Dependence of RF breakdown curve on electrode geometry in CCP reactor
The results of experimental and theoretical study of RF capacitively coupled discharge breakdown in reactor for reactive ion etching of semiconductors are presented. Taking into account complex geometry of the reactor with asymmetric electrodes the main attention has been paid to influence of geomet...
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| Cite this: | Dependence of RF breakdown curve on electrode geometry in CCP reactor / S.V. Dudin, A.N. Dakhov, V.A. Lisovskiy, V.M. Pletniov // Вопросы атомной науки и техники. — 2012. — № 6. — С. 193-195. — Бібліогр.: 10 назв. — англ. |
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irk-123456789-1092092016-11-22T03:03:08Z Dependence of RF breakdown curve on electrode geometry in CCP reactor Dudin, S.V. Dakhov, A.N. Lisovskiy, V.A. Pletniov, V.M. Низкотемпературная плазма и плазменные технологии The results of experimental and theoretical study of RF capacitively coupled discharge breakdown in reactor for reactive ion etching of semiconductors are presented. Taking into account complex geometry of the reactor with asymmetric electrodes the main attention has been paid to influence of geometric factor on the breakdown curve. Experiments have shown that the geometry of the electrodes has impact on the breakdown curve only at lowest gas pressure (<50 mTorr). In cylindrical configuration the curve has a region of ambiguity, while for asymmetric configuration similar to GEC reference cell the low pressure part of the breakdown curve is almost vertical. The experimental data are compared to the numerical simulation results obtained using the particle-in-cell/Monte Carlo (PIC/MCC) code. The comparison shows qualitative consistence of the results with general tendency of theoretical curves to be slightly shifted to higher pressures that can be explained by simultaneous action of different kinds of electron emission from the electrodes, while we accounted only for secondary electron emission. Both theory and experiment show influence of secondary electron yield from different electrode materials (aluminum, steel, graphite) on the low-pressure part of the breakdown curve. Представлены результаты экспериментальных и теоретических исследований кривой зажигания ВЧ-разряда в реакторе для ионного реактивного травления. С учетом сложной геометрии реактора с асимметричными электродами основное внимание было уделено влиянию геометрического фактора на кривую зажигания разряда. Эксперименты показали, что геометрия электродов оказывает существенное влияние на кривую зажигания в области низких давлений рабочего газа (<50 мТорр). Для цилиндрической геометрии камеры в области низких давлений существует область неоднозначности кривой зажигания, в то время как для асимметричной конфигурации близкой к GEC ячейке наблюдается практически вертикальный рост напряжения зажигания разряда с уменьшением давления газа. Наблюдается качественное согласие численых расчетов, полученых с использованием particle-in-cell/Monte Carlo (PIC/MCC) кода, с экспериментом. Общую тенденцию смещения рассчетных кривых зажигания в область более высоких давлений можно объяснить необходимостью корректного учета различных видов электронной эмиссии с электродов вдополнение к учтенной нами вторичной е-е-эмиссии. И теория, и эксперимент показывают существенное влияние вторичной элетронной эмиссии на кривую зажигания ВЧ-разряда в области низких давлений. Представлені результати експериментальних та теоретичних досліджень кривої запалювання ВЧ-разряду в реакторi для іонного реактивного травлення. З урахуванням складної геометрії реактора з асиметричними електродами основну увагу було приділено впливу геометричного фактора на криву запалювання розряду. Експерименти показали, що геометрія електродів робить істотний вплив на криву запалювання в області низьких тисків робочого газу (<50 мТорр). Для циліндричної геометрії камери в області низьких тисків існує область неоднозначності кривої запалювання, в той час як для асиметричної конфігурації близької до GEC осередку спостерігається практично вертикальне зростання напруги запалювання розряду при зменшенні тиску газу. Спостерігається якісна згода чисельних розрахункiв, отриманих з використанням particle-in-cell/Monte Carlo (PIC / MCC) коду, з експериментом. Загальну тенденцію зсуву розрахункових кривих запалювання в область більш високих тисків можна пояснити необхідністю коректного врахування різних видів електронної емісії з електродів в доповнення до врахованої нами вторинної е-е-емісії. Як теорія, так і експеримент показують істотний вплив вторинної елетронній емісії на криву запалювання ВЧ-розряду в області низьких тисків. 2012 Article Dependence of RF breakdown curve on electrode geometry in CCP reactor / S.V. Dudin, A.N. Dakhov, V.A. Lisovskiy, V.M. Pletniov // Вопросы атомной науки и техники. — 2012. — № 6. — С. 193-195. — Бібліогр.: 10 назв. — англ. 1562-6016 PACS 52.80.Pi http://dspace.nbuv.gov.ua/handle/123456789/109209 en Вопросы атомной науки и техники Національний науковий центр «Харківський фізико-технічний інститут» НАН України |
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Digital Library of Periodicals of National Academy of Sciences of Ukraine |
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Низкотемпературная плазма и плазменные технологии Низкотемпературная плазма и плазменные технологии |
| spellingShingle |
Низкотемпературная плазма и плазменные технологии Низкотемпературная плазма и плазменные технологии Dudin, S.V. Dakhov, A.N. Lisovskiy, V.A. Pletniov, V.M. Dependence of RF breakdown curve on electrode geometry in CCP reactor Вопросы атомной науки и техники |
| description |
The results of experimental and theoretical study of RF capacitively coupled discharge breakdown in reactor for reactive ion etching of semiconductors are presented. Taking into account complex geometry of the reactor with asymmetric electrodes the main attention has been paid to influence of geometric factor on the breakdown curve. Experiments have shown that the geometry of the electrodes has impact on the breakdown curve only at lowest gas pressure (<50 mTorr). In cylindrical configuration the curve has a region of ambiguity, while for asymmetric configuration similar to GEC reference cell the low pressure part of the breakdown curve is almost vertical. The experimental data are compared to the numerical simulation results obtained using the particle-in-cell/Monte Carlo (PIC/MCC) code. The comparison shows qualitative consistence of the results with general tendency of theoretical curves to be slightly shifted to higher pressures that can be explained by simultaneous action of different kinds of electron emission from the electrodes, while we accounted only for secondary electron emission. Both theory and experiment show influence of secondary electron yield from different electrode materials (aluminum, steel, graphite) on the low-pressure part of the breakdown curve. |
| format |
Article |
| author |
Dudin, S.V. Dakhov, A.N. Lisovskiy, V.A. Pletniov, V.M. |
| author_facet |
Dudin, S.V. Dakhov, A.N. Lisovskiy, V.A. Pletniov, V.M. |
| author_sort |
Dudin, S.V. |
| title |
Dependence of RF breakdown curve on electrode geometry in CCP reactor |
| title_short |
Dependence of RF breakdown curve on electrode geometry in CCP reactor |
| title_full |
Dependence of RF breakdown curve on electrode geometry in CCP reactor |
| title_fullStr |
Dependence of RF breakdown curve on electrode geometry in CCP reactor |
| title_full_unstemmed |
Dependence of RF breakdown curve on electrode geometry in CCP reactor |
| title_sort |
dependence of rf breakdown curve on electrode geometry in ccp reactor |
| publisher |
Національний науковий центр «Харківський фізико-технічний інститут» НАН України |
| publishDate |
2012 |
| topic_facet |
Низкотемпературная плазма и плазменные технологии |
| url |
http://dspace.nbuv.gov.ua/handle/123456789/109209 |
| citation_txt |
Dependence of RF breakdown curve on electrode geometry in CCP reactor / S.V. Dudin, A.N. Dakhov, V.A. Lisovskiy, V.M. Pletniov // Вопросы атомной науки и техники. — 2012. — № 6. — С. 193-195. — Бібліогр.: 10 назв. — англ. |
| series |
Вопросы атомной науки и техники |
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2025-07-07T22:42:36Z |
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2025-07-07T22:42:36Z |
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| fulltext |
ISSN 1562-6016. ВАНТ. 2012. №6(82) 193
DEPENDENCE OF RF BREAKDOWN CURVE ON ELECTRODE
GEOMETRY IN CCP REACTOR
S.V. Dudin, A.N. Dakhov, V.A. Lisovskiy, V.M. Pletniov
V.N. Karazin Kharkov National University, Kharkov, Ukraine
The results of experimental and theoretical study of RF capacitively coupled discharge breakdown in reactor for
reactive ion etching of semiconductors are presented. Taking into account complex geometry of the reactor with
asymmetric electrodes the main attention has been paid to influence of geometric factor on the breakdown curve.
Experiments have shown that the geometry of the electrodes has impact on the breakdown curve only at lowest gas
pressure (<50 mTorr). In cylindrical configuration the curve has a region of ambiguity, while for asymmetric
configuration similar to GEC reference cell the low pressure part of the breakdown curve is almost vertical. The
experimental data are compared to the numerical simulation results obtained using the particle-in-cell/Monte Carlo
(PIC/MCC) code. The comparison shows qualitative consistence of the results with general tendency of theoretical
curves to be slightly shifted to higher pressures that can be explained by simultaneous action of different kinds of
electron emission from the electrodes, while we accounted only for secondary electron emission. Both theory and
experiment show influence of secondary electron yield from different electrode materials (aluminum, steel, graphite)
on the low-pressure part of the breakdown curve.
PACS 52.80.Pi
INTRODUCTION
Gas discharge breakdown is one of the most basic
problems of gas-discharge physics, which has been
studying for more then 100 years [1-3]. Nevertheless,
despite the long history the breakdown physics is not
completely understood and permanently attracts attention
of researchers [4-7].
The radio frequency (RF) discharge ignition is very
specific case in which oscillatory motion of electrons
between electrodes may cause dramatic change of
Paschen curve [3,5]. The breakdown voltage drops
significantly comparing to the DC breakdown when the
electron oscillation amplitude became less than half of
inter-electrode gap. Another unusual feature of the RF
breakdown curve is the ambiguity region at low pressures
where the discharge can be ignited not only by increase of
the RF voltage amplitude but also by the amplitude
decrease [3-7].
A number of researchers studied features of the RF
breakdown curve experimentally and theoretically, so to
the moment influence of different factors has been
investigated such as kind of gas [7], oscillation frequency
[2-4,6], spacing between electrodes [4,7], discharge
chamber geometry [3,6]. It was also shown
experimentally that the electrode surface material has
evident impact on the low-pressure part of the RF
breakdown curve [8]. However, the influence of electron
emission on the RF breakdown process in chamber with
complex geometry has not been cleared.
The results of experimental and theoretical study of
RF capacitively coupled discharge ignition in chambers of
different shape are presented in this paper. The main
attention is paid to influence of secondary electron
emission and geometric factor on the breakdown curve.
1. EXPERIMENTAL SETUP
A schematic diagram of the experimental setup used in
our investigation is shown in Fig. 1. The experiments were
carried out in two different configurations: cylindrical and
similar to GEC reference cell. The sidewall of the vessel is
made of metal. The RF power is coupled to the stainless
steel bottom electrode with radius R = 6 cm via a matching
box; the top one and side wall are grounded. The central
part of the upper electrode is shower-like for gas feeding
into the chamber. The vessel is evacuated by a turbo
molecular pump down to a base pressure of about 10-5 Torr.
The experiments were performed in the argon pressure
range 20…700 mTorr. The RF power (13.56 MHz) is
supplied by an RF generator with maximum output power
of 500 W.
The main radius of the chamber is R = 10 cm and
height L = 7 cm. Inter-electrode gap at the chamber axis is
4 cm. To transform the chamber to cylindrical
configuration the stainless steel grid with the cell size
0.25 mm and optical transparency about 0.5 was installed
(see Fig. 1), so the discharge was ignited in the chamber
with inner diameter 12 cm and height 4 cm.
For measurement of the high-pressure part of the
breakdown curve the gas pressure was fixed, and then the
RF voltage was slowly increased until gas breakdown
occurs. The low-pressure part of the curve may be multi-
valued, therefore in this range we first decreased the gas
pressure, then fixed the RF voltage value and then
Fig. 1. Schematic diagram of the experimental set-up
194 ISSN 1562-6016. ВАНТ. 2012. №6(82)
increased the gas pressure slowly until gas discharge
ignition occur. At the moment of the discharge breakdown
the RF voltage shows a sharp change. The uncertainty in
the measured breakdown voltage amplitude Ubr was no
more then 2% over the whole Ubr range under study.
2. SIMULATION
The simulation was performed using two dimensional
particle-in-cell (PIC) model implemented by Tech-X
Copr. in OOPIC Pro code [9]. OOPIC Pro includes Monte
Carlo collision algorithms for modeling collisions of
particles with background gases that might result in the
ionization of the background gases and the production of
a pre-defined species of particle. The simulations were
performed for argon gas. Each macro particle included
one physical particle. In typical simulation ten thousands
particles were used. The uniform gas temperature was set
as 0.025 eV. The simulation grid and time steps were
chosen reasonably small, that computing process ensures
authentic physical results with minimal computing time.
The simulation time step should be significantly less than
the electron mean free time, than the grid cell crossing
time by the fastest particles, and than the RF period. Thus
the time step for the simulation was chosen as 10-10 s. The
grid step was 1 mm.
As an initial condition of the breakdown we accounted
for natural background ionization using random
generation of electrons appearing uniformly over the
entire volume of the chamber during one period of driving
RF voltage. To determine the breakdown voltage we used
condition of balance between creation of electrons by
ionization and secondary emission and their loss to the
walls. For each value of the gas pressure we searched the
RF voltage amplitude providing unchanged mean number
of electrons over several RF periods.
Vaughan secondary electron production model is used
for electron impact on the electrode surface that includes
energy and angular dependence of the emission yield
[10]. In the described simulations we assume that 10% of
the primary electrons are reflected from the surfaces so
the normal component of the incident particle’s velocity
has its sign reversed. Another 10% of the incident
particles are assumed to be scattered, i.e. all components
of the particle’s velocity are scaled by uniform (0,1)
random values keeping total energy unchanged.
3. RESULTS AND DISCUSSION
Fig. 2,a shows the breakdown curves of RF discharge
in cylindrical chamber in argon measured with the upper
electrode made of different materials (aluminium,
stainless steel and graphite). For high pressures (more
then 100 mTorr) the observed breakdown voltages match
for the all applicable materials, while at low pressures the
discharge curves are significantly affected by the
electrode material. The Fig. 2,a shows that with the
increase of the electron emission yield the low-pressure
part of the breakdown curve is shifted to the left and a bit
down. In all the experimental curves the region of
ambiguous dependence of the RF breakdown voltage on
the gas pressure is clearly visible at the lowest pressures.
The results of systematic calculations of the RF
breakdown curve for different secondary e-e emission
yields δ are shown in the Fig. 2,b. The simulations were
performed for low pressures (30…300 mTorr) in the RF
voltage range 80…500 V.
One can see from the Fig. 2,b that the simulation
results are qualitatively consistent with the experimental
data. All the breakdown curves demonstrate multivalued
dependence at lowest pressures and coinciding right-hand
branches. Similarly to the experimental curves the
calculated dependences are shifted to the left and a bit
down with δ growth.
General analysis for all the used electrode materials
shows that all the theoretic curves are slightly shifted to
the right in relation to the corresponding experimental
curves. The right-hand branches of the theoretic curves
are approximately 20 V higher then the experimental.
Presumably, this discrepancy appears since the model
takes into account only the electron induced secondary
electron emission, while for accurate description of the
RF breakdown it is of course necessary to consider all
types of electron emission: e-e and i-e emissions as well
as electron emission caused by photons and metastable
atoms.
Fig. 3,a,b shows the breakdown curves of RF
discharge in argon measured for cylindrical and for GEC
cell configurations as well as simulation results for the
mentioned chambers. Both the experimental and the
theoretical results demonstrate that the chamber extension
with the constant inter-electrode gap causes the deflection
of the low-pressure part of the breakdown curve.
Fig. 3. Breakdown curves for two chamber configurations
(similar to GEC cell – solid curves, cylindrical – dash
curves): a) experimental data, b) simulation result
Fig. 2. Breakdown curves for different top electrode
materials: a) experimental data, b) simulation result
ISSN 1562-6016. ВАНТ. 2012. №6(82) 195
The shift of the curve to lower pressures at high
voltages could be explained by appearing of longer
trajectories of electron oscillation between the bottom
electrode and upper corner of the chamber. The increase
of the electron path length L leads to decrease of the
breakdown pressure p in order to keep the similarity
parameter pL constant.
REFERENCES
1. C. Gutton, S.K. Mitra and V. Ylostalo. Sur la decharge
a haute frequence dans les gaz rarefies // Comptes rendus
Acad. Sci. 1923, № 176, p. 1871-1874.
2. J. Thomson The high-frequency glow discharge
//Philosophical Magazine. 1937, v. 23, p. 1-19.
3. S. Githens The influence of discharge chamber
structure upon the initiating mechanism of the high
frequency discharge // Physical Review. 1940, v. 57,
p. 822-828.
4. S.M. Levitskii // Soviet Physics - Technical Physics
1958, v. 2, p. 887.
5. H.B. Smith, C. Charles and R. W. Boswell. Breakdown
behavior in radio-frequency argon discharges // Physics of
Plasmas. 2003, v. 10, p. 875-881.
6. V. Lisovskiy, S. Martins, K. Landry, D. Douai,
J.–P. Booth, V. Cassagne and V. Yegorenkov. The effect
of discharge chamber geometry on the ignition of low-
pressure rf capacitive discharges // Physics of Plasmas.
2005, v.12, p. 1-8.
7. V. Lisovskiy, J.–P. Booth., K. Landry, D. Douai,
V. Cassagne. and V. Yegorenkov. Electron drift velocity
in argon, nitrogen, hydrogen, oxygen and ammonia in
strong electric fields determined from rf breakdown
curves // Journal of Physics D: Applied Physics. 2006,
v. 39, p. 660–665.
8. V.A. Lisovsky, V.D. Yegorenkov. Low-pressure gas
breakdown in combined fields // Journal of Physics D:
Applied Physics. 1994, v. 27, p. 2340-2348.
9. J. P. Verboncoeur, A. B. Langden. and N.T. Gladd. An
object-oriented electromagnetic PIC code // Computer
Physics Communications. 1995, v. 87, p. 199- 211.
10. J.R.M. Vaughan. A new formula for secondary
emission yield // IEEE Transactions on Electron Devices.
1989, v. 36, p. 1963-67.
Article received 20.09.12
ВЛИЯНИЕ ГЕОМЕТРИИ ЭЛЕКТРОДОВ ВЧ-РЕАКТОРА НА КРИВУЮ ЗАЖИГАНИЯ РАЗРЯДА
С.В. Дудин, A.Н. Дахов, В.А. Лисовский, В.М. Плетнев
Представлены результаты экспериментальных и теоретических исследований кривой зажигания ВЧ-разряда
в реакторе для ионного реактивного травления. С учетом сложной геометрии реактора с асимметричными
электродами основное внимание было уделено влиянию геометрического фактора на кривую зажигания
разряда. Эксперименты показали, что геометрия электродов оказывает существенное влияние на кривую
зажигания в области низких давлений рабочего газа (<50 мТорр). Для цилиндрической геометрии камеры в
области низких давлений существует область неоднозначности кривой зажигания, в то время как для
асимметричной конфигурации близкой к GEC ячейке наблюдается практически вертикальный рост напряжения
зажигания разряда с уменьшением давления газа. Наблюдается качественное согласие численых расчетов,
полученых с использованием particle-in-cell/Monte Carlo (PIC/MCC) кода, с экспериментом. Общую тенденцию
смещения рассчетных кривых зажигания в область более высоких давлений можно объяснить необходимостью
корректного учета различных видов электронной эмиссии с электродов вдополнение к учтенной нами
вторичной е-е-эмиссии. И теория, и эксперимент показывают существенное влияние вторичной элетронной
эмиссии на кривую зажигания ВЧ-разряда в области низких давлений.
ВПЛИВ ГЕОМЕТРІЇ ЕЛЕКТРОДІВ ВЧ-РЕАКТОРА НА КРИВУ ЗАПАЛЮВАННЯ РОЗРЯДУ
С.В. Дудін, О.М. Дахов, В.О. Лісовський, В.М. Плєтньов
Представлені результати експериментальних та теоретичних досліджень кривої запалювання ВЧ-разряду в
реакторi для іонного реактивного травлення. З урахуванням складної геометрії реактора з асиметричними
електродами основну увагу було приділено впливу геометричного фактора на криву запалювання розряду.
Експерименти показали, що геометрія електродів робить істотний вплив на криву запалювання в області
низьких тисків робочого газу (<50 мТорр). Для циліндричної геометрії камери в області низьких тисків існує
область неоднозначності кривої запалювання, в той час як для асиметричної конфігурації близької до GEC
осередку спостерігається практично вертикальне зростання напруги запалювання розряду при зменшенні тиску
газу. Спостерігається якісна згода чисельних розрахункiв, отриманих з використанням particle-in-cell/Monte
Carlo (PIC / MCC) коду, з експериментом. Загальну тенденцію зсуву розрахункових кривих запалювання в
область більш високих тисків можна пояснити необхідністю коректного врахування різних видів електронної
емісії з електродів в доповнення до врахованої нами вторинної е-е-емісії. Як теорія, так і експеримент
показують істотний вплив вторинної елетронній емісії на криву запалювання ВЧ-розряду в області низьких
тисків.
|