Split Contact Structure for DRAM Cell Resistance Reduction
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Solution Overview
Problem
The shrinking dimensions of DRAM cell contact structures lead to increased contact resistance and reduced process windows, necessitating an improved cell contact structure for DRAM devices without complicating the fabrication process.
Innovation Solution
A split contact structure is fabricated using a semiconductor substrate with upwardly protruding structures and patterned layers, where the first contact structure is directly on the sidewall of one protruding structure and the second contact structure is indirectly on the sidewall of another, with patterned layers extending in perpendicular directions, employing techniques like CVD and dry etching to form split cell contact regions.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Area of stationary object
If the dimension of the cell contact structure is shrunk to increase DRAM density, then the cell area is reduced, but the contact resistance increases and process window is reduced
Solution Approach 1:
The contact structure is divided into two separate contacts (first contact structure and second contact structure) positioned on opposite sidewalls of the protruding structure. This segmentation allows each contact to be optimized independently for electrical connection, reducing overall contact resistance while maintaining compact cell area.
Solution Approach 2:
The contact structures are positioned vertically on sidewalls rather than horizontally on the surface. This dimensional transition from planar to vertical arrangement reduces the horizontal footprint (cell area) while providing adequate contact area for low resistance through the vertical sidewall surfaces.
2Area of stationary object
If the dimension of the cell contact structure is shrunk to increase DRAM density, then the cell area is reduced, but the process window is reduced
Solution Approach 1:
The protruding structure serves as a self-aligned reference feature that automatically defines the positioning of both contact structures. The contacts are formed relative to this central feature, eliminating the need for additional alignment steps and maintaining a robust process window despite reduced dimensions.
Solution Approach 2:
The protruding structure is formed first as a preliminary feature that establishes the geometric framework for subsequent contact formation. This pre-established reference structure simplifies later processing steps and maintains manufacturing precision even as overall device dimensions are reduced.
3Reliability
If a split contact structure is implemented to reduce contact resistance, then contact resistance is reduced, but the fabrication process complexity increases
Solution Approach 1:
The formation of both contact structures is merged into a single fabrication sequence using the same protruding structure as a common reference. This unified approach allows two contacts to be created simultaneously through coordinated processing steps rather than requiring separate fabrication processes, thereby limiting the increase in overall process complexity.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
This approach reduces contact resistance and maintains process window integrity by creating a stable and efficient cell contact structure for DRAM devices, enhancing the density and performance of DRAM cells without increasing fabrication complexity.
Implementation Method 1
employing techniques like CVD and dry etching to form split cell contact regions
Implementation Method 2
employing techniques like CVD and dry etching to form split cell contact regions
Data Source
AI summary
A split contact structure includes a semiconductor substrate having a major surface; a first upwardly protruding structure disposed on the major surface; a first cell contact region in the major surface and being close to the first upwardly protruding structure; a second upwardly protruding structure disposed on the major surface; a second cell contact region in the major surface and being close to the second upwardly protruding structure; a first patterned layer stacked on the first upwardly protruding structure; a second patterned layer stacked on the first upwardly protruding structure; a first contact structure disposed on a sidewall of the first upwardly protruding structure and being in direct contact with the first cell contact region; and a second contact structure disposed on a sidewall of the second upwardly protruding structure and being in direct contact with the second cell contact region.