10T NOR-Type CAM Layout With Shared Contacts for Area Reduction
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Solution Overview
Problem
Existing 10T NOR-type content addressable memory (CAM) cells require a large area due to the need for numerous transistors, poly-to-poly distances for left-right cells, and active-to-active distances for upper-lower cells, limiting integration and search accuracy.
Innovation Solution
A layout structure for 10T NOR-type CAM cells is proposed, implementing shared active and poly contacts through layout reversals and arrangements, reducing horizontal and vertical areas by eliminating unnecessary distances between cells.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Area of stationary object
If traditional 10T NOR-type CAM cell layout is used, then device functionality is maintained, but area is large due to poly-to-poly distance requirements for left-right cells and active-to-active distance requirements for upper-lower cells
Solution Approach 1:
The patent merges the active contacts and poly contacts of adjacent CAM cells into shared contact structures. Specifically, the active contact of the first cell shares with the active contact of the third cell, and the poly contact of the first cell shares with the poly contact of the second cell. This merging eliminates redundant contact structures and reduces the overall area while maintaining proper electrical connections and signal isolation.
Solution Approach 2:
The patent employs layout reversal techniques that flip the conventional arrangement of contacts in specific dimensions. By reversing the layout of active contacts and poly contacts in alternating dimensions, the design achieves closer spacing between cells while maintaining signal integrity through proper routing and isolation structures.
2Measurement precision
If numerous transistors are used in 10T NOR-type CAM cell, then search accuracy is improved, but area increases significantly
Solution Approach 1:
The patent shares common transistor structures and contact regions between adjacent CAM cells. The shared active contacts and shared poly contacts reduce the total number of discrete transistor components needed, allowing for a more compact layout that maintains the 10T NOR-type architecture required for high search accuracy while reducing overall area consumption.
Data Source
AI summary
Disclosed is a layout structure of a 10T NOR-type CAM including a first CAM cell, a second CAM cell, a third CAM cell, and a fourth CAM cell, in which the first CAM cell and the third CAM cell share search line 1 (SL1) and bit line 1 (BL1), and the second CAM cell and the fourth CAM cell share SL0 and BL0, the first CAM cell and the second CAM cell share match line 1 (ML1) and word line 1 (WL1), and the third CAM cell and the fourth CAM cell share ML0 and WL0, and an active contact is shared between the first CAM cell and the third CAM cell and another active contact is shared between the second CAM cell and the fourth CAM cell share.