Etch Stop Film for Floating Gate Device Etching
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Solution Overview
Problem
Poor etch selectivity between etchants and inter-gate dielectric in floating-gate devices leads to poor etch profiles, microloading effects, and non-uniformity across multiple structures, affecting the fabrication of semiconductor devices.
Innovation Solution
Incorporating an etch-stop film, such as aluminum oxide, between the floating-gate structure and the inter-gate dielectric, which serves as an etch barrier, providing improved resistance to etching and enhancing etch uniformity by preventing the removal of the floating-gate structure during control gate material etching.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If etchant is used to remove control gate material, then control gate material is removed, but floating-gate structure is also partially removed due to poor etch selectivity
Solution Approach 1:
An etch-stop film is introduced as an intermediary layer between the floating-gate structure and the inter-gate dielectric. This film has high etch selectivity compared to the control gate material, allowing the etchant to remove the control gate material while stopping at the etch-stop film, preventing further etching of the floating-gate structure.
Solution Approach 2:
The etch-stop film changes the etching parameters by providing a distinct etch selectivity boundary. By selecting a material with appropriate etch resistance properties, the process window is expanded, enabling selective removal of control gate material while preserving the floating-gate structure.
2Productivity
If etchant is used to remove control gate material, then control gate material is removed, but etch uniformity deteriorates due to microloading effects
Solution Approach 1:
The etch-stop film acts as a uniform intermediary layer that provides consistent etch resistance across all structures. This uniformity compensates for microloading effects, ensuring that etching proceeds at a uniform rate across different feature sizes and densities.
3Length of moving object
If inter-gate dielectric is made thinner to reduce device size, then device dimensions are reduced, but etch selectivity becomes insufficient
Solution Approach 1:
The dielectric structure is segmented into multiple functional layers: the inter-gate dielectric for electrical isolation and the etch-stop film for process control. This segmentation allows each layer to be optimized independently - the inter-gate dielectric can be made thin for device scaling while the etch-stop film provides the necessary etch selectivity.
Solution Approach 2:
The etch-stop film serves as an intermediary layer that decouples the requirements for thin inter-gate dielectric from the requirements for high etch selectivity. It provides the etch barrier function without requiring the inter-gate dielectric to be thick.
Data Source
AI summary
Etch stop structures for floating gate devices are generally described. In one example, a floating gate device includes a semiconductor substrate having a surface on which one or more floating gate devices are formed, a tunnel dielectric coupled with the surface of the semiconductor substrate, a floating gate structure coupled with the tunnel dielectric, the floating gate structure having a first surface, a second surface, and a third surface, wherein the third surface is substantially parallel with the surface of the semiconductor substrate and wherein the first surface is substantially parallel with the second surface and substantially perpendicular with the third surface, an etch stop film coupled with the third surface of the floating gate structure, and an inter-gate dielectric coupled with the first surface and the second surface of the floating gate structure wherein the inter-gate dielectric comprises a material that is less resistant to an etchant that removes material of a control gate structure than the etch stop film.