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Space and phase resolved ion energy and angular distributions in single- and dual-frequency capacitively coupled plasmas
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10.1116/1.4822100
/content/avs/journal/jvsta/31/6/10.1116/1.4822100
http://aip.metastore.ingenta.com/content/avs/journal/jvsta/31/6/10.1116/1.4822100
View: Figures

Figures

Image of FIG. 1.
FIG. 1.

Properties of the ICP reactor. (a) Schematic showing the wafer on a substrate capacitively powered at LF and HF surrounded by dielectric focus rings. The 10 turn ICP coil surrounds the top of the reactor and is operated at 400 kHz. (b) The submesh insertion zone where IEAD will be analyzed. The radial positions where IEADs will be plotted are labeled.

Image of FIG. 2.
FIG. 2.

(Color online) Time averaged plasma properties for the base case conditions (Ar/O = 80/20, 2 mTorr, 50 sccm, LF = 2 MHz, V = 500 V, and DC bias = −400 V). (a) Electron density, (b) electron temperature, (c) total positive ion density, and (d) average gas temperatures. The electron and ion densities are log-scales with contour labels having units of 1011 cm−3. The electron temperature and average gas temperature are in linear-scales.

Image of FIG. 3.
FIG. 3.

(Color online) Time averaged IEDs for Ar+ at the middle of the bulk plasma to sheath region for the base case conditions (Ar/O = 80/20, 2mTorr, LF = 2 MHz, V = 500 V, DC bias = −400 V). (a) IED from bulk plasma to wafer. The approximate sheath and presheath boundaries are labeled in frame. Discontinuities in energy are caused by the mesh resolution in collecting statistics. (b) IEDs at selected positions over the full energy range. (c) IEDs at 4.5, 3.5, and 2.6 mm above the wafer over a lower range in energy.

Image of FIG. 4.
FIG. 4.

(Color) Time averaged IEADs for Ar+ as a function of height above the wafer. IEADs are plotted on a log scale over two decades. (a) IEADs from on wafer to the edge of the presheath for energies up to 900 eV and angles −15 to 15°. (b) IEADs from the presheath into the bulk plasma for energies up to 10 eV and angles −90 to 90°. The operating parameters are the base case (Ar/O = 80/20, 2 mTorr, LF = 2 MHz, V = 500 V, and DC bias = −400 V).

Image of FIG. 5.
FIG. 5.

(Color online) IEADs and electric field vectors as a function of radial position. (a) IEADs Ar+ 0.5 mm above wafer for the base condition (Ar/O = 80/20, 2 mTorr, LF = 2 MHz, V = 500 V, and DC bias = −400 V). The IEADs are separately collected over the center of the wafer ( = 1–3 cm), the middle of the wafer ( = 7–9 cm), the edge of the wafer ( = 13–15 cm), and the focus ring ( = 15–16 cm). The contours span two decades using a log scale. (b) Unit electric field vectors at the edge of the sheath and focus ring at the peak of the cathodic portion of the cycle.

Image of FIG. 6.
FIG. 6.

(Color) IEADs of Ar+at the middle of the wafer ( = 8 cm) for base condition (Ar/O = 80/20, 2 mTorr, LF = 2 MHz, V = 500 V, and DC bias = −400 V) at different heights above the wafer (top to bottom: 3.5, 2.6, 1.9, 1.2, and 0.5 mm). IEADs are shown averaged over 1/8 of the rf cycle for phases ending at ϕ = π/4 to 2π along each row. The rf bias cross zero (negative to positive) at ϕ = π.

Image of FIG. 7.
FIG. 7.

(Color) Properties of Ar+ ion transport at the middle of the wafer ( = 8 cm) for different pressures for otherwise the base case conditions. (Ar/O = 80/20, LF = 2 MHz, V = 500 V, and DC bias = −400 V). (a) IEADs as a function of pressure (2–20 mTorr). (b)IEDs at the middle of the wafer as a function of height from the bulk plasma to the wafer. With increasing pressure, the lower plasma density increases the thickness of sheath. The thicker sheath increases ion transit times and, coupled with the higher pressure, increases likelihood for collisions.

Image of FIG. 8.
FIG. 8.

(Color online) Time averaged electron density for Ar/O = 80/20, 2 mTorr, when the HF is varied from (a) 10, (b) 20, (c) 30, and (d) 60 MHz. V = 500 V, DC bias = −400 V. The maximum electron density, which increases with increasing HF, is noted in each frame with contour labels having units of 1011 cm−3.

Image of FIG. 9.
FIG. 9.

(Color online) Ar+ ion properties incident onto the wafer for single frequency biases from 2 to 60 MHz for otherwise the base case conditions (Ar/O = 80/20, 2 mTorr, V = 500 V, and DC bias = −400 V). (a) IEADs and (b) IEDs.

Image of FIG. 10.
FIG. 10.

(Color online) IEDs for Ar+ as a function of height above the wafer at the middle of the wafer for single frequency biases from 10 to 60 MHz for otherwise the base case conditions (Ar/O = 80/20, 2 mTorr, V = 500 V, and DC bias = −400 V). The left side of each figure is an energy scale up to 800 eV and on the right side on a scale up to 50 eV.

Image of FIG. 11.
FIG. 11.

(Color online) IEADs of Ar+ at the middle of the wafer ( = 8 cm) for frequencies (top to bottom) of 10, 20, 30, and 60 MHz for otherwise the base case condition (Ar/O = 80/20, 2 mTorr, V = 500 V, and DC bias = −400 V). The IEADs are shown 0.5 mm above the wafer averaged over 1/8 of the rf cycle for phases ending at ϕ = π/4 to 2π along each row. The rf bias cross zero (negative to positive) at ϕ = 0. With increasing frequency, IEADs become independent of phase.

Image of FIG. 12.
FIG. 12.

(Color) Experimentally measured IEDs using LIF for a 2.2 MHz bias at a radius of 11 cm (Ar/O = 80/20, 0.5 mTorr, V = 300 V, and V = −300 V). The IEDs are shown at heights above the wafer from 5.2 to 2 mm (top to bottom). The development of the IEDs through the presheath and sheath are shown. During the anodic cycle (phases 0–π), the sheath collapses, and ions drift close to the wafer with IEDs resembling the presheath. During the cathodic cycle (phases π–2π), ions are continuously accelerated through the thicker sheath.

Image of FIG. 13.
FIG. 13.

(Color online) Experimentally measured IEADs using LIF for a 2.2 MHz bias at a radius of 12.4 cm. The IEDs are shown at heights above the wafer from 2 to 5.2 mm (right to left). The narrowing of the IEADs is shown as the ions traverse the presheath and sheath. (Contours are on a log scale over two decades.)

Image of FIG. 14.
FIG. 14.

(Color) IEADs for a two frequency rf bias having LF = 2 MHz (V = 400 V) and HF = 10 MHz (V = 400 V) with the DC bias = −400 V, (a) Amplitude of the sheath potential during one 2 MHz period. The dashed lines mark the 10 MHz periods, and each column corresponds to each row below. (b) IEADs for Ar+ at the middle of the wafer for the entire 2 MHz cycle at a height of 0.5 mm. The IEAD for ϕ = 0 for the LF is in the top left corner. Each row of IEADs corresponds to a single 10 MHz cycle.

Image of FIG. 15.
FIG. 15.

(Color online) IEADs for a two frequency rf biases having LF = 2 MHz (V = 400 V) and HF = 20 MHz (V = 400 V) with the DC bias = −400 V. (a) Amplitude of the sheath potential during one 2 MHz period. The dashed lines mark two 20 MHz periods, and each column corresponds to each row below. (b) IEADs for Ar+ at the middle of the wafer for the entire 2 MHz cycle at a height of 0.5 mm. The IEAD for ϕ = 0 for the LF is in the top left corner. Each row of IEADs corresponds to two 20 MHz cycles.

Image of FIG. 16.
FIG. 16.

(Color online) IEADs for a two frequency rf bias having LF = 2 MHz (V = 400 V) and HF = 30 MHz (V = 400 V) with the DC bias = −400 V. (a) Amplitude of the sheath potential during one 2 MHz period. The dashed lines mark three 30 MHz periods, and each column corresponds to each row below. (b) IEADs for Ar+ at the middle of the wafer for the entire 2 MHz cycle at a height of 0.5 mm. The IEAD for ϕ = 0 for the LF is in the top left corner. Each row of IEADs corresponds to three 30 MHz cycles.

Image of FIG. 17.
FIG. 17.

(Color online) Sheath properties for LF = 2 MHz (V = 400 V and HF = 10, 20 and 30 MHz (V = 400 V) with the DC bias = −400 V. (a)Electron density at 1 mm above the middle of the wafer during one LF period. The increase of the HF produces a higher electron density. (b) Implied change in sheath thickness assuming a scaling of [e]−0.5. The sheath thickness varies within the rf period.

Image of FIG. 18.
FIG. 18.

(Color online) IEADs of Ar+ onto wafer for dual frequency excitation with LF = 2 MHz and HF = 30 MHz. The ratio of V/V = 0.5, 1.0, and 2.0 from left to right.

Image of FIG. 19.
FIG. 19.

(Color online) IEADs for a two frequency rf bias having LF = 2 MHz (V = 400 V) and HF = 30 MHz (V = 200 V), that is, V/V = 0.5, with the DC bias = −400 V. (a) Amplitude of the sheath potential during one 2 MHz period. The dashed lines mark three 30 MHz periods, and each column corresponds to each row below. (b) IEADs for Ar+ at the middle of the wafer for the entire 2 MHz cycle at a height of 0.5 mm. The IEAD for ϕ = 0 for the LF is in the top left corner. Each row of IEADs corresponds to three 30 MHz cycles.

Image of FIG. 20.
FIG. 20.

(Color online) IEADs for a two frequency rf bias having LF = 2 MHz (V = 250 V) and HF = 30 MHz (V = 500 V), that is, V/V = 2.0, with the DC bias = −400 V. (a) Amplitude of the sheath potential during one 2 MHz period. The dashed lines mark three 30 MHz periods, and each column corresponds to each row below. (b) IEADs for Ar+ at the middle of the wafer for the entire 2 MHz cycle at a height of 0.5 mm. The IEAD for ϕ = 0 for the LF is in the top left corner. Each row of IEADs corresponds to three 30 MHz cycles.

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/content/avs/journal/jvsta/31/6/10.1116/1.4822100
2013-10-01
2014-04-18
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752b84549af89a08dbdd7fdb8b9568b5 journal.articlezxybnytfddd
Scitation: Space and phase resolved ion energy and angular distributions in single- and dual-frequency capacitively coupled plasmas
http://aip.metastore.ingenta.com/content/avs/journal/jvsta/31/6/10.1116/1.4822100
10.1116/1.4822100
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