Memory Device Programming with Stepwise Program-Allow Voltage Control
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Solution Overview
Problem
As the bit number of data stored in a memory cell increases, the distance between threshold voltages of memory cells storing different data narrows, leading to reduced reliability in memory devices.
Innovation Solution
A memory device with a control circuit that controls a voltage generator and page buffer group to apply program allow voltages stepwise based on the number of program loops, and uses different program allow voltages for selected and unselected memory cells to manage threshold voltage distribution.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If the bit number of data stored in a memory cell increases, then the storage capacity is improved, but the distance between threshold voltages of memory cells storing different data narrows, leading to reduced reliability
Solution Approach 1:
The patent applies dynamics by making the program allow voltage adjustable and variable across different program loops. The voltage level is dynamically changed based on the number of program loops performed, allowing the system to adapt to the narrowing threshold voltage distance in multi-bit memory cells while maintaining reliable programming operations
Solution Approach 2:
The patent changes the voltage parameter (program allow voltage) as a function of program loop count. By increasing the program allow voltage in subsequent program loops, the system compensates for the reduced threshold voltage separation in high-capacity memory cells, thereby maintaining programming reliability while achieving high storage capacity
2Device complexity
If a fixed program allow voltage is applied to all selected bit lines, then the device complexity is reduced, but the threshold voltage distribution cannot be effectively managed, leading to reduced reliability
Solution Approach 1:
The patent implements a dynamic voltage control scheme where the program allow voltage is adjusted based on program loop count. This dynamic approach effectively manages threshold voltage distribution without requiring complex per-cell voltage control, achieving reliability improvement with moderate complexity increase
Solution Approach 2:
The patent segments the programming process into multiple program loops with different voltage levels. By dividing the programming operation into stages and applying different program allow voltages to different loops, the system effectively manages threshold voltage distribution while maintaining reasonable device complexity
Data Source
AI summary
A memory device, and an operating method of the memory device, includes a plurality of memory cells connected between word lines and bit lines and a voltage generator for generating a program voltage or a pass voltage, which is applied to the word lines. The memory device also includes a page buffer group for applying program allow voltages or a program inhibit voltage to the bit lines and a control circuit for controlling the voltage generator and the page buffer group in response to a command. In a program operation of selected memory cells connected to a selected word line among the word lines, the control circuit controls the page buffer group such that the program allow voltages are increased stepwise according to a number of program loops performed on the selected memory cells.