superconducting tunnel junctions in scientific instrumentation AIST - - PowerPoint PPT Presentation

LTD-16 2015 Grenoble

New application stages of superconducting tunnel junctions in scientific instrumentation

Masataka Ohkubo, Masahiro Ukibe, Shigetomo Shiki, Go Fujii, Nobuyuki Zen, Katsutoshi Takahashi

2015/07/22

AIST Shigeo Tomita, Nobuhiro Kim University of Tsukuba Toshiyuki Azuma RIKEN

Background

LTD-16 2015 Grenoble 2015/07/22

STJ detectors have a long history of more than 40 years. Many applications of STJ detectors have been proposed and some of them were not feasible for practical use as scientific instruments due to a low detection efficiency and a problem

• f thermal inflow and so on.

Improvement of the fabrication technique CRAVITY (Clean room for analog-digital superconductivity ) Fabrication of advanced superconducting devices

• A large scale STJ array with high performance (high DE[G1.44], quite

low leakage[G2.4], 3D-STJ[G1.42], SPA-STJ[G1.43])

• Superconducting signal processor (SFQ-TDC) [G2.48]

Original techniques

• Planarization process [Caldera process]
• xidation process [Ozone process]

• Room1 (Class 100) : Lithography-room（90m2）

・Single wafer cleaner ・i-line stepper ・Auto or semi coat/develop system ・Wafer processor for wet stripping

• f photoresist

・Wafer surface analyzer ・Microscopes

• Room2

(Class 1000-10000) :Deposition-room(70m2)

・Sputtering machines for Josephson junction（Nb/Al,NbN/TiN） ・Dry etching equipments （RIE, Asher） ・Auto and manual probers ・Thin film stress measurement system

• Room3 (Class10000)

:Deposition-room(100m2)

・TEOS-CVD（SiO2, SiON） ・CMP process equipments ・Nano search microscope

CRAVITY：Layout

Room 1

i-line stepper

Wafer processor for wet stripping of photoresist Auto coat/develop system Semiauto develop system Single wafer cleaner Sputtering machine for Nb/Al JJ [Ozone oxidization and mass spectrometer] Sputtering machine For Nb/Al JJ [Standard type] Sputter machine for NbN/TiN JJ RIEs CCP type:4,ICP type :1 TEOS-CVD

Process equipment Measurement instrument

Microscopes Auto and manual prober Alpha

• step

Thin film stress measurement CMP process equipments

Room 2 Room 3

Sputter machine for Nb wiring Sputter machine for SiO2 interlayer insulation film Multi target (6 targets) sputter machine RTA Alpha-step Laser microscope Nano search microscpe Ellipsometer Resistivity mapping system

• Utility space (30m2)

・Supply equipment of process gases ・Vacuum exhaust units ・DI-water system ・Waste HF tank

Access to https://unit.aist.go.jp/riif/openi/cravity/en/equipment/2-12expo.html#

Standard wafer size at every machine : 3inch

2015/07/22 LTD-16 2015 Grenoble

• Nb technology
• 10-kA/cm2 advanced process
• 2.5-kA/cm2 standard process
• Low-leakage(0.1 pA/mm2@200 A/cm2) tunnel junction process
• NbN technology
• SNS-junction process for 10-K operation
• Al technology
• Deep sub-μ trilayer-junction process

Available electronics at CRAVITY

Active layer including JJ and R Main GP and CPL 1st PTL layer DC power layer 2nd PTL layer

Junction

M7 M3 M5 M6 M8 M1 M2 M4 M9

Si Substrate SiO2

RES C5 C2 C3 C1 BC JC JJ

Main ground plane

Available technologies at CRAVITY

2015/07/22

Analog devices: STJ, SQUID, TES, and MKID Digital devices : SFQ circuits, and qubits

14.7 mm 4.7mm RF input

16 Microwave divider

Voltage generator（1 V×2）

Termination area

V- V+

ISEC 2015 NAGOYA

2015/07/22

Planarization process (Caldera process) Nb 9-layer structure Latest fabrication technology

Conventional Process

Advanced process(ADP )

ISEC 2015 NAGOYA

3D wiring for STJ detectors

ISEC 2015 NAGOYA 2015/07/08

3D-wiring 2D-wiring

JJ size and Pitch : 100 x 100 mm and > 120 mm L/S of Wires : 10/10 mm

~70% 7% 512 pixels Filling factor ~ 7% Filling factor ~ 70% sparse close-packed ~1.3 mm ~1.3 mm

10 mm

Sparse array

10 mm

Closed-packed array

Present status of STJ detector

LTD-16 2015 Grenoble 2015/07/22

7 times higher energy resolution than that of SDD

DR-P18 : Go Fuji

System energy resolution for 400 eV X-ray : 6.3 eV FWHM Intrinsic energy resolution : 4.7 eV FWHM (Pulser : 4.2 eV FWHM) The best energy resolution for Nb/Al STJ

100 200 300 300 350 400 450 500 Counts Energy (eV)

48 eV of SDD 6.3 eV of STJ

50 100 150 200 250 300 200 250 300 350 400 450 500 Counts Energy(eV)

400 eV X-ray Pulser x 0.1

Soft X-ray spectrum

6.7+/-1.0 eV (82 pixels) Histogram of DE@400 eV values for type-II STJs

Specifications and appearances

• Energy resolution of X-rays ： 10 eV
• Energy range of X-ray：100 eV - 15 keV

(<2 keV: Nb/Al STJ array, > 2keV:SSD）

• Pixel number ：100
• Maximum counting rate of X-rays： 1 Mcps
• Cooling : Automatic cryostat without a liquid

helium（operation temperature : 0.3 K）

Practical example of Nb/Al STJs made at CRAVITY

Superconducting fluorescence-yield X-ray absorption fine structure apparatus(SC-XAFS)

Feature：1. FY-XAFS apparatus utilizing a 100-pixel Nb/Al STJ array for soft X-ray detection.

• 2. XAFS

spectra of trace light elements in matrices can be obtained. 3. Information of atomic-scale local structures in advanced functional materials (semiconductor with low energy consumption, spintronics, solar cells, and magnetism) can be obtained. （Competitor: Advanced Light Source in USA）

Usage examples

380 400 420 440 460

Absorption [a.u.] Photon energy [eV]

3C 4H

Si site C site Si sites C sites

a b

Analysis of

• Trace light elements in wide gap semiconductor
• Na dopant in CIGS solar cells
• Mg dopant in LEDs.

Figure 1. XANES spectra of n-type dopant N atoms(300 ppm) in SiC in the as-implanted state and after annealing at 1400

• r

1800℃. Figure 2 Ab initio multiple scattering calculations. (a) XANES spectra calculated with FEFF8.424 for the N atoms in 4H- and 3C-SiC. (b) Crystal structure models of the N-doped

FEFF

• M. Ohkubo et al., Scientific Reports, 2, 831

DOI: 10.1038/srep00831 (2012). 2015/07/08 ISEC 2015 NAGOYA

Application fields of SC detectors

LTD-16 2015 Grenoble 2015/07/22

Materials analysis : dopant analysis for developing functional and structural

materials.

Absorption [a.u.] Photon energy [eV]

3C 4H

Si site C site Si sites C sites

a b

Electrostatic Storage Ring

SR

Physical chemistry

Mass analysis of neutral molecule fragments with dissociative recombination (DR)

Space physics

Determination of neutrino mass