Nonvolatile Memory Notched Word Lines for Erase Efficiency
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Solution Overview
Problem
Current nonvolatile memory devices face challenges in efficiently performing read, program, and erasure operations due to complex gate structures and high voltage requirements, which complicate design and manufacturing processes.
Innovation Solution
A split-gate nonvolatile memory device is designed with a floating gate and a memory gate separated by tunnel insulating films, where the word line is positioned closer to the floating gate than the memory gate, allowing for equal voltages during read operations and optimized voltage configurations for program and erasure operations without a dedicated erasure gate, simplifying the structure and process.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a dedicated erasure gate is added to enable efficient erasure operations, then erasure performance is improved, but device complexity increases
Solution Approach 1:
The word line is designed to perform multiple functions: it serves as both the word line for read operations and as the erasure gate for erasure operations. By applying negative voltage to the word line, charges are tunneling extracted from the floating gate, enabling erasure without requiring a separate dedicated erasure gate structure.
Solution Approach 2:
The patent combines the erasure gate function with the existing word line structure. Instead of adding a separate erasure gate, the word line is configured to receive negative voltages that enable charge extraction, merging two functions (word line control and erasure) into a single structural element.
2Productivity
If the word line is positioned closer to the floating gate than the memory gate, then charge tunneling efficiency is improved, but manufacturing precision requirements increase
Solution Approach 1:
The patent creates an asymmetric gate structure where the word line is positioned closer to the floating gate than the memory gate is. This local asymmetry concentrates the electric field in the region between the word line and floating gate, enhancing charge tunneling efficiency during read and erasure operations without requiring extreme manufacturing precision across the entire device.
Solution Approach 2:
The gate structure employs asymmetric positioning where the word line distance to the floating gate is intentionally made smaller than the memory gate distance to the floating gate. This asymmetric configuration optimizes the electric field distribution for charge tunneling while maintaining manufacturability through standard fabrication tolerances.
3Device complexity
If equal voltages are applied to the word line and memory gate during read operations, then device complexity is reduced, but read voltage control becomes more challenging
Solution Approach 1:
The asymmetric gate structure enables the word line to function as both the word line for read operations and the erasure gate for erasure operations. This multi-functionality reduces the number of separate voltage control circuits needed, simplifying the overall device complexity while maintaining adequate read operation performance.
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 configuration enhances charge tunneling efficiency, reduces read voltage, improves breakdown voltage characteristics, and simplifies the manufacturing process by eliminating the need for an erasure gate, leading to improved performance and reduced complexity.
Implementation Method 1
a second tunnel insulating film is located therebetween... a negative voltage that is sufficient to cause tunneling of charge from the floating gate to the word line through the second tunnel insulating film
Data Source
AI summary
Nonvolatile memory devices can include a floating gate on a substrate, with a first tunnel insulating film therebetween. A memory gate can be on the floating gate, with a blocking insulating film therebetween. A word line can be located at a first side of both the memory gate and the floating gate, with a second tunnel insulating film therebetween. The first side of the floating gate can protrude beyond the first side of the memory gate toward the word line.