Ring Oscillator Layout for Sensitive NBTI and PBTI Detection

Solution Overview

Problem

Current semiconductor devices equipped with ring oscillators face challenges in detecting Bias Temperature Instability (BTI) degradation, specifically Negative BTI (NBTI) and Positive BTI (PBTI), as they are not highly sensitive to these degradations, which affect transistor speed and reliability.

Innovation Solution

A semiconductor device with a ring oscillator configuration that alternately cascades first and second gate circuits with different drive powers, where the first gate circuits are configured as NAND circuits and the second gate circuits as NOR circuits, allowing for high sensitivity to NBTI or PBTI degradation by adjusting the drive power ratio between NAND and NOR circuits.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Measurement precision

If a conventional ring oscillator with uniform gate circuits is used, then the device complexity is low, but the sensitivity to NBTI or PBTI degradation is insufficient

Engineering Contradiction:

Improvesensitivity to degradationVSAvoidcomplexity of gate circuit configuration

Core Design Contradiction:

Measurement precisionVSDevice complexity

Solution Approach 1:

The patent applies local quality by differentiating the drive power of specific gate circuits (first and second gate circuits with different drive powers than third and fourth gate circuits) within the ring oscillator. This localized differentiation in drive power characteristics enables selective sensitivity to NBTI or PBTI degradation in specific transistor types while maintaining overall system functionality.

Inventive Principle:

Principle #3Local quality

Solution Approach 2:

The patent implements asymmetry by creating an unbalanced configuration where first and second gate circuits have different drive powers compared to third and fourth gate circuits. This asymmetric drive power distribution across the ring oscillator stages enhances the ability to detect asymmetric degradation patterns characteristic of NBTI and PBTI effects.

Inventive Principle:

Principle #4Asymmetry

2Measurement precision

If gate circuits with different drive powers are used to enhance degradation detection, then the sensitivity to NBTI or PBTI degradation improves, but the device complexity increases

Engineering Contradiction:

Improvedetection sensitivityVSAvoidcomplexity of ring oscillator configuration

Core Design Contradiction:

Measurement precisionVSDevice complexity

Solution Approach 1:

The patent applies local quality by differentiating the drive power of specific gate circuits (first and second gate circuits with different drive powers than third and fourth gate circuits) within the ring oscillator. This localized differentiation in drive power characteristics enables selective sensitivity to NBTI or PBTI degradation in specific transistor types while maintaining overall system functionality.

Inventive Principle:

Principle #3Local quality

Solution Approach 2:

The patent implements parameter changes by varying the drive power parameter of different gate circuits within the ring oscillator. Specifically, first and second gate circuits are configured with different drive powers than third and fourth gate circuits, creating distinct electrical characteristics that enhance degradation detection sensitivity without requiring complete redesign of the oscillator architecture.

Inventive Principle:

Principle #35Parameter changes

3Adaptability or versatility

If a ring oscillator detects both NBTI and PBTI degradation, then the monitoring capability is comprehensive, but the detection precision for each specific degradation type decreases

Engineering Contradiction:

Improvedegradation detection capabilityVSAvoiddetection precision for specific degradation

Core Design Contradiction:

Adaptability or versatilityVSMeasurement precision

Solution Approach 1:

The patent applies local quality by differentiating the drive power of specific gate circuits (first and second gate circuits with different drive powers than third and fourth gate circuits) within the ring oscillator. This localized differentiation in drive power characteristics enables selective sensitivity to NBTI or PBTI degradation in specific transistor types while maintaining overall system functionality.

Inventive Principle:

Principle #3Local quality

Solution Approach 2:

The patent implements segmentation by dividing the ring oscillator into distinct groups of gate circuits with different drive power characteristics. First and second gate circuits form one group with different drive powers than third and fourth gate circuits, allowing independent optimization for detecting NBTI or PBTI degradation respectively, thereby maintaining both versatility and precision.

Inventive Principle:

Principle #1Segmentation

Data Source

PatentUS10445206B2Semiconductor device

Publication Date: 2019.10.15 RENESAS ELECTRONICS CORP

AI summary

A ring oscillator for detecting a characteristic degradation of MOSFETs is required to be highly sensitive to NBTI degradation or PBTI degradation. A semiconductor device comprises a ring oscillator and a delay detecting circuit which detects a delay through gate circuits based on the oscillation frequency of the ring oscillator. The ring oscillator comprises an input terminal to which an oscillation control signal is input, an output terminal which outputs an oscillation signal, an oscillation control gate circuit having a first input terminal which is coupled to the input terminal and a second input terminal to which a terminal different from the input terminal is coupled, NAND circuits, and NOR circuits. The NAND and NOR circuits are cascade coupled alternately, plural inputs of the NAND circuits and of the NOR circuits are coupled together, and drive power of the NAND circuits differs from drive power of the NOR circuits.