BEOL Process Corner Sensing with Shielded Ring Oscillators
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Solution Overview
Problem
Existing integrated circuit (IC) back end of line (BEOL) process corner monitors, such as ring oscillators, lack adequate frequency discrimination to accurately detect and monitor IC BEOL process corners, which affects yield and performance optimization.
Innovation Solution
The proposed solution involves a ring oscillator with a shield net circuit that modifies the time delays of the ring oscillator stages through capacitive coupling, allowing for better frequency discrimination among IC BEOL process corners by toggling between two frequency states, thereby enhancing the sensitivity to resistance and capacitance values of the interconnections.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a conventional ring oscillator is used to monitor IC BEOL process corners, then the device can detect process variations, but the frequency discrimination is inadequate for accurate detection
Solution Approach 1:
The patent introduces a shield net circuit that can be dynamically toggled between two states (first state and second state) to modify the time delays of the ring oscillator stages. This dynamic adjustment allows the same hardware structure to produce different frequency states (first frequency state and second frequency state), thereby improving frequency discrimination without requiring multiple separate oscillators. The shield net circuit responds to a control signal to switch between states, enabling the system to adapt its measurement range and precision.
Solution Approach 2:
The patent changes the operational parameters of the ring oscillator by introducing a shield net circuit that modifies the time delays of the oscillator stages. By toggling the shield net between two states, the system can shift the operating frequency between a first frequency state (where the frequency is greater than a first intrinsic frequency state) and a second frequency state (where the frequency is less than a second intrinsic frequency state). This parameter change approach allows the same physical structure to provide enhanced frequency discrimination for monitoring IC BEOL process corners.
2Reliability
If the ring oscillator frequency is used to detect IC BEOL process corners, then process monitoring is enabled, but the sensitivity to resistance and capacitance values is insufficient
Solution Approach 1:
The patent introduces a shield net circuit as an intermediary element that couples to the ring oscillator stages. This shield net circuit acts as a mediator that enhances the sensitivity of the system to resistance and capacitance variations in the IC BEOL interconnections. By toggling the shield net between two states, it modulates the time delays of the oscillator stages, thereby amplifying the frequency response to process corner variations. This intermediary mechanism improves the detection accuracy of process corners without directly modifying the interconnections themselves.
3Productivity
If existing ring oscillator implementations are used, then the device can operate, but adequate frequency discrimination for monitoring is not achieved
Solution Approach 1:
The patent applies dynamics by introducing a shield net circuit that can be toggled between two states in response to a control signal. This dynamic switching allows the ring oscillator to operate in two distinct frequency states, providing enhanced frequency discrimination. The first frequency state offers one range of discrimination while the second frequency state provides another range, allowing the system to optimize measurements for different process corner conditions. This dynamic capability directly improves yield and performance optimization by enabling more precise process monitoring.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
This approach improves the monitoring and discrimination of IC BEOL process corners, leading to better design fidelity and reduced circuit margins, enabling more precise optimization of voltage settings and power savings.
Implementation Method 1
modifies the time delays of the ring oscillator stages through capacitive coupling
Data Source
AI summary
Aspects of the disclosure are directed to sensing integrated circuit (IC) Back End Of Line (BEOL) process corners. In one aspect, an apparatus for sensing IC BEOL process corners includes a ring oscillator including a plurality of ring oscillator stages configured to generate an output waveform with a frequency state; and a shield net circuit including a plurality of shield net stages corresponding to the plurality of ring oscillator stages, the shield net circuit having a toggle input. And, a method includes generating an output waveform with a frequency state using a ring oscillator that includes a plurality of ring oscillator stages; modifying a plurality of ring oscillator stage time delays through a coupling between a plurality of shield net stages and the plurality of ring oscillator stages; and selecting the frequency state using a toggle input of a shield net circuit which includes the plurality of shield net stages.