Method for manufacturing field oxygen with gradient thickness in trench and method for manufacturing sgt device

Abstract

The invention discloses a method for manufacturing field oxygen with gradually changing thickness in a trench, comprising: step 1, forming a trench in a semiconductor substrate; step 2, adopting a thermal oxidation process to form field oxygen; step 3, depositing to form a second Dioxide layer; step 4, fill the trench completely with the third material layer; step 5, remove the third material layer on the surface of the second oxide layer outside the trench; step 6, use the third material layer as self-alignment The mask is used for wet etching of the oxide layer, utilizing the characteristic that the wet etching rate of the second oxide layer is greater than that of the field oxygen, and the field oxygen along the side of the second oxide layer during wet etching The etching will be accelerated, and after the wet etching is completed, the oxygen field will form a structure with a gradually increasing thickness from top to bottom; Step 7, removing the third material layer. The invention also discloses a manufacturing method of the SGT device.

Description

Method for manufacturing field oxygen with graded thickness in trench and method for manufacturing SGT device technical field The present invention relates to a kind of semiconductor integrated circuit manufacturing method, particularly relate to a kind of field of thickness gradient in trench Oxygen manufacturing method; the present invention also relates to a trench gate (Split Gate Trench, SGT) device with shielded gate Manufacturing method. Background technique SGT device such as SGT MOS device is the advanced device structure of common trench gate (Trench) MOS device, as shown in Figure 1 It 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] A trench 103 is formed in the N-type epitaxial layer 102. [0005] The gate structure is fo...

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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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