Charge-Coupled Devices

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CCD.ppt P. DenesWhat t hey areWhy t hey are ubiquit ousAnd whos t he compet it ionHow t hey can be improvedP. DenesEngineering DivisionLawrence Berkeley Nat ional Laborat oryCCDs j ust keepgoi ng and goi ngand goi ngCCD.ppt P. DenesSt andar d Det ect orSt andar d Det ect orPhosphorFiberCouplingCCDCCD.ppt P. DenesSci ent i f i c CCDsSci ent i f i c CCDs CCD invent ed in 1969 by Boyle and Smit h (Bell Labs) as alt ernat ive t o magnet ic bubble memory st orage LST ( Large Space Telescope lat er Hubble) 1965 how t o image? Film was obvious choice, but -I t would cloud due t o radiat ion damage in spaceChanging t he film in t he camera not so t rivial 1972 CCD proposedDumbbell nebula - LBNL CCDBlue: H- at 656 nmGreen: SI I I at 955 nmRed: 1.02 mmCCD.ppt P. DenesConvent i onal 3-Phase CCDConvent i onal 3-Phase CCD Noiseless, ~ lossless charge t ransfer High gain charge-t o-volt age conversion V = q/ CFD Out put amplifier (source follower, or ) on-chip123RST VDDVDDOutFDVCCD.ppt P. DenesMany ways t o do t hi sMany ways t o do t hi s123Pixel 1 Pixel 2Q1Q2Q1Q2Q0I mplant modifies pot ent ial12Pixel 1 Pixel 2 Pixel 1 Pixel 2Q1Q2Q1Q2Q1Q23124Q1Q2Q1Q2Q1Q2CCD.ppt P. DenesSever al ar chi t ect ur esSever al ar chi t ect ur esVertical clocksHorizont al clocksFull frameVertical clocksHorizont al clocksFrame t ransferRapid shift from image t o st orageSlower readout of st orage during int egrat ionVertical clocksHorizont al clocksI nt erlineCCD.ppt P. DenesSur f ace vs bur i ed channel CCDSur f ace vs bur i ed channel CCD MOS capacit or Pot ent ial maximum at Si SiO2int erface CTE < 1 due t o t rapping at int erfaceVGPot ent i alDepthxdVGPot ent i alDepthxd Pot ent ial maximum not at Si SiO2int erface CTE t ypically > 99.9999%CCD.ppt P. DenesFr ont si de/ Backsi de I l l umi nat i onFr ont si de/ Backsi de I l l umi nat i on( )A EPI A POLY T Te e / /1 TEPI( )A EPITe /1 TEPIFill fact or < 1 Fill fact or = 1A0.2m@400 nmCCD.ppt P. DenesI magi ng Det ect or sI magi ng Det ect or s2D segment ed Si2D segment ed Si at t achedt o 2D segment ed Si 2D segment ed Si at t achedt o 1D segment ed Sior ot her elect ronics Monol i t hi csensor + r eadouton same subst r at eHybr i dSensor+ReadoutCCD.ppt P. DenesMonol i t hi c I mage Sensor sMonol i t hi c I mage Sensor s Passive Pixel Sensor Proposed 1968 No Reset , no in-pixel amplifierSELECT Act ive Pixel Sensor Also proposed 1968 Many ways t o make t he phot odiodeRESETSELECTCCD.ppt P. DenesCCD vs APSCCD vs APS APS t ransfers a volt age down t he column CCD (noiselessly) t ransfers a charge down t he column APS can be more sensit ive (source follower does not have t o drive off-chip) APS fill fact or < 1 in general Phot ogat e APS like a mat rix of individual CCDs Backside illuminat ion at t empt ed for APS, work-in-progressPG Xlike CCDOTGRESETSELECTFDCCD.ppt P. DenesGl ossar yGl ossar ySensor Quant um efficiency Probabilit y of det ect ion Energy spread Point spread funct ion (PSF) Conversion gain (may be in readout ) Volt s / ___ (elect ron, eV, ) Well dept h - QMAX Noise cont ribut ion, SENSORFr ont -end r eadout Noise cont ribut ion, ELECReadout Full-scale - VMAX Speed MPix/ s (less ambiguous t han fps)Syst em Frequency-dependent DQE or equivalent Dynamic Range = min(QMAX, VMAX) / SENSOR ELECSensor wit hpixel pit ch P dB = 20 log10(DR) bit s = log2(DR)CCD.ppt P. DenesCMOS, CMOS opt o and CCD pr ocessesCMOS, CMOS opt o and CCD pr ocessesGat en+ S n+ DChannel Lengt h L L / tOX tOX/ WDVV / CMOS driven byconst ant field scalingp subst rat eDopi ng - NA NACCD CMOStOX( )500 -100050Wel l dept h ( m)2.50.5deeper f or RFI mpl ant ( m)~ 1channel st op0.1S/ D i mpl ant sV 10< 3.3< 2.5< 1.x Pol y l ayer s 3 ( 2)12 f or anal ogSubst . qual i t yLow l eakageDont car eExcept opt oCCD.ppt P. DenesTr i pl e Pol y CCD Pr ocessTr i pl e Pol y CCD Pr ocessPoly 1Poly 2Poly 3Gat e oxideI LDCCD.ppt P. DenesWhy CCDs?Why CCDs? Low noise (noiseless charge t ransfer, do everyt hing t o make CFDsmall in order t o get large conversion gain) Fill-fact or = 1 ( for backside illuminat ion) Linear and easy t o calibrat e Long hi st or y of sci ent i f i c use Large area devices easier (cheaper) t o develop as CCDst han as st at e of t he art CMOS devices Readily wafer scale Commercially producedCCD.ppt P. DenesVer y Lar ge For mat CCDs ( and CMOS i mager s)Ver y Lar ge For mat CCDs ( and CMOS i mager s) Fairchild Wafer Scale Full Frame CCD 9216 x 9216 x 8.75 m pixel 80.64 x 80.64 mm2size CCD Eight 3-st age out put amplifiers Readout noise < 30e- @ 2/ fps Cypress CYI HDS9000 3710 x 2434 x 6.4 m pixel 23.3 x 15.5 mm2size APS 0.13 m imaging CMOS process Canon 16.7 MPix 36 x 24 mm24992 x 3328 Kodak 39 MPix 36 x 48 mm2CCD.ppt P. DenesEl ect r on-Mul t i pl yi ng CCDsEl ect r on-Mul t i pl yi ng CCDs Long serial regist er wit h avalanche mult iplicat ion pixels Gain (1+ )N~ 1% Good for single-phot on sensit ivit y Nonet heless, current devices have limit ed (12 bit ) dynamic range Excess noise fact or, FCCD.ppt P. DenesEM CCDEM CCDe2v-97 512x512TI -TC285 1004x1002~ 12 bit sCCD.ppt P. DenesPer sonal Pr ej udi cePer sonal Pr ej udi ce CMOS has overt aken CCD in t he consumer market short int egrat ion t ime leakage is not t hat import ant very high speed not required Limit ed analog performance ok - < 10 bit s linear, ~ 16 bit s logarit hmic Pixels! The t riumph of market ing over physics E. Fossum CCDs will cont inue t o dominat e size x dynamic range size x dynamic range x speed are what is needed by t he scient ific communit yCCD.ppt P. DenesDi r ect x-r ay det ect i onDi r ect x-r ay det ect i on Well est ablished use of CCDs in x-ray ast ronomy Excellent spect roscopic resolut ion possiblex-ray view of t he galact ic cent erCCD.ppt P. Denes and and Excellent spect roscopic resolut ion But only if not piled-up low rat e or fast readout N,MAX= Well Dept h / (E/ 3.6 eV) < 1000 9-10 bit ADC OK Would really profit from high-speed readout as S/ N is so high253035404550400 500 600 700 800 900 1000E [eV]FWHM [eV]I nt rinsic resolut ion in SiCCD.ppt P. DenesBack-i l l umi nat i on pr ef er r edBack-i l l umi nat i on pr ef er r ed0%10%20%30%40%50%60%70%80%90%100%10 100 1000 10000E [eV]Transmission [SiO2]1.5 nm10 nm100 nm1,000 nm10,000 nmThin window-dopedFront illuminationCCD.ppt P. Denes0%10%20%30%40%50%60%70%80%90%100%0 5000 10000 15000 20000 25000 30000E [eV]Transmission200 um300 um600 um20 umThi ck Si l i conThi ck Si l i contCCD.ppt P. DenesRadi at i on DamageRadi at i on Damage I onizat ion damage Charge t rapping in gat e oxide-Threshold shift Damage at t he SiO2 Si int erface-Surface dark current-Surface mobilit y loss CCDs have t hick oxidesCCD.ppt P. DenesFl ux f or 1 Rad i n gat e oxi deFl ux f or 1 Rad i n gat e oxi de1.E+081.E+091.E+101.E+111.E+121.E+131.E+141.E+151.E+161.E+171.E+181.E+191.E+20100 1000 10000E [eV]/cm2 for 1 Rad20 um200 um600 umCCD.ppt P. DenesLBNL CCDLBNL CCD CCD on high-resist ivit y, fully deplet ed silicon No t hinning needed Good red (and blue) response No field free regions for diffusion good PSF Bi as deplet es subst rat e independent ly of clock volt agesCCD.ppt P. DenesPSF measur ed wi t h pi nhol es at UCO Li ckPSF measur ed wi t h pi nhol es at UCO Li ckCCD.ppt P. Denes1stx-r ay i mages i n LBNL CCD1stx-r ay i mages i n LBNL CCD3,512 x 3,512 x 10.5m pixel CCD200 m t hickCu anode, 140K, 70 kHz5 m slit in semi-t ransparentst ainless st eelSpect rum of Row 1200CCD.ppt P. Denes650 m t hi ck CCD650 m t hi ck CCD55Fe Kand K. Resolut ion ~ 126 eV at 5.6 keVBe wi ndowCCD.ppt P. DenesBack-i l l umi nat ed CCDs f or l ow-ener gy eBack-i l l umi nat ed CCDs f or l ow-ener gy e Window should be t hin enough t o allow elect rons t o penet rat e Device should be t hick enough t o avoid radiat ion damage Excellent S/ N (3.6 eV/ e-h pair) Well dept hThin ent rance windows also good for elect ronsCCD.ppt P. Denes10 keV e10 keV e01002003004005006007000 1 2 3 4 5 6 7 8 9 10EDeposited [keV]10 nmBackscat t ered100 (t yp.)CCD.ppt P. Denes-dopi ng ~ 15 -dopi ng ~ 15 Nikzad et al SPI E 97CCD.ppt P. DenesCCDs ar e wonder f ulCCDs ar e wonder f ulBut t hey ar e sl owADC Parallel exposure Serial readout Vert ical clock Horizont al clock Ext ernal, high resolut ion ADCCCD.ppt P. DenesEasyEasyNow it get s more difficultCCD.ppt P. DenesI ncr ease ADC speedI ncr ease ADC speedNV, NH= # H, V pixelsBV, BH= H, V binningTV, TH= H, V shift t imeNport= # port sTCONV= t ot al conversion t ime including reset , summing well, ADC ADCADC ADC+ + = CONVport HHH HVVVf TN BNT BBTNT 12t op+ bot t om readoutCCD.ppt P. DenesFor exampl eFor exampl e Dalsa FT50M 1024 x 1024 x 5.6 m pixel Frame t ransfer / 2 port s 100 fps = 100 MPix/ s 11.1 bit s [ 67 dB] at 30/ 60 fps 10.1 bit s [ 61 dB] at 50/ 100 fpsI ncrease readout / ADC speedS/ F Limit at ionsRSTVDDOutVDDFDCLgm~ W/ L CG~ WL ~ CL/ gm RSTVDDOutVDDFDCLVDDCCD.ppt P. DenesLi mi t at i onsLi mi t at i ons Noise cont ribut ion from MR(reset swit ch) removed by CDS (correlat ed double sampling measure VRand VR+ VS) Noise cont ribut ions from MS(source follower) Thermal noise 1/ f noise Noise from current sourceH1H2H3RSTVDDOutFDOSW OTGVDDMRMSkTC df f H g kT V m n ) ( 4 ~ 22 dfff HWL CKVOXn1) ( ~ 22 ~ rat eCCD.ppt P. DenesAdd mor e por t sAdd mor e por t s Reset and out put t ransist ors need room Want t o minimize CFD Need space for t he out put st age!H1H2H3RSTVDDOSW OTGVDDFDRSTCCD.ppt P. DenesOne way t o gai n spaceOne way t o gai n spaceMI T Lincoln Labs mult i-port CCDCCD.ppt P. DenesFor exampl eFor exampl e Fairchild 456 512 x 512 x 8.7 m pixel I nt erline t ransfer / 32 port s 1000 fps = 250 MPix/ s On-chip current sources for 3-st age out put 2.5 Wat t sAt some point , adding more ADC port s becomes a connect ion nigh