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Role of the blocking capacitor in control of ion energy distributions in pulsed capacitively coupled plasmas sustained in Ar/CF4/O2
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10.1116/1.4863948
/content/avs/journal/jvsta/32/2/10.1116/1.4863948
http://aip.metastore.ingenta.com/content/avs/journal/jvsta/32/2/10.1116/1.4863948
View: Figures

Figures

Image of FIG. 1.
FIG. 1.

Operating system for this investigation. (a) Geometry of the DF-CCP chamber. The (10 MHz) is applied on the lower electrode, and the (40 MHz) is applied on the upper electrode. One of the two frequencies is operated in pulse mode with a few tens of kHz PRF. (b) Electrical schematic for the DF-CCP system. The BC is connected in series with the lower electrode.

Image of FIG. 2.
FIG. 2.

(Color online) Electron density (left) and temperature (right) when pulsing the power at different times during the pulsed cycle (as indicated in the lower figure). (Ar/CF/O = 75/20/5, 40 mTorr, 200 sccm, = 250 V at 10 MHz ,  = 250 V at 40 MHz in pulse mode with BC = 1 F, PRF = 50 kHz and 25% duty-cycle.) The electron density is modulated by about 30% during the pulse cycle while the electron temperature shows nearly instantaneous changes as the power toggles on and off, especially near the sheaths due to enhanced stochastic heating.

Image of FIG. 3.
FIG. 3.

(Color online) Electron density and temperature when pulsing the power at different times during the pulsed cycle (as indicated in the lower figure). (Ar/CF/O = 75/20/5, 40 mTorr, 200 sccm,  = 250 V at 10 MHz in pulse mode with BC = 1 F, PRF = 50 kHz and 25% duty-cycle,  = 250 V at 40 MHz ) Pulsing the power produces nominal intercycle changes in electron density and temperature over the pulse period as the majority of the power is dissipated in ion acceleration.

Image of FIG. 4.
FIG. 4.

(Color online) Plasma potential, , and dc-bias, , during one pulse period when pulsing the power (PRF = 50 kHz, 25% duty-cycle). (a) BC = 10 nF and (b) BC = 1 F. The sheath potential is . The power is always on and the power is on only during the pulse window of 25%. Due to the smaller RC time constant with the small BC, the dc-bias responds more quickly. Since the voltage amplitude of the power rides on the dc-bias, the maximum envelope of the plasma potential has the same shape as the dc-bias.

Image of FIG. 5.
FIG. 5.

(Color online) Plasma potential, , and dc-bias, , during one period when pulsing the power (PRF = 50 kHz, 25% duty-cycle). (a) BC = 10 nF and (b) BC = 1 F. The sheath potential is . The power is always on and the power is on only during the pulse window of 25%. The plasma potential is mainly determined throughout the pulse period by the voltage amplitude of the power. The dynamic range of dc-bias is larger with the smaller BC.

Image of FIG. 6.
FIG. 6.

(Color online) Total IEDs for all ions with different sizes of the BC for the base case (40 mTorr, 250 V at 10 MHz, 250 V at 40 MHz). (a) operation, (b) pulsing power, and (c) pulsing power. Pulsing has a PRF of 50 kHz and 25% duty-cycle. The IED is insensitive to the size of BC with operation while its shape depends on the size of BC with pulsed operation.

Image of FIG. 7.
FIG. 7.

(Color online) Total IEDs for all ions for different PRFs when pulsing the power with a 25% duty-cycle. (a) BC = 10 nF and (b) BC = 1 F. The IED becomes single-peaked in appearance with the smaller BC while the IED maintains a multiple-peaked shape with the larger BC. The IEDs with larger PRFs extend to the higher energies.

Image of FIG. 8.
FIG. 8.

(Color online) DC-bias as a function of normalized time (which is time divided by the length of each pulse period) with different PRFs when pulsing the power with a 25% duty-cycle. (a) BC = 10 nF and (b) BC = 1 F. The power is . During power-on period, the dc-bias becomes less negative with some overshoot with smaller PRFs.

Image of FIG. 9.
FIG. 9.

(Color online) Ion energy distributions for O+, Ar+, and CF + when pulsing the power. (a) BC = 10 nF and (b) BC = 1 F.

Image of FIG. 10.
FIG. 10.

(Color online) Total IEDs for all ions for different when pulsing the power with a 25% duty-cycle. (a) BC = 10 nF and (b) BC = 1 F. The IED extends to higher energies with the smaller BC.

Image of FIG. 11.
FIG. 11.

(Color online) DC-bias as a function of the normalized time (which is time divided by the length of each pulse period) with different PRFs when pulsing the power with a 25% duty-cycle. (a) BC = 10 nF and (b) BC = 1 F. The power is . If the size of BC is small enough for the dc-bias to response to the voltage on the electrode, the temporal behavior of dc-bias is similar for different PRFs.

Image of FIG. 12.
FIG. 12.

(Color online) IEDs for O+, Ar+, and CF + when pulsing the power. (a) BC = 10 nF and (b) BC = 1 F.

Image of FIG. 13.
FIG. 13.

(Color online) Total IEDs for all ions for different duty-cycles when pulsing the power with a PRF of 50 kHz. (a) BC = 10 nF and (b) BC = 1 F. The power is . The smaller duty-cycle tends to produce an extended energy range in the IED.

Image of FIG. 14.
FIG. 14.

(Color online) Temporal behavior of dc-bias with different duty-cycles when pulsing the power with a PRF of 50 kHz. (a) BC = 10 nF and (b) BC = 1 F. The power is . The dynamic range of the dc-bias is from 0 V to −200 V with the smaller BC while the range is only from −60 to −90 V with larger BC.

Image of FIG. 15.
FIG. 15.

(Color online) Total IEDs for all ions for different duty-cycles when pulsing the power with a PRF of 50 kHz. (a) BC = 10 nF and (b) BC = 1 F. The power is . The amplitude of the low energy peak diminishes while the amplitude of the high energy peak increases as the duty-cycle increases. The IED becomes similar to that of the case with further increase of the duty-cycle.

Image of FIG. 16.
FIG. 16.

(Color online) Temporal behavior of dc-bias with different duty-cycles when pulsing the power with a 50 kHz PRF. (a) BC = 10 nF and (b) BC = 1 F. The power is . The dynamic range is from −40 to +80 V with the smaller BC while the range is at most ±15 V at 25% duty-cycle with larger BC. Note that the range of oscillation the dc-bias is similar for different duty-cycles with the smaller BC while the range is shifted by duty-cycle with the larger BC.

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/content/avs/journal/jvsta/32/2/10.1116/1.4863948
2014-02-04
2014-04-20
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752b84549af89a08dbdd7fdb8b9568b5 journal.articlezxybnytfddd
Scitation: Role of the blocking capacitor in control of ion energy distributions in pulsed capacitively coupled plasmas sustained in Ar/CF4/O2
http://aip.metastore.ingenta.com/content/avs/journal/jvsta/32/2/10.1116/1.4863948
10.1116/1.4863948
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