Non-volatile Memory Suspend-Resume Verify Logic
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Solution Overview
Problem
Non-volatile memory devices experience degradation in program threshold voltage distribution and reliability due to time intervals between suspend and resume operations during program operations.
Innovation Solution
A non-volatile memory device with a control logic unit that performs an initial program verify operation using a different verify condition during suspend-resume operations, followed by a normal program verify operation, to maintain program threshold voltage distribution and reliability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If a suspend-resume operation is performed during program operation, then read operation can be executed, but program threshold voltage distribution degrades and reliability decreases
Solution Approach 1:
The patent applies preliminary action by performing an initial program verify operation immediately when a suspend command is received, before the actual suspend occurs. This initial verify uses a first program verify voltage that is higher than the normal verify voltage, proactively compensating for the voltage degradation that will occur during the suspend period. By acting in advance, the system prevents threshold voltage distribution degradation rather than correcting it after the fact.
Solution Approach 2:
The patent changes verify parameters dynamically based on operation state. During suspend-resume operations, it uses a first program verify voltage (higher voltage) for initial verify, then transitions to a second program verify voltage (lower voltage) for normal verify after resume. This parameter change adapts the verification process to the specific conditions created by suspend-resume operations, maintaining reliability while allowing the operation to proceed.
2Measurement precision
If a longer develop time is used during program verify, then measurement precision improves, but operation time increases
Solution Approach 1:
The patent applies partial action by using different develop time durations for different verify operations. The initial program verify operation uses a first develop time, while the normal program verify operation uses a second develop time. This partial differentiation allows the system to invest more time in verifies where it matters most (initial verify during suspend-resume) while reducing time investment in routine verifies, optimizing the balance between precision and speed.
Solution Approach 2:
The patent makes the develop time dynamic rather than static. The system automatically adjusts the develop time duration based on the operation context - using a first develop time for initial verify during suspend-resume operations and a second develop time for normal verifies. This dynamic adjustment allows the system to optimize measurement precision when needed while minimizing time loss during routine operations.
Data Source
AI summary
A non-volatile memory device includes a memory cell array including memory cells respectively connected to bit lines; and a control logic unit configured to control a program operation with respect to the memory cells. The control logic unit is configured to perform a normal program verify operation with respect to the memory cells by using a normal program verify condition, during the program operation, and, based on a suspend command that is received during the program operation, perform an initial program verify operation with respect to the memory cells by using an initial program verify condition that is different from the normal program verify condition.