Research on the special chiller for semiconductor industry based on fuzzy PID control

In semiconductor integrated circuit manufacturing, lithography, etching, physical vapor deposition, chemical vapor deposition and other processes, which need to use chiller for precise temperature control of process chamber. The special chiller for semiconductor industry is used to meet the process requirements of large load change and precise temperature control. The special chiller for semiconductor industry is composed of refrigeration system and circulation system. The refrigeration system includes four main parts: compressor, condenser, electronic expansion valve and evaporator, the circulation system is composed of water tank, circulating pump and heater. The system of chiller is a multivariable, nonlinear and time-varying complex system. The temperature control of chiller is affected by compressor frequency, evaporating pressure, suction pressure, heating power and other parameters, it is difficult to establish a mathematical model accurately. The traditional PID control is difficult to meet the control needs. Therefore, fuzzy PID control is adopted. Fuzzy control is applied to improve the system response when the system error is larger, and conventional PID regulator is used when the system error is smaller. The parameters of PID control are changed by using the idea of fuzzy PID, and PID control action is adjusted according to different error situation and control cycle, thereby, reasonable control and regulation of temperature are achieved.