A LDMOS Device Based On High-K Thin Film

In recent years, LDMOS has been widely used in smart power integrated circuit (SPIC) for its advantages such as strong drive capability, high breakdown voltage (BV), and good process compatibility. High-voltage LDMOS research mainly focuses on the trade-off between BV and on-resistance Ron, while the key to improving device’s performance is to reasonably design the drift region structure. High permittivity (high-k) thin film, covering on the surface of semiconductor, can adjust drift region’s electric flux to form the best variation lateral flux (VLF), and help to increase BV effectively, meanwhile reduce Ron obviously.In this Paper, A kind of LDMOS device with high BV and low Ron was researched. In this structure, the surface of drift region and channel region was covered by high-k thin film, which is used to adjust drift region’s electric flux and used as gate dielectric layer. Field plate technology was also adopted to reduce the peak field on the surface of reverse-biased PN junction. Between the high-k layer and field plate layer, oxide was brought in to cut down the high field at the edge of field plate. In this structure, drift region length is60μm, depth5μm, doping1E16cm3, high-k film permittivity200, thickness1μm, field plate length25μm.Firstly, simulation tool MEDICI was used to verify the device’s performance and investigate the relationship between structure parameters (such as drift region structure, gate plate length, high-k film thickness and permittivity). Secondly, process simulation tool TSUPREM4was used to research the fabrication of this device. In especial, the wet etch process of PZT and BST high-k films were investigated in laboratory. At last, the simulation result shows an820V LDMOS is achieved with on-resistance dropping to13.24Ω·mm2. The process simulation tool helped to develop a method of fabrication. The wet etch of high-k thin film research shows that the etching solution BOE+36%HCl+65%HNO3+H2O+buffer owns preferably etching effect, and satisfies the demand of process.