SiO 2 ETCH PROPERTY CONTROL USING PULSE POWER IN CAPACITIVELY COUPLED PLASMAS* Sang-Heon Song a) and Mark J. Kushner b) a) Department of Nuclear Engineering and Radiological Sciences University of Michigan, Ann Arbor, MI 48109, USA [email protected]b) Department of Electrical Engineering and Computer Science University of Michigan, Ann Arbor, MI 48109, USA [email protected]http://uigelz.eecs.umich.edu Nov. 2011 AVS * Work supported by DOE Plasma Science Center and Semiconductor Research Corp.
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SiO 2 ETCH PROPERTY CONTROL USING PULSE POWER IN CAPACITIVELY COUPLED PLASMAS * Sang-Heon Song a) and Mark J. Kushner b)
SiO 2 ETCH PROPERTY CONTROL USING PULSE POWER IN CAPACITIVELY COUPLED PLASMAS * Sang-Heon Song a) and Mark J. Kushner b) a) Department of Nuclear Engineering and Radiological Sciences University of Michigan, Ann Arbor, MI 48109, USA [email protected] - PowerPoint PPT Presentation
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SiO2 ETCH PROPERTY CONTROL USING PULSE POWER IN CAPACITIVELY COUPLED PLASMAS*
Sang-Heon Songa) and Mark J. Kushnerb)
a)Department of Nuclear Engineering and Radiological Sciences University of Michigan, Ann Arbor, MI 48109, USA
Rate coefficient of e-sources is modulated between electron source (electron impact ionization) and loss (attachment and recombination) during pulsed cycle.
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ANIMATION SLIDE-GIF
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Etch Properties:Variable Blocking Capacitor
PULSED CCP: PLASMA POTENTIAL & dc BIAS A small blocking capacitor allows the “dc” bias to follow the
change during the pulse period. Maximum ion energy gain = Plasma Potential – “dc” Bias
University of MichiganInstitute for Plasma Science & Engr.
PRF = 100 kHz, Duty-cycle = 25% LF = 10 MHz, 250 V HF = 40 MHz, pulsed 500 W
1 F 10 nF
ETCH PROFILE IN SiO2 & IEAD: 1 F With constant voltage, bias amplitude is constant but blocking
ETCH PROFILE IN SiO2 & IEAD: NO dc BIAS In absence of dc bias and for constant voltage, pulse power and is
effect on f() in large part determine etch properties.
University of MichiganInstitute for Plasma Science & Engr.
Pulsed HF 40 MHz 500 W LF 10 MHz 250 V, Blocking Cap. = 100 F
SHS_MJK_AVSAngle (degree)Width (m)
ANIMATION SLIDE-GIF
Cycle Average IEAD Etch Profile (600 sec)
Ener
gy (e
V)
Hei
ght (
m)
POWER NORMALIZED ER: Blocking Capacitor Power normalized etch rate is dependent not only on the pulse
repetition frequency (PRF), but also the value of the blocking capacitor on the substrate at lower PRF.
University of MichiganInstitute for Plasma Science & Engr.
Pulsed HF 40 MHz 500 W LF 10 MHz 250 V
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CW 250 100 50 kHz0.0
1.0
2.0
3.0
4.0
5.0
NO dc 10 nF 1 uF
A
B
C
A B C
F to Poly Flux ratio
Electron source rate coefficient is modulated with f() by pulse power.
Modulation is enhanced with smaller PRF.
E-SOURCES and FLUX RATIO: PRF
University of MichiganInstitute for Plasma Science & Engr.
SHS_MJK_AVS
Pulsed HF 40 MHz 500 W LF 10 MHz 250 V Blocking Cap. = 1 F
F to Poly Flux ratio
0.0
1.0
2.0
3.0
4.0
5.0
6.0
CW 250 100 50 kHz
Power normalized etch rate is large at 250 kHz with ion distribution extending to higher energies.
University of MichiganInstitute for Plasma Science & Engr.
Pulsed HF 40 MHz 500 W LF 10 MHz 250 V Without DC Bias on LF electrode
ETCH RATE: POWER NORMALIZED
CW 250 100 50 kHz
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Cycle Average IEAD Normalized Etch Rate
Angle (degree)
Ener
gy (e
V)
1
Pulsed HF 40 MHz 500 W LF 10 MHz 250 V Blocking Cap. = 1 F
University of MichiganInstitute for Plasma Science & Engr.
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EPD + Over Etch 50%
ETCH PROFILE: CRITICAL DIMENSION
2
(1/A)
(2/A)
CW 250 100 50 kHz
CD is compared at the middle and bottom of feature.
CW excitation produces bowing and an undercut profile.
Pulse plasma helps to prevent the bowing and under-cutting.
Smaller PRF has a tapered profile.
A
ETCH SELECTIVITY: Between SiO2 and Si
Pulsed HF 40 MHz 500 W LF 10 MHz 250 V Blocking Cap. = 1 F
University of MichiganInstitute for Plasma Science & Engr.
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CW 250 100 50 kHz
Silicon damage depth is compared in 2-D etch profile.
Pulsed operation helps to prevent the silicon damage.
Lower damage appears to be correlated with smaller F flux ratio at 250 kHz.
EPD + Over Etch 50%
CONCLUDING REMARKS
Extension of tail of f() beyond that obtained with CW excitation produces a different mix of fluxes to substrate.
Etch rate can be controlled by pulsed operation with different pulse repetition frequencies.
Blocking capacitor is another variable to control ion energy distributions and etch rates. Smaller capacitance allows “dc” bias to follow the plasma potential in pulse period more rapidly.
Etch rate is enhanced by pulsed power operation in CCP. Etch profile is improved with pulsed operation preventing
undercut. Etch selectivity of SiO2 to Si is also improved with PRF of 250 kHz
with a smaller fluorine flux ratio.
University of MichiganInstitute for Plasma Science & Engr.SHS_MJK_AVS