Formation method of double trench isolation structure

Abstract

A method for forming a double trench isolation structure includes: providing silicon-on-insulator comprising substrate silicon, a buried insulating layer and a top layer of silicon, and sequentially forming a liner layer, a hard mask layer and a second mask layer on the top layer of silicon; Using the patterned second mask layer as a mask, etching the hard mask layer to expose the liner layer to form a second opening; removing the second mask layer, forming a second opening on the hard mask layer and in the second opening Sacrificial layer; removing part of the sacrificial layer to expose the hard mask layer; forming a patterned first mask layer on the hard mask layer and the sacrificial layer, etching the hard mask layer, pad layer and part of the top layer of silicon Forming the first opening to a set depth, the second opening area partially overlaps the first opening area; removing the sacrificial layer and the first mask layer; etching the first opening to expose the buried insulating layer to form a first trench, and etching The second opening and part of the top silicon form a second trench. The method avoids the defect that the buried insulating layer in the overlapping region of the first trench and the second trench is etched through.

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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