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Characteristics of pulsed plasma doping sources for ultrashallow junction formation
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10.1063/1.2433746
/content/aip/journal/jap/101/6/10.1063/1.2433746
http://aip.metastore.ingenta.com/content/aip/journal/jap/101/6/10.1063/1.2433746

Figures

Image of FIG. 1.
FIG. 1.

Plasma properties for the base case (, ICP power, , ) and substrate bias. (a) Power, (b) total ion density, and (c) density. Note the depletion of ions in the sheath above the substrate and the islands of ions in the periphery of the reactor.

Image of FIG. 2.
FIG. 2.

Schematic of the pulsed voltage waveform. The base case voltage pulse is long with a pulse-off time of between the pulses. Four such voltage pulses are applied in the model to reach a quasi-steady-state.

Image of FIG. 3.
FIG. 3.

Plasma properties for the base case (, ICP power, , ) and substrate bias. (a) , (b) , and (c) densities. The densities are shown when the bias is midway through the fourth pulse.

Image of FIG. 4.
FIG. 4.

Fluxes to the wafer as a function of radius for the base case conditions (, ICP power, , ). (a) Ion fluxes and (b) neutral fluxes. and F are the major neutral radical fluxes. , , and are the dominant ion fluxes.

Image of FIG. 5.
FIG. 5.

(Color) Electron and densities at base case conditions (, , ) and substrate bias as a function of pressure. (a) 5, (b) 10, and (c) . The electron density decreases with increasing pressure and constant power due to a higher likelihood for attachment and large collisionality. These figures use a log scale plotted over 2 decades.

Image of FIG. 6.
FIG. 6.

(Color) IEADs averaged over the wafer for the base case conditions (, ICP power, , ) (a) IEADs for bias voltages of 1, 2.5, 5, and . The IEAD acquires an asymmetry as the bias voltage is increased. (b) IEADs for , , and ions for a bias of . IEADs for ions of the feedstock gases more prominent low energy tails due to ionization in the sheath. The energy peak of the IEAD is slightly higher for lighter ions along with a less prominent low energy tail. These figures use a log scale plotted over 2 decades.

Image of FIG. 7.
FIG. 7.

(Color) IEADs averaged over the wafer for the base case conditions (, ICP power, , ). (a) Total ion energy and angular distributions for different lengths of the bias ramp-up period, . The tail of the IEAD increases as the rate of increase of voltage decreases, as more ions enter the sheath during the ramp up and ramp down of voltage pulse. (b) IEADs for , , , and ions at base case conditions ( substrate bias) and . These figures use a log scale plotted over 2 decades.

Image of FIG. 8.
FIG. 8.

(Color online) IEADs typically have more prominent tails at higher biases. (a) Ion energy distributions for all ions integrated over angle striking the wafer for different bias voltages. (b) IEADs, averaged over the wafer, for , , , and ions at base case conditions and substrate bias. The distributions are plotted over 3 decades to emphasize the tail of the IEADs.

Image of FIG. 9.
FIG. 9.

(Color) Plasma properties as a function of ICP power for otherwise the base case conditions (, ICP power, , ). (a) IEADs for all ions, averaged over the wafer, for base case conditions with different ICP powers. The tail of the IEAD is less prominent at higher ICP powers due to there being a thinner sheath with less ionization in the sheath. (b) IEADs for , , , and ions at base case conditions and ICP power. Both figures are log scales plotted over 2 decades.

Image of FIG. 10.
FIG. 10.

Total ion density at the edge of the sheath and sheath thickness as a function of ICP power for otherwise the base case conditions (, , ) for a bias of . The ion densities are measured above the sheath at the center of the reactor. Increasing ICP power increases the ion density at the sheath edge and reduces the sheath thickness.

Image of FIG. 11.
FIG. 11.

Total ion flux as a function of radius for otherwise the base case conditions (, , , bias) for different ICP powers. The total ion flux increases with increasing ICP powers with more light ions due to a greater level of dissociation.

Image of FIG. 12.
FIG. 12.

(Color) Electron density for the base case conditions (, ICP power, , ) and substrate bias at different times during the pulse (as indicated in the lower figure). The impulsive application of the bias launches electrostatic waves into the plasma. These figures use a log scale plotted over 2 decades.

Image of FIG. 13.
FIG. 13.

(Color online) Electron density above the substrate (region indicated in the top frame) as the pulse voltage is ramped down for the base case conditions (, ICP power, , ) and substrate bias. The frames are for times indicated in the lower figure. The asymmetry in the sheath is maintained during its collapse. These figures use a log scale plotted over 2 decades.

Image of FIG. 14.
FIG. 14.

(Color online) Electron density above the substrate (region indicated in the top frame) at the end of the constant portion of the substrate voltage pulse for different pulse lengths. The results are otherwise for base case conditions (, ICP power, , ) and substrate bias. The sheath thickness increases with increasing pulse length as positive charge in the sheath is depleted by flow into the cathode. These figures use a log plotted over 2 decades.

Image of FIG. 15.
FIG. 15.

(Color) Ionization produced by the secondary electrons emitted from the substrate and accelerated by the sheath at different times during the pulse (as indicated in the lower figure). The conditions are the base case (, ICP power, , ) and substrate bias. The secondary electron emission coefficient varies with incident ion energy. Ionization is maximum in the sheath when electrons pass through the maximum cross section. Figure uses a log scale plotted over 2 decades.

Image of FIG. 16.
FIG. 16.

(Color) density for the base case conditions (, ICP power, , ) and substrate bias during the pulse and interpulse period (as shown in the lower figure). The varying thickness of the sheath (thicker above the substrate and thinner above the focus ring) results in isolation of an island of positive ions in the periphery of the reactor. Figure uses a log scale plotted over 2 decades.

Image of FIG. 17.
FIG. 17.

(Color) density for the base case conditions (, ICP power, , ) and substrate bias during the pulse and interpulse period (as shown in the lower figure). The negative ions trapped in the local maximum in plasma potential contribute to the stability of the islands of positive ions in the periphery of the reactor. Figure uses a log scale plotted over 2 decades.

Image of FIG. 18.
FIG. 18.

(Color online) Total ion density for the base case conditions (, ICP power, , ) and substrate bias at the end of the constant portion of the substrate voltage pulse for increasing height of the reactor. (a) 22, (b) 30, and (c) . As the height of the reactor increases, the sheath transitions from being thinner at the outer radius to being thinner at the inner radius. Figures use a log scale plotted over 2 decades.

Image of FIG. 19.
FIG. 19.

(Color online) Total ion energy and angular distributions at different radial positions along the wafer for increasing height of the reactor. (a) 22, (b) 30, and (c) . The IEADs transition from being angularly skewed inward (short reactor) to being angularly skewed outward (tall reactor). Figures use a log scale plotted over 2 decades.

Image of FIG. 20.
FIG. 20.

(Color online) Plasma characteristics for a reactor with a raised focus ring. (a) Total ion density when the bias is . (b) IEADs for the inner, middle, and outer regions of the wafer. The focus ring produces a more uniform sheath and so more symmetric IEADs. These figures use a log scale plotted over 2 decades.

Tables

Generic image for table
Table I.

reaction mechanism.

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/content/aip/journal/jap/101/6/10.1063/1.2433746
2007-03-23
2014-04-19
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752b84549af89a08dbdd7fdb8b9568b5 journal.articlezxybnytfddd
Scitation: Characteristics of pulsed plasma doping sources for ultrashallow junction formation
http://aip.metastore.ingenta.com/content/aip/journal/jap/101/6/10.1063/1.2433746
10.1063/1.2433746
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