Method for double-grid oxide layer in BCD (Bipolar, COMS and DMOS) process

Abstract

The invention provides a method for a double-grid oxide layer in a BCD (Bipolar, COMS and DMOS) process. The method comprises the following steps of: providing a semiconductor substrate, wherein the semiconductor substrate comprises a high-voltage device region and a low-voltage device region which are parallel to each other; forming a barrier layer on the semiconductor substrate in the low-voltage device region; forming a grid oxide layer of a high-voltage device, wherein the grid oxide layer of the high-voltage device is covered on the surface of the semiconductor substrate in the high-voltage device region; removing the barrier layer and exposing the surface of the low-voltage device region; and forming a grid oxide layer of the low-voltage device, wherein the grid oxide layer is covered on the grid oxide layer of the high-voltage device and the surface of the semiconductor substrate in the low-voltage device region, and the thickness of the grid oxide layer of the low-voltage device is smaller than that of the grid oxide layer of the high-voltage device. According to the method, the problem of field isolation electric leakage caused by etching of a field isolation structure in a double-grid oxide layer forming process can be solved, and the performance of the entire device can be improved.

Description

technical field [0001] The invention relates to BCD semiconductor process technology, in particular to a method for forming double gate oxide layers in the BCD process. Background technique [0002] The BCD process is a monolithic integration process technology that can manufacture Bipolar, CMOS and DMOS devices on the same chip, referred to as the BCD process. Since the BCD process combines the respective advantages of the above three devices, the BCD process has received more and more attention. In the BCD process, high-voltage drive devices and their modules are widely used in PDP drive, LCD drive, OLED drive, motor drive and other fields, and are research hotspots in recent years. However, in the BCD process, it is often necessary to integrate high-voltage devices and low-voltage devices on the same substrate for production. The thickness of the gate oxide layer of high-voltage devices and low-voltage devices is very different, which is called a double gate oxide layer ...

AI Technical Summary

Problems solved by technology

[0004] However, in the above method, since the previously formed thick oxide layer covers all areas of the high-voltage device and the low-voltage device at the same time, when the thick oxide layer in the low-voltage device area is etched and removed next, it will inevitably affect the semiconductor substrate. Field oxide layer (LOCOS) or shallow trench isolation structure (STI) cause mis-etching. The reason is that the thick oxide layer hardly grows on LOCOS or STI during the thermal growth process, so when the thick oxide layer is etched During etching, LOCOS or STI will be etched together to reduce the height of LOCOS or STI

[0005] Etching of isolation structures such as LOCOS or STI will cause isolation leakage problems and seriously affect device performance

Images