%

“…[13] Moreover, Dussart et al investigated the passivation mechanisms of Si trenches involved in SF 6 /O 2 cryogenic etching. [14] They showed that the passivating layer is removed during the increase of the wafer temperature leading to a very clean surface of the sidewalls after processing but numerical studies are limited. The same group wrote the topical review on cryogenic etching.…”

Section: Introductionmentioning

confidence: 99%

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Concurrent effects of wafer temperature and oxygen fraction on cryogenic silicon etching with SF₆/O₂ plasmas

Tinck

Tillocher

Georgieva

et al. 2017

Plasma Processes & Polymers

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Cryogenic plasma etching is a promising technique for high-control wafer development with limited plasma induced damage. Cryogenic wafer temperatures effectively reduce surface damage during etching, but the fundamental mechanism is not well understood. In this study, the influences of wafer temperature, gas mixture and substrate bias on the (cryogenic) etch rates of Si with SF 6 /O 2 inductively coupled plasmas are experimentally and computationally investigated. The etch rates are measured in situ with double-point reflectometry and a hybrid computational Monte Carlo -fluid model is applied to calculate plasma properties. This work allows the reader to obtain a better insight in the effects of wafer temperature on the etch rate and to find operating conditions for successful anisotropic (cryo)etching.

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“…Dussart et al 12,13 were able to systematically produce Si nanopillar structures for various etching recipes, including changes to SF 6 /O 2 gas flow ratios, sample stage temperature, chamber pressure, and plasma bias voltages. In addition, SiF 4 re-deposition on the Si surface was found to play an important role in creating pillar structures.…”

Section: Mechanism Of Nanopillar Structure Formationmentioning

confidence: 99%

Characterization of low-temperature bulk micromachining of silicon using an SF₆/O₂inductively coupled plasma

Jiang¹,

Keating²,

Martyniuk³

et al. 2012

J. Micromech. Microeng.

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The principal aim of this work was to characterize deep silicon etching at sample temperatures well-below room temperature, using SF 6 /O 2 inductively coupled plasma (ICP) for micro-electro-mechanical systems (MEMS) applications. In this paper, a study of the etch rates and etch profiles of deep silicon trenches has been undertaken for a series of etching parameters, including RF power, sample stage temperature, and O 2 gas flow rate. Based on the experimental observations, the formation of an SiO x F y passivation layer, the rate of ion collision through the sheath field, and the silicon crystallographic orientation, are found to be the three main parameters that affect the etching process. In addition, the formation mechanism of "black silicon" (nanopillar-based Si structures) has also been proposed based on the experimental data and a simple physical model. For the purpose of silicon bulk micromachining, an optimized recipe has been developed that is suitable for the fabrication of high aspect ratio Si cantilevers on silicon-on-insulator (SOI) based waveguide wafers.

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Passivation mechanisms in cryogenic SF₆/O₂etching process

Cited by 99 publications

References 25 publications

Study of the Roughness in a Photoresist Masked, Isotropic, SF[sub 6]-Based ICP Silicon Etch

Study of the Roughness in a Photoresist Masked, Isotropic, SF[sub 6]-Based ICP Silicon Etch

Concurrent effects of wafer temperature and oxygen fraction on cryogenic silicon etching with SF₆/O₂ plasmas

Characterization of low-temperature bulk micromachining of silicon using an SF₆/O₂inductively coupled plasma

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Passivation mechanisms in cryogenic SF6/O2etching process

Cited by 99 publications

References 25 publications

Study of the Roughness in a Photoresist Masked, Isotropic, SF[sub 6]-Based ICP Silicon Etch

Study of the Roughness in a Photoresist Masked, Isotropic, SF[sub 6]-Based ICP Silicon Etch

Concurrent effects of wafer temperature and oxygen fraction on cryogenic silicon etching with SF6/O2 plasmas

Characterization of low-temperature bulk micromachining of silicon using an SF6/O2inductively coupled plasma

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Passivation mechanisms in cryogenic SF₆/O₂etching process

Concurrent effects of wafer temperature and oxygen fraction on cryogenic silicon etching with SF₆/O₂ plasmas

Characterization of low-temperature bulk micromachining of silicon using an SF₆/O₂inductively coupled plasma