Process Corner Simulation Using Speed and Duty Cycle Signals
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Solution Overview
Problem
Current integrated circuit manufacturing processes lack effective methods to accurately monitor and adjust transistor characteristics across various process corners, particularly when adjustments are made in different directions, leading to inadequate testing data and challenges in aligning process adjustments with target ranges.
Innovation Solution
A process corner simulation system comprising a frequency generator, transistor sensitive circuit, and process corner simulator that generates simulation results based on speed and duty cycle information, enabling two-dimensional simulations to distinguish between different process corners.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If WAT DC parameters are used for process adjustments, then manufacturing process control is simplified, but the ability to monitor chip speed specifications and detect process corner changes is insufficient
Solution Approach 1:
The patent introduces a ring oscillator as an intermediary device that converts transistor performance characteristics into measurable frequency signals. The ring oscillator circuit includes five inverters connected in a loop with delay elements, transforming abstract transistor parameters into concrete frequency measurements that directly reflect process corner conditions and chip speed specifications.
Solution Approach 2:
The patent replaces direct electrical parameter measurement (DC parameters) with a dynamic frequency-based measurement system. By substituting static voltage/current measurements with dynamic oscillation frequency measurements, the system gains the ability to capture transient behavior and process corner variations that DC parameters cannot detect.
2Measurement precision
If ring oscillator is used to monitor chip speed, then speed detection capability is improved, but the ability to detect process adjustments in different directions is limited
Solution Approach 1:
The patent segments the process corner detection into five distinct measurement scenarios by introducing different test configurations and measurement points. The ring oscillator system is divided into multiple measurement paths that can independently detect different process corner conditions (FF, FS, SF, SS, and typical-typical), enabling comprehensive coverage of all process variation directions.
Solution Approach 2:
The patent adds a new dimension to process monitoring by measuring not only frequency but also the differential behavior of complementary transistor pairs. By introducing phase difference measurements and duty cycle analysis, the system transforms a one-dimensional frequency measurement into a multi-dimensional characterization that can distinguish process adjustments in opposite directions.
3Device complexity
If fewer detection points are used in WAT stage, then testing complexity is reduced, but the ability to ascertain process alignment with target range is compromised
Solution Approach 1:
The patent designs the ring oscillator-based test structure to serve multiple functions simultaneously: it measures frequency, detects process corners, verifies duty cycle, and validates process alignment all through a single integrated circuit element. This multi-functional approach eliminates the need for multiple separate test structures, reducing overall testing complexity while maintaining high measurement precision.
Data Source
AI summary
A process corner simulation system includes a frequency generator, a transistor sensitive circuit, and a process corner simulator. The frequency generator is used to generate a frequency signal. The transistor sensitive circuit is coupled to the frequency generator for receiving the frequency signal. The process corner simulator is coupled to the transistor sensitive circuit for receiving at least one output signal generated from the transistor sensitive circuit. The at least one output signal outputted from the transistor sensitive circuit includes speed information and duty cycle information. The process corner simulator uses a plurality of process corner models for generating a plurality of simulation results corresponding to different process corners according to the at least one output signal.