LCWS2002G/H Joint Session Fabrication of a Silicon Pixel/Pad for dE/dx Measurement H. Park (Kyungpook National U.) I.H. Park (Ewha Womans U.) J.S. Kang (Korea U.) Introduction Fabrication Condition Mask Design Silicon Test Summary

LCWS2002G/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 )

LCWS2002G/H Joint Session Ni 82MeV Ni : 82MeV/3.6eV  2  10 7 holes I max in Sensor = 24 [pA] I min 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  Z 2

LCWS2002G/H Joint Session limited condition: 1) Area : 79 * 79 cm 2 2) Channel # : 2560~2816 3) Electric power : 43.6 W 4) Possible weight : 12 kg Sensor size : 2.22 – 2.44 cm 2

LCWS2002G/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 cm 2 - array : 4x4 matrix in 4 inch wafer - space between sensor : 10  m & 60  m

LCWS2002G/H Joint Session Simulation ▣ Simulation ◦ 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 wafer After annealing Distance (um) Log 10 (Boron) #/cm  m Log 10 (Boron) #/cm 3 (111) 5Kohm N-type wafer After implantation

LCWS2002G/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: mm *Electron gun source: LaB6 cathode -Support *4” wafer, 4”,5”mask, piece *direct writing on wafer *Mix&Match (Hybrid lithography) *Mask Fabrication

LCWS2002G/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 : 11 B, 49BF 2, 31P, 75As *ENERGY : 30~70 keV, keV, 30~80keV *DOSE : 2E14~3E15, 2E14~1E16 ▣ Fabrication Condition at ISRC

LCWS2002G/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]

LCWS2002G/H Joint Session ▣ Test element in prototype sensor Test 1 Guard Various size pixels 0.5 cm cm cm cm 2 Test 2 Guard Different GAP size 60um10um 1.4*1.5 = 2.1 cm 2 Pattern3Test 3 Guard 0.7*0.75 = 0.5 cm 2 Wafer diameter : 4inch Thickness 500  m Wafer backside all Al metalized after Phosphorus diffusion

LCWS2002G/H Joint Session Al ▣ Leakage current measurement ⊙ Test equipment P I N chuck Al Picoammeter KEITHLEY Model 487 Voltage range: -500~500V Stepping: Manual, 10 V

LCWS2002G/H Joint Session ▣ Leakage current measurement_TEST1 Guard PIXEL SIZE 0.5 cm 2 / 2.1 cm 2 / 2.22 cm 2 / 2.43 cm 2 68nA 176nA 262nA 421nA 2.1cm 2 PIXEL Leakage current per 1cm 2 : 70nA/1cm 2 at 250volt

LCWS2002G/H Joint Session ▣ Source Test Equipment Gate Generator Shaper/Amplifier Discriminator Photodiode PreAmp(AmpTEK) for Photodiode PreAmp(Belle) for sensor

LCWS2002G/H Joint Session Beta Source 90 Sr(Ending point 2.28MeV) Gate Shaped signal Original signal 6um ▣ Source Test Equipment NIM CAMAC(Peak sense/2249BADC) Plastic scintillator + Photo diode : Triggering Preamp(Belle) for Sensor Preamp(AmpTek) for Photo diode Dark box Pb Photodiode sensor Sr_source

LCWS2002G/H Joint Session ▣ Source Test Result 2.1cm 2, guard ring HV = -250V 0.5 cm 2, guard ring HV = -250V Operating voltage : 250Volt Leakage current : 68nA Signal to noise Ratio : 5.2 Operating voltage : 250Volt Leakage current : 170nA Signal to noise Ratio : 7.6

LCWS2002G/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