Semiconductor Device Back-Tunneling Data Retention
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Solution Overview
Problem
Nonvolatile memory devices face data loss during programming operations due to holes in storage nodes, which affects data retention.
Innovation Solution
A semiconductor device and method that perform an erase operation followed by a back-tunneling operation using negative voltage and a program operation using positive voltage on selected memory cells, improving data retention by bi-directional programming.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a program operation is performed after an erase operation, then data can be written to memory cells, but holes exist in the storage node causing programmed data to be damaged or lost
Solution Approach 1:
The patent applies preliminary action by performing a back-tunneling operation before the program operation. This preliminary step fills holes in the storage node with electrons from the gate electrode, preparing the storage node to receive programmed data without damage. The back-tunneling operation is performed at a lower voltage level to safely fill holes before the main programming operation occurs.
Solution Approach 2:
The patent ensures continuity of useful action by seamlessly integrating the back-tunneling operation into the programming sequence. The back-tunneling operation continues the electron injection process from the gate electrode, maintaining the useful action of filling the storage node with electrons. This continuous action ensures that holes are filled before programming, preventing data loss while maintaining efficient operation.
2Reliability
If conventional program operation is used, then programming is simple, but data retention characteristics are poor due to holes in storage nodes
Solution Approach 1:
The patent applies segmentation by dividing the programming operation into two distinct steps: a back-tunneling operation to fill holes in the storage node, and a program operation to write data. This segmentation allows each operation to be optimized independently, with the back-tunneling operation focusing on hole filling at lower voltage and the program operation focusing on data writing. This segmentation improves data retention while managing complexity through structured operation sequences.
Solution Approach 2:
The patent utilizes parameter changes by varying the voltage level applied during different operations. The back-tunneling operation uses a lower voltage level to safely fill holes in the storage node, while the program operation uses a higher voltage level for effective data writing. This parameter change strategy allows the same physical structure to perform multiple functions with optimized parameters, improving data retention without excessive complexity increase.
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
Enhances data retention characteristics by effectively managing electron injection and hole removal in storage nodes, improving the threshold voltage distribution and reducing data loss during programming.
Implementation Method 1
performing a back-tunneling operation by injecting electrons into a storage node from a gate electrode of a memory cell selected among the plurality of memory cells
Implementation Method 2
performing a program operation by injecting electrons into the storage node from a channel layer of the selected memory cell
Data Source
AI summary
A method of operating the semiconductor device includes performing an erase operation on a plurality of memory cells, performing a back-tunneling operation by injecting electrons into a storage node from a gate electrode of a memory cell, selected among the plurality of memory cells, and performing a program operation by injecting electrons into the storage node from a channel layer of the selected memory cell.