cornell nanoscale facility dry etch capabilities · plasmatherm 770-icp • dual chamber icp •...
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CNF TCN, page 1
Cornell NanoScale Facility
Dry Etch Capabilities
Vince Genova
CNF Research Staff
NNCI Etch Workshop
Cornell University
May 24, 2016
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CNF TCN, page 2
Dry Etch Systems
• High Density Plasma (ICP): PlasmaTherm Versaline DRIE
Unaxis (PT) 770 DRIE
PlasmaTherm 770 (dual chamber)
Oxford PlasmaLab 100-380
Trion Minilock III
Oxford PlasmaPro 100 Cobra
• RIE (parallel plate):
PlasmaTherm 720/740 (dual chamber)
PlasmaTherm 72
Oxford PlasmaLab 80 (2)
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CNF TCN, page 3
Dry Etch Systems
• Dry release: Xactix XeF2
Primaxx uetch
• PR strip/ash: Aura 1000
Branson barrel system
Glenn 1000
Yes CV200RFS
Anatech Resist Strip
• Ion Milling: AJA ion mill
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CNF TCN, page 4
PlasmaTherm Versaline DRIE
• Timed multiplexed process
(C4F8, SF6, Ar)
• Si and Ge DRIE
• SOI, HAR processes
• PR, SiO2, Al2O3 (ALD) masks
• 110:1, 340:1, >1000:1
selectivity
• 50:1 AR (trench), 200:1 (lines)
• Typical etch rates ~ 6-8um/min
• 100 mm wafer size, clamped
• Endpoint works OES
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CNF TCN, page 5
Versaline DSEIII-TMP deep silicon etch
35:1 aspect ratio
Oxide selectivity = 333:1
Etch rate = 8um/min
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CNF TCN, page 6
Versaline DSEIII-TMP deep silicon etch
PR mask selectivity 120:1
Etch rate 8um/min
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CNF TCN, page 7
ALD alumina and Plasmatherm Versaline Silicon DRIE etching
ALD alumina has shown to be a good etch mask for the new Versaline DRIE
silicon etcher. The selectivity to silicon has been shown to be 2000:1. In the image
above 15nm of ALD alumina was used to etch 25 microns into silicon. The alumina
can be etched in a chlorine plasma or wet etched in basic developer.
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CNF TCN, page 8
Plasmatherm Versaline DRIE
Germanium
Ge DRIE: PR mask
R7-IAT DOE: 4um/min
Ge DRIE: SiO2 mask
R5-IAT DOE: 3.5um/min
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CNF TCN, page 9
Plasmatherm Versaline
Ge DRIE with Al2O3 (70nm) mask
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CNF TCN, page 10
Unaxis (Plasmatherm) 770 SLR
DRIE
• Time multiplexed process
(SF6, C4F8, Ar)
• SF6 based release etch
• Mixed etch (SF6+C4F8+O2)
aka “photonics etch”
• Typical DRIE etch rates ~
2um/min.
• PR and oxide masks with 50:1
and 200:1 selectivity.
• Aspect ratios up to 20:1
• 100mm, 150mm clamped
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CNF TCN, page 11
Unaxis 770
Photonics or “mixed etch”
(SF6+C4F8) Silicon (100)
ASML DUV features
5:1 to UV210 PR
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CNF TCN, page 12
Unaxis 770
Photonics or mixed etch
SF6+C4F8
N+ polysilicon
200nm ASML lines
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CNF TCN, page 13
Plasmatherm 770-ICP
• Dual chamber ICP
• Left chamber – shallow silicon
(<10um), single xtal and polyxtalline.
- Cl2 based chemistry
- silicon oxide mask only (20:1)
- 200nm/min etch rate
- 100mm clamped
• Right chamber – III-V’s (Ga and In
based materials) including ternaries
and quaternaries.
- PR, SiO2, Si3N4, and Ni masks.
- 100mm clamped
- non-heated electrode
- Cl2, BCl3, SiCl4, CH4, H2, SF6, O2
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CNF TCN, page 14
Plasmatherm 770 ICP
GaAs etch using BCl3 chemistry
with pecvd oxide mask.
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CNF TCN, page 15
Plasmatherm 770 ICP
Ebeam defined SOI waveguide
structure using HSQ mask etched with Cl2/BCl3/H2 chemistry.
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CNF TCN, page 16
Plasmatherm 770 ICP
Annealed P+ polysilicon on oxide
etched in Cl2/BCl3 chemistry with PECVD oxide mask.
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CNF TCN, page 17
Trion Minilock III ICP
• Chrome etching only
• Cl2, O2, Ar based chemistry
• Up to 200mm wafers
• Up to 7” square mask plates
• Nanoimprint template fabrication (P-NIL)
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CNF TCN, page 18
Trion Minilock III ICP
Chrome etched with Cl2/O2/Ar
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CNF TCN, page 19
Oxford Plasmalab 100-ICP
• Silicon based dielectric etching (oxide,
nitride, low stress nitride)
• Quartz and fused silica etching (no
borofloat, Pyrex, etc)
• Recent upgrade to 12 line gas pod and
installation of gas ring in close
proximity to the substrate.
• Low F/C ratio gas chemistries (C4F8,
C2F6, C4F6, CH2F2, CHF3)
• Other gases (CF4, SF6, O2, Ar, N2,
He)
• Switchable manifold for the
showerhead or gas ring for low F/Cs.
• Enhanced selectivity to ebeam and
deep UV resists
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CNF TCN, page 20
Oxford 100 ICP
90nm linewidth ASML DUV
(248nm) silicon nitride etched with CHF3/O2
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CNF TCN, page 21
Oxford 100 ICP
119nm linewidth ASML DUV
(248nm) defined silicon dioxide etched with CHF3/O2.
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CNF TCN, page 22
Oxford 100 ICP
E-beam lithographically defined
68nm lines etched into fused silica with C4F8/CO2 using chrome mask.
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CNF TCN, page 23
Oxford Instruments Plasma-Lab 100-380 ICP with Gas Ring
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CNF TCN, page 24
C4F6/O2 SiO2 chamber/ring DOE
0
0.5
1
1.5
2
2.5
3
0 20 40 60 80
SPR
RIE(W)
C4F6/O2 OXIDE DOE1
RING
CHAMBER
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CNF TCN, page 25
CH2F2 nitride additive ring DOE
0
50
100
150
200
250
300
350
2000 2200 2400 2600 2800 3000
ER(nm/min)
ICP(W)
CH2F2 NITRIDE RING
O2
HE
AR
CO2
0
0.5
1
1.5
2
2.5
3
3.5
4
4.5
5
2000 2200 2400 2600 2800 3000
SPR
ICP(W)
CH2F2 NITRIDE RING
o2
HE
AR
CO2
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CNF TCN, page 26
CH2F2/HIGH He OXIDE ETCH (RING)
CH2F2/He=20/80, 3000/60W, 4mT
Oxford 100-380 ICP
1um oxide, 155nm/min, SPR=4.4:1
UV210
2um oxide 155nm/min SPR=5.8 AR=7.3
UV210
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CNF TCN, page 27
CH2F2(ring)/high He thick(10um) SiO2 etch
Oxford 100-380 ICP
CH2F2/He(20/80), 3000/60W, 4mT
160nm/min, SPR=5.75:1 (i-line PR) Note: minimal RIE-LAG effects
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CNF TCN, page 28
Plasmatherm 720/740 RIE
• 720: Cl2 based shallow silicon etch
(single xtal or polycrystalline)
- oxide mask only, 30:1 selectivity
- up to 200mm wafers
- etch rates up to 100nm/min
- 2D materials (WSe2, NbSe2, GaSe)
• 740: metal etching (mostly Al, but also
Al2O3, Cr, Ta, W and Nb)
- Cl2 based chemistry
- CH4 sidewall passivation
- SF6/O2 for post etch passivation PE
mode.
- up to 200mm wafers.
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CNF TCN, page 29
Plasmatherm 720/740
Tantalum etch SF6/N2
ASML UV210
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CNF TCN, page 30
Tungsten Etch PT740
ASML UV210 PR mask:
SF6/N2=40/12, 100W, 10mTorr
ASML UV210 PR mask:
SF6/N2=40/12, 100W, 10mTorr
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CNF TCN, page 31
Tungsten Etch PT740
SiO2 mask
SF6/N2=40/25 10mTorr, 125W
SiO2 mask
SF6/O2=40/12, 10mTorr, 125W
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CNF TCN, page 32
Oxford Plasmalab 80s RIE
• Parallel plate conventional RIE
• Fluorine based chemistry: CF4, CHF3,
SF6.
• Additives: Ar, O2, H2
• Primarily used to etch silicon based
materials.
• 2 plasmalab 80 systems: 82 is limited
to CMOS approved materials, while 81
includes other substrates such as III-V
materials.
• DUV ARC (AR3) etch is available on
both systems.
• Up to 200mm wafers.
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CNF TCN, page 33
Plasmatherm 72 RIE
• Conventional parallel plate RIE
• Fluorine based chemistry: CF4, CHF3,
SF6.
• Additive gases include O2 and H2.
• Used mostly to etch silicon based
materials, but other materials such as
W and Ta are etched as well.
• Very few material restrictions, III-V
materials ok
• Up to 200mm wafers.
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Xactix XeF2 vapor phase etch system
• Chemical isotropic etch of silicon, poly
silicon, and amorphous silicon
• Large loading effect with respect to the
amount of exposed silicon.
• Noticeable RIE-LAG aperture effect.
• Highly selective to silicon oxide, silicon
nitride, resist, and metals such as Cr
and Al. Not those metals that react
with atomic fluorine.
• Ability to add nitrogen as a buffer gas
to enhance nitride selectivity and to
lessen surface roughness.
• Up to 150mm wafers.
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CNF TCN, page 35
Primaxx uetch vapor HF system
• Vapor phase isotropic etch of silicon oxide.
• Thermal, PECVD, and TEOS oxides.
• No doped oxides such as BSG, BPSG, PSG, due to formation of acids/corrosion.
• No resist masking.
• Selective to silicon, Al, Al2O3, TiW, SiC and LPCVD low stress silicon nitride.
• VHF, EtOH, and N2 are reaction
components.
• Typical process pressures 50-150 torr.
• Process temperature 45C.
• Controlled thermal oxide etch rates up to
200nm/min.
• Need to O2 ash prior to etch to remove any CFx on surface acting as an inhibitor.
• If Si3N4 is present, need to hotplate bake at >160C to remove reaction product.
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CNF TCN, page 36
Primaxx HF system
Successful release of silicon beams
25um in length, 500nm in width from SOI 2um BOX layer.
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Plasma Ashing/Strip
• Aura 1000: downstream
-4” cassette to cassette
-heating option
- up to 4um/min rate
• Anatech SCE-110-RF resist strip
- ICP
- 1000W
-O2/N2
-Bosch polymer removal
• Glenn 1000: multi-shelf electrode
configuration.
- powered, grounded, or floating.
- strip or descum.
• YES CV200RFS: 40kHz plasma
isolated by grounded perforated
metal plate.
- strip or descum
- heated to 250C.
- N2 and Ar are available.
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CNF TCN, page 38
AJA Ion Mill
• 22cm Kaufman RF-ICP Ar ion source
• Water cooled stage
• Up to 180 degree tilt with rotation up to
25 rpm
• Wafer sizes up to 150mm
• Beam energies up to 1000eV
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CNF TCN, page 39
Oxford Cobra NGP ICP
• Wide temp. electrode (-150C->400C)
• 100mm wafers, mechanically clamped
• Low frequency (350kHz) bias on electrode
• Ocean optics OES
• 12 line gas pod
• Current gases: HBr, Cl2, BCl3, H2, CH3OH, SF6, O2, and Ar
• Later additions: NH3, CO, C4F8
• Current processes: HBr silicon etch and CH3OH/Ar magnetics etch
• Deep silicon cryogenics etch
• Later: mixed silicon etch SF6/C4F8 and NH3/CO magnetics etch
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CNF TCN, page 40
Oxford Cobra NGP ICP
Magnetics Etch
• CH3OH/Ar Magnetics Etch
• Ni, Fe, Co ferromagnetic based alloys
• Magnetic tunnel junctions MTJs (Cu,
Ru, MgO, PtMn…)
• Generation of volatile carbonyl
compounds
• Highly selective to Ta, Ti, Al2O3
• Ability to stop on thin (few nm)
interfaces
• Non-corrosive chemistry
• Slow etch rates < 10nm/min
• No sidewall redeposition
• Suitable for nanoscale patterning
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CNF TCN, page 41
Oxford Cobra NGP ICP
HBr silicon etch
HBr/Ar=20/10sccm, 40/1500W, 8mTorr
PR mask: 177nm/min, SPR=3.3:1
HBr=20, no Ar, 40/1500W, 8mTorr
SiO2 mask: 227nm/min, SOX=22:1
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CNF TCN, page 42
Oxford Cobra NGP ICP
HBr silicon etch
HBr/Ar=20/7sccm, 30/1500W, 11mTorr
PR mask: 133nm/min, SPR=4.2:1
HBr/Ar=20/7sccm, 30/1500W, 11mTorr
ZEP mask: 75nm gaps 95nm/min, S-ZEP=3:1
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CNF TCN, page 43
Oxford Cobra NGP ICP
Ultra-Nanocrystalline Diamond (UNCD) Etch
• Ultra-nanocrystalline diamond thin films are
increasingly used in MEMS sensors and actuators (high biocompatibility).
• UNCD films composed of nanograins (less than tens of nanometers) that can lead to
large surface roughness.
• Addition of a small percentage of SF6(1.5sccm) to an O2/Ar (50/5sccm) leads to smooth etch morphology.
• SF6 assists in the preferential etching of
amorphous carbon at intergrain boundaries.
• Aluminum used as an etch mask.
• Etch rates of 270nm/min with selectivity to Al
of 40:1 with etch parameters of 2800W/50W at 5mTorr.
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CNF TCN, page 44
Future Plans for the Etch Area
• Retrofit the Plasmatherm 770L from a Cl2 based Si etch ICP chamber to a Cl2 based metal etch
chamber.
• Recommission the chlorine based Plasmatherm 720/740 system for more exotic materials such
as selenides, etc.
• Add C4F8 to the Oxford Cobra ICP so that the mixed (SF6+C4F8) “photonics etch” can be moved, making the Unaxis(PT)770 a dedicated Bosch DRIE system.
• Make the HBr Si etch in the Oxford Cobra ICP the premier nanophotonics etch process (especially with the enhanced SOI process capability).
• Wish list: a dedicated photomask ICP etch system for high resolution ASML DUV masks.