Development of 109-pixel NbTiN/Al Hybrid MKID

for 100-GHz band continuum observations
University of Tsukuba / NAOJ
Yosuke Murayama
on behalf of the MKID Camera Team

3th June, 2019

Outline
1. Background, Scientific motivation
2. 100-GHz band MKID camera
3. Commissioning with the Nobeyama 45-m telescope
4. Development NbTiN/Al Hybrid MKID

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1 Background

1.1 Survey of Distant Galaxies
T. Suwa, et al.(2010)

Motivation- To understand the star-formation history
and the evolution of galaxies

Dust emission from distant galaxies- Dust (particle size <1um) in distant galaxies radiates

luminous in the infrared band.
- We could observe the emission in mm/submm/THzband as the results of redshift.

Multiband observation (100 GHz + submm, IR)
SED model of dusty galaxy: Dust temperature
42K, “Arp220-like” infrared galaxy(Color: difference of the redshift z)- We can obtain the photometric redshift (photo-z),
luminosity, temperature and star-formation rate (SFR)of the distant galaxies.
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1 Background

1.2 Survey with single dish telescope + radio camera
Single dish telescope + radio camera- Wide Field-of-View (FoV) single dish telescope and radio camera (hundreds ~ thousand pixels)
are important to make distant galaxies survey efficiently.
color: opticalcontour: submm (𝜈=350GHz)

Survey of distant galaxies
by single dish + camera

High angular resolution observation
by radio interferometer
ALMA(© NAOJ)
Multipixel Camera
a few of beams
A.W. Blain, et al.(2002)

4

1 Background

1.3 Follow-up high-resolution observation
Identify photo-z

Riechers+(2013)

Follow-up observation by radio interferometer- Radio interferometers, like ALMA, have ultra-high angular resolution.

Increase the number of high-z objects detection withsingle dish + camera (=> determine photo-z)
ALMA 100-GHz spectroscopy

High-resolution molecular line observation by ALMA(=> More accurate determination of redshift z than photo-z)

Statistically understand distribution, distance, SFR of galaxies
5Weiß+(2013)

1 Background

1.4 mm/sub-mm/THz wavelength Camera Projects
Nobeyama
camera100-GHz band Observation

Antarctic THz
Telescope 3-band
T. Suwa, et al.(2010)
1.3 THz

100 GHz

850 GHz

400 GHz• Nobeyama 45-m radio telescope• 100-GHz band camera

400-GHz/850-Ghz/1.3-THz bands Observation

SED model of dusty galaxy: Dust temperature
42K, “Arp220-like” infrared galaxy(Color: difference of the redshift z)• Antarctic THz Telescope (10-m)• 3-bands camera

62 MKID camera

2.1 100-GHz band MKID Camera
Nobeyama 45-m telescope + 100-GHz band MKID camera- Field-of-View (FoV) 3 arcmin. antenna & radio camera help us
survey 100-GHz bandSpecification of our camera
Continuum observation frequency

100-GHz band (85-120 GHz)

FoV~ 3 arcmin.

Polarization

Linear & Single polarization

Detector

Microwave Kinetic Inductance Detector(MKID)

Cold optics

Refractive optics using Si lenses

Number of pixel

109 pixel

Operation temperature< 200 mK7

2 MKID camera

2.3 Microwave Kinetic Inductance Detector
Microwave Kinetic Inductance Detector (MKID) is one of the superconducting
resonator (Day, et al.(2003))
MKID

Resonant frequency in microwave 𝒇𝟎:

𝑓0 =1 1
1=
4𝑙 𝐿𝐶
4𝑙𝒉𝝂

antenna

1AlSi(𝐿𝑚 +𝐿𝑘 )𝐶𝑙: Length of resonator, 𝐶: Capacitance, 𝐿𝑚: Magnetic inductance,
𝐿𝑘: Kinetic inductance (depends on the density of Cooper-pairs)

BeforePhotonincident stategap energy) break the Cooper-pairs in the MKID
 Change in kinetic inductance 𝐿𝑘
 Change in resonance frequency shift 𝛥𝑓

S21 [dB]

Incident photons (𝒉𝝂 > 𝟐𝚫; Higher than superconducting

quasiparticles

𝑓0′
Cooper-pair

𝛥𝑓 𝑓0
Microwave Frequency [GHz]8

2 MKID camera

2.4 Status of 109-pixel MKIDs device in dark
Item Name

Device data

Superconducting film (thickness) / deposition

Al (~150 nm) / e-beam evaporator

3-inch wafer

Si wafer (>10 kΩ∙cm)

Quality factor

6 × 104 (median of 82-MKIDs)

Quasiparticle lifetime [μs]120 (averaged 5-MKIDs)

Amplitude 𝑁𝐸𝑃𝑑𝑎𝑟𝑘 @10Hz [W / Hz1/2]

3.2 × 10−16 (averaged 25-MKIDs)

Phase 𝑁𝐸𝑃𝑑𝑎𝑟𝑘 @10Hz [W / Hz1/2]

1.8 × 10−16 (averaged 25-MKIDs)

Sensitivity: Noise Equivalent Power NEP [W/Hz1/2]
𝑁𝐸𝑃𝑑𝑎𝑟𝑘 [W/Hz1/2]

101 resonances could be readout.
(=>Yield: 93%)

Switching frequency= 10 Hz

Backgroundsensitivity limit:10-16
Noise frequency [Hz]93. Commissioning

3.1 Camera Installation to the telescope
45-m telescope

MKID camera(packed)

Inside the telescope (Receiver cabin)On-sky observations: 18th May 2018 ~ 1st June 2018-

Scan type: raster-scan observation (2x2 ,3x3,4x4 arcmin2)-Objects: the planets (Jupiter, Venus and Mars), galaxy, QSO=> We obtained the beam pattern, sensitivity and efﬁciency

measurements
Carry in Nobeyama 45-m telescope10Current Problems- [Optics] Low transmittance: 𝝉 ~ 34%-

Subwavelength structure on silicon lens

The reflection loss is about 30% on the surface of silicon=> Anti-reflection coating/structure is needed- [Detector] Higher 𝑵𝑬𝑷𝒅𝒂𝒓𝒌-𝑁𝐸𝑃𝑑𝑎𝑟𝑘 (Goal):
𝑁𝐸𝑃𝑑𝑎𝑟𝑘, 𝐴𝑚𝑝 @10Hz:

10−17 W/ Hz
3.2 × 10−16 W/ Hz- [Detector] Low optical efficiency: 𝜼𝒐𝒑𝒕 ~ 3%
-𝑁𝐸𝑃𝑜𝑝𝑡 (Goal):
𝑁𝐸𝑃𝑜𝑝𝑡 @10Hz:-𝑵𝑬𝑷𝒐𝒑𝒕 =< 10−16 W/ Hz : limited by the atmosphere~ 10−15 W/ Hz

𝑵𝑬𝑷𝟐𝒅𝒆𝒕 + 𝑵𝑬𝑷𝟐𝒑𝒉𝒐𝒕𝒐𝒏 + 𝑵𝑬𝑷𝟐𝒈−𝒓 /(𝝉𝜼𝒐𝒑𝒕 )2∝ 𝑁𝐸𝑃𝑑𝑎𝑟𝑘
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4. Development of Hybrid MKID

4.1 𝑁𝐸𝑃𝑑𝑎𝑟𝑘 Calculation
Requirement]~10−17

Optical NEP [W Hz −1/2]≤ 10−16Dark NEP [W Hz−1/2𝜂𝝉𝒒𝒑 𝜹𝑨
2𝑁𝐸𝑃𝑑𝑎𝑟𝑘, 𝐴 = 𝑺𝑨 (𝝎)Δ 𝜹𝑵𝒒𝒑

Measurement (device installed NRO45m)

3.2 × 10−16(Averaged 25 kids)@10 Hz~ 10−15−2Baselmans+2008
2222(1 + 𝜔 𝜏𝑞𝑝 )(1 + 𝜔 𝜏𝑟 )

𝜂: efficiency of quasiparticle creation ~ 0.57, Δ: superconducting gap energy,
𝜔: noise frequency, 𝜏𝑟 : resonator ring time

Important Parameters•

𝑺𝑨 [1/Hz]: Noise spectrum density in Amplitude readout

•𝜹𝑨𝑄
∝ :
𝜹𝑵𝒒𝒑𝑉

•

Responsivity of MKID in Amplitude readout(𝑄: Q-factor, 𝑉: Volume of the resonator)
𝝉𝒒𝒑 [sec.]: Lifetime of quasiparticles

124. Development of Hybrid MKID

4.2 Improvement of Responsivity
𝜹𝑨𝜹𝒇𝑄
∝∝ :
𝜹𝑵𝒒𝒑
𝜹𝑵𝒒𝒑𝑉Responsivity of MKIDMKIDThickness:𝒕antenna

AlSiAlSi

Cross-section of a MKID
Al thickness[nm]

Responsivity
𝜹𝒇/𝜹𝑵𝒒𝒑 [Hz]Commissioning device

150~ 0.011

Test thinner Al device

50~ 0.080

MKID Device

Resonance frequency shift [Hz]- Reduce resonator volume 𝑽

Commissioning MKID device
𝒕~150nm

Test MKID device𝒕 ~ 50nm: Number of quasiparticle13

4. Development of Hybrid MKID

4.3 NbTiN/Al Hybrid MKID
Quasi-particles are created around the antenna because the both CPW
central line and GND plane are made of Al.

But by using NbTiN/Al hybrid MKID, the radiation (90 GHz < f < 120 GHz)
will be absorbed only in the Al central line.

S. J. C. Yates+2011,
R. M. J. Janssen+2013• NbTiN (for GND plane) gap energy: ~1.1 THz• Al (for resonators’ CPW center line): ~90 GHz

R. M. J. Janssen+2013

NbTiN/Al hybrid can
improve optical efficiency 𝜂𝑜𝑝𝑡 .

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4. Development of Hybrid MKID

4.4 Development NbTiN/Al MKID
[Step 1] Test hybrid MKID device (chip size 20cm x 12cm)* Check fabrication parameters and the NbTiN/Al contact region[Step 2] 109-pixel hybrid MKID device (3-inch wafer)*For Nobeyama 45-m radio telescope camera
3 inch20 mm
12 mm

Test hybrid device
18-kids

109-pixel hybrid device

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4. Development of Hybrid MKID

4.5 Fabrication Flow
Our MKID have been developing in the Advanced Technology Center,
National Astronomical Observatory in Japan, Mitaka.
6. ICP-RIE

7. Remove Resist

1. Si wafer cleaning(Piranha & BHF solution)

Si (𝜙 = 3")

NbNbTiNTiNSiSi

8. Al Sputtering
2. NbTiN Spuutering
NbTiN
Si~200 nm

NbTiNSi

4. Exposure UV
3. Coating Resist=>Baking 1 μm

AlAlTiNSi•

9. Patterning& wet-etch Al••ResistUVNbAlTiNSi••photomask
10. Remove Resist

ResistNbTiN
SiAlNb

5. Develop

NbTiN
SiNbAlSi

Wafer: 3-inch Si, 10 kΩcm,FZ, non-doped
Al film: AJA
NbTiN film: CS-200ET(Tc~13K, 𝜌~160 𝜇Ωcm)
Exposure: Aligner
Etching: Wet etch for Al
ICP-RIE for NbTiN

TiN
164. Development of Hybrid MKID

4.7 SEM image: NbTiN/Al contact region• Taper: Good• Al short-end seems to connect NbTiN GND plane.

Aluminum
thickness ~ 50nm

Si wafer
NbTiN
thickness ~ 200nm

resonator
short-end

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Summary
Summary- To understand the evolution process of the galaxies,
we have been developing 100-GHz band camera for the NRO45m telescope.
- In the commissioning during 2018.05 - 2018.06, we observed the planets, galaxy,QSO.

Future development- Measurement optical efficiency of Hybrid MKID
- Improvement of the pattering process to increase detector yield of Hybrid MKIDsAcknowledgement
We would like to thank the Nobeyama Radio Observatory staff for their support.
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