Manufacturing method of three-section type oxide layer shielding gate trench MOSFET structure

Abstract

The invention relates to a manufacturing method of a three-section type oxide layer shielding gate trench MOSFET structure. A source-drain breakdown voltage of a traditional SGT device is controlled by the thickness of an oxide layer, the higher the breakdown voltage is, the thicker the required thickness of the oxide layer is, but in order to obtain lower Rsp, the unit cell size needs to be reduced as much as possible. According to the invention, the deep trench is filled with the borosilicate glass BSG material through a CVD process, boron in the borosilicate glass BSG material is diffused into the Si material on the periphery of the deep trench through a thermal process to form a P column, the BSG concentration and the annealing temperature are changed to adjust the high width and concentration of the P column, and charge balance between the P column and the N-type epitaxial layer is achieved. According to the invention, a thick shielding electrode dielectric layer does not need tobe grown in the trench, the BSG has good high-temperature backflow characteristic and good trench filling capability, and the trench CD can be greatly reduced, so that the unit cell size can be reduced, the same breakdown voltage is realized by adopting an epitaxial wafer with higher doping concentration, and the Rsp of the device is reduced.

Description

technical field [0001] The invention belongs to the technical field of semiconductor power devices, and in particular relates to a method for manufacturing 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] Figure 15 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 ...

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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