3D Memory Word Line Voltage Slope Control for Faster Reads
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Solution Overview
Problem
The limitation of maximum current consumption in read operations of three-dimensional memory devices hinders the increase in read voltage levels, leading to longer read times and potential hot carrier injection issues due to the increasing number of word lines.
Innovation Solution
A memory device that classifies word lines into edge and center groups, applying different voltage slope characteristics to optimize read performance by controlling the slope of word line voltages, thereby reducing peak current consumption and prepulse periods.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If the number of word lines is increased to improve integration density, then storage capacity is improved, but peak current consumption increases and read time becomes longer
Solution Approach 1:
The patent divides word lines into three distinct groups (first edge group, center group, and second edge group) and applies different voltage slope control strategies to each group. This segmentation allows the system to optimize read performance for each group independently, enabling faster read times while managing peak current consumption effectively across the entire memory array.
Solution Approach 2:
Different voltage slope characteristics are applied to different spatial regions of the memory array. Edge groups (first and second) receive voltage slopes optimized for their proximity to selection lines, while the center group receives slopes optimized for its position away from edges. This local quality approach ensures that each region operates at optimal performance characteristics.
2Productivity
If the read voltage level is increased to shorten read time, then read performance is improved, but peak current consumption exceeds maximum limits
Solution Approach 1:
The patent implements dynamic voltage slope control where the slope of voltage increase is adjusted based on the specific time period (prepulse, read, or program period) and the specific word line group. During prepulse periods, different slopes are applied to edge groups versus center groups, and during read periods, the slopes are further optimized. This dynamic adjustment allows the system to achieve fast read times while keeping peak current consumption within maximum limits.
Solution Approach 2:
The voltage slope parameter is changed based on operational conditions. The control logic generates slope control signals that adjust the voltage slope according to the current operational period and word line group. This parameter change strategy enables the system to optimize read performance by using steeper slopes when needed while maintaining current consumption within acceptable boundaries.
3Loss of time
If the voltage slope is increased to reduce prepulse period, then read performance is improved, but hot carrier injection increases
Solution Approach 1:
The patent segments word lines into edge groups and center groups, applying different voltage slopes to each during prepulse periods. Edge groups receive voltage slopes optimized for their proximity to selection lines, enabling faster channel formation with reduced hot carrier injection. Center groups receive gentler slopes that minimize hot carrier effects while still achieving adequate channel preparation. This segmentation allows the system to reduce prepulse periods effectively without excessive hot carrier injection.
Data Source
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AI summary
A memory device and an operating method thereof adjust a slope of a word line voltage. The memory device includes a memory cell array including a plurality of cell strings, a voltage generating circuit configured to generate a word line voltage provided to a plurality of word lines, and a control logic configured to output a slope control signal adjusting a voltage level variation characteristic of the word line voltage provided from the voltage generating circuit, wherein, during a prepulse period of a read operation of the memory device, a slope of a first word line voltage provided to an edge group including one or more word lines, the edge group adjacent to a string selection line is greater than a slope of a second word line voltage provided to a center group including one or more word lines in a center region.