Reserved Memory Cell Activation for Capacity Expansion
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Solution Overview
Problem
In memory systems, redundancy memory cells are often underutilized, leading to inefficiencies as reserved memory cells are not effectively utilized, resulting in wasted capacity and potential reliability issues due to defective normal memory cells.
Innovation Solution
A memory system with a memory device comprising a normal memory cell area and a redundancy memory cell area, including a replacement memory cell region and a reserved memory cell region, where a register generates signals to activate and assign addresses for reserved memory cells, allowing replacement memory cells to replace failed normal memory cells and reserved memory cells to be used without replacing any failed cells, thereby optimizing memory usage and addressing reliability concerns.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If redundancy memory cells are included in the memory device, then reliability is improved by replacing defective normal memory cells, but reserved memory cells remain underutilized leading to wasted capacity
Solution Approach 1:
The reserved memory cell region is designed to serve multiple functions: it can replace defective normal memory cells when needed, and simultaneously function as additional usable memory capacity when no defects occur. This multi-functional design resolves the contradiction by making the redundancy memory cells universally applicable to both reliability enhancement and capacity expansion.
Solution Approach 2:
The memory system dynamically activates or deactivates the reserved memory cell region based on the presence and location of defective normal memory cells. When defects are detected, the reserved region is activated to replace them; when no defects exist, the reserved region remains inactive or is used as additional capacity. This dynamic adaptability allows the system to optimize both reliability and effective capacity based on actual conditions.
2Reliability
If reserved memory cells are activated to replace defective normal memory cells, then reliability is improved, but the complexity of memory management increases due to address assignment and activation control
Solution Approach 1:
A register is introduced as an intermediary component to manage the activation and address assignment of the reserved memory cell region. The register stores control information that enables the memory controller to efficiently manage the reserved region without requiring complex management logic. This intermediary simplifies the overall system by providing a dedicated storage element for control data.
Solution Approach 2:
The reserved memory cell region is pre-configured with its own address space and control registers during manufacturing, allowing it to be activated and integrated into the memory system without requiring complex runtime management. The address assignment and activation control information are prepared in advance, reducing the complexity of real-time memory management operations.
3Reliability
If the memory device uses traditional redundancy management, then defective cells are replaced, but the reserved memory cells cannot be used to increase effective capacity leading to inefficiency
Solution Approach 1:
The reserved memory cell region is designed to serve dual purposes: compensating for defective normal memory cells and increasing effective memory capacity. This universal design allows the same hardware resources to fulfill both reliability and productivity goals, eliminating the inefficiency of unused reserved cells while maintaining defect compensation capabilities.
Solution Approach 2:
The system changes the operational parameters of the reserved memory cell region based on the presence of defects. When no defects are present, the reserved region is configured as usable memory capacity, increasing effective storage. When defects are detected, the parameters are changed to activate the reserved region for replacement purposes. This parameter-based control enables flexible optimization of both reliability and productivity.
Data Source
AI summary
A memory system includes a memory device and a controller. The memory device includes a memory cell array including a normal memory cell area and a redundancy memory cell area, the redundancy memory cell area having a replacement memory cell region and a reserved memory cell region; a register suitable for generating a first signal indicating existence of the reserved memory cell region; and a fuse unit suitable for activating the reserved memory cell region based on the first signal. The controller assigns an address for accessing a reserved memory cell of the reserved memory cell region based on the first signal. A replacement memory cell in the replacement memory cell region replaces a failed memory cell in the normal memory cell region, and the reserved memory cell in the reserved memory cell region remains without replacing any failed memory cell in the normal memory cell region.