DRAM Storage Node Contact Self-Aligned Fabrication
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Solution Overview
Problem
The increasing integration density of dynamic random access memory (DRAM) devices complicates their fabrication, particularly in achieving precise overlapping of storage node contacts with active areas without offset, and requires additional masks, making the process more complex.
Innovation Solution
A method of fabricating memory devices involves forming an oxide layer and isolation structures on a semiconductor substrate, creating a recess between the isolation structure and the bit line, and aligning the storage node contact within this recess to ensure complete overlap with the active area without additional masks, using self-alignment processes to simplify the fabrication steps.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If additional masks are used to achieve precise alignment of storage node contact with active area, then manufacturing precision is improved, but device complexity increases
Solution Approach 1:
The isolation structure serves a dual function: it electrically isolates adjacent memory cell units and simultaneously provides alignment reference for forming the storage node contact. The etching process uses the isolation structure as a self-aligned mask, eliminating the need for additional alignment masks and reducing fabrication complexity while maintaining precise alignment.
Solution Approach 2:
The isolation structure performs multiple functions: electrical isolation between memory cells and alignment reference for the storage node contact. This multi-functionality reduces the total number of process steps and masks required, simplifying the fabrication process while ensuring precise alignment.
2Productivity
If integration density is increased to reduce device scale, then productivity is improved, but manufacturing precision becomes more difficult to achieve
Solution Approach 1:
The isolation structure provides self-aligned etching stops that automatically define the storage node contact position relative to the active area. This self-alignment mechanism maintains precise alignment even as feature sizes are reduced for higher integration density, eliminating the need for additional corrective process steps.
Solution Approach 2:
The isolation structure is formed beforehand to establish the alignment reference before the storage node contact formation process. This preliminary positioning ensures that subsequent etching and deposition steps are automatically aligned, maintaining precision as device dimensions are scaled down for higher density.
Data Source
AI summary
A method of fabricating a memory device includes forming an oxide layer on a semiconductor substrate, and forming an isolation structure in the semiconductor substrate and the oxide layer to define an active area. The method also includes forming a word line and a bit line in the semiconductor substrate, wherein the bit line is above the word line. The method further includes removing the oxide layer to form a recess between the isolation structure and the bit line, and forming a storage node contact in the recess. In addition, from a top view, the storage node contact of the memory device overlaps a corresponding portion of the active area.