Deceleration of silicon etch rate at high aspect ratios

Research output: Contribution to journalArticleScientificpeer-review

28 Citations (Scopus)

Abstract

The molecular-flow conductance of a high aspect ratio feature can limit the etching species arriving at the bottom of the feature and thus limit the etch rate. A simple conductance model can predict the etch rate of the time-domain multiplexed etch process with good results at moderate-aspect ratios (5–20) for trenches, but at very high aspect ratios (>20) the conductance model breaks down. Other mechanisms are needed to explain the deceleration of etch rate and almost complete etch stop. In this article the reasons for etch stop at the bottom of deep features are discussed. Measurement results of deep silicon etching are presented. Very deep holes and trenches were etched into silicon to study the effect of process parameters. At moderate aspect ratios the bottom of the hole is nearly flat and the sidewalls are vertical. At high aspect ratio the sidewalls start to bow and the feature bottom turns into a sharp spearhead. The shape of the feature can have an impact on the step coverage of the passivation layer deposition during the passivation step and on passivation removal during the etch step, leading to excessive sidewall etching and reduced etch rate at the feature bottom. The nonzero sidewall reaction probability and flow conductance of tapered tubes were studied by Monte Carlo simulation. The main reason for deceleration of etching seems to be the loss of etchant species due to sidewall reactions combined with feature closure by ion-limited passivation polymer etching.
Original languageEnglish
Pages (from-to)1385 - 1389
Number of pages5
JournalJournal of Vacuum Science and Technology A: Vacuum, Surfaces and Films
Volume18
Issue number4
DOIs
Publication statusPublished - 2000
MoE publication typeA1 Journal article-refereed

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Deceleration
Silicon
deceleration
high aspect ratio
Aspect ratio
Etching
Passivation
passivity
etching
silicon
aspect ratio
molecular flow
etchants
bows
closures
Polymers
breakdown
Ions
tubes
polymers

Cite this

@article{959da8637f2f4bc8bf9b2bd3aa2a3729,
title = "Deceleration of silicon etch rate at high aspect ratios",
abstract = "The molecular-flow conductance of a high aspect ratio feature can limit the etching species arriving at the bottom of the feature and thus limit the etch rate. A simple conductance model can predict the etch rate of the time-domain multiplexed etch process with good results at moderate-aspect ratios (5–20) for trenches, but at very high aspect ratios (>20) the conductance model breaks down. Other mechanisms are needed to explain the deceleration of etch rate and almost complete etch stop. In this article the reasons for etch stop at the bottom of deep features are discussed. Measurement results of deep silicon etching are presented. Very deep holes and trenches were etched into silicon to study the effect of process parameters. At moderate aspect ratios the bottom of the hole is nearly flat and the sidewalls are vertical. At high aspect ratio the sidewalls start to bow and the feature bottom turns into a sharp spearhead. The shape of the feature can have an impact on the step coverage of the passivation layer deposition during the passivation step and on passivation removal during the etch step, leading to excessive sidewall etching and reduced etch rate at the feature bottom. The nonzero sidewall reaction probability and flow conductance of tapered tubes were studied by Monte Carlo simulation. The main reason for deceleration of etching seems to be the loss of etchant species due to sidewall reactions combined with feature closure by ion-limited passivation polymer etching.",
author = "Jyrki Kiiham{\"a}ki",
year = "2000",
doi = "10.1116/1.582359",
language = "English",
volume = "18",
pages = "1385 -- 1389",
journal = "Journal of Vacuum Science and Technology A: Vacuum, Surfaces and Films",
issn = "0734-2101",
publisher = "American Vacuum Society AVS",
number = "4",

}

Deceleration of silicon etch rate at high aspect ratios. / Kiihamäki, Jyrki.

In: Journal of Vacuum Science and Technology A: Vacuum, Surfaces and Films, Vol. 18, No. 4, 2000, p. 1385 - 1389.

Research output: Contribution to journalArticleScientificpeer-review

TY - JOUR

T1 - Deceleration of silicon etch rate at high aspect ratios

AU - Kiihamäki, Jyrki

PY - 2000

Y1 - 2000

N2 - The molecular-flow conductance of a high aspect ratio feature can limit the etching species arriving at the bottom of the feature and thus limit the etch rate. A simple conductance model can predict the etch rate of the time-domain multiplexed etch process with good results at moderate-aspect ratios (5–20) for trenches, but at very high aspect ratios (>20) the conductance model breaks down. Other mechanisms are needed to explain the deceleration of etch rate and almost complete etch stop. In this article the reasons for etch stop at the bottom of deep features are discussed. Measurement results of deep silicon etching are presented. Very deep holes and trenches were etched into silicon to study the effect of process parameters. At moderate aspect ratios the bottom of the hole is nearly flat and the sidewalls are vertical. At high aspect ratio the sidewalls start to bow and the feature bottom turns into a sharp spearhead. The shape of the feature can have an impact on the step coverage of the passivation layer deposition during the passivation step and on passivation removal during the etch step, leading to excessive sidewall etching and reduced etch rate at the feature bottom. The nonzero sidewall reaction probability and flow conductance of tapered tubes were studied by Monte Carlo simulation. The main reason for deceleration of etching seems to be the loss of etchant species due to sidewall reactions combined with feature closure by ion-limited passivation polymer etching.

AB - The molecular-flow conductance of a high aspect ratio feature can limit the etching species arriving at the bottom of the feature and thus limit the etch rate. A simple conductance model can predict the etch rate of the time-domain multiplexed etch process with good results at moderate-aspect ratios (5–20) for trenches, but at very high aspect ratios (>20) the conductance model breaks down. Other mechanisms are needed to explain the deceleration of etch rate and almost complete etch stop. In this article the reasons for etch stop at the bottom of deep features are discussed. Measurement results of deep silicon etching are presented. Very deep holes and trenches were etched into silicon to study the effect of process parameters. At moderate aspect ratios the bottom of the hole is nearly flat and the sidewalls are vertical. At high aspect ratio the sidewalls start to bow and the feature bottom turns into a sharp spearhead. The shape of the feature can have an impact on the step coverage of the passivation layer deposition during the passivation step and on passivation removal during the etch step, leading to excessive sidewall etching and reduced etch rate at the feature bottom. The nonzero sidewall reaction probability and flow conductance of tapered tubes were studied by Monte Carlo simulation. The main reason for deceleration of etching seems to be the loss of etchant species due to sidewall reactions combined with feature closure by ion-limited passivation polymer etching.

U2 - 10.1116/1.582359

DO - 10.1116/1.582359

M3 - Article

VL - 18

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EP - 1389

JO - Journal of Vacuum Science and Technology A: Vacuum, Surfaces and Films

JF - Journal of Vacuum Science and Technology A: Vacuum, Surfaces and Films

SN - 0734-2101

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