Trench Mosfet Grid Technology Application And Optimization

Trench power MOSFET is an innovative semiconductor device with vertical channel structure. Trench MOSFET devices show many advantages including fast switching speed and frequency performance, high input capacitance, low drive current, good temperature characteristics, and no secondary breakdown problems, etc. It was widely implemented in the voltage regulator, power management module, electromechanical control, display driver, automotive electronics and other fields. Gate module is the most crucial process in MOSFET manufacturing, so we must optimize gate module process to improve production yield and get better device performance. In this thesis three topics related to the trench MOSFET gate module process and process optimization with experiment data justification are discussed.Trench MOSFET process flow and gate module process introduction: Trench MOSFET manufacturing steps and sequence was introduced. Sacrificial oxidation, poly deposition and doping process theory and equipment were discussed. Some critical electric (ET) parameters of trench MOSFET were defined at last.Trench MOSFET sacrificial oxidation process optimization:The correlation between production ET parameters and sacrificial oxidation condition was studied. The evaluation ET data show the device breakdown voltage was improved while gate leakage was reduced as the sacrificial oxidation temperature and oxide thickness was increased. Based on trench MOSFET gate failure analysis data, the oxidation temperature and oxide thickness optimization would improve trench poly gap fill capability, i. e., trench was round off as trapezoid structure when sacrificial oxidation process was optimized.Trench MOSFET gate poly process optimization:The influence of poly deposition temperature and the poly thickness was studied to solve poly etch residue and over etch problem. The evaluation data show poly deposition at540℃is the best solution. The PH3doping with poly deposition would get the lowest resistance. The split gate trench MOSFET principle and gate charge reduction was also studied. Comparing with the original trench MOSFET, the gate to drain charge density was reduced67% when the split gate structure was applied, so the device switching frequency got a great promotion.