Nonvolatile Memory Fabrication via Conductive Layer Annealing
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Solution Overview
Problem
Current methods for fabricating nonvolatile memory devices face challenges in ensuring reliable contact between floating gates and control gates due to voids formed in the control gate structure, which can lower the reliability of the semiconductor device.
Innovation Solution
A method involving the formation of a conductive layer on a gate insulating film with voids, followed by annealing to allow the conductive layer to flow and fill gaps between floating gates and isolation films, thereby eliminating voids and enhancing the contact between control and floating gates.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a conductive layer is formed on the gate insulating film, then the control gate structure is created, but voids form in the control gate reducing reliability
Solution Approach 1:
The patent applies preliminary action by forming a mandrel structure before the control gate, which serves as a template to guide the conductive layer formation. The mandrel is removed after the control gate is formed, leaving a void-free structure. This preliminary structure enables subsequent layers to be formed without voids, directly resolving the reliability issue.
Solution Approach 2:
The mandrel acts as an intermediary element during the fabrication process. It is temporarily present to ensure proper conductive layer formation, then removed. This intermediary structure prevents direct void formation in the control gate while maintaining the necessary contact between floating gate and control gate.
2Reliability
If the gate insulating film extends over the isolation film, then the control gate structure is formed, but gaps and voids are created reducing device performance
Solution Approach 1:
The mandrel structure is formed in advance to define the precise geometry of the control gate. This preliminary action ensures that the conductive layer conforms to the desired shape without gaps or voids, simplifying the final structure while maintaining high reliability.
Solution Approach 2:
The patent changes the physical state and properties of materials during the fabrication process. The mandrel material is selected to be removable after serving its purpose, and the conductive layer properties are adjusted during deposition to ensure complete coverage without voids, thereby simplifying the final structure.
3Manufacturing precision
If conventional fabrication methods are used, then the manufacturing process is simple, but voids form in the control gate lowering reliability
Solution Approach 1:
By introducing the mandrel as a preliminary structure, the patent achieves high manufacturing precision in the control gate. Although this adds steps to the fabrication process, the mandrel-based approach provides a template that simplifies subsequent layer formation, ultimately making the complex precision requirement more manageable.
Solution Approach 2:
The mandrel serves as an intermediary that bridges the gap between simple fabrication processes and high precision requirements. It provides a physical template that guides material deposition, ensuring void-free structures without requiring extremely complex fabrication techniques.
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 prevents the formation of voids in the control gate, improving the reliability and performance of nonvolatile memory devices by ensuring consistent and effective data storage and retrieval.
Implementation Method 1
annealing the conductive layer to such an extent that part of the conductive layer flows from the level of an upper portion of the floating gate down to the level of a lower portion of the floating gate over an upper portion of the isolation film
Implementation Method 2
annealing the conductive layer to such an extent that the conductive layer flows enough to eliminate the voids
Data Source
AI summary
A method of fabricating a nonvolatile memory device includes providing an intermediate structure in which a floating gate and an isolation film are disposed adjacent to each other on a semiconductor substrate and a gate insulating film is disposed on the floating gate and the isolation film, forming a conductive film on the gate insulating film, and annealing the conductive film so that part of the conductive film on an upper portion of the floating gate flows down onto a lower portion of the floating gate and an upper portion of the isolation film.