Manufacturing method of field oxide with gradually changed thickness in trench and manufacturing method of SGT device

Abstract

The invention discloses a manufacturing method of field oxide with gradually changed thickness in a trench. The method comprises: a step 1, forming a trench in a semiconductor substrate; a step 2, forming field oxygen by adopting a thermal oxidation process; a step 3, depositing to form a second oxide layer; a step 4, completely filling the trench with a third material layer; a step 5, removing the third material layer on the surface of the second oxide layer outside the trench; a step 6, carrying out wet etching of the oxide layer by taking the third material layer as a self-alignment mask. By utilizing the characteristic that the wet etching rate of the second oxide layer is greater than the wet etching rate of the field oxygen, the field oxygen along one side of the second oxide layer can accelerate etching in the wet etching process and can form a structure with gradually increased thickness from top to bottom after the wet etching is finished; and a step 7, removing the third material layer. The invention further discloses a manufacturing method of the SGT device.

Description

technical field [0001] The invention relates to a method for manufacturing a semiconductor integrated circuit, in particular to a method for manufacturing field oxygen with gradually changing thickness in a trench; Manufacturing method. Background technique [0002] SGT devices such as SGT MOS devices are advanced device structures of ordinary trench gate (Trench) MOS devices, such as figure 1 Shown is a schematic structural diagram of an existing SGT MOS device; taking an N-type device as an example, the existing SGT MOS device includes: [0003] An N-type epitaxial layer (EPI) 102 is formed on the surface of an N+ semiconductor substrate such as a silicon substrate 101 . [0004] The trench 103 is formed in the N-type epitaxial layer 102 . [0005] The gate structure is formed in the trench 103 , including: a bottom dielectric layer 104 , a source polysilicon (source poly) 105 , a polysilicon gate 106 , an interpolysilicon dielectric layer 107 and a gate dielectric laye...

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Problems solved by technology

[0018] However, in reality, because of the voltage drop on the source polysilicon 105, the potential decreases from deep to shallow. Although the electric field intensity at the bottom of the trench can be raised, the entire electric field distribution cannot be leveled, and the effect of increasing BV cannot be maximized.

like figure 2 shown, is figure 1 The simulation diagram of the shown device and the corresponding electric field intensity distribution simulation curve; curve 201 is the electric field intensity distribution curve along the dotted line AA, and curve 202 is the electric field intensity distribution curve along the dotted line BB, as can be seen, the electric field intensity at the dotted line AA place is higher Large, at the bottom of the trench 103, there will be a peak electric field intensity as shown by the dotted circle 203, but the electric field intensity in the area shown by the dotted circle 204 cannot be pulled up, so the effect of increasing BV cannot be maximized

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