PMOS Gate Protection Circuit for Burn-In NBTI Prevention
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Solution Overview
Problem
During a burn-in test, the Negative Bias Temperature Instability (NBTI) effect causes damage to PMOS devices in chips due to high bias voltage and temperature, leading to degradation of electrical parameters.
Innovation Solution
A protection circuit is designed to apply a high-level signal to the gate of P-type transistors, preventing the NBTI effect by ensuring the input signal is always a high-level signal during the burn-in test, thereby avoiding damage to the transistors.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a burn-in test is performed on the chip, then the reliability of the chip can be verified, but the NBTI effect causes damage to PMOS devices due to high bias voltage and temperature
Solution Approach 1:
The protection circuit applies a preliminary counteracting action by forcing the gate voltage of PMOS devices to remain at high level during burn-in test, which prevents the NBTI effect from occurring in the first place. The control circuit detects burn-in test mode and activates the protection mechanism before significant degradation can occur, thereby protecting the PMOS devices from the harmful negative bias stress that would normally cause threshold voltage shifts and device degradation.
2Productivity
If high bias voltage is applied to the gate of PMOS devices during burn-in test, then the test can be conducted, but the NBTI effect degrades electrical parameters
Solution Approach 1:
The protection circuit dynamically adjusts the gate voltage condition based on the operating mode. During normal operation, the circuit allows normal voltage swings for proper logic operation. During burn-in test mode, the circuit dynamically switches to a protective state that maintains high gate voltage to prevent NBTI effect. This dynamic adaptation enables the system to satisfy both normal operational requirements and burn-in test requirements without permanent device degradation.
3Ease of operation
If normal operation mode is used, then the circuit functions properly, but PMOS devices are vulnerable to NBTI effect during burn-in test
Solution Approach 1:
The protection circuit acts as an intermediary between the burn-in test environment and the PMOS devices. It includes intermediate components such as control circuits, voltage selection circuits, and switching elements that mediate the interaction between the test conditions and the sensitive PMOS devices. This intermediary layer translates the burn-in test mode detection into appropriate protective voltage conditions, isolating the PMOS devices from direct exposure to harmful negative bias stress while allowing the test to proceed.
Data Source
AI summary
A protection circuit can be applied in a chip, and include: a first protection unit and a first element to be protected, wherein the first protection unit is configured to receive a first input signal and a control signal, and is configured to output a first output signal, the first element to be protected includes a first P-type transistor, and a gate of the P-type transistor is configured to receive the first output signal. When the chip enters a burn-in test, the first output signal is a high-level signal.