3D Clock Distribution Network Reducing Skew and Parasitic Load
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Solution Overview
Problem
Two-dimensional clock distribution networks in microprocessors face challenges with clock skew and jitter, leading to timing uncertainties and decreased timing margins due to stringent power and timing requirements.
Innovation Solution
A three-dimensional clock distribution network is implemented, featuring a clock source tier and vertically stacked clock tree tiers connected by conductive lines and inductive tiers, which reduces parasitic load, floor plan size, and skew through the use of inter-layer vias and conductive traces, ensuring simultaneous clock signal delivery across multiple points.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If a two-dimensional clock distribution network is used, then the layout is simple and easy to manufacture, but clock skew and jitter increase leading to timing uncertainties
Solution Approach 1:
The patent transitions from a two-dimensional clock distribution network to a three-dimensional network by stacking multiple clock distribution tiers vertically. This dimensional change allows clock signals to be distributed through multiple layers with controlled skew, reducing timing uncertainties while maintaining manufacturing feasibility through standard semiconductor fabrication processes.
2Area of stationary object
If the clock distribution network is extended to cover larger area, then more circuitry is served, but parasitic load increases reducing operating speed
Solution Approach 1:
By distributing clock signals across multiple vertical tiers rather than extending a single two-dimensional network, the patent reduces the horizontal trace length and associated parasitic capacitance and resistance. The three-dimensional arrangement allows broader coverage while maintaining shorter signal paths and lower parasitic loads.
Solution Approach 2:
The clock distribution network is segmented into multiple tiers, each handling a portion of the overall distribution. This segmentation divides the large-area distribution task into smaller, manageable units with lower parasitic loads, improving operating speed while maintaining extensive coverage.
3Productivity
If more clock distribution tiers are added, then clock signal reaches more destinations simultaneously, but device complexity increases
Solution Approach 1:
The patent organizes clock distribution tiers in a vertical three-dimensional stack rather than spreading them horizontally. This vertical arrangement improves distribution efficiency by enabling simultaneous delivery to multiple destinations across tiers while managing complexity through systematic inter-layer via connections and standardized tier designs.
Data Source
AI summary
An integrated circuit includes a clock source tier and at least two clock distribution tiers disposed in a vertical stack with the clock source tier. The clock source tier includes a clock circuit. Each of the at least two clock distribution tiers includes a clock distribution circuit. Each clock distribution circuit includes at least one pair of cross-coupled inverters.