Programmable Clock Tree Tuning for Deep-Submicron Skew Control
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
In high-speed synchronous deep submicron integrated circuits, variations in metal and semiconductor trace resistance and capacitance due to fabrication processes lead to significant clock tuning challenges, requiring precise adjustments on a flip-flop or register basis to optimize performance.
Innovation Solution
The implementation of tunable clock distribution structures using antifuse or phase change memory elements, with programmable inverters that adjust capacitance or resistance to fine-tune clock signals, and diagnostic methods to determine and program optimal delays across the IC, minimizing clock skew and maximizing clock frequency.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If traditional clock distribution structures are used in deep submicron integrated circuits, then manufacturing simplicity is maintained, but clock skew and timing errors increase due to fabrication process variations in metal and semiconductor traces
Solution Approach 1:
The patent applies local quality by making each clock branch individually tunable through programmable delay elements. Each branch can have its delay characteristics independently adjusted to compensate for local fabrication variations in metal and semiconductor traces, ensuring that each clock signal arrives at its destination with the correct timing despite process variations.
Solution Approach 2:
The patent implements dynamics by introducing programmable delay elements that allow the clock distribution structure to be dynamically tuned after fabrication. The delay characteristics of each clock branch can be programmed to compensate for fabrication variations, transforming a static, fixed-delay structure into a dynamic, adjustable one that can adapt to actual process variations.
2Manufacturing precision
If clock tuning is performed on a chip-wide basis using traditional methods, then device complexity is minimized, but manufacturing precision deteriorates due to inability to compensate for per-via, per-wire fabrication variations
Solution Approach 1:
The patent applies segmentation by dividing the clock distribution network into multiple independent, tunable branches. Each branch contains programmable delay elements that can be independently adjusted, allowing precise compensation for fabrication variations in each specific path without requiring complex global tuning mechanisms.
Solution Approach 2:
The patent implements parameter changes by introducing programmable delay elements that allow the electrical characteristics (delay time) of each clock branch to be adjusted. This enables precise tuning of clock timing parameters to compensate for fabrication variations in resistance and capacitance of metal and semiconductor traces.
3Productivity
If high-speed clock frequencies are used, then productivity is improved, but reliability decreases due to increased sensitivity to fabrication process variations in trace resistance and capacitance
Solution Approach 1:
The patent applies local quality by enabling individual tuning of each clock branch to compensate for local fabrication variations. At high clock frequencies where timing margins are tight, each branch can be independently adjusted to ensure accurate timing arrival, preventing timing errors that would otherwise occur due to process variations in resistance and capacitance.
Solution Approach 2:
The patent implements feedback through programmable delay elements that can be tuned based on measured or simulated timing requirements. This allows the clock distribution system to be optimized for high-frequency operation by adjusting delay parameters to compensate for fabrication variations, ensuring reliable timing even at elevated clock speeds.
Data Source
AI summary
A memory-like structure composed of variable resistor elements for use in tuning respective branches and leaves of a clock distribution structure, which may be used to compensate for chip-by-chip and/or combinatorial logic path-by-path delay variations, which may be due, for example, to physical variations in deep submicron devices and interconnections, is presented. A single system clocked scan flip-flop with the capability to perform delay test measurements is also presented. Methods for measuring combinatorial logic path delays to determine the maximum clock frequency and delays to program the variable resistors, as well as methods for calibrating and measuring the programmed variable resistors, are also presented.