Reverse Bias Voltage Adjustment for Memory Burn-In Protection
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Solution Overview
Problem
During burnin-test mode in memory technology, transistors are easily affected by voltage differences between the source and drain terminals, leading to potential damage due to excessive voltage values.
Innovation Solution
A reverse bias voltage adjuster is implemented, comprising an operating voltage generating circuit and a voltage adjusting circuit with a switch, which reduces the operating voltage in burnin-test mode to a second voltage value less than the normal value, maintaining the reverse bias voltage at a reference grounding voltage level, thereby reducing the voltage difference between the source and drain terminals.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If reverse bias voltage is applied to substrate in burnin-test mode, then memory operational motion is tested, but voltage difference between source and drain terminals exceeds rated voltage scope causing transistor damage
Solution Approach 1:
The patent implements dynamic voltage adjustment by introducing a control circuit that dynamically modifies the reverse bias voltage level based on operational mode. A switch element ( transistor M1) is controlled by a control signal (BTM) to connect or disconnect the reverse bias voltage path, thereby dynamically adapting the voltage conditions to prevent damage during burnin-test while maintaining proper operation during normal function.
Solution Approach 2:
The patent changes the voltage parameter of the reverse bias signal based on operational mode. By detecting the burnin-test mode and adjusting the reverse bias voltage magnitude through the controlled switch, the system transforms the harmful high voltage difference into a safe level, thus resolving the contradiction between testing requirements and transistor protection.
2Reliability
If reverse bias voltage is increased for thorough testing, then memory reliability is improved, but transistor damage risk increases
Solution Approach 1:
The patent applies preliminary anti-action by preemptively reducing the reverse bias voltage magnitude before it can cause damage. The control circuit detects burnin-test mode activation and immediately adjusts the voltage level through the controlled switch, preventing the harmful effect from occurring in the first place while still allowing thorough reliability testing to proceed.
Data Source
AI summary
A reverse bias voltage adjuster is provided. The reverse bias voltage adjuster includes an operating voltage generating circuit and a voltage adjusting circuit. The operating voltage generating circuit generates an operating voltage according to a burnin-test signal, a power start signal, and a reverse bias enable signal. In a normal operation mode, the operating voltage is a first voltage value, and in a burnin-test mode, the operating voltage is a second voltage value, wherein the second voltage value is less than the first voltage value. The voltage adjusting circuit is provided with a switch, and in an initial time interval in the burnin-test mode, the voltage adjusting circuit adjusts voltage value of the reverse bias by turning on the switch.