Method for forming 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 film layer; 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, on the hard mask layer and the first Form the first mask layer in the second opening, use the first mask layer as a mask, etch the hard mask layer, liner layer and part of the top layer silicon to a set depth to form the second opening, the first opening area Partially overlapping with the second opening area; removing the first mask layer; continuing to etch the top layer silicon exposed by the first opening to the buried insulating layer to form a first trench, and the second opening is also etched simultaneously, The liner layer and the top layer of silicon are exposed to 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 after the formation of the first trench and the second trench.

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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