MRAM Isolation Structure Using Vertical Gate for Size Reduction
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Solution Overview
Problem
Conventional shallow trench isolation structures in semiconductor devices are large, leading to increased size of memory apparatuses, and there is a need to reduce the size of isolation structures between cell units while maintaining effective isolation in magnetic random access memory (MRAM) devices.
Innovation Solution
A novel isolation structure for MRAM devices is proposed, featuring a trench in a fin line substrate with an oxide layer, a liner layer, a nitride layer partially filling the trench, and a gate-like structure fully filling the trench, which includes a polysilicon or high-K dielectric and metal layer, and optionally a spacer on the sidewall, designed to reduce the width of the isolation structure while maintaining isolation effectiveness.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a conventional shallow trench isolation (STI) structure is used to isolate cell units, then the isolation effect is maintained, but the size of the isolation structure and the overall memory apparatus becomes large
Solution Approach 1:
The patent introduces a vertical gate-like structure that extends downward into the trench to provide isolation, rather than relying solely on the horizontal oxide layer. This vertical dimension allows the isolation function to be achieved with a smaller horizontal footprint, directly resolving the contradiction between maintaining isolation effectiveness and reducing the area occupied by the isolation structure
Solution Approach 2:
The gate-like structure is nested within the trench region, with the oxide layer forming the upper portion and the gate-like structure extending downward into the trench. This nested configuration allows both the oxide layer and the gate-like structure to contribute to isolation within a compact vertical space, reducing the overall horizontal area required while maintaining effective isolation between cell units
2Area of stationary object
If the size of isolation structures between cell units is reduced, then the overall size of the memory apparatus is minimized, but the isolation effect may be compromised
Solution Approach 1:
By transitioning from a primarily horizontal isolation approach (oxide layer) to a vertical isolation approach (gate-like structure extending into the trench), the patent achieves effective isolation with a reduced horizontal footprint. This allows the memory apparatus size to be minimized while maintaining the isolation effect through the vertical extension of the gate-like structure
Solution Approach 2:
The isolation structure combines the oxide layer and the gate-like structure into a composite configuration, where the oxide layer provides upper isolation and the gate-like structure (comprising conductive material) provides deeper isolation within the trench. This composite approach ensures robust isolation effectiveness while allowing for compact horizontal dimensions
Data Source
AI summary
An isolation structure is disposed between fin field effect transistors of a magnetic random access memory (MRAM) device. The isolation structure includes a fin line substrate, having a trench crossing the fin line substrate. An oxide layer is disposed on the fin line substrate other than the trench. A liner layer is disposed on an indent surface of the trench. A nitride layer is disposed on the liner layer, partially filling the trench. An oxide residue is disposed on the nitride layer within the trench at a bottom portion of the trench. A gate-like structure is disposed on the oxide layer and also fully filling the trench.