Three-section type oxide layer shielding gate trench MOSFET structure

Abstract

The invention relates to a three-section type oxide layer shielding gate trench MOSFET structure, which is positioned on an epitaxial substrate, a region is arranged under a source trench of the MOSFET structure, the region is filled with a material opposite to the epitaxy, and charge balance is realized by a P column formed by diffusion of a diffusion source and the epitaxy. According to the structure, the groove is filled with the BSG material through the CVD technology, and then Boron is automatically diffused into the silicon material on the periphery of the groove through the thermal process to form the P column, the high width and concentration of the P column can be effectively adjusted by changing the BSG concentration and the annealing temperature, and charge balance between the Pcolumn and the N-type epitaxial layer is achieved. By adopting the SGT MOSFET structure and the process structure, a thicker shielding electrode dielectric layer does not need to be grown in the trench, and meanwhile, the BSG has a good high-temperature backflow characteristic and a good trench filling capability, so that the trench CD can be reduced to a great extent, and the unit cell size canbe reduced; and the same breakdown voltage is realized by adopting an epitaxial wafer with higher doping concentration, so that Rsp of the device is reduced, and market competitiveness is enhanced.

Description

technical field [0001] The invention belongs to the technical field of semiconductor power devices, and in particular relates to a three-stage oxide layer shielding gate trench MOSFET structure. Background technique [0002] The SGT (Shield-Gate-Trench, shielded gate trench) structure introduces horizontal depletion based on the vertical depletion (P-Body / N-Epi junction) of the traditional trench MOSFET due to its charge coupling effect, making the device The electric field changes from a triangular distribution to an approximately rectangular distribution. In the case of epitaxial specifications with the same doping concentration, the device can obtain a higher breakdown voltage, and this structure is widely used in the field of medium and low voltage power devices. [0003] image 3 For the traditional SGT (Shield-Gate-Trench, shielded gate trench) structure, a trench is first formed by etching, and then a shielding electrode dielectric layer is grown in the trench, usual...

AI Technical Summary

Problems solved by technology

Single or multiple unequal energy injections cannot achieve a more ideal junction shape, hindering the further development of advanced SGTs

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