Research On Smart Control System Of Four Point Probe Tester Based On SOPC

With the rapid development of the microelectronics industry, the research of thesemiconductor materials is more and more in-depth and the measurement of thecorresponding performance parameters is becoming more and more demanding. One of theimportant parameters of semiconductor materials is resistivity, which is measured by thefour-probe tester. At present, a four-probe tester with high degree of intelligence is expensive,and most of the traditional four-probe testers are still in the manual stage. The four-probetester is regarded as an indispensable tool for measuring resistivity of semiconductor materials.The traditional ones, which have the disadvantages of finding measurement points manuallyand low accuracy and efficiency, can not meet the needs of industry and the development ofthe times. Therefore, research on the intelligent control system based on the existing manualfour-probe tester is very necessary.Based on SOPC, a study on the intelligent control system of four-probe tester is carriedout in the dissertation. In the study, the overall design of the intelligent control system isdesigned by using the upper computer and the lower computer to control the peripheralhardware circuit. The overall design of control system mainly includes three parts: the uppercomputer, the lower computer and the peripheral hardware circuit. The lower computercustomizes a Nios II core and designs the related procedures in the Nios II IDE to achieve thecore control function. The upper computer designs a friendly man-machine interface whichcould control the lower computer and process and display the data transmitted from the lowercomputer. In the design of the peripheral hardware circuit, the constant current source circuit,differential amplifier circuit and the communication circuit are designed. A/D conversion chip(A/D7492) is used to transform and transmit measurement data and the combination of L297and L298is used to control the stepper motor and the probe head. Compared with the originalmanual four-probe testers, this intelligent control system has a high degree of intelligence,which can be operated by the upper computer. With the help of this intelligent control system,the test bench could be controlled to move to a specified location. The measurement datacould be sent to the upper computer to display in the man-machine interface and stored in thecomputer.The dissertation carries out the simulation testing on part of the module and the wholesystem respectively and the results show that the system basically achieves the expected effect.The system can better complete the tasks, such as the four-probe tester manual probe headmoving mechanically, data testing, data display and data storage and so on. At the same time,this intelligent control system owns better portability which also has positive significance forthe study and improvement of other instruments.