MONOS Gate Insulation Protrusion Prevents Dielectric Breakdown
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Solution Overview
Problem
The end of the insulation film (ONO film) between the substrate and the gate electrode in MONOS memories is susceptible to dielectric breakdown due to electric field concentration, especially when it is retreated from the side surface of the gate electrode, leading to reliability issues in semiconductor devices.
Innovation Solution
A method for manufacturing semiconductor devices where a polysilicon film is processed to form a control gate electrode, and an offset spacer is formed to cover the side surface of the control gate electrode, using this spacer as a mask to process the insulation film, ensuring the ends of the ONO film protrude outwardly from the side surfaces of the control gate electrode, thereby preventing dielectric breakdown.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If the end of the insulation film is retreated from the side surface of the gate electrode, then the manufacturing process is simplified, but dielectric breakdown occurs due to electric field concentration
Solution Approach 1:
An offset spacer is formed on the side surface of the control gate electrode before processing the insulation film. This spacer serves as a preliminary protective structure that prevents the insulation film end from being retreated, thereby preventing dielectric breakdown while maintaining manufacturing feasibility.
Solution Approach 2:
The offset spacer acts as an intermediary element between the control gate electrode and the insulation film. It mediates the relationship by providing a physical barrier that prevents the insulation film from being over-etched, thus protecting against electric field concentration without complicating the manufacturing process.
2Reliability
If the insulation film end is aligned with the gate electrode side surface, then dielectric breakdown is prevented, but manufacturing precision requirements increase
Solution Approach 1:
The offset spacer serves as a mediator that eliminates the need for precise alignment between the insulation film and gate electrode. By providing a physical stop, it allows the insulation film to be processed with standard precision while still achieving the desired protective effect.
Solution Approach 2:
The offset spacer structure enables the insulation film processing to be self-regulating. The spacer's physical presence automatically prevents over-etching, making the process less dependent on precise positioning and more robust to manufacturing variations.
Data Source
AI summary
In a MONOS memory having an ONO film, dielectric breakdown and a short circuit are prevented from occurring between the end of the lower surface of a control gate electrode over the ONO film and a semiconductor substrate under the ONO film. When a polysilicon film formed over the ONO film ON is processed to form the control gate electrode, the ONO film is not processed. Subsequently, a second offset spacer covering the side surface of the control gate electrode is formed. Then, using the second offset spacer as a mask, the ONO film is processed. This results in a shape in which in the gate length direction of the control gate electrode, the ends of the ONO film protrude outwardly from the side surfaces of the control gate electrode, respectively.