Formation method of double trench isolation structure

Abstract

The invention discloses a dual-shallow trench isolation structure forming method, which comprises the following steps of: providing silicon on insulator (SOI) comprising substrate silicon, a buried insulating layer and top layer silicon, and sequentially forming a backing layer, hard mask layer and a first mask layer on the top layer silicon; etching the hard mask layer, the backing layer and a part of the top layer silicon to a set depth to form a first opening by taking a first mask layer pattern as a mask; removing the first mask layer, forming a second mask layer on the hard mask layer and in the first opening, and etching a part of the hard mask layer to expose the backing layer to form a second opening by taking a second mask layer pattern as the mask, wherein the area of the second opening is partially overlapped with the area of the first opening; removing the second mask layer; and continuously etching the top layer silicon exposed out of the first opening to the buried insulating layer to form a first trench, and simultaneously etching the second opening to expose the backing layer and the top layer silicon to form a second trench. By the method, the shortcoming that the buried insulating layer in the overlapped area of the first and second trenches is etched through after the first and second trenches are formed is overcome.

Description

technical field [0001] The invention relates to the technical field of semiconductor manufacturing, in particular to a method for forming a double trench isolation structure. Background technique [0002] Integrated circuits based on silicon-on-insulator (Silicon On Insulator, SOI) have the characteristics of low voltage, low power consumption, high speed, and high integration, and are the mainstream process for the development of semiconductor technology to the nanoscale. A bipolar transistor is a very important device unit in an analog integrated circuit. A bipolar transistor based on a silicon-on-insulator process needs to use a dual-trench isolation (Dual-STI) structure, which requires a special manufacturing method. For existing methods of forming double trench isolation structures, refer to the appended figure 1 , 1A, 1B to attached Figure 5 , 5A, 5B. [0003] refer to figure 1 , 1A, 1B, where, attached figure 1 is a top view of the semiconductor structure, Fig...

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Problems solved by technology

Since the etchant continues to etch the buried insulating layer 101 until the substrate silicon 100, the SOI device is etched through

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