Bit Line Contact Pitch Layout for Short-Free Trench Isolation
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Solution Overview
Problem
Semiconductor devices with bit line contacts in trenches experience electrical leakage due to half-profile trenches, which lead to shorts between bit lines and capacitor contacts or moats, necessitating a solution to prevent such leakage.
Innovation Solution
The method involves forming a substrate with bit line contacts in trenches having different pitches, where the outmost row of trenches has an integral profile, and using a protective layer with a zigzag edge to define etching regions, ensuring isolation spacers are formed on both sides of the bit line contacts to prevent electrical shorts.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Area of stationary object
If trenches with half profile are used at the edge of cell region, then the substrate area is utilized more efficiently, but electrical leakage occurs between bit line and cell contact due to absence of isolation spacer
Solution Approach 1:
The patent applies asymmetry by forming different trench profiles at different locations: full-profile trenches in the central region and half-profile trenches at the edge region. This asymmetric design allows efficient substrate utilization at edges while maintaining electrical isolation where needed through selective placement of bit line contacts and isolation spacers
Solution Approach 2:
The patent implements local quality by providing different trench configurations and isolation structures at different locations within the cell region. Specifically, bit line contacts are selectively formed in full-profile trenches in the central region while edge regions use half-profile trenches with adjusted contact formation, ensuring electrical isolation is provided locally where required
2Productivity
If bit line contacts are formed in all trenches, then the device density is increased, but electrical shorts occur when trenches have half profile due to missing isolation spacers
Solution Approach 1:
The patent applies local quality by selectively forming bit line contacts only in full-profile trenches in the central region, while excluding half-profile trenches at the edge from receiving bit line contacts. This selective approach maintains high device density where full isolation can be provided while avoiding electrical shorts in regions where isolation spacers cannot be formed
Solution Approach 2:
The patent segments the cell region into a central region with full-profile trenches and an edge region with half-profile trenches, applying different contact formation strategies to each segment. This segmentation allows the device to achieve high density in the central region while maintaining reliability by avoiding contact formation in edge regions prone to electrical leakage
Data Source
AI summary
A semiconductor device is provided. The semiconductor device includes a substrate defining a plurality of trenches; and a plurality of bit line contacts disposed on the substrate, wherein at least one of the plurality of bit line contacts is disposed within one of the trenches defined by the substrate, wherein the plurality of trenches has a first row and a second row, and a pitch of the first row is different from a pitch of the second row.