R&D activity in Bari for the ALICE Inner Tracking System upgrade

Transcription

1 R&D activity in Bari for the ALICE Inner Tracking System upgrade Referee Meeting, 24 Giugno 2011 Vito Manzari INFN Bari

2 ALICE Pixel Material Budget Ø Contributions to one current Pixel layer Carbon fiber support: 200 µm Cooling tube (Phynox): 40 µm wall thickness Grounding foil (Al-Kapton): 75 µm Silicon pixel chip: 150 µm ² 0.16% X 0 Bump bonds (Pb-Sn): diameter ~15-20 µm Silicon sensor: 200 µm ² 0.22% X 0 Multilayer Al/Kapton pixel bus: 280 µm ² 0.48% X 0 SMD components Glue (Eccobond 45) and thermal grease Two main contributors: silicon and multilayer flex (pixel bus) 2

3 Hybrid Pixel R&D: Material Budget Ø How can the material budget be reduced? Reduce silicon front-end chip thickness Reduce silicon sensor thickness Reduce interconnect bus contribution - reduce power Reduce edge dead regions on sensor - reduce overlaps to avoid gaps Review also other components - average contribution ~0.02% Ø What can be a reasonable target Hybrid pixels overall material budget: 0.5 % X 0 ü silicon: 0.16% X 0 overall (100µm sensor + 50µm front end chip), at present 0.38% ü bus: 0.24% X 0, at present 0.48% ü others: 0.1% X 0 overall, at present 0.24% Monolithic pixels: % X 0 (e.g. STAR HFT) 3

4 Hybrid Pixel R&D: Material Budget Ø To reduce the silicon contribution to the overall material budget Threefold activity Thin Planar Sensor based on the current ALICE layout ü bump-bonded to present ALICE front-end chip for testing Thin Planar Active Edge Sensor based on the current ALICE layout ü bump-bonded to present ALICE front-end chip for testing Thinning the existing ALICE front-end chip ü Bump-bonded to standard ALICE sensor 200 µm thick for testing And then combine them 4

5 Hybrid Pixel R&D: Thin Planar Sensor Ø Procurement, Processing and Handling of 100µm thick wafers is an issue Ø Alternative: Epitaxial Wafers to be thinned during the bump-bonding process Epitaxial wafers provide a mean to use very thin sensor wafers carrier wafer included for free First tests of epitaxial sensors by PANDA (D. Calvo et al.) [see NIM A 595(2008)] Ø ALICE Epi-Pixel sensor Goal: achieve a sensor thickness of 100 µm (~ 0.11% X 0 ) Test with the ALICE pixel front-end chip (optimized for 200µm sensor) Epitaxial wafers produced by ITME (Poland) - Substrate thickness 525µm, doping n/sb, resistivity Ωcm, <111> - Epitaxial layer thickness µm, doping n/p, resistivity 2000±100 Ωcm 5

6 ALICE Epi-Pixel Sensor Ø 5 sensor wafers fabricated at FBK Ø 3 wafers processed at VTT - successfully through all process steps, including thinning and back side patterning - Overall thickness: µm (i.e. epi layer + 10 µm) Ø 5 singles flip-chip bonded to the current ALICE pixel front-end chip - electrical tests: ~30 na at 20V at RT, min. threshold ~ 1500 el., ~30 missing pixels 6

7 Beam Test of Epi-Pixel detector Ø Beam test of ALICE Epi-Pixel detector November 2010 CERN SPS: positive beam (pions, protons), 350 GeV/c, up to 10 4 particles/spill Duty cicle 49s, Flat top 9s, Trigger rate 3KHz ALICE 3D-Pixel detector samples were also tested - Double-sided Double-Type Column (DDTC) from FBK multi-project wafer Ø Tracking Telescope 4 ALICE standard Pixel detector arranged in 2 stations - each station contains 2 pixel detectors arranged in cross-geometry ü pixel cell dimensions 50 x 425 µm 2 - Estimated tracking precision 10µm both in x and y directions Ø Trigger Self-triggering: FastOr logic combining the information from the tracking planes 7

8 Beam Test Set-up Single assembly mounted on test card SPS beam test set-up 8

9 Beam Test Measurements Track Efficiency Cluster size Space accuracy Objectives vs Depletion Voltage Threshold Particle Crossing Angle Online beam spot Tracking Station 1 3D-sensor Epi-sensor Tracking Station 2 9

10 Residuals and Efficiency ALICE SPD Ø NIM paper in preparation Thr (DAC) Thr (el.)

11 Planar Pixel Sensor with Active Edge Ø Standard detectors Dead region (cracks and damages) a + d 500 µm Ø Active edge to limit dead region Cut lines not sawed but etched with Deep Reactive Ion Etching (DRIE) and doped Standard Detector Active Edge Detector Ø R&D in collaboration with FBK Within the MEMS2 agreement FBK-INFN Epitaxial wafer in order to achieve an Active Edge 100µm thick Planar Sensor 11

12 Processing w thicknesses Active Edge Detector Ø Main process steps and critical issues Attach support wafer ü provides mechanical Various detector support designs after trench on 6 etching inch wafer (SOI, wafer bonding, ) Trench opening by Deep Reactive Ion Etching (DRIE) - 5 x 5 cm ü dimensional aspect 1/20, 2 deep etching ( µm) Inside trench doping ü solid source technology Wafer Layout and Detector Struc Main edgeless strip detectors - 50 µm edge distance Baby edgeless strip detectors - 1 x 1 cm 2-20µm, 50µm, 100µm edge distance Trench filling with Medipix polysilicon edgeless pixel detectors: ü spin coating with standard photoresist is challenging due to trench x 1.4 cm 2 Remove devices from - support 20 µm & 50 wafers µm edge (after distance bumping in case of pixel sensors) 50µm, 10 Edge implan 12

13 Active Edge Detector 13

17 ALICE Pixel with Active Edge Ø Recall ALICE Epi-Pixel detector Planar pixel sensor on epitaxial high resistivity silicon wafer ü Remove the bulk by back-grinding after the bumping to achieve a 100 µm thick sensor Ø Combine with the capability to etch a trench to achieve an Active Edge Thin pixel detector Scribe Line Trench 17

18 ALICE Pixel with Active Edge trench Guard ring pixel Scribe line passivazione N+ ossido P+ P+ epi substrato Dead area 18

19 Front-end Chip Thinning Ø Current ALICE chips: 150 µm thinned during bump bonding process Ø Thickness reduction will make inherent stresses come out stronger Ø First experience during the ALICE production Ø Thinning process needs to be well studied and tuned to produce coherent results S. Vahanen, VTT 19

20 Front-end Chip Thinning R&D Ø Study using dummy components with IZM Berlin Hybrid detector dummy components, i.e sensors and chips, based on ALICE layout Specific IZM process for thinning: - Glass support wafer during full process - Laser release of the support wafer Sensor wafers (200 µm) in processing, ASIC wafers ready in 4 weeks First components back by end July 2011 Si sensor [μm] X0 [%] ASIC [μm] X0 [%] X 0 total [%] First R&D step R&D target

21 Front-end Chip Thinning R&D *+,- #+,0$B66(/CA2 D *(/01)&) )5$B00)1&:+ E)1:(66 FA18!"#$%&'() 97001)5$#+,0?,:,-.$1'$%&'()$ 95&:@ %&'()$ *+,--, )5$#+,0 37/0$31-4, )5$%&'() *(/01)&)2$%&'()$ 31-4,-.$51$67001)5$ 8&'() 9(-61) 97001)5$%&'() #1-5&:5$'1)/&5,1- ;<,:)1=37/0,-.> 97001)5$#+,0$!(A(&6(!"#$%&'()*!+&,"-*+$'()%./"#(0)'10 21

22 Front-end Chip Thinning R&D 1/02 4/0,+G$$(9#*H K 1(9,-&'&H!",,-&%+G,,&-'./ ;'$(&+<(#-2=02> "$02>?@AB(*('$(+)*"( CD+!%(,E+F*0,+4/0,+G$$(9#*H -I 4/0,$%'.J )*'$$+$",,-&%./0, 1/ :!"#$%&'%( ;(I%E+ 4/0,+'I%(&+#"9, #-2=02> $0L( CMNCC+99O+5PNC+FQA3R: B0>/%E+ 4&-$$+$(.%0-2 -I %/( I0&$% #"9, &-S 5H(**-S *02(: )*'$$+$",,-&%./0,!"#$%&'%( 1/ :!"#$%&'()*!+&,"-*+$'()%./"#(0)'10 22

23 Front-end Chip Thinning R&D /012$3$"#$&43.$ 56&78$9:&7.99)%8&;<,9&2$3$"#$ 2'34%&0)3&,%//*/5 #( 6%,73&*10 D*103(0E 1.$$C $#1.;0 %(!0)3,%))*0),"*: )0;0%&0 AB=>$3!"*,7 1.$$C &.6&!)%!0 8'39%))*0)3,"*: )0;0%&0?0;0%&01 5;%&&,%))*0),"*: L"*/,"*: $#1.;0 1#E/Q 1.$$C $#1.;0& %(!0)3,%))*0),"*: )0;0%&0!"#$%&'()*!+&,"-*+$'()%./"#(0)'10 23

24 Polyimide MicroChannel cooling Wtot = 1.6 cm OUT IN q = 0.4 W/cm 2 Ltot = 20 cm Pyralux PC 1020 (polyimide) 200µm Pyralux LF7001 (Kapton ) 24µm Pyralux LF110 (Kapton ) 50µm SENSOR READOUT CHIP SMD COMP SENSOR READOUT CHIP SMD COMP CARBONFIBER SUPPORT COOLING TUBE 24

25 MicroChannel Simulation (Fluent 6.2) Ø Assuming ΔT max = 3 C Leakless (underpressure) system Top Layer T water in 15 C L = 20 cm W= 1.6 cm T water out 18 C T water in 15 C C C T water out 18 C 16 channels 800 x 200 µm 2 IN OUT Axonometric view of a single channel Inlet section Middle section Outlet section 25

26 MicroChannel Production Ø Main fabrication process steps (R. De Oliveira, CERN TM-MPE-EM) Sheet 50 µm of LF110 Lamination 200 µm photoimageable coverlay (4 layers of PC1020) Creation of the grooves (800 x 200 µm 2 ) by photolithography 180 C Gluing by hot pressing the LF µm lid 180 C for 10h Pyralux PC 1020 (polyimide) 200µm Pyralux LF7001 (Kapton ) 24µm Pyralux LF110 (Kapton ) 50µm 26

27 MicroChannel Material Budget Material Radiation length [cm] Kapton 28.6 H 2 O 36.1 % Xo Single channel Cross section µm Ø Material budget of the ALICE Pixel cooling (Phynox tube + C4F10) O.8 % X 0 27

28 Richieste finanziarie Ø Richieste straordinarie 2011 ü Sviluppo di sensori sottili per rivelatori a pixel ibridi ü Produzione di un run di sensori a pixel epitassiali planari sottili di tipo active edge presso la ditta FBK nell ambito dell accordo MEMS2 con l INFN - 25 keur Cons. ü Sviluppo di microcanali in polietilene per il raffreddamento ü Sviluppo e realizzazione dei raccordi per la connessione del bus di microcanali al sistema di test, valvole pneumatiche e non, misuratori di pressione e temperature, modulo di lettura per PLC - 5 keur Cons. ü Acquisto di un flussimetro integrato con valvola di regolazione, pompa micro gear, microfiltro, scambiatore di calore - 4 keur Inv. 28

29 Richieste finanziarie Ø Richieste Preventivi 2012 ü ü ü ü Completamento R&D sensori sottili active edge con layout ottimizzato: Run FBK - 25 keur Cons. Test dei microcanali di geometria reale: Produzione componenti, componentistica ed allestimento laboratorio - 5 keur Cons., 4 keur Inv. Assemblaggio di rivelatori per test di laboratorio e su fascio e di moduli dummy - 5 keur Cons. Test beam al CERN: 2 settimane x 3 persone = 6 settimane + 6 viaggi XX keur ME 29