Switchable Gate Bias Clamp Circuit for Faster Reliability Testing

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Solution Overview

Problem

Existing semiconductor devices face challenges in efficiently protecting I/O circuits from electrostatic discharge (ESD) events and ensuring reliable gate oxide integrity during reliability acceleration tests, particularly due to the limited flexibility and practicality of current clamping circuits in handling varying voltage levels.

Innovation Solution

Implementing a bias clamp circuit with switchable clamp voltage paths, including a voltage clamp, a switch, and a voltage booster, allowing the gate bias voltage to be adjusted to either a first or second level based on the need for reliability acceleration testing, using existing circuit elements to enhance protection and accelerate testing without compromising device reliability.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If a fixed voltage clamp circuit is used to protect the gate oxide during normal operation, then the gate oxide integrity is maintained, but the testing time for reliability acceleration is excessively long

Engineering Contradiction:

Improvegate oxide integrityVSAvoidtesting time

Core Design Contradiction:

ReliabilityVSLoss of time

Solution Approach 1:

The bias clamp circuit transitions from a static fixed-voltage design to a dynamic adjustable-voltage design. The circuit can switch between a first clamp voltage level during normal operation to protect gate oxide, and a second higher clamp voltage level during reliability acceleration testing. This dynamic adjustment allows the circuit to adapt to different operational requirements, maintaining protection while reducing testing time.

Inventive Principle:

Principle #15Dynamics

Solution Approach 2:

The invention changes the voltage parameter of the bias clamp circuit based on operational mode. During normal operation, the clamp voltage is set to a first level sufficient for gate oxide protection. During reliability acceleration testing, the clamp voltage is increased to a second higher level to accelerate testing without compromising device integrity. This parameter adjustment resolves the contradiction between protection and testing efficiency.

Inventive Principle:

Principle #35Parameter changes

2Productivity

If the clamp voltage is increased to accelerate reliability testing, then the testing time is reduced, but the risk of damaging the gate oxide increases

Engineering Contradiction:

Improvetesting speedVSAvoidgate oxide integrity

Core Design Contradiction:

ProductivityVSReliability

Solution Approach 1:

The bias clamp circuit dynamically adjusts its clamp voltage level based on the operational phase. During reliability acceleration testing, the circuit temporarily increases the clamp voltage to a second higher level to accelerate the testing process. When normal operation resumes, the circuit switches back to the first clamp voltage level to ensure gate oxide protection. This dynamic control enables high-speed testing without permanent damage risk.

Inventive Principle:

Principle #15Dynamics

Solution Approach 2:

The circuit employs periodic switching between different clamp voltage levels corresponding to different operational modes. The bias clamp circuit alternates between a protection mode (first clamp voltage) and an acceleration mode (second clamp voltage), with each mode activated during its appropriate phase. This periodic action allows the system to achieve both fast testing and reliable protection at different times.

Inventive Principle:

Principle #19Periodic action

3Device complexity

If a simple fixed-voltage clamp circuit is used, then the circuit complexity is low, but the adaptability to different testing and operation modes is limited

Engineering Contradiction:

Improvecircuit complexityVSAvoidvoltage level adaptability

Core Design Contradiction:

Device complexityVSAdaptability or versatility

Solution Approach 1:

The bias clamp circuit is segmented into multiple independent voltage clamp paths, with each path configured to provide a specific clamp voltage level. The first clamp voltage path provides protection-level clamping during normal operation, while the second clamp voltage path provides acceleration-level clamping during testing. This segmentation allows the circuit to offer multiple voltage levels without requiring a completely complex redesign, maintaining relative simplicity while enhancing adaptability.

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

The bias clamp circuit is designed with multi-functionality to serve both normal operation and reliability acceleration testing modes. By incorporating multiple clamp voltage paths that can be selectively activated, the circuit becomes universal in its application, handling both protection and acceleration requirements within a single integrated structure. This reduces the need for separate circuits for different modes.

Inventive Principle:

Principle #6Universality (Multi-functionality)

Data Source

PatentUS12587010B2Method for adjusting gate bias clamp voltage, semiconductor device, and bias clamp circuit using the same

Publication Date: 2026.03.24 TAIWAN SEMICONDUCTOR MANUFACTURING CO LTD

AI summary

The present disclosure provides a bias clamp circuit, which includes a plurality of switchable clamp voltage paths, configured to selectively clamp a gate bias voltage of a vulnerable circuit to a first voltage or a second voltage based on whether a reliability acceleration test is performed on the vulnerable circuit or not. The second voltage is higher than the first voltage.