Shield gate groove type field effect transistor with low on-resistance and preparation method thereof

Abstract

The invention relates to a shield gate trench field effect transistor with low on-resistance. The shield gate trench field effect transistor comprises a substrate region, a drift region, a matrix region, a source region, a trench region, a drain electrode and a source electrode, the trench region comprises a shield gate, a control gate, an insulating layer and a metal gate; the shielding grid is of a variable doping concentration structure, and the doping concentration of the shielding grid is gradually reduced from top to bottom. When the transistor is blocked in the forward direction, the doping concentration of the part, close to the substrate area, of the shielding grid is low. Therefore, the part, close to the substrate area, of the shielding grid is easier to deplete under the same external voltage, namely, the part close to the substrate area has a thicker depletion layer width. The width of the depletion layer is inversely proportional to the capacitance of the stray capacitance, so that the stray capacitance formed between the shield gate and the substrate region is smaller, the stray capacitance formed between the shield gate and the substrate region is weakened, and the switching speed of the device is further improved.

Description

technical field [0001] The present application relates to the technical field of power semiconductor devices, and in particular, to a shielded gate trench field effect transistor with low on-resistance and a preparation method thereof. Background technique [0002] Shielded gate trench field effect transistors (Split Gate Trench, SGT) have been widely used in important low-voltage fields such as power management. SGT has high channel density and good charge compensation effect. In addition, the shielded gate structure effectively isolates the coupling between the control gate and the drain, thereby significantly reducing the transfer capacitance. [0003] Therefore, SGT has lower specific on-resistance, smaller conduction and switching losses, and higher operating frequency. [0004] In the SGT device, due to the electric field concentration effect and the high polysilicon doping concentration of the shielding gate, when the SGT device is blocked in the forward direction, ...

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Problems solved by technology

[0004] In the SGT device, due to the electric field concentration effect and the high doping concentration of polysilicon in the shield gate, when the SGT device is forward-blocked, the charge flux emitted by the ionized donor in the withstand voltage region is concentrated in the trench region shield At the corner of the gate, the peak voltage at the corner of the shield gate in the trench area is higher, and it is easier to be broken down here

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