2002.8.29 LCWS2002 G/H Joint Session
Fabrication of a Silicon Pixel/Pad for dE/dx Fabrication of a Silicon Pixel/Pad for dE/dx MeasurementMeasurement
H. Park (Kyungpook National U.)
I.H. Park (Ewha Womans U.)J.S. Kang (Korea U.)
• Introduction
• Fabrication Condition
• Mask Design
• Silicon Test
• Summary
2002.8.29 LCWS2002 G/H Joint Session
Introduction CREAM
The first Ultra Long Duration Balloon (ULDB) payload
The objective - To observe cosmic ray spectral features - To observe abundance charges that might be related to a supernova acceleration limit (1TeV to 500 TeV )
2002.8.29 LCWS2002 G/H Joint SessionNi
82MeV
Ni : 82MeV/3.6eV 2107 holes
Imax in Sensor = 24 [pA]Imin in Sensor = 5 [fA]
Si-PIN diode Structure
Al 1um P+ 0.6um
(1,1,1) 5 kΩ N-type
N+1.0um
DC type
Current
High Energy Particle
(1,1,1) 5 kΩ N-type
AC type
Current
- Determine particle’ identification - The deposit energy in silicon, dE/dx Z2
2002.8.29 LCWS2002 G/H Joint Session
limited condition:
1) Area : 79 * 79 cm2
2) Channel # : 2560~2816
3) Electric power : 43.6 W
4) Possible weight : 12 kg
Sensor size :
2.22 – 2.44 cm2
2002.8.29 LCWS2002 G/H Joint Session
Wafer
- high resistivity n-type - (1,1,1) orientation
- 4 inch wafer - thickness of 500 m - one side polished
Silicon Sensor and Design in Korea
Sensor
- sensor size : 1.5 x1.4 cm2
- array : 4x4 matrix in 4 inch wafer
- space between sensor : 10 m & 60 m
2002.8.29 LCWS2002 G/H Joint Session
SimulationSimulation
The purpose To find conditions for the implantation process
Tool -TSUPREM4 The industry-standard 1D/2D process simulation tool -Simulate etching, deposition, lithography, implantation, diffusion -Output : stresses, boundaries of various layers, impurity distribution
Distance (um)
(111) 5Kohm N-type waferAfter annealing
Distance (um)
Log
10
(Bor
on)
#/cm
3
0.6 m
Log
10
(Bor
on)
#/cm
3
(111) 5Kohm N-type waferAfter implantation
2002.8.29 LCWS2002 G/H Joint Session
Fabrication Condition at ISRC (ISRC:Inter-university Semiconductor Research Center)• E-beam lithography Facilities :
-E beam lithography system *Leica Cambrige EBMF 10.5 *Acceleration voltage: 30kV *Beam diameter: 50nm *Beam shape: Gaussian beam *Scan speed: 10MHz *Field size: 1.6384mm *Electron gun source: LaB6 cathode
-Support *4” wafer, 4”,5”mask , piece *direct writing on wafer *Mix&Match (Hybrid lithography) *Mask Fabrication
2002.8.29 LCWS2002 G/H Joint Session
• ISRC E-beam lithography Facilities : -Resolution
*wafer: 0.2 m, mask: 2 m
-E beam resist
*positive type: PMMA(polymethylmethacrylate)
*negative type: SAL 601
• high ion implantation :
- SOURCE : 11B, 49BF2, 31P, 75As
*ENERGY : 30~70 keV, 30-75 keV, 30~80keV
*DOSE : 2E14~3E15, 2E14~1E16
Fabrication Condition at ISRC
2002.8.29 LCWS2002 G/H Joint Session
Mask Design• Program : -Layout (Cadence) >> stream out to GDS file format
• mask detail:
- mask #1 : for p+ implantation
- mask #2 : for metal deposition ( width: 10 um smaller than p+ implantation)
[mask #1] [mask #2]
2002.8.29 LCWS2002 G/H Joint Session
Test element in prototype sensor
Test 1
Guard
Various size pixels
0.5 cm2
2.1 cm2
2.22 cm2
2.43 cm2
Test 2
Guard
Different GAP size
60um 10um
1.4*1.5 =
2.1 cm2
Pattern3
Test 3Guard
Guard
0.7*0.75 =
0.5 cm2
Wafer diameter : 4inchThickness 500 mWafer backside all Al metalized after Phosphorus diffusion
2002.8.29 LCWS2002 G/H Joint SessionAl
Leakage current measurement
⊙ Test equipment
P I N
chuck
Al
Picoammeter
KEITHLEY Model 487 Voltage range: -500~500VStepping: Manual, 10 V
2002.8.29 LCWS2002 G/H Joint Session
Leakage current measurement_TEST1
Guard
PIXEL SIZE
0.5 cm2 / 2.1 cm2 / 2.22 cm2 / 2.43 cm2
68nA
176nA
262nA
421nA
2.1cm2 PIXEL
Leakage current per 1cm2
: 70nA/1cm2 at 250volt
2002.8.29 LCWS2002 G/H Joint Session
Source Test Equipment
Gate GeneratorShaper/Amplifier
DiscriminatorPhotodiode
PreAmp(AmpTEK) for Photodiode
PreAmp(Belle) for sensor
2002.8.29 LCWS2002 G/H Joint Session
Beta Source 90Sr(Ending point 2.28MeV)
Gate
Shaped signal
Original signal
6um
Source Test
EquipmentNIMCAMAC(Peak sense/2249BADC)Plastic scintillator + Photo diode : TriggeringPreamp(Belle) for SensorPreamp(AmpTek) for Photo diode
Dark box
Pb Pb
Photodiode
sensorSr_source
2002.8.29 LCWS2002 G/H Joint Session
Source Test Result
2.1cm2 , guard ring
HV = -250V
0.5 cm2 , guard ring
HV = -250V
Operating voltage : 250Volt Leakage current : 68nASignal to noise Ratio : 5.2
Operating voltage : 250Volt Leakage current : 170nASignal to noise Ratio : 7.6
2002.8.29 LCWS2002 G/H Joint Session
• C-V measurement (Depletion voltage)
• Test of the next prototype sensor fabricated at ETRI and ISRC I-V , C-V , Test structure to check the fabrication, Source test• Cosmic/beta source test after integration Sr beta source test cosmic muon test Work to do : pedestal vs MIP -> S/N ratio, cross talk, check channel to channel gain variation.
• Preparation of CERN beam test ( middle of Oct.) The beam line is the H8 line with the T6 target We will use fragments of 20 GeV/N Pb nuclei
Summary