with the help of……. - huji.ac.ilchem.ch.huji.ac.il/~porath/nst2/lecture 4 notes - e-beam...
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1
e-Beam Lithography
Danny Porath 2002
(Cumming et. al.)
With the help of…….
1. Yosi Shacam – TAU2. Delft people (Emile Van der Drift)
and site3. …
Nice Simulations: http://www.matter.org.uk/tem/sitemap.htm
Outline SEM/TEM:
1. Examples, links and homework
2. Lithography: e-Beam, direct
3. Etching and process
Internet Sites“Handbook of Microlithography, micromachining and
microfabrication”, Editor P. Rai-Choudhury.http://www.matter.org.uk/tem/sitemap.htm
http://www.cnf.cornell.edu/spiebook/toc.htmhttp://dsa.dimes.tudelft.nl/
http://www.dimes.tudelft.nl/http://www.dimes.tudelft.nl/2001/report.pdf
http://www.eng.tau.ac.il/~yosish/courses.htmlhttp://www.jcnabity.com/
http://www.ece.gatech.edu/research/labs/vc/theory/photolith.htmlhttp://www.ece.gatech.edu/research/labs/vc/....
Homework 41. Read the paper:
“Metal Nanoparticles, Nanowires and contact electrodes self-assembled on pattered monolayer templates – a bottom up chemical approach”Hoeppener et. al., Advanced Materials 14(15), 1036 (2002).
- Emphasize the lithography part.2. Choose a (complicated) lithography example form the web or a paper and
explain how it was done.3. For Mashkianim: Read/brows the paper: (just for review)
“Nanometer-scale lithography for large lateral structures”J. Romijn and E. Van der Drift, Physica B 152, 14 (1988).
Also at: http://dsa.dimes.tudelft.nl/usage/publications/nanometer/nanometer.html
Examples
(Cumming et. al.)
2
Examples
(Glasgow University.)
Optical micrograph of a 140 GHz low noise amplifier
Examples
(Glasgow University.)
Lines and spaces in Shiply UV5 resist written using e-beam lithography
Examples
(Glasgow University.)
Cell growth along lithographically patterned lines
Examples (DIMES- DELFT)
Examples (DIMES- DELFT)Bonding
(Delft University.)
3
Post-processing surface micromachining
(Delft University.)
polyimide as sacrificial layer for an all-dry etch release of microstructures
Post-processing surface icromachining
(Delft University.)
Polyimide as sacrificial layer for an all-dry etch release of microstructures
Post-processing surface micromachining
(Delft University.)
Sacrificial layer is used to avoid stickingWind Sensor
(Delft University.)
Using the sensor,wi nd-speed and direction may be determined with an inaccuracy of ± 2° and ± 5%respectively in the range 0 -25 m/s.
Diamond Membranes
(NASA)
Fabricating Diamond Membranes Using Reactive-Ion Etching
CVD
Scratch
Al Evaporation
RIE
The Delft DIMES Team
4
Overview (based on: http://dsa.dimes.tudelft.nl/usage/techno_intro/Introduction_technology.htm)
1. Nanofabricationa) Conceptb) Trends
2. Pattern definition3. Resist4. Wet chemicals5. Pattern transfer
a) Subtractive: Etching, Multilayer maskingb) Additive: Deposition
6. Inspection7. Examples
Concept
Controlled realisation of a 3-dimensional
structure
Dimensions, accuracies and tolerances in
the nano-range
Step-by-step process, layer by layer
Integration to a complete process
Feedback loop between process and
performance
Multilevel MetalizationState of The Art Applications
Molecular DevicesNanomechanical structuresNanomagnetic structuresNanofluidicsOn-chip integration & “Lab on a chip”
TechnologyFabrication beyond limitsAtomic scale techniques
Process Design ……A matter of making choices
filmsubstrate substrate
Etch Deposit
Start
After mask removal
substrate
maskAfter lithography
mask
Different approaches …. Different results!!!
Within each layer Pattern Definition
Resist layer technologyExposurePattern development
Pattern transferAdditiveSubtractive
Mask removalInspection
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Pattern Definition Radiation source
PhotonsElectronsX-rayIons
ApproachShadow mask – controlledDirect write
Mask Controlled Optical lithography
light source
Mask
contact proximity projection
Substrate + resist
gap
optical
system
Limitations – Diffraction Limited Optical lithography
Resolution K1λ/NADepth of Focus K2λ/(NA)2
From µm down to 50 nm!!!
Direct Write e-Beam lithography
e-
electron gun
beam blanker
deflection coils, lenses
vacuum chamber
mechanical drive
table position monitor
substrate
film
resist
table
computer control
Performance EBPG-5
Details down to 20 nm! Alignment within 50 nm
heavy metal
topography
Limitations (1) e-Beam lithography
Resolution factorBeam quality (~1 nm)Secondary electrons (lateral range – a few nm)Beam focus on surface
Performance recordsOrganic resist PMMA ~ 7 nmInorganic resist, b.v. AIF3 ~ 1-2 nm
diaphragm
substrate
beam
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Limitations (2) e-Beam lithography
Forward scatteringHigh keV, thin resist layerBack scattering
Electron rangeAmount f(atom number)
10 KV 25 KV 50 KV
X-ray Lithography Shadow mask concept – λ=1 nm
Projection concept – λ=13.7 nm
Pyrex
SiBoron nitride
polyimide
Au absorber protective coating
X-ray Lithography (NSL@MIT)
X-ray lithography done with the JMAR laser plasma x-ray source.
X-ray mask X-ray replication
& liftoff (Ti/Au)
Resist Processing Resist
Substrate
Mask
coating
exposure
development
positive negative
pattern transfer
resist strip
Typical Resist Materials (e-Beam 100 kV, Optical 300-400 nm)
Substrate exposurePMMA* e-beam 600 µC/cm2 (+) +and
-
SNR e-beam, DUV µC/cm2 140 -
HSQ (FOX-12) e-beam µC/cm2 500 -
SAL 603 e-beam 3-5 µC/cm2 -
NEB 22-2A e-beam µC/cm2 18 -
HPR NUV 50-100 mJ/cm2 +
AZ NUV 50-100 mJ/cm2 +
AZ, HPR image reversal
NUV 50-100 mJ/cm2 -
* BROAD RANGE OF PRODUCTS
Mask writingPBS e-beam 36 µC/cm2 +
SAL605 e-beam 7 µC/cm2 -
Resist Coating Spin processViscositySpin speedSurfaceDirect ambient
Step coverage
Adhesion
H | O |
H | O |
H | O |
hydrophylic hydrophobic
Si | O |
R R
Si | O |
R R
Si | O |
R R
primer
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Resist Thickness R
topography coverage
dry etch erosion R
lift-off
resolution
pinholes
R
R
R
Resist Issues (1) Materials
Glass temperature Tg – pattern stabilityMolecular weight resolution Substrate atomic number Z proximity effectsChemical composition etch resistance
adhesion
ProcessDevelopment (strength, time, temperature) Baking (time, temperature) Post-treatment: descum, native oxide strip
Resist Issues (2) Materials
Descum
Wet Chemical Treatment ……An example…
Inspection
post-bake
pre-bake
exposure
spin coating
film deposition
resist strip
clean
development rinse and dry
pattern transfer
surface treatment
Wet ChemicalsSubstrate cleaning
fuming HNO3H2SO4/H2O2 (piranya)RCA-process
HCl/H2O2 (metallic) NH4OH/H2O2 (organic)
Resist technologyketone solvents Acetone IPA
Mask removalfuming HNO3PRS
Wet etchingstrong acids alkaline agents
Wet EtchantsH2O sloluble
Nitric acid HNO3
Hydrofluoric acid HFPhosphoric acid H3PO4
Hydrochloric acid HClSulfuric acid H2SO4
Acetic acid H4C2O4
Potassium hydroxide KOHMask strippers (PRS, etc.) strong alkaline
TOXIC, HazardousSafety handling
protection (gloves, glasses) sequence of mixing sequence of diluting
Moisture attackbeneficial role of H2O
special application kits
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Organic LiquidsH2O insloluble
Flamableheating ‘Au-bain-Marie’
Toxic vapoursmandatory extraction conditions
Insoluble residuesacetone/IPA treatment
Etching
(Darling et. al.)
Dry EtchingProfile control
Characteristics
High resolution
Dry Etchingmechanism (1)
diffusion to surface
adsorption
reaction desorption
diffusion into bulk gas
plasma
generation of etchant species
gas flow
ion bombardment
radicals
Dry Etching+ +
Mask
mechanism (2)
• reaction
• desorption
• passivation
sidewall passivation
ion-induced etching
(e.g. O, CF 2 )
(e.g. F, Cl)
ions
Dry Etchingreactive ion etching RIE)
Vp Vdc
rf
plasma bulk
sheath ions radicals
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Etching Machine
(Aultimut)
Fluorine basedSi, Ge, SiC, W, Nb, Mo, SiO2, Si3N4
Clorine basedGaAs, InP,GaN, Al, Ti, Cr, Al2O3
Very dificult to etchAu, Pt, Pd, Cu, Ni, Co, Fe,…
Dry Etching
Dry Etchingprocess issues
nonselective selective
Mask
etch stop
nonselective selective
isotropic anisotropic
Profile
micromasking
איכול איזוטרופי
מסכה
רזיסט
שכבה מאוכלת
Litho bias
Etch bias
אנאיזוטרופיאיכול
מסכה
רזיסט
שכבה מאוכלת
Litho bias
אנאיזוטרופיאיכול פלזמה
יונים ספוחים אטומי ם אינרטים
רזיסט
פולי
אוקסייד
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Reaction Mechanism For C2F6 Etching Si
(ftp://uigelz.ece.uiuc.edu/pub/presentations/dzhang_avs99.pdf)
A CxFy polymer layer is formed on the Si surface in coincidence with Si etching. The steady state passivation layer thickness is a balance of CFx deposition, ion sputtering and F etching of the layer.
Si etching precursor (F) needs to diffuse through the passivation layer.
בעיות באיכולארוזיה של הרזיסט
התזה של הרזיסט
יצירת שוחות
Wet vs. Dry Etching
Wet etching Dry etching
selectivity ++ --
Dimension control -- ++
Advanced Mask Technologies
e-
image layer
film
intermediate
mask layer
substrate
expose develop dry etch dry etch dry etch F/Cl O 2 F/Cl
pmma
Positive tone with HR PMMADry etch purpose
Image layer to be baked at temperatures lower than used for the bottom mask layer!!
Advanced Mask TechnologiesDecoupling of imaging and actual mask functionNegative tone with Si-containing e-beam resist
Dry etch purpose
Image layer to be baked at temperatures lower than used for the bottom mask layer!!
e-
image layer
film
mask layer
substrate
expose develop dry etch dry etch O 2 F/
SNR
oxide
Advanced Mask TechnologiesLift-off purpose – double layer resist
o Dedicated solvents to avoid layer mixingo Short descum after developmento Optional native oxide stripo Film deposition temperature not too high
high mol. weight
low(er) mol weight
PMMA
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Electroplating
resist plating base substrate
e-beam litho electrogrowth + mask removal
patterning
Deposition Evaporation
methods: e-gun or resistive directional flux (ideal for lift-off!)
Sputteringmethods: ion beam or plasma non-directional flux (improved step coverage)
Evaporation
viscous
substrate
molecular flow
real source
virtual source region
e-gun heating
resistive heating
Sputtering
plasma bulk
ionstarget
film
DC/RF
DC/RF
shutter
substrate bias
sputter source
Substrate bias:
• fine tuning film morphology, roughness,..
• substrate cleaning
Thin Film Deposition IssuesStep coverage
Surface diffusion flux directionality
Film morphologyTemperature Ion treatment
StressThermal Growth induced
AdhesionCompatibility film-substrate StressBeneficial role few nm Ti, Cr or NiCr
Step coverageevaporation
sputtering
Lift-off performance
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Step coverageImpact process conditions (temperature, pressure)
conformal : high surface diffusion
nonconformal ; long mean free path
nonconformal ; short mean free path
InspectionTip techniques
with CCD-camera for on-chip inspectionStylus (α-step)
Height resolution 5 nmLateral resolution ≥ 15 µm
AFMHeight resolution monolayerLateral resolution ≤ nm
MicroscopyOptical microscopy (1 µm) Dark field, Interference contrast, luminescence Scanning Electron M. (≤ 1 nm)
20-25% of fabrication time!
InspectionPlasma
Optical emission reactive species Langmuir probe ion flux
SubstrateLaser interferometry etch rate, endpointQuartz crystal layer thickness Ellipsometry surface constitution
layer growth Fluoroptic probe temperature
In situ process diagnostics
Ex situ process diagnostics Wafer curvature stress buildup Ellipsometry layer thickness
InspectionX-ray photoelectron spectroscopy XPSAuger electron spectroscopy AESSecondary Ion mass spectroscopy SIMSElectron Microprobe analysis EMPA Transmission Electron Micr. TEM/EDX
Chemical analysis
CharacteristicsSensitivity Lateral
resolutionSamplingdepth
XPS %At 1 mm2 nm
AES %At m µ nm
SIMS ppm 0.001 mm2 nm - m µ
EMPA %At m µ ≥ 0.2 µm
TEM/EDX %At nm p.m.
Self-Assembly Lithography (Sagiv@Weizmann)
Nanostructure made of a single layer of oriented molecules, self-assembled on a nanoelectrochemically patternedmonolayer surface on silicon (AFM image)
Self-Assembly Lithography (Sagiv@Weizmann)
Nanostructure made of a single layer of oriented molecules, self-assembled on a nanoelectrochemically patternedmonolayer surface on silicon (AFM image)
13
Self-Assembly Lithography (Sagiv@Weizmann)
Nanostructure made of a single layer of oriented molecules, self-assembled on a nanoelectrochemically patternedmonolayer surface on silicon (AFM image)
Self-Assembly Lithography (Sagiv@Weizmann)
Nanostructure made of a single layer of oriented molecules, self-assembled on a nanoelectrochemically patternedmonolayer surface on silicon (AFM image)
Self-Assembly Lithography
(Sagiv@Weizmann)
Self-Assembly Lithography
(Sagiv@Weizmann)
9 nm
The RIE process (Reactive Ion Etching)
A dry etching process used in microelectronic manufacturing:
Applications:
1. Fast and ultra high surface cleaning
2. Surface activation
3. Photo-resist stripping
4. Semiconductor etching
Etching Machine
(Aultimut)
14
תהליכי איכול יבש
לחץתהל יך טור 0.1-100איכול פ לזמ ה
טו ר 0.001-0.1(RIE) רא ק ט יביאיכול בגז 10-3-10-5י וני) MILLING( כרסום torr
איכול רטוב
איכול ר טוב הנו בדרך כלל איזו ט רופי
HF -איכול תחמוצת ב
SiO2+6HF--> H2+SiF6+6H2O
איכול סיל יקוןHNO3+HF+CH3COOH -חומצי
.KOH, NaOH, CsOH etc. -בסיסי
פוספו ר ית חומצה -איכול אלומ יניו ם
איכול בפלזמהפלזמ ה של ג זים הלוגנים מאכ לת סילי קון ואת רו ב
המ יק רואלק ט רוניק ה השכבות הדקות בת עשיי ת
ניתן לק בל פ לזמ ה המ אכל ת פו טורזיס ט באי טיו ת . רבה יחסי ת
,CF4מקובל ל השת מ ש בגזים המ כיל ים פ לואור כ מו CHF3, NF3ועוד
משת משי ם גם ב כלור או ב ת רכוב ות כלור
ניתן להש ת מש בת רכובות יוד וברום
?מה קובע את איכות האיכול כימ יי ת ה גז
השאיב ה הלחץ החל קי ב תא וקצב הז רי מ ה או מה ירו ת צו רת ח יבור , ג יאומט ר יה, חומרי ם-תא ה ר יאקצ יה
).RIEרגיל או ( המ תח הספק , תד ר ה עבודה-העי רו ר
טמ פ ר טורה איכות ה רזיס ט תלוי בנ יקוי - ה מתא כלאיכות הש טח
יוני )MILLING(כרסום
יונים ה פוגע ים בפני השטח יכו לים ל הת יז חומ ר ש ק אופמן ”מקור מקובל לי ציר ת יוני ק רוי ע
סריג מחומם פולט אל קטרונ ים
) חיובית(אנודה
אטומי ארגון
אלק טרונים
יוני ארגון אנרגטיים
סריג שלילי
פרוסה
בעיות באיכולארוזיה של הרזיסט
התזה של הרזיסט
יצירת שוחות
15
)RIE( ראקטיביאיכול גז
RF -הפ רוסות מחוב ר ות לאלק ט רודת ההלחץ החל קי נ מ וך בה רבה מאש ר בא יכול ב פלז מ ה
כמו , האיכול מ בוסס על שי לוב ש ל איכול כי מיי היו נים ”ע ) או התז ה(ע ם כ רסום , באיכול בפלז מה . הפוגע ים בש טח
RIE ישנ ה כיוו ניות , אנאיזוט רו פינותן איכולבאיכול
הכי מיה נותנ ת א ת הסל ק טיב יות
RIE -בעיות ב
יתכן ונוצר נ זק למוליך למחצ ה זיהומי ם -התז ת מ תכות מ האלק ט רודה הנ גדית
ניק ל ועוד, מת כת יי ם כ מו ברזלע ל (ופלואורידים ) על ס ילי קון (ק רב ידים יצי רת
). אלומיניום
מערכות פל זמה לניקוי
פלזמ ה של ח מצ ן לניקוי פו טורז י סט פלזמ ה של פלוא ור לנ יקוי ש כבו ת דקו ת ש ל תח מוצת
מר יאק טו רים פלזמ ה של כלו ר לנ יקוי שכבו ת דקות של סי ליקון
. א פי טקס י אליותממ ע רכות גידול גביש
בקרת תהליכי איכול: מגדי רי ם פ ר מ טר ים ק ר יט יים
רוחב קו
שיפוע צד
נזק
: מוצאים מת אם בינם ל פ רמ ט רי ם של ה תהל יךמה י רות ז ר ימ ת הג ז והכי מי ה , הספ ק חש מלי, לחץ.שלו
)CMP(כימי -איכול מכנו
שילוב של אי כול כי מי עם ל י טוש מכנ י
SLURRY
PADפרוסה
F, כוח
?CMPמה מאפיין
יחסי לז מן הלי ט וש
. יחסי לכוח ה אנכ י ולמה ירו ת ה יח סית ב ין הפ רוסה לפד
DISHING אפק ט של -תלוי ב מ רווח בין הקווים
16
CMP של נחושת
תלוי ב היס טור י ה של הש כבות
משפי ע על התנ ג דות הקווים ועל האמ ינות של הם
DAMASCENE -משמש להגד ר ת המולי כים בת ה ליך ה
Dual-Damasceneתהליך
b.
M2
d.a.
c. f.
ILDM1
ResistCap layer
b. e.
M2
a) Insulator deposition + Mask 1b) Mask 2c) Strip maskd) Selective stud etche) Barrier, metal and stud depositionf) CMP
RIE Simulation
(http://uigelz.ece.uiuc.edu/Projects/HPEM-ICP/)
Ar/Cl2/BCl3 gas mixture at 10 mTorr is used to etch a poly-Si wafer
RIE Simulation
(http://uigelz.ece.uiuc.edu/Projects/HPEM-ICP/)
Electron Density and etching profile
RIE Simulation, 600 W, 100 V
(http://uigelz.ece.uiuc.edu/Projects/HPEM-ICP/)
Electric field and power deposition. The short skin depth confines the electric field near the coil. Capacitive coupling produces ion acceleration into the wafer
RIE Simulation, 600 W, 100 V
(http://uigelz.ece.uiuc.edu/Projects/HPEM-ICP/)
Chlorine ions are the dominant charged species
17
RIE Simulation, 600 W, 100 V
(http://uigelz.ece.uiuc.edu/Projects/HPEM-ICP/)
Chlorine atoms are the major etching species of the poly-Si. They produce an etch product of SiCl2
RIE Simulation, 600 W, 100 V
(http://uigelz.ece.uiuc.edu/Projects/HPEM-ICP/)
Some of the etch product is reionized as SiCl2+ and SiCl+ and accelerated
into the wafer. BCln+ ions are also plentiful
RIE Simulation, 600 W, 100 V
(http://uigelz.ece.uiuc.edu/Projects/HPEM-ICP/)
Some of the etch product is reionized as SiCl2+ and SiCl+ and accelerated
into the wafer. BCln+ ions are also plentiful
Effect of asymmetric pumping
(http://uigelz.ece.uiuc.edu/Projects/HPEM-ICP/)
Cl2 is injected through a symmetric array of nozzles from the top insulator. The gas is pumped either symmetrically through 3 evenly spaced pump ports or through a single pump port
Effect of asymmetric pumping
(http://uigelz.ece.uiuc.edu/Projects/HPEM-ICP/)
Electron impact dissociation of Cl2produces Cl atoms which is the primary etching species. The Cl atoms are consumed on the poly-Si wafer on the substrate. The top shows the Cl2 density at the top of the reactor (10 mTorr, 150 sccm). The bottom shows the Cl atom density just above the wafer. The Cl2density shows scalloping resulting from the injection nozzles. The Cl density at the wafer is essentially symmetric, though there is some small amount of biasing towards the pump ports.
The same values when using asymmetric pumping. The Cl reactant density clearly shows side-to-side dependencies. There is also some asymmetry in the Cl2 density at the top of the reactor. These asymmetries are functions of of gas pressure, reactive sticking coefficients and power deposition. .
Electron impact dissociation of Cl2produces Cl atoms which is the primary etching species. The Cl atoms are consumed on the poly-Si wafer on the substrate. The top shows the Cl2 density at the top of the reactor (10 mTorr, 150 sccm). The bottom shows the Cl atom density just above the wafer. The Cl2density shows scalloping resulting from the injection nozzles. The Cl density at the wafer is essentially symmetric, though there is some small amount of biasing towards the pump ports.
Symmetric Asymmetric
Si2F6 Etching of Si
(http://uigelz.ece.uiuc.edu/Projects/HPEM-ICP/)
Simulations of C 2 F 6 etching of Si in an ICP reactor
18
Reaction Mechanism For C2F6 Etching Si
(ftp://uigelz.ece.uiuc.edu/pub/presentations/dzhang_avs99.pdf)
A CxFy polymer layer is formed on the Si surface in coincidence with Si etching. The steady state passivation layer thickness is a balance of CFx deposition, ion sputtering and F etching of the layer.
Si etching precursor (F) needs to diffuse through the passivation layer.
סיכוםתהל יכי האי כול נחוצים להגד ר ת קווי המולי כים
. והמגע ים, ב טכנולוגי ת האיכול, איכות האי כול ת לויה בלי תוג רפ י ה
. ובניקוי פנ י הש טחתופש א ת מקומו כט כנולוגיה ) CMP( כימ י -איכול מ כנו
.קר י טי ת לנחושת הדרי שות מביצו עי ה איכול היב ש הולכות ומח מ ירו ת ע ם
. יר ידת המ מדים