Flash Memory Hot Carrier Injection Control Voltage
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Solution Overview
Problem
As the geometric dimensions of flash memory cells shrink, hot carrier injection programming methods often result in overshooting carriers that disturb adjacent cells, leading to unintended programming due to the reduced distance between cells.
Innovation Solution
A circuit and program scheme that applies a control voltage to adjacent cells based on their threshold voltage, which is less than the programming voltage, to mitigate disturbance during hot carrier injection programming, using a control circuitry that communicates with memory cells to manage bit line and word line voltages effectively.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If geometric dimension is shrunk to increase storage density, then storage capacity is improved, but hot carriers may pass the selected cell and enter neighboring cells causing disturbance
Solution Approach 1:
The patent applies different voltage levels to different cells locally. The selected cell receives a high programming voltage to induce hot carrier injection, while adjacent cells receive a lower control voltage that prevents hot carrier injection. This local differentiation of voltage conditions allows the selected cell to be programmed without disturbing adjacent cells, even when geometric dimensions are shrunk and cells are closely spaced.
Solution Approach 2:
The patent applies a control voltage to adjacent cells before and during the programming process to preemptively prevent hot carriers from entering those cells. By establishing this protective voltage condition in advance, the patent counteracts the potential harmful effect of hot carrier overshooting that becomes more likely when cell dimensions are reduced.
2Productivity
If programming voltage is applied to selected cell to achieve hot carrier injection, then programming speed is improved, but adjacent cells may be unintentionally programmed
Solution Approach 1:
The patent implements local quality control by applying a high programming voltage specifically to the selected cell's control gate while applying a lower control voltage to adjacent cells' control gates. This spatially differentiated voltage application ensures that hot carrier injection occurs only in the selected cell, maintaining both fast programming speed and high programming accuracy without unintentional programming of adjacent cells.
Solution Approach 2:
The patent uses the control gate voltage as an intermediary mechanism to control hot carrier injection. By carefully selecting and applying different voltage levels to different control gates, the patent mediates between the need for high programming voltage (for speed) and the need to prevent over-programming (for accuracy), allowing the programming process to proceed rapidly and reliably.
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 effectively reduces interference with adjacent cells during programming, ensuring precise control over hot carrier injection and minimizing disturbance, thereby enhancing the programming efficiency and accuracy of target cells in flash memory systems.
Implementation Method 1
A hot carrier injection is a mechanism adopted for programming a non-volatile memory. It is usually to elevate the lateral channel electric field to a high order, such as over 105 V/cm, to invoke a hot carrier injection.
Implementation Method 2
the control voltage is dependant on the threshold voltage of the control cell and the control voltage is less than the programming voltage
Data Source
AI summary
A non-volatile memory system includes a bit line and a plurality of memory cells associated with the bit line and coupled in a serial manner. The system further has a control circuitry in communication with the memory cells, wherein the control circuitry programs a target cell selected from the memory cells by applying a bit line voltage on the bit line in order to promote hot carrier injection into the target cell. The circuit also applies a programming voltage on the target cell under a hot carrier injection mechanism. Moreover, the circuit also applies a control voltage on a control cell, which is adjacent to the target cell when programming the target cell, wherein the control voltage is dependent on the threshold voltage of the control cell and the control voltage is less than the programming voltage.