Field oxide layer isolation structure of ldmos transistor and its preparation method

Abstract

The present invention provides a field oxide layer isolation structure of an LDMOS transistor and a preparation method thereof, the preparation method comprising: providing a semiconductor substrate; sequentially forming a first oxide layer and a second oxide layer on the semiconductor substrate; forming a patterned photoresist layer on the second oxide layer; and using the patterned photoresist layer as a mask, performing an etching process on the second oxide layer, and removing the patterned photoresist layer The photoresist layer is used to form the field oxide layer isolation structure of the LDMOS transistor. The present invention replaces the field oxide layer isolation structure of the existing ONO stack with a stacked field oxide isolation structure composed of the first oxide layer and the second oxide layer to reduce the electrical resistance of the field oxide layer isolation structure to the LDMOS transistor. The influence of characteristics. Further, a protective layer is formed on the second oxide layer to reduce damage to the isolation structure of the field oxide layer by a subsequent ion implantation process and cleaning process.

Description

technical field [0001] The invention relates to the field of semiconductor integrated circuit manufacturing, in particular to a field oxide layer isolation structure of an LDMOS transistor and a preparation method thereof. Background technique [0002] The BCD process is a process for fabricating a bipolar junction transistor (Bipolar Junction Transistor, BJT), a complementary metal oxide semiconductor (CMOS), and a diffused metal oxide semiconductor (DMOS) on the same chip. In the process of preparing LDMOS (Laterally Diffused Metal Oxide Semiconductor) transistors using BCD technology, field plates are usually used to reduce the electric field and increase the voltage, such as figure 1 As shown, the field plate is extended from the polycrystalline gate across the field oxide layer (Field Oxide, FOX, referred to as Field Oxygen). It is often necessary to use ONO (Oxide-Nitride-Oxide, oxide / nitride / oxide) stacked structure as the field oxide isolation structure of the LDMOS...

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Problems solved by technology

[0003] However, this structure leads to an adaptive shift in electrical characteristics such as detected drain current, drain voltage, etc., which affects the electrical characteristics of LDMOS transistors

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