Research On Micro-area Resistivity Testing Device With Temperature Control

The rapid development of science and technology has promoted the large-scale production of integrated circuits,and has also led to the reduction of chip size.Silicon wafer is the substrate material of the chip in the integrated circuit.When the diameter of the silicon wafer is required to increase,it also needs to have good micro-area characteristics.Therefore,in order to meet the performance requirements of integrated circuit,it is very important to measure the resistivity of silicon wafer in micro-area.Resistivity always varies with ambient temperature.Therefore,the influence of ambient temperature on resistivity of silicon wafer can not be ignored.According to the survey,most of the existing resistivity testing devices do not take into account the effect of temperature on resistivity.So it is necessary to design a micro-area resistivity testing device with temperature control.Firstly,by summarizing the significance of micro-area resistivity measurement and the influence of temperature on resistivity,and comparing the research status and advantages and disadvantages of resistivity testing devices at home and abroad,the necessity of research on micro-area resistivity measurement devices with temperature control is proposed.Secondly,the measurement methods of resistivity were compared and analyzed.The EIT measurement method based on Electrical Impedance Tomography(EIT)was used as the measurement method of the device and the working principle of EIT was introduced.According to the principle of EIT measurement method and the requirement of temperature control.The initial design of the micro-area resistivity measurement device with temperature control was put forward,and the optimization was carried out.Thirdly,the control system of micro-area resistivity testing device with temperature control based on STM32 was designed.It mainly included STM32 minimum system,EIT test system,constant temperature circuit,serial communication module,touch screen module and vacuum pump module.The EIT test system included constant current source module,voltage measurement module and multichannel analog switch module,and constant temperature and electricity module.The constant temperature circuit included temperature acquisition module and temperature control module.Serial communication module transmitted the data measured by EIT test system to PC for processing.Touch screen module was used for real-time display of measurement parameters and temperature set by users.Vacuum pump module adsorbed the sample to be measured on the electrode to keep it fixed in the measurement process.Finally,the software system and algorithm design of the control system of the micro-area resistivity testing device with temperature control were carried out,including the design of ARM processing program and EIT image reconstruction program,and an improved gray-scale image display algorithm was proposed,which determined the corresponding relationship between resistivity and grayscale value,and can more intuitively display the resistivity distribution of the micro-area.The influence of different temperatures on resistivity was analyzed.The stability and reliability of the measurement system were verified by testing the system performance of the micro-area resistivity testing device with temperature control,including temperature control function test,voltage stability test and channel consistency test.The micro-area resistivity testing device with temperature control was compared with 4D-333 A of Four Dimensions in the United States at the same temperature for resistivity measurement,which verified the accuracy of the measurement results.