HV Shifter Compensation for P-Channel Transistor Degradation
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Solution Overview
Problem
In 3D NAND flash memory devices, the high-voltage shifter (HV shifter) complexity and size increase due to transistor degradation, which complicates the high-voltage supply system and requires more chip area and resources, leading to higher costs and reduced memory density.
Innovation Solution
A high-voltage shifter circuit with a signal transfer circuit and a compensator circuit that uses a P-channel transistor to transfer high-voltage inputs and a control signal to compensate for transistor degradation, reducing the number of components and complexity by employing a high-voltage control signal generator to provide a support voltage for a specified time period.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If transistor degradation compensation is implemented in the high-voltage shifter, then reliability is improved, but device complexity increases
Solution Approach 1:
The patent applies preliminary action by proactively compensating for transistor degradation before it significantly impacts performance. A compensation mechanism is implemented that adjusts the high-voltage shifter operation in advance to account for expected degradation, thereby maintaining reliability without requiring complex real-time monitoring and adjustment systems.
Solution Approach 2:
The patent employs parameter changes by modifying operational parameters of the high-voltage shifter to compensate for transistor degradation. Specifically, voltage levels and timing parameters are adjusted to maintain proper shifter function despite degradation, achieving improved reliability through parameter optimization rather than structural complexity increases.
2Reliability
If degradation compensation mechanisms are added to the HV shifter, then reliability is improved, but chip area increases
Solution Approach 1:
The patent applies merging by integrating the degradation compensation functionality into the existing high-voltage shifter structure. The compensation mechanism shares circuit elements and layout space with the primary shifter function, thereby improving reliability without proportionally increasing chip area. The compensation circuits are merged with the signal transfer path to minimize area overhead.
3Reliability
If the HV shifter is designed to compensate for transistor degradation, then reliability is improved, but manufacturing cost increases
Solution Approach 1:
The patent applies self-service by implementing a degradation compensation mechanism that automatically adjusts its operation based on the actual state of the transistors. The system monitors its own performance and self-corrects for degradation without requiring external calibration or complex manufacturing processes, thereby improving reliability while keeping manufacturing costs manageable through automated self-adjustment.
Data Source
AI summary
Discussed herein are systems and methods for compensating degradation of a transistor in a high-voltage (HV) shifter configured to transfer an input voltage to an access line, such as a global wordline. An embodiment of a memory device comprises a group of memory cells, and a HV shifter circuit including a signal transfer circuit and a compensator circuit. The signal transfer circuit includes a P-channel transistor to transfer a high-voltage input to an access line. The compensator circuit can provide a control signal to the signal transfer circuit by coupling a support voltage higher than a supply voltage (Vcc) to the signal transfer circuit for a specified time period to compensate for degradation of the P-channel transistor. The transferred high voltage is used to charge the access line to selectively read, program, or erase memory cells.