Polysilicon Gate Segmentation for Residue-Free Trench Etching
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Solution Overview
Problem
The challenge in semiconductor manufacturing lies in completely removing or filling materials within high-aspect-ratio fins and the narrow trenches between them, due to their dense arrangement and small spacing, which complicates the removal of dummy polysilicon gates in replacement metal gate processes.
Innovation Solution
A method involving the formation of a preliminary structure with a substrate and fins, followed by a first polysilicon layer and an amorphous silicon layer, where the amorphous silicon layer is thermally transformed into a second polysilicon layer with a different crystal plane composition, facilitating easier removal of polysilicon layers using specific etchants like NH4OH, thereby avoiding residue issues.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If fins are disposed in high density with small spacing, then device integration is improved, but material removal from trenches becomes difficult
Solution Approach 1:
The patent divides the polysilicon gate material into two distinct segments: a first polysilicon layer and a second polysilicon layer. The first layer is designed to be easily removable, while the second layer remains. This segmentation allows selective removal of the first layer through trenches using etchants like NH4OH, solving the material removal difficulty while maintaining the integrated fin structure.
Solution Approach 2:
The patent applies different properties to different parts of the gate structure. The first polysilicon layer has specific crystal plane composition characteristics that make it susceptible to etching by NH4OH, while the second polysilicon layer has different properties that make it resistant to the same etchant. This local quality differentiation enables selective removal in the trench regions without affecting other areas.
2Reliability
If dummy polysilicon gate is formed for replacement metal gate process, then gate control efficiency is improved, but complete removal of dummy gate becomes difficult
Solution Approach 1:
The dummy polysilicon gate is segmented into two layers with different removal characteristics. The first polysilicon layer can be completely removed through the trenches using NH4OH etching, while the second layer remains to provide the necessary gate control function. This segmentation resolves the contradiction between complete removal and maintaining gate control.
Solution Approach 2:
The patent changes the crystal plane composition parameter of the polysilicon layers to create different etching responses. By controlling the crystal orientation and composition during formation, the first layer becomes highly susceptible to NH4OH etching while the second layer remains stable, enabling selective removal while preserving gate functionality.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
This method enables efficient removal of silicon material from trenches between fins and adjacent structural features, ensuring compatibility with existing manufacturing processes and minimizing residue, thus improving the semiconductor structure formation efficiency.
Implementation Method 1
the amorphous silicon layer is thermally transformed into a second polysilicon layer with a different crystal plane composition
Implementation Method 2
the amorphous silicon layer is thermally transformed into a second polysilicon layer
Implementation Method 3
facilitating easier removal of polysilicon layers using specific etchants like NH4OH
Data Source
AI summary
A method for forming a semiconductor structure includes the following steps. First, a preliminary structure is provided. The preliminary structure includes a substrate and a plurality of fins formed on the substrate. Then, a first polysilicon layer is formed on the substrate. The first polysilicon layer covers at least portions of the fins. An amorphous silicon layer is formed on the first polysilicon layer.