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.
228Y.
MatsunagaFig.10.11Two-dimensionalpotentialdistributionatdetectionsection.(a)Nosignalelectron.(b)3,600signalelectron
potential.AsshowninFig.10.4b,thesurfacepotentialinthedetectorsectionisloweredbysignalcharge,comparedtothatfornosignalcharge.ThesensingcapacitanceiscalculatedwiththeamountofsignalchargeandthedifferenceinthesurfacepotentialsbetweenFig.10.11a,bwhichcorrespondstothecharge/voltageconversiongainofthedetector.Theresultantsensingcapacitanceis0:22fF= mperFPPlength.
10.2.2.3Evaluation
Thedeviceisevaluatedata7.16-MHzclockfrequency,whichistwicetheNTSCcolorsubcarrierfrequency.Thesignalduty,whichisthesignaloutputperiodtotheclockcycletimeratio,isapproximately75%,whichwasdeterminedbya35nspositiveresetpulse.Themeasuredcharge-to-voltageconversiongainofthisdetectorisshowninFig.10.12asasolidline.Itwasmeasuredbyinjectingaseriesofchargepacketsintothesensingchannel.Theconversiongainislinearoverachargepacketrangefrom20to4,500electrons/packet,anditisashighas220 V/electron.Themeasuredconversiongainishigherthanthatobtainedfromthesimulatedsensingcapacitancevaluebyabout20%.Athree-dimensionaldevicesimulationmaybeneededformoreaccurateestimation,becausethedifferencebetweenthemeasurementandthecalculationcanbeduetopotentialdistributionperpendiculartothesignalelectrontransferdirection.
Theoutputnoiseofthenewdetectorwasmeasuredusingaspectrumanalyzer.Figure10.13showsnoisespectraforthedevice,bothintheresetoperationandinthetransferoperation.Intheresetoperation,residualchargeinthesensingchannelincludesresetnoise(kTCnoise)chargeduetothethermalnoisegeneratedintheresetgate(RS).Conversely,inthetransferoperation,theresetnoiseiscompletelysuppressed,becausenoresidualchargeexistsinthesensingchannel.Theoverall
