Semiconductor Feature Etching With Oxidation to Reduce Scalloping
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Solution Overview
Problem
Existing etching methods for creating through-vias and trenches in semiconductor applications result in sidewall thickness variation, leading to ineffective filling and reduced yield, and are impractical for high-volume manufacturing due to high costs associated with plasma etching and slow etch rates.
Innovation Solution
A three-step etching process involving a first etch process using a hard mask layer, an oxidation process to oxidize the sidewalls, and a second etch process using a different etching gas to reduce sidewall thickness variation, while maintaining a high overall etch rate, is employed to form features with reduced sidewall thickness variation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If existing etching methods are used to create through-vias and trenches, then the etching process can be performed, but large sidewall thickness variation (scalloping) occurs resulting in ineffective filling and reduced yield
Solution Approach 1:
The etching process is divided into multiple discrete steps (first etch process, oxidation process, second etch process) rather than using a single continuous etch. This segmentation allows each step to address specific aspects of sidewall formation, with the oxidation step specifically targeting sidewall smoothing to reduce scalloping.
Solution Approach 2:
The oxidation process is performed as a preliminary action between the two etching processes to modify the sidewall surface before the final etching step. This preliminary oxidation creates a smoother sidewall profile that prevents subsequent scalloping and ensures effective filling.
2Manufacturing precision
If plasma etching is performed with high precision requirements, then sidewall uniformity can be improved, but the cost increases and etch rate decreases making it impractical for high volume manufacturing
Solution Approach 1:
The etching process is divided into multiple discrete steps (first etch process, oxidation process, second etch process) rather than using a single continuous etch. This segmentation allows each step to address specific aspects of sidewall formation, with the oxidation step specifically targeting sidewall smoothing to reduce scalloping.
Solution Approach 2:
The process changes the chemical parameters by introducing oxidation gas between etching steps, transforming the sidewall surface chemistry to reduce scalloping. This parameter change enables achieving high precision sidewalls without requiring excessively slow plasma etching conditions throughout the entire process.
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
The method effectively reduces sidewall thickness variation, improving the robustness and fillability of features, thereby enhancing the yield and reliability of semiconductor devices while enabling faster and more cost-effective high-volume manufacturing.
Implementation Method 1
performing an oxidation process to oxidize a sidewall of the features by supplying an oxidation gas
Data Source
AI summary
Embodiments of the present disclosure relate to methods for patterning a material layer on a substrate. The method includes forming a hard mask layer on a material layer disposed on a substrate. The material layer includes a plurality of first layers and a plurality of second layers alternately formed over the substrate. The method further includes performing a first etch process to form features in the material layer through the hard mask layer by supplying a first etching gas; performing an oxidation process to oxidize a sidewall of the features by supplying an oxidation gas; and performing a second etch process to etch the sidewall of the features formed in the material layer by suppling a second etching gas.