SRAM Pass Gate Transistor Probing via Isolation
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Solution Overview
Problem
Current methods for testing individual transistors in SRAM circuits are inefficient, often requiring significant layout changes and disrupting the normal operating environment, which can lead to inaccurate measurements due to local layout effects and congestion in metal layers.
Innovation Solution
A method that involves connecting gate, source, and drain probes to specific transistors in SRAM circuits while keeping other transistors disconnected to avoid unwanted effects, utilizing existing SRAM wiring for probing and maintaining minimal layout disruption, allowing for non-destructive access to FET terminals in real SRAM environments.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If traditional testing methods are used to test individual transistors in SRAM circuits, then layout changes and metal layer disruptions are required, but this causes local layout effects and measurement inaccuracies
Solution Approach 1:
The patent extracts the transistor under test from the complex SRAM circuit environment by selectively probing only the target transistor while leaving other transistors unprobed. This isolation approach removes the disturbing influence of surrounding circuit elements on the measurement, thereby improving measurement accuracy without requiring comprehensive layout changes.
Solution Approach 2:
The patent segments the probing process by connecting probes to only specific terminals (gate, source, or drain) of the target transistor while leaving other transistors in the SRAM circuit unconnected. This selective segmentation allows accurate measurement of individual transistor characteristics without the complexity of probing the entire circuit.
2Reliability
If all transistors in SRAM circuit are connected for probing, then comprehensive testing is achieved, but other transistors have unwanted effects on the transistor being probed
Solution Approach 1:
The patent extracts the target transistor from the interacting transistor network by selectively probing only the desired transistor while leaving others unprobed. This extraction eliminates the harmful interactions and unwanted effects that would occur if all transistors were simultaneously connected during probing, thereby improving testing reliability.
3Ease of operation
If significant layout changes are made to access transistor terminals, then probing capability is improved, but manufacturing complexity and time increase
Solution Approach 1:
The patent utilizes the existing SRAM circuit layout and metal layers to provide the necessary probing access. By leveraging the self-service capability of the existing circuit design, the method achieves good probing capability without requiring significant additional layout changes or manufacturing complexity.
Data Source
AI summary
A technique relates probing a pass gate transistor in a static random access memory (SRAM) circuit. A gate probe is connected to a gate metal layer of the SRAM circuit, the gate metal layer being coupled to a gate of the pass gate transistor. A source probe is connected to a source metal layer of the SRAM circuit, the source metal layer being coupled to a source of the pass gate transistor. A drain probe is connected to a drain metal layer of the SRAM circuit, the drain metal layer being coupled to a drain of the pass gate transistor, the SRAM circuit comprising other transistors along with the pass gate transistor. The other transistors are free from connections for the probing so as not to cause the other transistors to have an unwanted effect on the pass gate transistor being probed.