Advanced ACTPol Multichroic Horn-Coupled Polarimeter Array ...

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Advanced ACTPol Multichroic Horn-Coupled Polarimeter Array Fabrication on 150 mm Wafers Shannon M. Duff NIST for the Advanced ACTPol Collaboration LTD16 22 July 2015 Grenoble, France

Transcript of Advanced ACTPol Multichroic Horn-Coupled Polarimeter Array ...

Page 1: Advanced ACTPol Multichroic Horn-Coupled Polarimeter Array ...

Advanced ACTPol MultichroicHorn-Coupled Polarimeter Array Fabrication on 150 mm Wafers

Shannon M. Duff – NISTfor the Advanced ACTPol Collaboration

LTD1622 July 2015Grenoble, France

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Why Long-λ Detectors for CMB?

LTD16, 22 July 2015 2

• Already helped establish ΛCDM, allowing for new understanding of universe

• Technology to enable measurement of polarization and temperature anisotropies

– Inflationary gravitational waves– Sum of neutrino masses

Credit: Naess et. al.

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Atacama Cosmology Telescope (ACT)

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1. MBAC (2008-2010)• 3 x 1000 pixel TES bolometer focal planes• 150 GHz, 220 GHz, 280 GHz

2. ACTPol (2013-2016)• 3 TES polarimeter focal planes• 2 x 500 pixel (1000 TES) 150 GHz polarimeters• 1 x 255 pixel (1020 TES) 90/150 GHz polarimeters

3. Advanced ACTPol (2016 onward)• Staged deployment of TES polarimeters in 5 bands• 1 x 503 pixel (2012 TES) 150/230 GHz polarimeters• 2 x 430 pixel (3440 TES) 90/150 GHz polarimeters• 1 x 40 pixel (160 TES) 28/41 GHz polarimeters

12 m

mass = 52 tons

construction finished in 2007

3rd Generation

Scaling (pixel count, bands per wafer, # wafers)

Simplification (fabrication, layout)

Production time (# wafers, fab time)

4th Generation…

Instrument Generations

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Atacama Cosmology Telescope (ACT)

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1. MBAC (2008-2010)• 3 x 1000 pixel TES bolometer focal planes• 150 GHz, 220 GHz, 280 GHz

2. ACTPol (2013-2016)• 3 TES polarimeter focal planes• 2 x 500 pixel (1000 TES) 150 GHz polarimeters• 1 x 255 pixel (1020 TES) 90/150 GHz polarimeters

3. Advanced ACTPol (2016 onward)• Staged deployment of TES polarimeters in 5 bands• 1 x 503 pixel (2012 TES) 150/230 GHz polarimeters• 2 x 430 pixel (3440 TES) 90/150 GHz polarimeters• 1 x 40 pixel (160 TES) 28/41 GHz polarimeters

12 m

mass = 52 tons

construction finished in 2007

3rd Generation

Scaling (pixel count, bands per wafer, # wafers)

Simplification (fabrication, layout)

Production time (# wafers, fab time)

4th Generation…

In same focal plane footprint, Advanced ACTPol to achieve 40% increase in

mapping speed at 150 GHz + entirely new frequency band at 230 GHz!

Instrument Generations

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Multichroic Feedhorn-Coupled Polarimeters

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• Repeatable band edges• Excellent noise performance• ~1 ms time constants• Excellent beam properties• High coupling efficiencies

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Multichroic Detector Cell• Couple light from horn to

TL via OMT, separate x& y linear polarizations

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Advanced ACTPol 150/230 GHz Pixel

8.5

mm x1 x2

y1

y2

x2

x1

y1

y2

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Multichroic Detector Cell• Couple light from horn to

TL via OMT, separate x& y linear polarizations

• CPW to MS transition

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Advanced ACTPol 150/230 GHz Pixel

8.5

mm

CPW to MS

x2

x1

y1

y2

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Multichroic Detector Cell• Couple light from horn to

TL via OMT, separate x& y linear polarizations

• CPW to MS transition• Filter into two bands

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Advanced ACTPol 150/230 GHz Pixel

8.5

mm

230 GHz150 GHzx2

x1

y1

y2

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TE11 mode (y1-y2)

Multichroic Detector Cell• Couple light from horn to

TL via OMT, separate x& y linear polarizations

• CPW to MS transition• Filter into two bands• Combine lowest order

mode/reject others

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Advanced ACTPol 150/230 GHz Pixel

150 hybrid

230 hybrid

8.5

mm

x2

x1

y1

y2

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Multichroic Detector Cell• Couple light from horn to

TL via OMT, separate x& y linear polarizations

• CPW to MS transition• Filter into two bands• Combine lowest order

mode/reject others• TES detects polarization

and bands

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Advanced ACTPol 150/230 GHz Pixel

150 x-pol

230 y-pol150 y-pol

230 x-pol

150 hybrid

230 hybrid

8.5

mm

x2

x1

0.3

mm

TES bolometer

y1

y2

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ACTPol Detectors• Successful integration of first multichroic

polarimeter arrays in the ACT (90/150 GHz)• Polarimeter arrays fabricated on 3 inch

wafers, tiled in assembly• Feedhorns fabricated monolithically on 150

mm wafers

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ACTPol 90/150 GHz detector array

ACTPol assembly

Nibarger et al JLTP (2011)Grace et al JLTP (2013)

ACTPol feedhorn array

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ACTPol to Advanced ACTPol

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Wafer Count Pixel Count TES Count

ACTPol90/150 GHz

5 x 3 inch wafers 255 1020

Advanced ACTPol150/230 GHz

1 x 150 mm wafer 503 2012

150

mm

ACTPol90/150 GHz

AdvancedACTPol

150/230 GHz

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Simplifications and Improvements

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ACTPol Advanced ACTPolSimplifications &

Improvements

Wafer count 5 x 3 inch 1 x 150 mm Pixel density, cost, time

Unit steps 85 steps 63 steps Risk, time, scalability

TES material MoCu AlMnTc uniformity, reproducibility,

eliminates lithography step(s), post-deposition tuning

Dielectric material

SiOx SiNx Improves detection efficiency

Microwave components

Cross-over Cross-underMinimize reflections/crosstalk,

eliminate 2 layers

LithographyStepper + contact

printerStepper Yield, dimensions, speed

Layout Manual Partially automated Speed, flexibility, risk

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150 mm Detector Arrays• Historically, detector arrays fabricated on 3 inch wafers• To scale to 3rd Generation+, necessary to move to 150 mm wafers

– Sensitivity increases as detector arrays become more dense

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150 mm Detector Arrays• Historically, detector arrays fabricated on 3 inch wafers• To scale to 3rd Generation+, necessary to move to 150 mm wafers

– Sensitivity increases as detector arrays become more dense

• Scaling fabrication processes is non-trivial

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150 mm

Uniformity

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150 mm Detector Arrays• Historically, detector arrays fabricated on 3 inch wafers• To scale to 3rd Generation+, necessary to move to 150 mm wafers

– Sensitivity increases as detector arrays become more dense

• Scaling fabrication processes is non-trivial

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150 mm

Uniformity Wiring density

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150 mm Detector Arrays• Historically, detector arrays fabricated on 3 inch wafers• To scale to 3rd Generation+, necessary to move to 150 mm wafers

– Sensitivity increases as detector arrays become more dense

• Scaling fabrication processes is non-trivial

17LTD16, 22 July 2015

150 mm

Uniformity Wiring density

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150 mm Detector Arrays• Historically, detector arrays fabricated on 3 inch wafers• To scale to 3rd Generation+, necessary to move to 150 mm wafers

– Sensitivity increases as detector arrays become more dense

• Scaling fabrication processes is non-trivial

18LTD16, 22 July 2015

150 mm

Uniformity Wiring density

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150 mm Detector Arrays• Historically, detector arrays fabricated on 3 inch wafers• To scale to 3rd Generation+, necessary to move to 150 mm wafers

– Sensitivity increases as detector arrays become more dense

• Scaling fabrication processes is non-trivial

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150 mm

Uniformity Wiring density

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150 mm Detector Arrays• Historically, detector arrays fabricated on 3 inch wafers• To scale to 3rd Generation+, necessary to move to 150 mm wafers

– Sensitivity increases as detector arrays become more dense

• Scaling fabrication processes is non-trivial

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150 mm

Uniformity Wiring density

250 µm

15 meters of 5 µm-wide wiring with 1 µm-wide spacing

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SiNx index uniformitySiNx thickness uniformity

Process Control is Important

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Requirement Methods

TES5% Tc uniformity across wafer AlMn composition

10% Rn uniformity across wafer AlMn thickness

Microwave componentsPassband edges within ~1% of

design

Dielectric thicknessDielectric constantEtch dimensions

Thermal propertiesPsat, τ within factor of 2 of

design

LPCVD thicknessTES leg etch dimensionsTES material properties

BLING thicknessBackside etch (stop on oxide)

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Why AlMn TESes?

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• ACTPol TES material = MoCu bilayer– Dielectric adhesion to MoCu challenging– Thickness of Mo sets Tc thickness uniformity across wafer critical– Tc = 150 mK requires thin (~65 nm) Mo film, reproducibility more difficult– Tc depends on MoCu interface

• Advanced ACTPol TES material = AlMn alloy (2000 ppm Mn in Al)– Concentration of Mn in Al sets Tc, thickness sets Rn

– Fewer process steps

Tc vs Mn concentration

0 1000 2000 3000

0.5

1

0

T c/T

c0

Mn concentration (ppm)

Tc uniformity, 2000 ppm AlMn

Temperature (mK)110 120 130 140 150 160 170 180 190100

No

rmal

ized

Res

ista

nce

-0.2

0

0.2

0.4

0.6

0.8

1.0

1.2

~1% uniformity

150 mm

See also: Dale Li “Transition Edge Sensors for Advanced ACTPol”

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Increase Detection Efficiency

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• Improvement in dielectric loss tangent by more than a factor of 2• ~15% increase in overall detection efficiency

Stoichiometry Compressive stress [MPa] Loss tangent

ACTPol SiOx Si-rich 150 2.0e-3

Advanced ACTPol SiNx stoichiometric 4 7.8e-4

• Lower dielectric loss higher overall efficiency• Fabricated Nb-SiOx/SiNx-Nb microwave resonators to probe

dielectric properties– Necessary to appropriately design passbands and other microwave

components

Benefits of SiNx

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Simplifying Allows for Scaling

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• ACTPol has 3rd wiring layer, only needed for 2 cross-overs per pixel

Si

LPCVD SiOx

LPCVD SiNx

Nb W1

Nb W2

Nb W3

SiOx I1

SiOx I2

• To simplify fabrication process AND improve microwave performance, Advanced ACTPoleliminates 3rd wiring layer by implementing microwave cross-under

*Not shown: TES, Au, BL, FSP, DE

cross-under

cross-over

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Optimized Microwave Cross-Under• Cross-under achieves 2 things

– Minimizes reflections and cross-talk– Simplifies fabrication by eliminating W3 layer

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4 um wide microstrip in crossover region

(reduces crosstalk)

Tapered section brings extra capacitance as close to midpoint as

possible (reduces maximum reflection)

Wide microstrip adds extra capacitance to balance excess inductance

SiNx Cross-Under Model

SiNx Cross-Over Model

15 µ

m

W1W2

cross-under

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Multichroic Test Pixels

• In order to test and optimize Advanced ACTPol process improvements, must fabricate and characterize test pixels

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Advanced ACTPol 150/230 GHz test pixel

Advanced ACTPol150/230 GHz test pixel 1

Advanced ACTPol150/230 GHz test pixel 2

Advanced ACTPol90/150 GHz test pixel

8.5 mm

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150/230 GHz Multichroic Test Pixels Work

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150/230 GHz Multichroic Passbands

• Passbands near identical in X and Y• Good agreement between prediction

and measurement• Tc, Psat, τ, G, and noise as expected• Early efficiency estimates promising

See also: Jason Austermann (poster), Hannes Hubmayr (talk), Shawn Henderson (talk)

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Ready to Scale to 150 mm

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• Simplification and optimization precedes scaling to manufacturable processes for next generation CMB experiments– Wafer count decreased cost and time savings, increased pixel

density– Total number of fabrication steps decreased time savings, risk

reduction– AlMn TESes reproducible/uniform Tc, simplified fabrication– SiNx dielectric improved detection efficiency, lower stress film– Microwave cross-under minimized reflections/crosstalk, simplified

fabrication– Full stepper lithography increased yield, reproducible dimensions,

time savings– Semi-automated layout time savings, design change flexibility, risk

reduction

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Ready to Scale to 150 mm

29LTD16, 22 July 2015

• Simplification and optimization precedes scaling to manufacturable processes for next generation CMB experiments– Wafer count decreased cost and time savings, increased pixel

density– Total number of fabrication steps decreased time savings, risk

reduction– AlMn TESes reproducible/uniform Tc, simplified fabrication– SiNx dielectric improved detection efficiency, lower stress film– Microwave cross-under minimized reflections/crosstalk, simplified

fabrication– Full stepper lithography increased yield, reproducible dimensions,

time savings– Semi-automated layout time savings, design change flexibility, risk

reduction

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Thank you!