Formation method of double trench isolation structure

Abstract

The invention discloses a forming method of a double-trench isolation structure. The method comprises the following steps: providing a silicon substrate, burying silicon-on-insulator (SOI) of an insulating layer and a top silicon layer, and forming a liner layer, a hard mask layer and a first mask layer on the top silicon layer; etching the hard mask layer, the liner layer and a part of the top silicon layer at desired depths by using the patterned first mask layer as a mask, to form a first opening; removing the first mask layer, and forming a sacrificial layer on the hard mask layer and in the first opening; removing a part of the sacrificial layer to expose the hard mask layer; forming a patterned second mask layer on the hard mask layer and the sacrificial layer, etching the hard mask layer to expose the liner layer by using the patterned second mask layer as a mask, to form a second opening, in which the second opening region is partially overlapped with the first opening region; removing the second mask layer and the sacrificial layer; and etching the first and the second openings at the same time by using the hard mask layer as a mask, to form first and second trenches of desired depths, in which the buried insulating layer is exposed from the first trench and the top silicon layer is exposed from the second trench. The method avoids the problem that the buried insulating layer in the overlay region of the first and the second trenches is over-etched.

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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