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
Fig.10.1Planeviewof
conventional oating
diffusioncharge
detector221
Fig.10.2Plainviewofnew
oatingwell
detector
[2,3].Figure10.3showsacross-sectionalviewofthedetectiontransistoracrossthesensingchannel.Ashallowp-wellwithasensingchannelinitandsource/drainpCregionsareformedonann-typesubstrate.TheholecurrentintheP-channeldetectiontransistorismadeto ownotalongthesilicon–silicondioxideinterfacebutratherunderneaththesensingchannel.Asaresult,suppressionof1=fnoisewhichiscausedbysilicon–silicondioxidetrapscanbeexpected.ChargepacketsclockedalongtheCCDchannelaretransferredintothesensingchannel.Thechargepacketsdirectlymodulatethechannelconductanceinthedetectiontransistor.
Thesensingcapacitanceforthedetectiontransistorcanbesmallerthanthatforthewidelyused“ oatingdiffusiondetector.”Thesmallsensingcapacitancehasbeenachievedbythesmallersensingregion,inwhichthesensingchannelandtheP-typechannelforthedetectiontransistorarecrossed.Moreover,a“double-gatestructure”isintroducedforsmallersensingcapacitance.Inthisstructure,a1,000nm
