基于单片机的数字时钟设计--外文翻译(2)

10Low-NoiseElectronicImagingwithDouble-GateFETs

Fig.10.5Potentialpro les

alongthedirection

perpendiculartodevice

surface223

thepotentialpro lesalongthedirectionperpendiculartothesurface.ThesolidlineandthedottedlinearethoseundertheFPPandundertheoutputgate(OG),respectively.Theabruptpotentialpro leunderthesensingchannelisessentialforthesignalchargeinthesensingchanneltomodulatethedetectiontransistorchannelconductanceeffectively.ThesourceanddrainregionsoftheP-channeldetectiontransistoraremadebyself-alignmentwiththeoutputgate(OG),resetgate(RS)andtheFPP.ThesourceisconnectedtotheP-channelloadtransistormadebyajunction-typeFETincorporatedintothesamechip.ThejunctionFETissuperiorforsuppressing1=fnoisecomparedtoaMOS-FET[4]

Acharge(electron)packettransferredintothesensingchannelthroughtheoutputgate(OG)isconvertedtoavoltagesignal,usingthe rststagesource-followerwhichconsistsofthedetectiontransistorandtheloadtransistor.Anoutputsignalisgeneratedusingthesecondstagesource-followerconstructedwithn-channelMOStransistors.Toremovethecharge(electron)packetfromthesensingchannelregionintoresetdrain(RD),apositivepulseisappliedtotheresetgate(RS).Thenthesensingchanneliscompletelydepletedinaso-called“transferoperation.”Thus,thedetectorhasnoresetnoise[5–7].

10.2.1.2DeviceSimulation

Atwo-dimensionaldevicesimulatorwasutilizedfordesigningthedetector.Inaconventionaldetector,aneffectivesensingcapacitanceisdeterminedapproximatelybythegateoxidecapacitanceofadetectiontransistor[2,3].Forhighsensitivity,lowsensingcapacitancehasbeenachievedbyemployinga1 mthickgateoxideforthedetectiontransistor.Figure10.6ashowsasimulatedpotentialpro leforelectronsinthedetectingsection.Apotentialpocketisobservedattheedgeoftheoutputgate(OG).Thepotentialpocketcausesnotonlycharge(electron)transferlossbutalsotransfernoise.Toeliminatethepocket,theFPPhasbeeninsertedunderthepotentialcontrolgate(G).Thepotentialpro leinthenewdetectorwiththeFPPisshowninFig.10.6b.Thepotentialpocketvanishes,whichenablesthenewstructuretoobtainreducedtransferlosssuf cientfortherealizationofalow-noisedetector.

Abstract Virtually complete charge transfer can be achieved with charge coupleddevices(CCDs)intheburiedchannelconfigurationbecausetheburiedchannelCCDintroduces no transfer noise. However, conventional charge detectors incorporatedinto CCDs have a comparably large noise, which consists of thermal noise and 1/fnoisefromMOS transistorin theoutputchargedetectors.

224Y.

MatsunagaFig.10.6Potentialpro lesalongthedirectionperpendiculartodevicesurface.(a)Detectiontransistorwithonly1 mthickgateoxide(b)DetectiontransistorwithFPP

10.2.1.3Evaluation

Thedetectorwasevaluatedata7.16MHzclockfrequency,correspondingtotwicetheNTSCcolorsubcarrierfrequency.Thesignaldutyde nedbythesignaloutputperiodintheclockcyclewasapproximately70%,whichwasdeterminedbya40nspositivepulsesuppliedtotheresetgate(RS).Thecharge/voltageconversiongainofthedetectorwasmeasuredbyinjectingaseriesofchargesinapacketintotheCCDfromaninjectiondiodehavingacapacitanceofabout1fF.Thesizeofthechargepacketwascalculatedfromtheresetdraincurrent.Theresultantoutputamplitudewasobservedthroughanoscilloscope.Theoutputsignalbandwidthis20MHzunder7pFcapacitanceload.TheresultsofthemeasurementsareshowninFig.10.7Therelationbetweeninjectionchargequantityandoutputvoltageislinearoverarangeofchargepacketsfrom40to2,000electrons/packet,witharesponsivityof76 V/electron.Theoutputnoiseofthenewdetectorwasmeasuredusingaspectrumanalyzer.Figure10.8showsthenoisespectraofthedetector,bothinresetoperationandintransferoperation.Intheresetoperation,residualchargeinthesensingchannelincludesresetnoise(kTCnoise),chargeduetothermalnoisegeneratedinthechannelregionoftheresetgate(RS).Conversely,inthetransferoperation,nonoisechargeexists,becausethesignalchargeinthesensingchanneliscompletelytransferredintotheresetdrainbyapplyingapositivepulsetotheresetgate.The1=fnoisebelow2MHz,whichisobservedinthenoisespectrumforthetransferoperation,isgeneratedbythedetectiontransistor.TheoverallRMSnoisevalueinthetransferoperation,withinthefrequencyrangeof10kHz–3.58MHz,was64 Vrmsatroomtemperature.Thevalueforthe“ oatingsurfacedetector”withtheFPPstructure,whichisfabricatedonthesamesubstrateforcomparisonandisdescribedbelow,was84 Vrmsunderthesamemeasuringconditions.Thedifferenceinthenoisevaluesiscausedbythe1=fnoiseduetosilicon–silicondioxideinterfacetraps.AsshowninFig.10.7,thenewdetectorwithacharge/voltageconversiongainashighas76 V/electron,anoiselevelaslowas64 Vrmsanda70%signaldutyratio,achievesaneffectivereadoutnoiseaslowas1.2electronsrms.

Abstract Virtually complete charge transfer can be achieved with charge coupleddevices(CCDs)intheburiedchannelconfigurationbecausetheburiedchannelCCDintroduces no transfer noise. However, conventional charge detectors incorporatedinto CCDs have a comparably large noise, which consists of thermal noise and 1/fnoisefromMOS transistorin theoutputchargedetectors.

10Low-NoiseElectronicImagingwithDouble-GateFETs

225Fig.10.7Charge/voltageconversioncharacteristicsandnoise

levels

Fig.10.8Noisespectrainresetoperationandintransferoperation

Abstract Virtually complete charge transfer can be achieved with charge coupleddevices(CCDs)intheburiedchannelconfigurationbecausetheburiedchannelCCDintroduces no transfer noise. However, conventional charge detectors incorporatedinto CCDs have a comparably large noise, which consists of thermal noise and 1/fnoisefromMOS transistorin theoutputchargedetectors.

226Y.Matsunaga10.2.2FloatingSurfaceType

Analternativelow-noiseandwidedynamicrangechargedetectorcalled“double-gate oatingsurfacedetector”differsfromthe oatingwelltypeinthattheP-channelFETcurrent owsatthesilicon–silicondioxideinterface.Anadvantageofthistypeisitshighconversiongainduetothesmallsensingareacomparedtothe oatingwelltype.Thedeviceachievesacharge-to-voltageconversiongainof220 V/electronandadynamicra …… 此处隐藏：6600字，全部文档内容请下载后查看。喜欢就下载吧 ……