Flexible Standard Cell Layout Architecture for IC Area Optimization
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Solution Overview
Problem
The design of standard cells in integrated circuits often results in area penalties due to the need for spacing active regions from cell boundaries, leading to physically disconnected active regions that require metal lines for electrical connection, which degrades device performance.
Innovation Solution
The design includes standard cells with gate strips forming PMOS and NMOS transistors, where the cell pitch is not equal to integer times the gate pitch, allowing for continuous active regions and reduced chip area usage by aligning source regions with cell boundaries and using filler cells to complete active regions.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If active regions are spaced apart from cell boundaries to avoid design rule violations, then design rules are satisfied, but chip area increases and active regions become physically disconnected
Solution Approach 1:
The standard cell is divided into two independent halves, each containing a complete set of transistors and active regions. This segmentation allows each half to be designed independently with proper spacing from boundaries, while the overall cell achieves higher density through the non-integer pitch arrangement of the two halves
Solution Approach 2:
The cell pitch is deliberately designed to be a non-integer multiple of the gate pitch, creating an asymmetric layout where the two halves of the cell are positioned at different offsets from the boundaries. This asymmetric arrangement allows active regions to be optimally positioned within each half while maintaining proper boundary spacing
2Reliability
If active regions are spaced apart from cell boundaries, then design rules are satisfied, but device performance degrades due to physically disconnected active regions requiring metal lines for connection
Solution Approach 1:
By segmenting the cell into two independent halves, each with its own complete transistor structures, the patent enables continuous active regions within each half while avoiding the need for inter-connecting metal lines between separated active regions, thus maintaining device performance
Solution Approach 2:
The patent transitions from a conventional single-pitch cell design to a dual-pitch cell design where the cell pitch is a non-integer multiple of the gate pitch. This dimensional change in the layout architecture allows active regions to remain continuous within each cell half while satisfying boundary spacing requirements
Data Source
AI summary
An integrated circuit layout includes a standard cell, which includes a first gate strip and a second gate strip parallel to each other and having a gate pitch; a first boundary and a second boundary on opposite ends of the first standard cell; and a third boundary and a fourth boundary on opposite ends of the first standard cell and parallel to the first gate strip and the second gate strip. A cell pitch between the third boundary and the fourth boundary is not equal to integer times the gate pitch. A PMOS transistor is formed of the first gate strip and a first active region. An NMOS transistor is formed of the first gate strip and a second active region.