Slit Etching in Silicon Substrates Using Carbon-Free Mask
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Solution Overview
Problem
The etching process for forming slits in silicon substrates often damages silicon oxide in shallow trench isolation (STI) structures, affecting the performance and reliability of semiconductor devices.
Innovation Solution
A process involving an etching gas composition of Cl2, CF4, and CHF3 with specific molar ratios is used, where a mask layer without carbon, such as TEOS or silicon nitride, is formed to expose the substrate, allowing for slit formation with high etching selectivity that simultaneously removes the mask layer and prevents damage to silicon oxide in STI structures.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If conventional etching process is used to form slits in substrate, then slits can be formed between STI structures, but silicon oxide in STI structures is exposed and damaged by the etching process
Solution Approach 1:
A mask layer is formed on the substrate before the etching process to define the slit pattern. The mask layer is positioned to expose only the substrate regions where slits need to be formed, while protecting the STI structures from etching damage
Solution Approach 2:
The etching gas composition is optimized with specific molar ratios (CF4 to CHF3 ratio of 0.5-0.8, F to Cl ratio of 0.4-0.8) to achieve high etching selectivity between the mask layer and substrate, enabling precise slit formation while minimizing damage to silicon oxide in STI structures
2Manufacturing precision
If additional step of removing mask layer is added, then mask layer can be completely removed after slit formation, but process complexity and time increase
Solution Approach 1:
The etching process is designed to simultaneously perform two functions: forming slits in the substrate and removing the mask layer. The etching gas composition and parameters are optimized to etch both the substrate and mask layer at appropriate rates, eliminating the need for a separate mask removal step
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 process enhances the performance and reliability of semiconductor devices by preventing silicon oxide damage during slit etching, reducing the number of process steps, and maintaining high etching selectivity, resulting in improved device performance and reduced costs.
Implementation Method 1
An etching process is performed to the substrate by using the mask layer as a mask, so as to form a slit in the substrate. The etching gas includes Cl2, CF4 and CHF3
Implementation Method 2
The etching gas includes Cl2, CF4 and CHF3, a molar ratio of CF4 to CHF3 is about 0.5-0.8, and a molar ratio of F to Cl is about 0.4-0.8
Data Source
AI summary
A process of forming a slit in a substrate is provided. A mask layer is formed on a substrate, wherein the mask layer does not include carbon. An etching process is performed to be substrate by using the mask layer as a mask, so as to form a slit in the substrate. The etching gas includes Cl2, CF4 and CHF3, a molar ratio of CF4 to CHF3 is about 0.5-0.8, and a molar ratio of F to Cl is about 0.4-0.8, for example. Further, the step of performing the etching process simultaneously removes the mask layer.