Development On Wafer Type Testing System Based On Embedded System

Currently, the test equipment of wafer conductive type is analog circuit generally, the level of visualization is lower, which is not beneficial for subsequent development and only could distinguish conductivity type functionally. For this situation, a wafer type tester was developed by the method of hot and cold probe based on 32-bit ARM processor, which extends two functions, include testing thermoelectric current of different wafer with temperature variation and distinguishing different doping concentration of the same doping type under the same condition.The hardware of test system mainly includes main control module, thermoelectric current detection module, thermal probe temperature controlled module, display module, power module, voltage reference module and so on.The 32-bit ARM processor STM32F103ZET6 is used as main control chip, through designing corresponding peripheral circuit, the internal resources of this chip including ADC, timer and PWM, are fully utilized, which decreases the complexity of the system effectively. The thermoelectric current detection module uses high-precision instrumentation amplifier INA114 as the core device to design amplification circuit, after testing and calibration, the effective detection of thermoelectric current detection module ranges from-130 nA to +160nA, and has a good linearity between-96 nA and +117nA. The temperature detection module of hot probe uses Pt1000 thermistor as temperature sensor, the maximum internal temperature of the hot probe can reach 170 °C. The classical PID algorithm is used to control the temperature of the hot probe, In the setting of tip temperature at 60 °C(internal temperature 145 °C), the temperature can achieve stability in five minutes or so, the temperature fluctuations is within 0.5 °C.In the aspects of software, modular approach is used. C language is used to write program to achieve the control of 10.4 inches LCD screen, touch screen input, internal AD operation, serial communication, thermoelectric current collection, hot probe temperature collection, cold probe temperature collection and other functions. After the completion of the debugging of the program, through the main program, the whole test system completes the logic function and the sub-time scheduling of subprogram, the whole program run steadily.According to the design requirements, thermal probe in internal heating type is designed and prototype tester is producted, realizing the expected function, and operation is stable and reliable. The test system has the advantages of real-time display curve, simple and flexible touch control and can be used for subsequent development, digitization and so on, and has strong practical application significance.