Split-Gate Nonvolatile Memory Gate Insulating Film Protection
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Solution Overview
Problem
In the manufacturing of split-gate type nonvolatile memory devices, the thin gate insulating film between control gate electrodes is prone to damage during etching, leading to substrate penetration and reliability issues due to its thinness and vulnerability during the removal of control gate polysilicon.
Innovation Solution
A protective film, such as an organic film or silicon nitride film, is formed over the gate insulating film between control gate electrodes to prevent damage during the etching process, ensuring reliable removal of unnecessary control gate electrodes and protecting the gate insulating film.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If a thin gate insulating film is used for the control gate MOS to enable high-speed and low-power-consumption reading, then reading performance is improved, but the gate insulating film becomes damaged during etching and substrate penetration occurs
Solution Approach 1:
A protective film is formed on the gate insulating film before the etching process to prevent damage during subsequent processing steps. This preliminary protective action allows the thin gate insulating film to be used for high-speed reading without risking damage during manufacturing
Solution Approach 2:
An organic protective film is introduced as an intermediary layer between the gate insulating film and the etching environment. This mediator protects the thin gate insulating film from direct exposure to harmful etching conditions while allowing the desired thin film structure to be maintained for high-speed operation
2Ease of manufacture
If chemical dry etching is used to remove control gate polysilicon, then polysilicon removal is effective, but the gate insulating film disappears simultaneously and substrate penetration occurs
Solution Approach 1:
The organic protective film serves as a mediator that selectively protects the gate insulating film during chemical dry etching of the control gate polysilicon. This intermediary layer prevents the etchant from attacking the gate insulating film while allowing complete removal of the polysilicon layer
Solution Approach 2:
The protective film provides localized protection specifically to the gate insulating film regions that are vulnerable during etching, while allowing the etching process to proceed effectively on the polysilicon. This selective local protection enables differential treatment of different materials in the structure
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 enhances the reliability and manufacturing yield of split-gate type nonvolatile memory devices by preventing substrate penetration and maintaining the integrity of the gate insulating film, thereby improving performance and reducing defects.
Implementation Method 1
a protective film is formed to cover a gate insulating film exposed between the control gate electrodes before unnecessary control gate electrodes are removed
Implementation Method 2
there is a possibility that substrate penetration occurs at the time of CG polysilicon removal on the source side by chemical dry etching
Data Source
AI summary
A method of manufacturing a split-gate type nonvolatile memory improving reliability and manufacturing yield. In a method of manufacturing a split-gate type nonvolatile memory in which a memory gate electrode is formed prior to a control gate electrode, a protective film is formed to cover the gate insulating film exposed between control gate electrodes before unnecessary control gate electrodes are removed.