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