lc filter developments at sron marcel bruijn informal cis/eureca meeting utrecht, 18 oct. 2006

LC filter developments at SRONLC filter developments at SRON

Marcel BruijnMarcel Bruijn

Informal CIS/Eureca meetingInformal CIS/Eureca meeting

Utrecht, 18 oct. 2006Utrecht, 18 oct. 2006

LC-filter update, Utrecht, 18 oct. 2006 2

ContentsContents

• Fabrication – wafers sofarFabrication – wafers sofar• Coils – critical currentCoils – critical current• New mask setNew mask set• Fabrication plansFabrication plans• Measurement setupMeasurement setup• Capacitor measurementsCapacitor measurements• Measurement plansMeasurement plans


FabricationFabrication

• Coils:Coils: TT065-13TT065-13 Nb(100)/SiO(250)/Nb(350)Nb(100)/SiO(250)/Nb(350) Nov. 2005Nov. 2005

• Coils+CapCoils+Cap TT070_22bTT070_22b 20 nm AlOx20 nm AlOx Feb. Feb. 20062006

typ. Nb-basedtyp. Nb-based• FiltersFilters LC01-1LC01-1 15 nm AlOx, SiO isol.15 nm AlOx, SiO isol. May 2006May 2006• FiltersFilters LC01-2LC01-2 15 nm AlOx, P-I isol. (180)15 nm AlOx, P-I isol. (180) May 2006May 2006• FiltersFilters LC01-3LC01-3 12 nm AlOx, P-I isol. (250)12 nm AlOx, P-I isol. (250) June 2006June 2006

Lithographic yield went up to 100% Nitride route abandoned


CoilsCoils

• Tested inTested in Resonance circuitsResonance circuits 4-wire critical current measurements4-wire critical current measurements

• TT065_13TT065_13 Tc < 4.2 KTc < 4.2 K High resistivity, low quality NbHigh resistivity, low quality Nb

• TT070_22bTT070_22b Q in resonance limited to ~ 500 by critical currentQ in resonance limited to ~ 500 by critical current Tc ~8 KTc ~8 K Critical current between 10 and 100 µACritical current between 10 and 100 µA Suspected: step coverages and central contactSuspected: step coverages and central contact


Coils (continued)Coils (continued)

• LC01 coilsLC01 coils Tc of base & top layers ~ 8.5 K, wiring 8.8 KTc of base & top layers ~ 8.5 K, wiring 8.8 K Teststructures show sometimes wide transitionsTeststructures show sometimes wide transitions Coils show two transitions, at 7 K and 2.5 KCoils show two transitions, at 7 K and 2.5 K Adhesion problems on poly-imideAdhesion problems on poly-imide

• Suspicions:Suspicions: Insufficient quality of Nb layers (high-rho, low-RRR)Insufficient quality of Nb layers (high-rho, low-RRR) Step coverage limits Ic (flat test meanders show good Ic)Step coverage limits Ic (flat test meanders show good Ic) Geometric limitations to performanceGeometric limitations to performance


New mask setNew mask set

2”wafer

A,B: Eureca

T1: LC filtersT2,4: Coils & striplinesT3,5,6: LC’s & coils with pick-

up coilsT7-10: Coils with p-u


New mask set (2)New mask set (2)

T2,4: Coils & striplines

Variations to investigate critical current


New mask set (3) – test structuresNew mask set (3) – test structures


New mask set (4)New mask set (4)

T3: LC and coils with pick-up coils

Can be used with SQUID read-out


Fabrication plansFabrication plans

1.1. 2” wafer with coils2” wafer with coils Fabrication facilities of TU-Delft (Klapwijk)Fabrication facilities of TU-Delft (Klapwijk) Good Nb layersGood Nb layers Sputtered SiOSputtered SiO22 insulation insulation

2.2. 2” wafer with LC circuits2” wafer with LC circuits Using experience of 1.Using experience of 1. Including AlOx 12 nm from PhilipsIncluding AlOx 12 nm from Philips

3.3. Transfer to 4” waferTransfer to 4” wafer When SRON facilities are online again.When SRON facilities are online again.


Measurement setupMeasurement setup


Ceramic capacitorsCeramic capacitors

• Syfer 1 nF + NP0 3.3 nFSyfer 1 nF + NP0 3.3 nF• T = 300 K: T = 300 K: Q = 17.3Q = 17.3• T = 10 K:T = 10 K: Q = 57Q = 57• T = 8.2 K:T = 8.2 K: Q = 483Q = 483• T = 4.2 K:T = 4.2 K: Q = 548Q = 548 f = 2.6577 MHzf = 2.6577 MHz• T = 4.2 K:T = 4.2 K: Q = 648 Q = 648 nylon screw i.p.v. Cunylon screw i.p.v. Cu

• Syfer 1 nFSyfer 1 nF• T = 4.2 K: T = 4.2 K: Q = 1840Q = 1840 f = 5.2510 MHzf = 5.2510 MHz

RResresr = 1/ = 1/ωωCQ = 14.6 mΩCQ = 14.6 mΩ

=> C = 1.13 nF & L = 810 nH=> C = 1.13 nF & L = 810 nHWhere: C or L?

Later: in L max. 3 mΩ


Lithographic capacitorsLithographic capacitors


Lithographic capacitors - exampleLithographic capacitors - example

LC01-3

3.6 mm2

C = 4.47 nF

T = 4.2 K

I ~ 1 mA

Q = 260

RESR = 27 mΩ


Lithographic AlOx capacitorsLithographic AlOx capacitors

WaferWafer AlOxAlOx

[nm][nm]SizeSize

[mm[mm22]]CC

[nF][nF]εεrr Isol.Isol. Al-Al-

WiresWiresQQmaxmax RResresr

[mΩ][mΩ]

RRNN

Estim.Estim.

LC01-3LC01-3 1212 3.63.6 16.116.1 6.06.0 Poly-IPoly-I 3+33+3 350350 2020 1313

LC01-1LC01-1 1515 3.63.6 11.911.9 5.65.6 SiOSiO 4+44+4 320320 25.625.6 1010

1+11+1 150150 5454 4040

4+94+9 380380 21.921.9 66

LC01-1LC01-1 1515 1.01.0 3.353.35 5.75.7 SiOSiO 3+63+6 815815 19.119.1 99

TT070TT070 2020 2.02.0 4.984.98 5.55.5 SiOSiO 4+64+6 10901090 11.611.6 88

=> max. 3.6 mΩ in coil & Intrinsic Q much higher


Example high-Q measurementExample high-Q measurement

TT070-22b

2.0 mm2

C = 4.98 nF

I = 2.6 µA

Q = 900 ± 50

RESR = 14 mΩ


Critical current in C’sCritical current in C’s

0

200

400

600

800

1000

1200

1 10 100 1000 10000

Current (u-Amp)

Q

LC01-3 16.1 nF LC01-1 11.9 nF 8 wires LC01-1 11.9 nF 2 wires

LC01-1 11.9 nF 13 wires LC01-1 3.35 nF TT070 4.98 nF

•Critical current shows large variation•Poly-imide covered steps -> much larger Ic (but bad adhesion)•Step coverage needs improvement

- Sloped steps- SiO2 deposition better ??


Measurement plansMeasurement plans

• Try again Tanaka wireTry again Tanaka wire• Measurement in KelvinoxMeasurement in Kelvinox• Independent accurate measurement of RIndependent accurate measurement of RNN of Al wires at 4.2 K of Al wires at 4.2 K• Measurement of (much) smaller C’s (LC01)Measurement of (much) smaller C’s (LC01)

Q = L / √C RQ = L / √C Resresr

• Wait for new L’s and C’sWait for new L’s and C’s

• SEM inspections for stepsSEM inspections for steps• FIB ?FIB ?

lc filter developments at sron marcel bruijn informal cis/eureca meeting utrecht, 18 oct. 2006

Documents

mlcfilter update

performancelcfilter

higherlcfilter update

outlcfilter update

lc filter developments

lc filterst2

coils striplinest3

coils striplinesvariations