Step Pass Voltage Control in Semiconductor Memory Word Lines
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Solution Overview
Problem
The challenge in semiconductor memory devices is the instability of program operations due to voltage coupling effects between memory cells, particularly when manufacturing processes narrow the gaps between memory cells, leading to voltage level changes in non-selected word lines.
Innovation Solution
The solution involves driving adjacent word lines in a semiconductor memory device using a step voltage during program operations. This method includes applying a first step pass voltage to non-selected word lines closest to the selected word line and a second step pass voltage to the next adjacent non-selected word lines, thereby stabilizing the program operation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If manufacturing processes narrow the gaps between memory cells to increase density, then storage capacity is improved, but voltage coupling effects between adjacent word lines increase causing program operation instability
Solution Approach 1:
The patent applies different voltage levels to different groups of non-selected word lines based on their distance from the selected word line. Specifically, first non-selected word lines adjacent to the selected word line receive a first voltage level, while second non-selected word lines further away receive a second voltage level. This localized differentiation compensates for the increased coupling effects caused by narrowed gaps between memory cells, thereby maintaining program operation stability while preserving high storage capacity.
2Device complexity
If a single pass voltage is applied to all non-selected word lines, then device complexity is reduced, but voltage overshoot in adjacent word lines causes program operation failure
Solution Approach 1:
The patent changes the voltage parameter applied to non-selected word lines based on their position relative to the selected word line. By applying a first voltage level to first non-selected word lines and a second voltage level to second non-selected word lines, the patent prevents voltage overshoot that would occur with a uniform pass voltage. This parameter differentiation ensures reliable program operation while managing device complexity through systematic voltage control.
3Reliability
If step voltages are applied to different non-selected word lines to prevent voltage overshoot, then program operation stability is improved, but device complexity increases
Solution Approach 1:
The patent segments the non-selected word lines into at least two groups: first non-selected word lines adjacent to the selected word line and second non-selected word lines further away. Each group is assigned a different voltage level during the program operation. This segmentation approach enables precise control of voltage overshoot in each region while keeping the control logic systematic and manageable, thus improving program operation stability without excessive complexity increase.
Data Source
AI summary
A semiconductor memory device may include a memory cell array circuit and a word line driving circuit. The memory cell array circuit may be connected with a plurality of word lines to store data in a program operation. The word line driving circuit may drive a selected word line among the word lines using a program voltage in the program operation. The word line driving circuit may drive each of non-selected word lines adjacent to the selected word line using a step pass voltage including at least two step voltages.