Research Of Front End ASIC Of SiC Radiation Detector

The third-generation semiconductor radiation detectors represented by SiC detectors have high detection accuracy,low noise level and high radiation damage resistance.Therefore,they have very broad application prospects in nuclear energy,aerospace,medical,industrial and nuclear safety detection.However,the current signal output by the SiC detector is very weak.It requires a dedicated front-end readout circuit to amplify the signal,reduce the noise and shape it to obtain a measurable order of magnitude for digital processing,and ensure that the energy range and time information of the signal are not lost and are not affected by noise.Based on the above requirements,this paper designs and implements a front-end readout ASIC for the extremely narrow pulse weak current signal output by the grooved SiC neutron detector system.The main research work completed is as follows:Firstly,the readout and processing technology has an important influence on the performance of the radiation detector.Therefore,this paper studies the signal readout and processing technology of the radiation detector,determines and completes the circuit design of the main modules of the front-end readout circuit,and analyzes the principle of each module in detail.Aiming at the characteristics of the weak current narrow pulse signal output by the trench SiC neutron detector,a low noise charge sensitive preamplifier is used to convert the charge signal into a voltage signal to meet the requirements of low noise and fast response.At the same time,the high impedance circuit is used to replace the traditional charge discharge module,which has the characteristics of small layout area and high linearity compared with the traditional module.Then,the filter shaping circuit,discriminator and peak holding circuit are used to reduce the overall pulse width and broaden the peak width to ensure the energy information and time information of the signal.Secondly,the high temperature circuit design of the charge sensitive amplifier under the bulk silicon process and the high temperature circuit design under the FDSOI process are completed.Aiming at the performance degradation or even device failure of bulk silicon process in high temperature environment,a MOS diode connection method is proposed as a leakage current compensation diode.Compared with ordinary diodes,the layout design is more reasonable and the parameter design is simple.According to the zero temperature coefficient point bias voltage theory,the high temperature resistance circuit design of bulk silicon process is completed by iterative design method.Aiming at the good high temperature resistance of SOI process,the design of charge sensitive amplifier under SOI process and the performance comparison with bulk silicon process at 210°C are completed.Finally,the layout design of the front-end readout circuit is completed in 0.18μm process,and the layout design of the charge sensitive amplifier is proposed.The final four-channel and test channel layout area is 1.12mm×1.5mm.The post-simulation results show that the equivalent input charge range is 1.14fC～22.35fC,the charge conversion gain is 71.19m V/fC,the peak time is 74ns,the nonlinear error is controlled within 1.6%,and the equivalent noise charge is 54e~-.The readout circuit meets the design requirements and has the characteristics of low noise and high linearity.It can read and amplify the output signal of SiC trench neutron detector.