Nonvolatile Memory Cell Backgate Potential Control
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Solution Overview
Problem
Conventional nonvolatile semiconductor storage devices experience miswriting issues in nonselected memory cells due to unnecessary potential differences generated during programming operations.
Innovation Solution
The memory control circuit sets the backgate and source of the memory cell to the same potential during programming operations, eliminating the potential difference between them and preventing miswriting in nonselected memory cells.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional programming operation is used with potential difference between backgate and source, then programming speed is improved, but miswriting in nonselected memory cells occurs
Solution Approach 1:
The patent applies equipotentiality by setting the backgate and source to the same potential during programming operations. This eliminates the potential difference that causes miswriting in nonselected memory cells, while the control circuit manages the equipotential condition to prevent programming disturbances.
2Reliability
If backgate and source are set to same potential, then miswriting prevention is improved, but manufacturing complexity increases due to additional mask layers
Solution Approach 1:
The patent merges the backgate potential control with the source potential control by setting them to the same potential level. This combining of potential references simplifies the manufacturing process by reducing the need for separate potential control structures and minimizing additional mask layers.
3Manufacturing precision
If conventional potential difference is maintained, then device structure is simpler, but programming precision deteriorates due to miswriting
Solution Approach 1:
The patent changes the potential parameter relationship between backgate and source from having a potential difference to being at the same potential. This parameter change eliminates programming precision issues caused by miswriting, while the control circuit manages the new potential configuration.
Data Source
AI summary
A nonvolatile semiconductor storage device has floating-gate memory cells and a memory control circuit which controls them. During programming operation of the memory cells, the memory control circuit makes the potentials at the backgate and source of the memory cells equal. For example, during programming operation of the memory cells, the memory control circuit short-circuits together the backgate and source of the memory cells. For another example, during programming operation of the memory cells, the memory control circuit switches from a state where the potentials at the backgate and source of the memory cells are equal to a floating state.