Selective Etching of Silicon Nitride Using Plasma Pre-Treatment
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Solution Overview
Problem
Existing etching methods struggle to selectively etch regions made of different materials, such as silicon nitride and silicon oxide, without deposit formation during plasma etching, which can lead to inefficiencies and material damage.
Innovation Solution
A method involving modifying the substrate regions using hydrogen and oxygen plasmas to create distinct etching rates, allowing for selective etching with fluorine plasma while minimizing deposition, by forming first and second modified regions with different etching characteristics.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If plasma etching using hydrofluorocarbon gas is performed to selectively etch silicon nitride with respect to silicon oxide, then etching selectivity is improved, but deposit formation occurs on the substrate
Solution Approach 1:
The patent applies preliminary action by performing plasma treatment with oxygen or nitrogen-containing gas before the main etching process. This pre-treatment modifies the surface of the silicon oxide region, making it more resistant to subsequent fluorocarbon-based etching, thereby preventing deposit formation while maintaining etching selectivity.
Solution Approach 2:
The patent changes process parameters by using different gas compositions and plasma conditions in sequential steps. The first plasma treatment uses oxygen or nitrogen-containing gas at specific power and pressure conditions, followed by etching with fluorocarbon gas at different parameters, achieving both selectivity and deposit prevention.
2Device complexity
If conventional plasma etching is used to etch different material regions, then etching process is simple, but material damage occurs and selectivity is insufficient
Solution Approach 1:
The patent segments the etching process into multiple distinct steps: first plasma treatment with oxygen/nitrogen-containing gas, then main etching with fluorocarbon gas. Each step serves a specific function - the first step prepares surfaces with different resistance characteristics, while the second step performs selective removal, achieving high precision without excessive overall complexity.
Solution Approach 2:
The patent introduces an intermediary plasma treatment step that modifies the substrate surfaces before main etching. This intermediary step creates different surface states on silicon nitride and silicon oxide regions, enabling selective etching in the subsequent fluorocarbon plasma without direct material damage.
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 enables selective etching of silicon nitride with respect to silicon or germanium regions, achieving a selectivity ratio of 10:1 and preventing deposit formation, thus improving etching precision and reducing material damage.
Implementation Method 1
modifying at least a portion of the first region, which includes a surface of the first region, using hydrogen plasma, to form a first modified region
Implementation Method 2
modifying at least a portion of a second region, which includes a surface of the second region, using oxygen plasma, to form a second modified region
Implementation Method 3
selectively etching the first modified region with respect to the second modified region using fluorine plasma
Data Source
AI summary
An etching method selectively etches a first region of a substrate with respect to a second region of the substrate. At least a portion of the first region, which includes the surface of the first region, is modified by plasma to form a first modified region. At least a portion of the second region, which includes the surface of the second region, is modified by plasma to form a second modified region. The first modified region is selectively etched with respect to the second modified region by plasma.