Multi-Layer Contact Plug Structure for Semiconductor Alignment
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Solution Overview
Problem
As semiconductor devices integrate more densely, patterning processes lead to misalignment, reducing the contacting area between storage contact plugs and active regions, which deteriorates the reliability of the semiconductor device.
Innovation Solution
The semiconductor device design includes first contact plugs that overlap the border between active regions and a device isolation layer, with lengths greater than the active regions, and second contact plugs on these first plugs, arranged in L- and reverse L-shapes to enhance alignment and contact area, along with third contact plugs on center regions, all made from materials like poly-silicon and metals.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If the area of a unit cell is reduced to increase integration, then productivity is improved, but manufacturing precision deteriorates due to misalignment
Solution Approach 1:
The contact plug structure transitions from a single-layer design to a multi-layer stacked configuration, adding vertical dimensionality. First contact plugs are formed at opposite ends of active regions, second contact plugs are formed on the first contact plugs, creating a three-dimensional contact structure that compensates for lateral misalignment issues
Solution Approach 2:
The first contact plugs are formed in advance at the opposite ends of active regions before the second contact plugs are formed. This preliminary positioning ensures that even if misalignment occurs during subsequent patterning processes, the initial contact structure is already established and can accommodate the misalignment
2Reliability
If misalignment occurs during patterning, then manufacturing precision deteriorates, but reliability must be maintained
Solution Approach 1:
The multi-layer contact plug structure acts as a cushioning mechanism against misalignment. By having first contact plugs extend beyond the active region boundaries and second contact plugs formed on them, the structure creates a tolerance buffer that absorbs alignment errors without compromising the electrical connection
Solution Approach 2:
The second contact plugs are formed on top of the first contact plugs, creating a nested hierarchical structure. This nesting ensures that the contact pathway is established through multiple levels, providing redundant contact paths that maintain reliability even when lateral alignment is imperfect
Data Source
AI summary
A semiconductor includes a plurality of active regions that are separated from each other on a substrate by a device isolation layer and extend in a first direction, the active regions having two opposite ends and a center region; wordlines that are buried in and cross the active regions and extend in a second direction, which is different from the first direction, wherein a wordline that crosses an active region crosses between one of the two opposite ends and the center region of the active region; first contact plugs on the two opposite ends of the active regions, each contact plug overlapping a border between the active region and the device isolation layer; and second contact plugs formed on the first contact plugs.