Effects of Mask Pattern Geometry on Plasma Etching Profiles

Fukumoto, Hisao; Eriguchi, Koji; Ono, Ken

doi:10.1143/jjap.48.096001

Cited by 12 publications

(11 citation statements)

References 55 publications

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“…There are many reasons why masks may not have the perfect geometry, as is often assumed in plasma simulations [ 40 ]. The physical model presented here, using top-down Monte Carlo ray tracing, is able to qualitatively reproduce and predict many phenomena observed in plasma etched profiles.…”

Section: Resultsmentioning

confidence: 99%

Effect of Mask Geometry Variation on Plasma Etching Profiles

et al. 2023

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It is becoming quite evident that, when it comes to the further scaling of advanced node transistors, increasing the flash memory storage capacity, and enabling the on-chip integration of multiple functionalities, “there’s plenty of room at the top”. The fabrication of vertical, three-dimensional features as enablers of these advanced technologies in semiconductor devices is commonly achieved using plasma etching. Of the available plasma chemistries, SF6/O2 is one of the most frequently applied. Therefore, having a predictive model for this process is indispensable in the design cycle of semiconductor devices. In this work, we implement a physical SF6/O2 plasma etching model which is based on Langmuir adsorption and is calibrated and validated to published equipment parameters. The model is implemented in a broadly applicable in-house process simulator ViennaPS, which includes Monte Carlo ray tracing and a level set-based surface description. We then use the model to study the impact of the mask geometry on the feature profile, when etching through circular and rectangular mask openings. The resulting dimensions of a cylindrical hole or trench can vary greatly due to variations in mask properties, such as its etch rate, taper angle, faceting, and thickness. The peak depth for both the etched cylindrical hole and trench occurs when the mask is tapered at about 0.5°, and this peak shifts towards higher angles in the case of high passivation effects during the etch. The minimum bowing occurs at the peak depth, and it increases with an increasing taper angle. For thin-mask faceting, it is observed that the maximum depth increases with an increasing taper angle, without a significant variation between thin masks. Bowing is observed to be at a maximum when the mask taper angle is between 15° and 20°. Finally, the mask etch rate variation, describing the etching of different mask materials, shows that, when a significant portion of the mask is etched away, there is a notable increase in vertical etching and a decrease in bowing. Ultimately, the implemented model and framework are useful for providing a guideline for mask design rules.

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Section: Resultsmentioning

confidence: 99%

Effect of Mask Geometry Variation on Plasma Etching Profiles

et al. 2023

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“…In effect, the smoothing with increased Γ n 0 /Γ i 0 and T s is less significant for 2D ripples at θ i = 45°and 75°t han for 3D random roughness features at θ i = 0°, because the shadowing effects for neutrals are lower for 2D than for 3D features. [93][94][95] The smoothing with increased Γ n 0 /Γ i 0 and T s is also less significant at increased E i , where the increased directionality of incoming ion fluxes is assumed to increase the flux of ions directly incident on the bottom of roughness features that starves for neutrals, and thus to effectively lower the effects of neutral shadowing.…”

Section: B Similarity Between Reduced Ion Reflection and Enhanced Smmentioning

confidence: 99%

Origin of plasma-induced surface roughening and ripple formation during plasma etching: The crucial role of ion reflection

Hatsuse

Nakazaki

Tsuda

et al. 2018

Journal of Applied Physics

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Plasma-induced surface roughening and ripple formation has been studied based on Monte Carlo simulations of plasma-surface interactions and feature profile evolution during Si etching in Clbased plasmas, with emphasis being placed on the role and effects of ion reflection from microstructural feature surfaces on incidence. The simulation model included the effects of Cl + ion reflection (and/or its penetration into substrates) through calculating the momentum and energy conservation in successive two-body elastic collisions with substrate Si atoms every ion incidence. The "reflection coefficient r i " was then further introduced in the model (0 ≤ r i ≤ 1), representing the fraction of ions incident on surfaces with the reflection/penetration calculation scheme turned on. The coefficient r i is, in a sense, a measure of the reflection probability for impacts of an ion species onto Si surfaces relative to that for Cl + impacts. Simulations for ion incidence angles of θ i = 0°, 45°, and 75°onto substrate surfaces with incident energies in the range E i = 20−500 eV showed that as r i is slightly decreased from unity, the roughness decreases substantially, and the ripple formation fades away: the roughness remains at the low level of stochastic roughening during etching for decreased r i ≤ r i * ≈ 0.95−0.75 (the critical r i * tends to be lower at higher E i and θ i ) with no ripple structures at off-normal θ i . This elucidates that the ion reflection is indispensable in surface roughening and rippling during plasma etching, and their degree relies significantly on the reflectivity of ions. Simulations further showed that at intermediate off-normal θ i = 45°, the ripple wavelength increases significantly with decreasing r i , while the increase in amplitude is relatively less significant; thus, sawtooth-like ripple profiles pronounced for r i = 1 tend to be collapsed with decreasing r i . These effects of reduced ion reflection on plasma-induced surface roughening and ripple formation are discussed in terms of effectively enhanced smoothing due to neutral reactants, which competes with the roughening and rippling caused by ion bombardment. Published by AIP Publishing.

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“…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: 99%

“…These fluorocarbon‐based plasmas could possibly be extended beyond sidewall preservation during etch to PAS processes. 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 . This effect, known as RIE lag, results in major difficulties for etching of high‐aspect ratio features .…”

Section: Introductionmentioning

confidence: 99%

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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Effects of Mask Pattern Geometry on Plasma Etching Profiles

Cited by 12 publications

References 55 publications

Effect of Mask Geometry Variation on Plasma Etching Profiles

Effect of Mask Geometry Variation on Plasma Etching Profiles

Origin of plasma-induced surface roughening and ripple formation during plasma etching: The crucial role of ion reflection

Controlling Asymmetric Photoresist Feature Dimensions during Plasma-Assisted Shrink

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