Word Line Boosting With Dynamic VPASS to Limit Program Disturb
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Solution Overview
Problem
Existing memory devices face issues with VPASS disturb during programming operations, where unselected word lines are unintentionally programmed due to high VPASS voltages, compromising channel boosting and leading to programming errors.
Innovation Solution
A dynamic application of different pass voltages (VPASS) is applied to various word lines within a memory block based on their location relative to the selected word line, using up to three distinct VPASS voltages to ensure adequate channel boosting while minimizing VPASS disturb.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a high VPASS voltage is applied to unselected word lines during programming, then channel boosting is adequate, but VPASS disturb occurs causing unintentional programming of unselected memory cells
Solution Approach 1:
The patent applies different VPASS voltage levels to different groups of unselected word lines based on their proximity to the selected word line. Word lines immediately adjacent to the selected word line receive a first VPASS voltage level, while other unselected word lines receive a second, lower VPASS voltage level. This local differentiation reduces VPASS disturb to unselected memory cells while maintaining adequate channel boosting for the selected word line.
Solution Approach 2:
The patent changes the VPASS voltage parameter from a single uniform level to multiple differentiated levels during programming operations. By dynamically adjusting VPASS voltage levels based on word line position relative to the selected word line, the system optimizes the balance between channel boosting and VPASS disturb prevention.
2Productivity
If a single VPASS voltage level is applied to all unselected word lines, then device complexity is low, but programming performance deteriorates due to either insufficient channel boosting or excessive VPASS disturb
Solution Approach 1:
The patent segments the set of unselected word lines into different groups based on their proximity to the selected word line. The first group includes word lines immediately adjacent to the selected word line, while the second group includes other unselected word lines. Each group receives a tailored VPASS voltage level, improving programming performance without excessive complexity.
Solution Approach 2:
The patent implements dynamic VPASS voltage control where the voltage levels applied to unselected word lines change based on the programming operation being performed. The system dynamically selects which VPASS voltage level to apply to which word line group, optimizing programming performance while managing complexity through systematic control.
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 reduces VPASS disturb and maintains effective programming by optimizing voltage application, thereby reducing programming errors and improving memory device performance.
Implementation Method 1
causing electrons to navigate into the charge trapping materials of the memory cells to be programmed and raise the threshold voltages
Implementation Method 2
the unselected word lines in the memory block receive a VPASS voltage. Generally, the VPASS voltage must be high enough to ensure adequate channel boosting but cannot be so high as to cause VPASS disturb
Data Source
AI summary
The memory device includes a memory block, which includes a plurality of memory cells arranged in a plurality of word lines. The memory device also includes control circuitry in communication with the memory block. The control circuitry is configured to perform a programming operation to program the memory cells of a selected word line of the plurality of word lines. During the programming operation, the control circuitry is configured to apply a programming pulse VPGM to a selected word line to the selected word line, apply a first pass voltage to a first set of word lines of the plurality of word lines, the first set of word lines being adjacent the selected word line, and apply a second pass voltage to a second set of word lines of the plurality of word. The first pass voltage is greater than the second pass voltage.