DRAM Word Line Dynamic Timing via Intermediate Voltage
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Solution Overview
Problem
The frequent pull-down operation of word lines in semiconductor memory devices, such as DRAM, leads to increased data decay in neighboring lines, particularly when a word line is repeatedly accessed, known as a 'row hammer' effect, which affects data integrity.
Innovation Solution
Implementing a dynamic timing mechanism where a word line is driven to an intermediate voltage after access, remaining at this level until another word line within the same group is accessed, thereby reducing the frequency of returning to an inactive state and minimizing data decay.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a word line is frequently pulled down to an inactive state after access, then the memory system maintains proper voltage levels for subsequent operations, but data decay increases in neighboring word lines due to the row hammer effect
Solution Approach 1:
The patent introduces an intermediate voltage level (third voltage level) between the active high voltage and the inactive low voltage. When a word line is accessed, it is driven to the high voltage level, then after the access operation completes, it is driven to the intermediate voltage level instead of immediately returning to the low inactive level. This intermediate voltage state acts as a mediator that reduces the frequency of full pull-down operations to the inactive state, thereby minimizing the row hammer effect on neighboring word lines while still maintaining proper voltage levels for subsequent operations.
2Object-generated harmful factors
If a word line is driven to an intermediate voltage level after access, then the frequency of pull-down operations is reduced and data decay is minimized, but the device complexity increases due to additional voltage level control
Solution Approach 1:
The patent changes the voltage parameter of the word line from a binary state (active high or inactive low) to a ternary state by introducing an intermediate voltage level. The word line voltage is controlled to transition through three distinct levels: a first high voltage level during active access, a second intermediate voltage level after access completion, and a third low inactive voltage level for complete inactivation. This parameter change allows the system to reduce the frequency of transitions to the lowest inactive state, thereby reducing data decay in neighboring lines while managing the increased voltage control complexity through systematic state management.
Data Source
AI summary
Apparatuses, systems and methods for dynamic timing of row pull-down operations are described herein. When a word line is accessed, the row decoder may drive that word line to an active voltage, and then to an intermediate voltage. The row decoder may maintain that word line at the intermediate voltage until another word line in the same group of word lines as the accessed word line receives an access command, at which point the first word line is driven to an inactive voltage. For example, if the word lines are grouped by bank, then after an access to a first word line, the first word line may be maintained at the intermediate voltage until a second wordline in the same bank as the first word line is accessed. This may help to mitigate the effect on other nearby word lines of driving a word line to the inactive voltage.