IC Power Distribution Network Using Orthogonal Metal Layers
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Solution Overview
Problem
Current integrated circuit power distribution networks face inefficiencies due to wide power rails consuming routing resources, limiting signal routing capabilities and increasing chip size, especially in standard-cell designs with tight pitch constraints like 7.5-track cells.
Innovation Solution
The implementation of a power distribution network with internal power pins and rails oriented in directions orthogonal to the standard cell layout, utilizing vertical and horizontal metal layers to minimize power rail width and maximize signal routing resources, including buried power rails and power straps to efficiently connect power rails across layers.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Power
If wide power rails are provided in metal layer M2 to supply power to standard cells, then power delivery capability is improved, but routing resources are consumed and chip size increases
Solution Approach 1:
The patent introduces a third metal layer (M3) above the traditional two-layer structure. Power rails are distributed across M2 and M3 layers, with vertical connections via vias. This three-dimensional power distribution approach reduces the width requirement of individual power rails in M2, freeing up horizontal routing resources while maintaining adequate power delivery capability through the added vertical dimension.
2Power
If wide power rails are provided in metal layer M2, then power delivery capability is improved, but signal routing capabilities are limited
Solution Approach 1:
By adding metal layer M3 for power distribution, the patent creates a separated functional architecture where M2 can be dedicated to signal routing and M3 handles power delivery. This layer separation resolves the conflict between power delivery and signal routing adaptability, as each layer can be optimized for its specific function without compromising the other.
Solution Approach 2:
The power distribution function is segmented across multiple metal layers (M2 and M3) rather than concentrating it in a single layer. This segmentation allows M2 to focus on signal routing while M3 provides power delivery, with vertical vias connecting the layers. The segmentation eliminates the need for wide power rails in M2, thereby preserving signal routing capabilities.
3Ease of manufacture
If power rails run perpendicular to gate orientation at cell height frequency, then power distribution is simplified, but routing resources in lowest metal layers are consumed
Solution Approach 1:
The patent maintains the simple perpendicular orientation of power rails relative to gate orientation but distributes these rails across M2 and M3 layers. This vertical distribution reduces the horizontal footprint of power rails in any single layer, freeing up routing resources in the lowest metal layers while preserving the manufacturing simplicity of the perpendicular alignment approach.
Data Source
AI summary
An integrated circuit (IC) power distribution network is disclosed. In one aspect, the IC includes a stack of layers formed on a substrate. The IC includes standard cells with parallel gate structures oriented in a direction y. Each cell includes an internal power pin for supplying a reference voltage to the cell. The stack includes metal layers in which lines are formed to route signals between cells. The lines in each metal layer have a preferred orientation that is orthogonal to that of the lines in an adjacent metal layer. A first layer is the lowest metal layer that has y as a preferred orientation while also providing routing resources for signal routing between the cells. A second layer is the nearest metal layer above this first layer. The IC includes a power distribution network for delivering the reference voltage to the power pin.