Embed Size (px)
Citation preview
Advancing the Standard Doc Daugherty, Steven Neuhaus
LAB Shape Fidelity
LAB: E-Beam Lithography Simulation to Optimize
Nanoparticle Self Assembly Devices
University of Pennsylvania
One of the country's most sophisticated interdisciplinary research and
teaching facilities for nanoscale science and engineering
Krishna P. Singh Center for Nanotechnology
Krishna P. Singh Center for Nanotechnology➢ Supports research in many fields
➢ Allows the university to bring together many nanotechnology and materials-development groups
➢ Foster collaboration among groups that may have previously conducted their work independently
➢ Large Centers in the Building➢ QNF – Quattrone Nanofabrication Facility➢ NBIC – NanoBio Interface Center➢ NCF – Nanoscale Characterization Facility
➢ Faculty Research Laboratories➢ Electrical, Mechanical, Bio- and Chemical
Engineering➢Materials Science➢ Physics, Chemistry and Biology
➢ The cleanroom is operated by QNF staff➢ Nearly 200 researchers use the cleanroom
in a calendar year➢ 10,800 sq ft of clean space for
nanotechnology research➢ Eight full-time technical staff keep it
running (lean)➢ Manage approximately 12,000 sq ft of total
lab space, supported by an additional 15,000 sq ft of mechanical space
➢ Capital equipment replacement valued in excess of $25M➢ Largest collection of university
nanofabrication equipment on the east coast between Boston and Atlanta
➢ Dedicated microfluidics cleanroom / lab-on-chip foundry
➢ Unique laser micromachining facility➢ Integrated with 3-D printing AddLab
Krishna P. Singh Center for Nanotechnology
➢ Nearly 200 researchers annually➢ 15% of users are from outside Penn➢ Large use from local universities ➢Mix of small/large companies
Life Sciences (33%)
Optics & Optoelectronics (17%)
Physics (17%)
Mechanical Devices (15%)
Materials (8%)
Electronics (8%)
Chemistry (2%)
Life Sciences (33%)
Optics & Optoelectronics (17%)
Physics (17%)
Mechanical Devices (15%)
Materials (8%)
Electronics (8%)
Chemistry (2%)
Application CaseTemplate-Assisted Self Assembly – Improving Shape Fidelity & Yield
Template-Assisted Self-Assembly (TASA)
- Can construct assemblies
with interparticle spacings
on the single-nm scale
- Geometric constraints
allow us to make
reproducible structures (statistics)
- Scalable to large area
- Should be applicable to
any stable colloid system
Precise placement of NCs in
patterns defined by template
geometry
LAB Shape Fidelity
Template-Assisted Self-Assembly (TASA)
Flauraud, V. et al. Nat. Nanotechnol. 12, 73–80 (2017). Scale bars 250nm.
Close-packed OpenShape-selective
heterostructures
LAB Shape Fidelity
Absorption enhancement
Γ𝑎𝑏𝑠 ∝ 𝝁 ⋅ 𝑬 2 Greybush, N. J. et al. ACS Nano (2014)
Surface Plasmon Enhanced Luminescence
Gargas, D. J. et al. Nat. Nanotechnol. (2014)
Emission enhancement
Γ𝑒𝑚 ∝ LDOS
LAB Shape Fidelity
Advancing the Standard
9
• The target design is the device on the left, patterned with large array spacing
• The critical CDs are the size of each central region (50 nm) and the 3 extended arms of the polygons (100 nm)• Important that center region is not too
large that nanoparticles fill it
• Current results not acceptable and TASA does not give high yields
Problem Statement
LAB Shape Fidelity
Target 1st Result
Advancing the Standard
10
Tool: Elionix ELS-7500EX (50 kV system)
Resist: 80 nm PMMA (180 C, soft bake, 90 seconds)
Exposure: 320 μC/cm² dose, 50 pAcurrent, 75 μm field size, writing grid = 1 nm, beam step size 1.25 nm.
Development: IPA:DI water 3:1, 60 seconds, then quench in IPA in 30 seconds and blow dry
Initial Process Conditions
LAB Shape Fidelity
Target 1st Result
Advancing the Standard
11
In this talk we will cover strategies and techniques for using BEAMER, LAB and TRACER together to solve problems in e-beam lithography
BEAMER has a variety of advanced dose correction and pattern modification techniques, let’s evaluate them with LAB simulation to pick a well reasoned next trial
Approach
LAB Shape Fidelity
Advancing the Standard
12
E-beam Lithography
3D PSFs
PSFs
GPF, VEP, V30, CON
+
3D Resist Profile
GDS
LAB Shape Fidelity
Advancing the Standard
13
Estimating blur from simulation
LAB Shape Fidelity
30 nm blur 50 nm blur 70 nm blur 80 nm blur 90 nm blur
• Both E-beam simulation and advanced corrections in BEAMER and LAB requires setting a beam blur – the effective spot size due to beam size, defocus, noise, forward scattering and more…
• There is process calibration, but using BEAMER E-BEAM simulation, we can estimate the blur by matching to SEM image
• Ambiguity – which is the actual dose where the feature edges fall?
Advancing the Standard
14
Estimating blur from simulation
LAB Shape Fidelity
Assuming a 50 nm blur
This is a reasonable assumption, not a guarantee
Advancing the Standard
15
Let’s explore the key learnings from analysis & simulation.
1. Standard PEC (Long Range Correction)
2. Standard PEC (Long & Short Range Correction)
3. Corner-PEC
4. Shape-PEC (Overdose Undersize)
5. Manual Pattern Modification
Evaluating Options
LAB Shape Fidelity
Advancing the Standard
16
Before considering PEC, the proper base dose for PEC needs to be found
1. Correct base dose can be found by measuring the center of a 1:1 Line Space Grating
200 nm lines in 4B x 4B grating
2. Expose the grating at increasing dose in a dose matrix
3. Measure the center of the pattern where pattern density is exactly 50%
4. Choose dose where line and space are same width
The result adjusted the dose from 320 μC/cm² to 192 μC/cm²
Base Dose Determination
LAB Shape Fidelity
Advancing the Standard
17
PEC (Long-Range Correction Only)
• Long range PEC merely increased the dose factor by 63%
• 63% increase of 192 is 312 μC/cm² -> previous base dose was actually very close to ideal for a no PEC scenario. No expected gain.
PEC (Long Range + Short Range Correction with blur of 50 nm)
• Short range results are asymmetric, even with some pattern optimization. This sometimes happens with very small isolated elements. Not ideal.
• Decided to abandon these two routes.
Standard PEC options
LAB Shape Fidelity
PEC LR+SR
PEC LR
Advancing the Standard
18
At this time, the user decided to switch to switch to a new process:
Tool: Elionix ELS-7500EX (50 kV system)
Resist: 80 nm ZEP520A (180C soft bake, 90 seconds)
Exposure: 106 μC/cm² dose, 30 pAcurrent, 75 μm field size, writing grid = 3 nm, beam step size 3.75 nm.
Development: o-xylene, for 70 seconds seconds, then quench in IPA in 30 seconds and blow dry
Getting better, but still needs improvement, now what?
ZEP Process
LAB Shape Fidelity
Target 2nd Result
Advancing the Standard
19
• UPenn offers contrast curves for their standard resist products
• LAB offer resist development rate modeling• Models: Simple Threshold, Mack4, and
Development Rate
• For E-Beam, Development Rate is preferable
• This ZEP contrast curve was entered into LAB material database• Gives development rate at any point
XYZ in resist during simulation of resist development
LAB
LAB Shape Fidelity
https://repository.upenn.edu/cgi/viewcontent.cgi?a
rticle=1033&context=scn_protocols
Advancing the Standard
20
• With this in hand, we proceeded with 3 simulation trials to pick the next exposure.• Corner-PEC
• Shape-PEC (Overdose Undersize)
• Manual Layout Modification
Next Steps
LAB Shape Fidelity
Corner-PEC
Shape-PEC ODUS
Manual Layout Modification
Advancing the Standard
21
• Corner-PEC allows “framing” a shape with shapes with alternate dose factors
• Selectively lower doses in interior of shape and inner corners, and raise dose in outer corners to improve shape fidelity
• Results:• Simulation CD match to targets looked
good
• However, large sidewall angle change due to lower interior dose
• No trial run
• Further adjustments would be needed but still possible candidate
Corner-PEC
LAB Shape Fidelity
Advancing the Standard
22
Shape-PEC ODUS
LAB Shape Fidelity
• Shape-PEC is a strategy that allows adjusting the shape edges to correct for short range effects
• It also allow “Overdose/Undersize”, to improve image contrast
• Results: • At 1.5x overdose, not promising. Interior
region already not resolving.
• Later experimental trial showed anticipated failure.
• Steeper sidewalls
Advancing the Standard
23
Manual Pattern Modification
LAB Shape Fidelity
• Manual modification: Because of results of previous trials, we decided to try using BEAMER layout operations manually adjust the pattern. The result kept the “lobes” at the same size, but removed the interior area.
• Results:• Simulation results are good for CD &
straight sidewalls. Decided to run next trial.
• Trial results still need a improvement, but design to wafer is now close enough
• Successful device yield through TASA achieved
Advancing the Standard
24
Results & Future Work
LAB Shape Fidelity
• BEAMER, LAB and TRACER can work together to enable smart planning of experimental trials
• No single correction technique is suited for all cases
• Sometimes, the simplest answer may be the best one
• Future work:• Further tune the size of the “lobes” as they
are undersized slightly, to increase yield
Advancing the Standard
25
Thank You!
HeadquartersGenISys GmbH
Eschenstr. 66
D-82024 Taufkirchen (Munich)
GERMANY
+49-(0)89-3309197-60
+49-(0)89-3309197-61
USA OfficeGenISys Inc.
P.O. Box 410956
San Francisco, CA
94141-0956
USA
+1 (408) 353-3951
Japan / Asia Pacific OfficeGenISys K.K.
German Industry Park
1-18-2 Hakusan Midori-ku
Yokohama 226-0006
JAPAN
+81 (0)45-530-3306
+81 (0)45-532-6933
Advancing the Standard
25LAB Shape Fidelity
