Floating Gate Tip Control via Selective Etching Masks
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Solution Overview
Problem
The existing method of manufacturing non-volatile memory with a floating gate structure struggles to suppress variation in the width of the tip portion opposed to the control gate, leading to degraded characteristics due to the difficulty in distinguishing the etching rates between the first spacer and the gate oxide film, resulting in deviations in the shape of the gate oxide film.
Innovation Solution
A method involving the use of a spacer insulating film, a first insulating film, and a second insulating film as masks to selectively remove the second insulating film, allowing for the exposure of the tip portion of the floating gate, thereby increasing the difference in etching rates and preventing lateral removal of the gate oxide film.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If the first spacer and gate oxide film are made of the same material to simplify manufacturing, then manufacturing complexity is reduced, but the etching rate difference between the first spacer and gate oxide film decreases, making it difficult to reliably remove all of the first spacer without laterally removing the gate oxide film
Solution Approach 1:
The insulating layer is divided into multiple distinct layers: a first insulating layer (spacer insulating film) and a second insulating layer (gate oxide film). These layers are formed with different materials having different etching rates, allowing selective removal of the first insulating layer while preserving the second insulating layer. This segmentation resolves the contradiction by enabling both manufacturing feasibility and etching selectivity through layered structure.
Solution Approach 2:
Different regions of the insulating layer are assigned different materials with different etching characteristics. The first insulating layer uses a material with higher etching rate (e.g., silicon nitride) while the second insulating layer uses a material with lower etching rate (e.g., silicon oxide). This local differentiation of material properties enables selective etching to expose the floating gate tip portion without lateral removal of the gate oxide film.
2Manufacturing precision
If all of the first spacer is removed to suppress variation in tip portion width, then manufacturing precision of tip portion width is improved, but the gate oxide film shape deviates from design due to lateral removal
Solution Approach 1:
A second insulating layer is formed in advance on the first insulating layer before the etching process. This preliminary action creates a protective barrier that prevents lateral etching of the gate oxide film during subsequent processing. The second insulating layer is strategically positioned to cover the gate oxide film while allowing access to the floating gate tip portion, thus enabling complete removal of the first spacer without compromising the gate oxide film shape.
Solution Approach 2:
The second insulating layer acts as an intermediary protective layer between the etching process and the gate oxide film. It mediates the etching process by being selectively removed in specific regions to expose the floating gate tip while protecting the gate oxide film from lateral removal. This intermediary layer enables precise control of tip portion width while maintaining gate oxide film integrity.
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 effectively suppresses variation in the width of the tip portion, maintaining the designed shape of the gate oxide film and improving the characteristics of the non-volatile memory without degrading its performance.
Implementation Method 1
a part of the conductive layer for the floating gate is removed by using a spacer insulating film, a first insulating film, and a second insulating film as a mask; the tip portion of the floating gate is further exposed by selectively removing the second insulating film among the second insulating film, the insulating layer for the gate insulating film, and the spacer insulating film
Data Source
AI summary
A semiconductor device having good characteristics without variation and a method of manufacturing the same are provided. A part of a conductive layer for a floating gate is removed by using a spacer insulating film, a first insulating film, and a second insulating film as a mask. A floating gate having a tip portion is formed from the conductive layer for the floating gate, and a part of an insulating layer for a gate insulating film is exposed from the floating gate. The tip portion of the floating gate is further exposed by selectively removing the second insulating film among the second insulating film, the insulating layer for the gate insulating film, and the spacer insulating film.