Single-Sided Access Device With Multi-Finger Sidewall Gate
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Solution Overview
Problem
The challenge in DRAM applications is to produce arrays of vertical double-gate FinFET devices with suitable performance characteristics, particularly in shrinking memory cell area and maintaining high-speed performance due to electrical coupling effects as word line spacing decreases.
Innovation Solution
A single-sided access device with a multi-finger sidewall gate and trench isolation structure is developed, where the active fin structure is sandwiched by the trench isolation and sidewall gate, with a gate dielectric layer in between, to enhance access drive current and device performance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Area of moving object
If vertical double-gate FinFET devices are used to shrink memory cell area, then device density is improved, but electrical coupling effects worsen due to decreased word line spacing
Solution Approach 1:
The gate structure is segmented into multiple fingers that engage with the active fin structure from opposite sides. This segmentation allows the gate to wrap around the fin structure, providing effective control while maintaining spatial separation that reduces electrical coupling between adjacent word lines.
Solution Approach 2:
The device employs an asymmetric single-sided access configuration where the gate structure is positioned to engage the fin structure from one side with multi-finger contacts. This asymmetric arrangement optimizes the control gate-to-channel overlap while maintaining adequate spacing to minimize electrical coupling between adjacent devices.
2Area of moving object
If word line spacing is reduced to increase device density, then memory cell area is improved, but device performance deteriorates due to electrical coupling
Solution Approach 1:
The gate structure transitions from a planar configuration to a three-dimensional wrap-around configuration that engages the fin structure from opposite sides. This dimensional change allows the gate to maintain effective control over the channel while the vertical fin structure provides natural electrical isolation, enabling reduced word line spacing without performance degradation.
3Power
If access drive current is increased to improve device performance, then switching speed is improved, but device complexity increases
Solution Approach 1:
The source and drain regions are merged into a continuous active fin structure that extends between the multi-finger gate contacts. This merging creates a unified current path that maximizes drive current while the simple trench isolation and gate stacking provide the necessary device definition without adding structural complexity.
Data Source
AI summary
A single-sided access device includes an active fin structure comprising a source contact area and a drain contact area separated from each other by an isolation region therebetween; a trench isolation structure disposed at one side of the active fin structure, wherein the trench isolation structure intersects with the isolation region between the source contact area and the drain contact area; a sidewall gate disposed under the isolation region and on the other side of the active fin structure opposite to the trench isolation structure so that the active fin structure is sandwiched by the trench isolation structure and the sidewall gate, wherein the sidewall gate has multi-fingers that engage with the active fin structure; and a gate dielectric layer between the sidewall gate and the active fin structure.