Process Corner Indicator Circuit for Per-Die Voltage and Frequency Tuning
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Solution Overview
Problem
Current VLSI chip design and manufacturing processes lack precise control over transistor characteristics, leading to suboptimal performance due to process gradients across and within wafers, resulting in inefficient power usage and lower yields, as they typically cater to the worst-case process corner.
Innovation Solution
A process corner indicator circuit is integrated into each die, utilizing a clock generator circuit that operates at a lower supply voltage to differentiate between process corners, allowing for a digital code representation of the die's process corner without complex characterization, enabling adjustment of operating conditions for improved performance and power efficiency.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If design is optimized for slow process corner to ensure all die work, then reliability is improved, but productivity deteriorates due to lower operating frequency and higher power consumption
Solution Approach 1:
The patent applies local quality by determining the specific process corner characteristics of each individual die and configuring it to operate optimally for its specific corner rather than using a universal conservative design. This allows each die to have customized operating parameters (frequency, voltage) matched to its local process characteristics, thereby improving both reliability and productivity simultaneously.
2Productivity
If design is optimized for typical or fast process corner to improve productivity, then operating frequency is improved, but reliability deteriorates as slow process corners may not operate properly
Solution Approach 1:
The patent implements local quality by measuring and identifying the process corner of each die individually, then configuring that specific die to operate at optimal frequency and voltage for its measured corner. This ensures that fast corners run at high frequencies while slow corners run at conservative frequencies, with each die operating reliably at its own optimized parameters rather than forcing all die to a single conservative setting.
3Use of energy by moving object
If advanced process power controller is used to detect slack and lower voltage, then power consumption is reduced, but device complexity increases due to characterization collaterals required
Solution Approach 1:
The patent extracts the essential process corner information by measuring only the delay characteristics of a simple inverter chain, removing the need for complex characterization collaterals. By isolating and measuring just the critical delay parameter that directly indicates process corner, the invention simplifies the measurement apparatus while still enabling accurate process corner determination and subsequent power optimization.
4Ease of manufacture
If simple process is used to quickly and cheaply provide process corner information, then ease of manufacture is improved, but measurement precision may deteriorate
Solution Approach 1:
The patent uses a simplified model approach by measuring the delay of a basic inverter chain, which serves as a representative copy of the overall process characteristics. This simple inverter delay measurement accurately captures the process corner information needed without requiring complex measurement systems, achieving both ease of manufacture and sufficient measurement precision for process corner determination.
Data Source
AI summary
A process corner indicator circuit can be included with each die formed from a silicon wafer in order to quickly and easily give a determination of process corner. A clock generator circuit of the indicator circuit can include an array of flip-flop elements, and can be run at a lower operating voltage, such that the differences in delay in the generated timing signal are accentuated for different process corners. The period of the timing signal can be determined using slow and fast clock counters, with the slow clock counting a number of cycles of the timing signal and the fast clock counting a number of cycles of a fixed frequency. The count produced by the fast clock can correspond to the delay in the clock generator circuit, giving an indication of the process corner of the die.