Pattern shape effects and artefacts in deep silicon etching

Kiihamäki, Jyrki; Franssila, Sami

doi:10.1116/1.581761

Cited by 77 publications

(53 citation statements)

References 13 publications

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“…PAS shares the issue of feature impact on incident particles for deposition into asymmetric features as has been discussed for aspectratio-dependent-etching using fluorocarbon plasmas and plasma-enhanced atomic layer deposition. [15,17,24] The cause of non-uniform deposition and etching in small features has been explained by several processes including ion shadowing/deflection, neutral shadowing, and Knudsen transport of neutrals. [15,17] As ions in our deposition plasma have only low energies and are highly directional, the neutral behavior may dominate deposition onto the feature sidewalls.…”

Section: Discussionmentioning

confidence: 99%

“…[15,17,24] The cause of non-uniform deposition and etching in small features has been explained by several processes including ion shadowing/deflection, neutral shadowing, and Knudsen transport of neutrals. [15,17] As ions in our deposition plasma have only low energies and are highly directional, the neutral behavior may dominate deposition onto the feature sidewalls. The solid angle of acceptance on a sidewall changes drastically in small asymmetric features and neutrals may experience shadowing.…”

Section: Discussionmentioning

confidence: 99%

“…Etching applications in asymmetric features and features with high AR show problems with getting sufficient passivation of sidewalls and available etch reactants at the bottom of features. [15,16] This effect, known as RIE lag, ratio features. [17,18] This work investigates the problem of shrinking asymmetric holes uniformly, the physical limitations of depositing in shadowed features, and which plasma parameters can give the best results.…”

Section: Introductionmentioning

confidence: 97%

See 2 more Smart Citations

Controlling Asymmetric Photoresist Feature Dimensions during Plasma-Assisted Shrink

Fox-Lyon

Metzler

Oehrlein

et al. 2014

Plasma Process. Polym.

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Plasma-assisted shrink (PAS) of features, involving plasma deposition onto sidewalls to shrink features has been described in the past for symmetric features. In this work we explore shrinkage of asymmetric features using fluorocarbon-based plasma deposition. Using top-down and cross-section scanning electron microscopy, we find the dependencies of this shrink process on top-down blanket deposition thickness, pressure, source power, and deposition plasma chemistry with the aim of achieving the best 1:1 length to width shrink (DL:DW) of asymmetric features.

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Section: Discussionmentioning

confidence: 99%

Section: Discussionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 97%

See 1 more Smart Citation

Controlling Asymmetric Photoresist Feature Dimensions during Plasma-Assisted Shrink

Fox-Lyon

Metzler

Oehrlein

et al. 2014

Plasma Process. Polym.

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“…15 Detailed guidelines for cryoetch optimization have been given by de Boer et al 3 However, all processes have to be optimized because the results are influenced not only by process parameters but also by other factors such as the size and the shape of mask opening, aspect ratio of the etched features, pattern loading, and masking material. 16,17 Parameters for two etch processes that are used to investigate the mask material effects are presented in Table II. "Base line" process results in vertical sidewalls with a reasonably high etch rate and small undercutting in "through-wafer" process the etch rate is maximized.…”

Section: A Characterization Of Etch Rate Profile and Process Parammentioning

confidence: 99%

Mask material effects in cryogenic deep reactive ion etching

Sainiemi¹,

Franssila²

2007

Journal of Vacuum Science &Amp; Technology B: Microelectronics and Nanometer Structures Processing, Measurement, and Phenomena

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Articles you may be interested inCryogenic silicon etching in inductively coupled SF 6 /O 2 plasma has been studied, especially the behavior of mask materials. Suitability of eight different mask materials for cryogenic silicon deep reactive ion etching has been investigated. Three of the five photoresists suffered from cracking during cryogenic etching. We clarified the stages of the etching process and identified two mechanisms behind the cracking: thermal expansion mismatch and mechanical deformation from wafer clamping and backside helium pressure. Also thickness of the photoresist plays a role in cracking, but, contrary to common conception that all thick resists suffer from cracking in cryogenic etching, we found that SU-8 negative resist did not crack, even for very thick layers. This is explained to be due to its high cross-linking density. All three hard mask materials had high selectivities and were free of cracking problems. However, aluminum mask resulted in poor surface quality, while thermally grown SiO 2 and amorphous Al 2 O 3 deposited by atomic layer deposition showed smooth surfaces and sidewalls. Silicon dioxide had selectivity of 150:1, while Al 2 O 3 selectivity was 66 000:1. This extreme selectivity of Al 2 O 3 mask, combined with good surface quality, is shown to be highly beneficial in both shallow and through-wafer etching.

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“…1(a)] since they are exposed to the full IAD independent of the etch depth reached, while narrower trenches show local sidewall features such as barreling or bowing. [12][13][14] Depending on the ratio between the width and the depth of a structure, substantial fractions of ions may be lost by wall collisions, known as shadowing. 15 Consequently, the ion flux necessary for bottom passivation removal and ion etch assistance is decreased, ultimately limiting etch rates.…”

Section: Introductionmentioning

confidence: 99%

Sacrificial structures for deep reactive ion etching of high-aspect ratio kinoform silicon x-ray lenses

Stöhr

Michael-Lindhard

Hübner

et al. 2015

Journal of Vacuum Science &Amp; Technology B, Nanotechnology and Microelectronics: Materials, Processing, Measurement, and Phen

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O. (2015). Sacrificial structures for deep reactive ion etching of high-aspect ratio kinoform silicon x-ray lenses. Journal of Vacuum Science and Technology. Part B. Microelectronics and Nanometer Structures, 33(6), [062001]. DOI: 10.1116/1.4931622 Sacrificial structures for deep reactive ion etching of high-aspect ratio kinoform silicon x-ray lenses This article describes the realization of complex high-aspect ratio silicon structures with feature dimensions from 100 lm to 100 nm by deep reactive ion etching using the Bosch process. As the exact shape of the sidewall profiles can be crucial for the proper functioning of a device, the authors investigated how sacrificial structures in the form of guarding walls and pillars may be utilized to facilitate accurate control of the etch profile. Unlike other sacrificial structuring approaches, no silicon-on-insulator substrates or multiple lithography steps are required. In addition, the safe removal of the sacrificial structures was accomplished by thermal oxidation and subsequent selective wet etching. The effects of the dimensions and relative placement of sacrificial walls and pillars on the etching result were determined through systematic experiments. The authors applied this process for exact sidewall control in the manufacture of x-ray lenses that are very sensitive to sidewall shape nonuniformities. Compound kinoform lenses for focusing hard x-rays with structure heights of 200 lm were manufactured, and the lenses were tested in terms of their focusing ability and refracting qualities using synchrotron radiation at a photon energy of 17 keV. A 180 lm long line focus with a waist of 430 nm at a focal length of 215 mm was obtained.

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Pattern shape effects and artefacts in deep silicon etching

Cited by 77 publications

References 13 publications

Controlling Asymmetric Photoresist Feature Dimensions during Plasma-Assisted Shrink

Controlling Asymmetric Photoresist Feature Dimensions during Plasma-Assisted Shrink

Mask material effects in cryogenic deep reactive ion etching

Sacrificial structures for deep reactive ion etching of high-aspect ratio kinoform silicon x-ray lenses

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