MOS Transistor Process Corner Detection via Ring Oscillator Timing
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Solution Overview
Problem
Current process corner detection methods for MOS transistors are insufficient for analog integrated circuits, as they do not separately evaluate the performance of internal NMOS and PMOS transistors, which is necessary for precise circuit design and performance assurance.
Innovation Solution
A method and device using a ring oscillator with an odd number of oscillation units, each composed of a PMOS and an NMOS transistor, to measure the period and maintaining time of oscillation signals at high and low levels, allowing for the determination of nine distinct process corners, including specific combinations of fast, typical, and slow modes for both NMOS and PMOS transistors.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a conventional process sensor using a ring oscillator is used to detect process corners, then the detection can be performed with a simple structure, but the detection results are insufficient for analog integrated circuits as they do not separately evaluate NMOS and PMOS transistor performance
Solution Approach 1:
The patent segments the detection function by separating the evaluation of NMOS and PMOS transistor performance. Instead of detecting only the overall oscillation period, the invention measures the high-level maintaining time (reflecting PMOS performance) and low-level maintaining time (reflecting NMOS performance) independently. This segmentation enables precise separate evaluation of both transistor types while using the same ring oscillator structure.
2Loss of information
If the ring oscillator detects only the overall oscillation period, then the device complexity remains low, but the detection completeness is insufficient for analog circuits requiring separate NMOS and PMOS evaluation
Solution Approach 1:
The patent adds temporal dimensionality to the detection by measuring not just the total oscillation period but also the duration of high-level and low-level states within each cycle. This dimensional expansion of measurement parameters enables extraction of separate NMOS and PMOS performance information from the same oscillation signal without adding hardware complexity.
Data Source
AI summary
Method and device for detecting the process corner of a transistor are provided. The process corner detection method includes providing a ring oscillator. The ring oscillator includes an odd number of oscillation units connected in series and an output port of one of the oscillation units serves as the output port of the ring oscillator to output an oscillation signal. Each oscillation unit is constructed based on a PMOS transistor and an NMOS transistor. The process corner detection method further includes measuring the period of the oscillation signal and the maintaining time of the oscillation signal at a high level and a low level in each cycle; and determining the process corner of the PMOS transistor and the NMOS transistor in the oscillation unit based on the period of the oscillation signal and the maintaining time of the oscillation signal at a high level and a low level in each cycle.