Configurable Ring Oscillator for Isolating Interconnect Loading
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Solution Overview
Problem
The extraction of circuit simulator parameters from test structures is a complex and time-consuming process, often confounded by the effects of interconnect loading and transistor variations, which complicates the isolation and calibration of parameters in circuit simulation tools like SPICE.
Innovation Solution
A configurable ring oscillator is operated in two distinct configurations with varying interconnect paths to isolate the effects of interconnect loading from transistor performance, allowing for the calibration of interconnect-dependent and transistor-dependent circuit simulator parameters through frequency measurements, enabling precise parameter extraction and reducing the complexity of the process.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If multiple different ring oscillators are fabricated to isolate interconnect effects, then measurement precision improves, but device complexity and time consumption increase
Solution Approach 1:
The ring oscillator is designed with configurable interconnect paths that can be dynamically switched between different configurations (first configuration with first interconnect, second configuration with second interconnect). This dynamic reconfiguration allows the same physical oscillator to serve multiple measurement purposes, eliminating the need for multiple separate oscillators while maintaining measurement precision.
Solution Approach 2:
A single ring oscillator is designed to perform multiple functions by switching between different interconnect configurations. The oscillator can measure both interconnect-dependent parameters and transistor-dependent parameters sequentially, making one device universally applicable for multiple parameter extraction tasks that previously required multiple dedicated test structures.
2Reliability
If traditional parameter extraction methods are used involving multiple test structures, then comprehensive parameter calibration is achieved, but time consumption increases
Solution Approach 1:
The configurable ring oscillator allows sequential switching between different interconnect configurations during the parameter extraction process. This dynamic reconfiguration enables comprehensive parameter calibration to be performed on a single device over time, rather than requiring parallel testing of multiple devices, thus maintaining calibration completeness while reducing overall time consumption.
Solution Approach 2:
The parameter extraction process uses periodic switching between different oscillator configurations. The oscillator is operated in the first configuration to extract interconnect-dependent parameters, then switched to the second configuration to extract transistor-dependent parameters, creating a periodic measurement cycle that efficiently comprehensively calibrates all parameters without requiring continuous parallel testing.
Data Source
AI summary
A configurable ring oscillator is operated in a first configuration so that an oscillating signal passes from a first node to a second node through a first signal path. A first measurement of an operational characteristic is made. The ring oscillator is operated in a second configuration where an oscillating signal passes from the first node to the second node through a second signal path. A second measurement is made. The first and second measurements are used to determine a circuit simulator parameter. If the first path has little interconnect and the second path has substantial interconnect, then the effect on circuit operation due to interconnect loading can be isolated from the effects on circuit operation due to variations in transistor performance. If the first and second paths are laid out to be identical, then the first and second measurements are usable to determine a circuit simulator mismatch parameter.