Research Of The Pt Diffused Fast Recovery Diode

The fast recovery diode is widely applied in switching power circuit and related field following the development of the electrical power and electronics in recent year. In fast recovery diode production, the method to reduce minority carrier lifetime and to shorten switching speed is to introduce recombination centre into the device. Platinum diffusion has the feasibility to reduce the reverse recovery time t_rr that can be analyzed by energy band theory of platinum and lifetime theory. In addition, platinum diffusion is suitable for large quantity production because of low cost. The feasibility of platinum diffusion to control minority carrier lifetime is analyzed theoretically in the thesis.The parameters characteristics and testing theory of fast recovery diode are introduced in details by the paper.This paper studied the several key steps about the manufacture processes of fast recovery diode. First, adjusted the platinum diffusion temperature and time to control the reverse recovery time t_rr effectively. The results could be controlled within 35ns to 500ns with certain platinum diffusion temperature. Secondly, modified the LPCVD nitride deposition system to reduce the reverse current leakage. The results showed the reverse current leakage have been controlled to nano ampere. Thirdly, meliorated the glass passivation process to remove the bubbles between silicon nitride and glass passivation layer. Finally, confirmed that the IP760 glass powder form FERRO Corporation of US is the suitable glass powder for fast recovery diode by a series of experiments. This glass powder is good for the uniformity and stabilization of reverse recovery time t_rr.The properties of platinum diffusion diode are studied by a series of experiments. The main diode parameters named reverse recovery time t_rr, forward voltage drop V_F and leakage current I_R (especially at high temperature) are comparatively analyzed. The temperature characteristics of reverse recovery time t_rr are also analyzed .The excellent selections between t_rr and V_F (t_rr within 80～500 ns, V_F within 0.9～1.3V )were obtained using cheap CZ wafer instead of expensive epitaxial wafer. Besides, the- between platinum diffusion conditions and diode parameters are investigated. The reasons of influence between parameters of fast recovery diode are also explained in theory.