Metal-Assisted Etching for Defect-Suppressed High-Aspect Trenches
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Solution Overview
Problem
The metal-assisted etching method for high aspect ratio trenches in semiconductor substrates often results in processing defects such as porous Si near the upper end of the side wall due to the diffusion of metal catalysts.
Innovation Solution
The method involves forming a first metal catalyst layer with a lower diffusion coefficient, followed by a second metal catalyst layer with a higher diffusion coefficient, and subsequent etching using these catalysts to suppress metal catalyst diffusion and prevent porous defects.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If metal-assisted etching is used to process high aspect ratio trenches, then etching capability is improved, but processing defects such as porous Si occur near the upper end of the side wall
Solution Approach 1:
The patent divides the metal catalyst layer into multiple segments with different properties. Specifically, it uses a first metal catalyst layer (e.g., Pt or Pd) and a second metal catalyst layer (e.g., Au) with different diffusion coefficients. The first layer suppresses diffusion at the upper end of the trench, while the second layer enables effective etching, thus segmenting the functions to resolve the contradiction between etching capability and defect prevention.
Solution Approach 2:
The patent applies different metal catalyst materials at different locations or layers to achieve local optimization. The first metal catalyst layer is positioned to specifically address the diffusion problem at the upper end region, while the second metal catalyst layer provides the necessary catalytic activity for etching. This local differentiation of material properties resolves the contradiction by tailoring catalyst characteristics to specific functional requirements.
2Manufacturing precision
If metal catalyst diffusion is suppressed to prevent porous defects, then manufacturing precision is improved, but etching efficiency may be reduced
Solution Approach 1:
The patent segments the catalyst function into two distinct layers: the first metal catalyst layer (Pt/Pd) that suppresses diffusion and prevents defects, and the second metal catalyst layer (Au) that maintains high etching efficiency. This segmentation allows each layer to optimize its specific function without compromising the other, resolving the contradiction between precision and productivity.
Solution Approach 2:
The patent creates a composite catalyst structure by combining different metal catalyst materials (e.g., Pt/Pd and Au) in a layered configuration. This composite structure integrates the low-diffusion properties of Pt/Pd with the high catalytic activity of Au, achieving both defect reduction and maintained etching efficiency simultaneously.
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 approach effectively suppresses the formation of porous regions near the upper end of the trench, enabling the high aspect ratio trench processing with reduced defects and increased productivity.
Implementation Method 1
The metal-assisted etching (MacEtch) method is, for example, an etching method using a noble metal or the like as a catalyst
Implementation Method 2
a processing defect such as porous Si occurs near an upper end portion of the side wall defining the trench
Data Source
AI summary
According to one embodiment, an etching method is provided. The etching method includes: forming a layer containing a first metal catalyst at a surface containing a semiconductor; first etching using the first metal catalyst; forming a layer containing a second metal catalyst having a larger diffusion coefficient than that of the first metal catalyst at the layer containing the first metal catalyst; and second etching using the second metal catalyst.