Research On Source Measure Unit Of Integrated Circuit Test

Integrated circuit testing technology is an important part of integrated circuit application field.In order to ensure the quality and reliability of integrated circuit,advanced and reliable testing equipment must be adopted.The Source Measure Unit(SMU)can provide accurate programmable constant-voltage and constant-current four-quadrant output for integrated circuit testing,while monitoring and calibrating the output signal through the internal measurement circuit,and has overvoltage and overcurrent protection mechanism to ensure the safety and reliability of the test.It has the advantages of high test accuracy,fast response speed and strong flexibility.The specific work of this thesis is as follows:(1)This thesis firstly expounds the research background and significance of the source measurement unit,introduces the basic components of SMU,analyzes and explains the working principle of each part of the SMU module,and introduces the application of the source measurement unit test combined with the testing requirements of integrated circuits.(2)According to the test requirements,a test system based on parameter measurement unit AD5522 is designed.On the basis of studying the working principle of AD5522,in order to further improve the test accuracy of the source measuring unit,a closed-loop testing method for data correction is proposed.In this scheme,the ADC converter circuit of AD7685 is designed,which is used to collect the output voltage of AD5522,calibrate the error by least square method,recalculate the DAC control word of AD5522 and write it into the register,so as to meet the precision requirements of the system.Finally,the designed SMU is used to test the DC parameters of linear voltage regulator AMS1117-3.3.(3)Because the output power of the test chip AD5522 is limited,it cannot meet the test requirements of high power load.Therefore,a source measurement unit based on integrated operational amplifier is studied in this thesis,and a power amplifier circuit with complementary output stage is designed to achieve the power output of ±1A/±30V of SMU.Aiming at the problem of loop oscillation under capacitive load,a phase compensation scheme is designed to improve the stability of the system.Under the condition of capacitive load of 50 n F,the compensated phase margin of the system is reached and the frequency characteristics of the system are improved.In order to further improve the stability of the source measurement unit,this thesis studies a digital-assisted source measurement unit scheme,and designs a new all-digital DAC and all-digital ADC to replace the conventional data converter.In the Pulse signal modulation part of all-digital DAC,based on the method principle of Dyadic Digital Pulse Modulator(DDPM),A Double Data Rate-Dyadic Digital Pulse Modulator(DDR-DDPM)method is proposed in this thesis,which uses two sides along D flip-flop to form a shift register of binary pulse code to improve the conversion time utilization rate of all-digital DAC.(4)In the compensation control algorithm part,aiming at the problems such as system oscillation and slow response speed caused by load instability of SMU circuit,PID closedloop control algorithm is introduced to carry out pole-zero compensation for the system,improve the frequency characteristics of the system,and to some extent give consideration to the system stability and response speed.