Voltage-Setting Transistor Peak Voltage Reduction via Capacitive Coupling
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Solution Overview
Problem
In memory devices, particularly in NAND string configurations, the high peak voltages required for voltage-setting transistors lead to increased size and power consumption, and the threshold voltage of these transistors varies based on their operating point, complicating the programming and sensing operations.
Innovation Solution
The approach involves reducing the peak voltage driven by the voltage-setting transistor through an initial level and subsequent coupling by a capacitor connected to its control gate, with the amount of coupling varying based on the assigned data state of the memory cell, allowing for more accurate voltage setting at the source and drain terminals.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Power
If high peak voltages are used for voltage-setting transistors, then the transistors can provide sufficient drive capability for programming operations, but the device size and power consumption increase
Solution Approach 1:
The patent applies preliminary action by pre-charging the control gate of the voltage-setting transistor to an initial voltage level before the actual programming operation. This pre-charging phase prepares the transistor to operate at lower peak voltages during the main programming pulse, thereby reducing power consumption while maintaining sufficient drive capability. The initial voltage is set based on the assigned data state, optimizing the transistor's operating point in advance.
Solution Approach 2:
The patent changes the voltage parameter dynamically by adjusting the initial control gate voltage based on the assigned data state (e.g., S0-S7 states). Different initial voltages are applied depending on which data state the memory cell is being programmed to, allowing the voltage-setting transistor to operate more efficiently across different programming conditions. This parameter adjustment reduces the peak voltage swing required during programming.
2Adaptability or versatility
If the threshold voltage of voltage-setting transistors is allowed to vary based on operating point, then the transistors can adapt to different programming conditions, but the programming and sensing operations become more complex
Solution Approach 1:
The patent systematically changes the control gate voltage parameter based on the assigned data state to compensate for threshold voltage variations. By establishing specific initial voltage levels for different data states (S0-S7), the method creates a predictable relationship between the control gate voltage and the resulting source/drain terminal voltages. This structured parameter change approach maintains adaptability while reducing operational complexity through standardized voltage levels.
Solution Approach 2:
The patent implements feedback by using the assigned data state information to determine the appropriate initial control gate voltage. The system receives feedback about which data state is being programmed and adjusts the voltage-setting transistor's operating point accordingly. This feedback mechanism allows the system to adapt to different programming conditions automatically without requiring complex manual intervention or additional circuitry.
3Manufacturing precision
If accurate voltage setting at source and drain terminals is achieved, then programming precision is improved, but the circuit complexity increases due to additional control mechanisms
Solution Approach 1:
The patent introduces the control gate of the voltage-setting transistor as an intermediary element that mediates between the programming control logic and the source/drain terminals. By controlling the gate voltage, the system indirectly and precisely controls the source and drain voltages without requiring direct voltage control circuits at each terminal. This intermediary approach achieves accurate voltage setting while avoiding the complexity of multiple independent control circuits.
Solution Approach 2:
The patent replaces direct mechanical/electrical voltage control mechanisms with field-effect control through the voltage-setting transistor. Instead of using complex voltage divider networks or multiple voltage sources to set precise voltages at source and drain terminals, the system uses the transistor's electric field control capability. The gate voltage controls the channel conductivity, which in turn controls the voltage distribution, achieving precise voltage setting through field effect rather than direct electrical connection.
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 method reduces the peak voltage requirements, lowers power consumption, and compensates for the body effect of the voltage-setting transistor, enabling more precise control over programming and sensing operations while minimizing size and power costs.
Implementation Method 1
a capacitor control circuit configured to increase the voltage of the control gate to an elevated level above the initial level by increasing a voltage of another terminal of the capacitor
Data Source
AI summary
The peak voltage at which a voltage-setting transistor is driven is reduced while the body effect of the transistor is also compensated. The voltage-setting transistor is driven at an initial level and then coupled higher by a capacitor which is connected to the control gate of the voltage-setting transistor. The amount of coupling can vary as a function of an assigned data state of a memory cell connected to the transistor by a source line and/or bit line. The capacitor may have a body which is common to a set of memory cells. The voltage can be set prior to applying a program voltage to the control gate of a memory cell to control a programming speed of the memory cell based on its assigned data state. The voltage can also be set in connection with a sensing operation.