Flash Memory Trench Structure for Program Disturbance
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Solution Overview
Problem
Flash memory devices experience program disturbance phenomena due to the injection of hot carriers into program-inhibited cells during programming operations, causing unintended changes in threshold voltage and potential malfunctions.
Innovation Solution
Forming trenches in junction regions between word lines and select lines on a semiconductor substrate to minimize hot carrier injection, with the trenches being shallower than the junction regions and potentially forming concave shapes to reduce electric field and carrier movement.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If programming operation is performed on selected memory cells, then data storage capability is improved, but program disturbance occurs in program-inhibited cells due to hot carrier injection
Solution Approach 1:
A charge blocking layer is introduced as an intermediary between the channel region and the floating gate of program-inhibited cells. This layer blocks hot carriers generated during programming operations from being injected into the floating gate, thereby preventing program disturbance while allowing normal programming of selected cells.
Solution Approach 2:
The charge blocking layer is selectively formed only in regions corresponding to program-inhibited cells, where it blocks hot carrier injection. In regions of selected cells to be programmed, the layer is not formed or is removed, allowing normal programming operation. This localized application resolves the contradiction by differentiating treatment between different cell regions.
2Ease of manufacture
If conventional programming operation is performed without additional structures, then manufacturing simplicity is maintained, but threshold voltage changes occur in program-inhibited cells
Solution Approach 1:
The invention modifies the electrical parameters of program-inhibited cells by introducing a charge blocking layer that changes the charge distribution characteristics. This layer prevents unwanted charge accumulation in the floating gate during programming, thereby maintaining precise threshold voltage control without complicating the overall manufacturing process significantly.
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
Prevents program disturbance by reducing hot carrier injection into program-inhibited cells, thereby maintaining the integrity of threshold voltage and preventing malfunctions during programming operations.
Implementation Method 1
program disturbance phenomena due to the injection of hot carriers into program-inhibited cells during programming operations
Data Source
AI summary
The present invention relates to a flash memory device and a fabrication method thereof. A trench may be formed within a junction region between word lines by etching a semiconductor substrate between not only a word line and a select line, but also between adjacent word lines. Accordingly, the occurrence of a program disturbance phenomenon can be prevented as the injection of hot carriers into a program-inhibited cell is minimized in a program operation.