Study On Fabrication Technology And Characteristics Of Platinum Doping SFRD

Owing to fast switch speed characteristic, super fast recovery diode (SFRD) is widely applied to power electronic technique. The switch speed of diode is determined by the minority-carrier lifetime in silicon and recombination centers in silicon may shorten the minority-carrier lifetime. Compared with Aurum doping, electron irritation, ion irradiation, Platinum (Pt) may provide ideal recombination centers except that Pt doping device have worse trade-off curve between forward voltage drop (VF) and reverse recovery time (Trr). The base width may be controlled exactly by using epitaxial wafer to fabricate SFRD, which could resolve poor trade-off curve of Pt doping device.The processes of fabricating SFRD are introduced and researching process was focused on. Solid-state boron diffusion process was improved successfully by combining thermal oxidation cycle into drive-in cycle, without reducing uniformity of diffusion results. Trr could be controlled from 20 to 100 nanoseconds by adjusting Pt diffusion temperature ranging from 900 to 940℃. Poly silicon layer between Si3N4 and silicon may reduce interface stress and surface state density as a buffer layer, and polySi-Si3N4-glass multi-layer composition film could be applied to SFRD fabrication in this thesis. In addition, the glass bubbles in the interface between Si3N4 and glass disappear by depositing oxide thin film on Si3N4. Compared with laser cutting method, blade cutting method resulted in higher leakage current of device. Blade cutting method was improved by changing sawing direction from the front side of wafer to the backside, which can reduce process mechanical damage to device.Electrical parameters of SFRD were tested and electrical characteristics are analyzed. Device with thin base have good trade-off curve between VF and Trr. Not only does Trr have relation to Pt doping but Trr increases with the chip-size increasing. With the temperature rising, VF decreases and Trr increases. Besides, IR rises sharply with the temperature rising. The lower Trr, the larger IR.Characteristics of SFRD fabricated in this thesis meet international standard of similar production. And the processes are relatively simple, which may be applied to production.