An integrated circuit electrostatic protection Circuit (ESD) process

A while ago a friend said they had a project in which there was a process circuit for ESD protection. I couldn't understand it at the time. But then the more I see the more I understand. Now share with you. is also a contribution to high-tech. The right of the regulator diode plays the role of the control voltage, when the regulator diode conduction, will be in its high over a current, the current through the resistance below, will cause the voltage on both sides of the lower resistance rise, this time will make the left transistor transmit junction voltage to the transistor conduction trigger voltage 0.7V, This time the transistor is working in a magnified state. The large currents can flow from the transistor. The benefits of this electrostatic protection circuit are two-way. On the one hand, it increases the discharge capacity of ESD (electrostatic protection), on the one hand, reduces the capacitance of ESD protection circuit. Discharge capability we can see from the transistor amplification in this circuit above. But the lower capacitance will be seen from the bottom of the process schematic diagram. The regulated voltage of the Zener diode is determined by the doped concentration of the PN junction of N+ and p+. Because the current does not flow so much, the area of the PN Junction can be made smaller, thus reducing the capacitance of the Zener diode. Furthermore, the overall capacitance of this circuit is smaller than the single-regulator diode in the case of the same discharge capability of the entire circuit and the ESD protection of the single-regulator diode.        The data says it can be as small as one PF. This circuit in the specific semiconductor process design, there are many places to rely on design experience to adjust, such as the concentration of ions in that place, as well as the thickness and width of some layers, these small changes will cause the circuit of one or several components of the parameters have changed greatly. Therefore, in the design of integrated circuits, the most important is the design of the implementation of the process, he will directly determine the success of your design results. is a deliberately, but also an experience to live.