Seamless Contact Plug Formation via Reverse Memory Mandrel
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Solution Overview
Problem
The down-scaling of integrated circuits leads to increased aspect ratios of contact plugs, making it difficult to fill contact openings without seam holes, which reduces the effective conducting area and causes reliability issues, as the thickness of Inter-Layer Dielectric (ILD) does not scale proportionally with the reduction in contact plug dimensions.
Innovation Solution
The formation of contact plugs involves creating a reverse memory layer with high etching selectivity, using Atomic Layer Deposition (ALD) for gap-filling, and employing reverse memory posts as an etching mask to pattern the metallic layer, ensuring no seam holes are formed and maintaining controlled dimensions, thereby preventing voids and improving mechanical strength.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If the horizontal dimensions of contact plugs are reduced to accommodate integrated circuit down-scaling, then the density and integration level improve, but the aspect ratio of contact plugs increases and seam holes form during filling
Solution Approach 1:
A mandrel structure is formed at the bottom of the contact opening before filling the contact plug. This preliminary structure serves as a foundation that prevents seam hole formation during the subsequent filling process, allowing contact plugs to be successfully formed even with high aspect ratios associated with down-scaled dimensions
Solution Approach 2:
The mandrel acts as an intermediary structure between the contact opening and the metallic contact plug material. This intermediate element facilitates the filling process by providing a nucleation site and structural support, enabling complete filling without voids or seam holes in high aspect ratio contact openings
2Strength
If the thickness of Inter-Layer Dielectric (ILD) is not reduced proportionally with contact plug dimensions, then the mechanical strength and processability are maintained, but the aspect ratio of contact plugs increases making filling difficult
Solution Approach 1:
The mandrel structure is formed in advance at the bottom of the contact opening, providing a structural foundation before the contact plug filling process. This preliminary action enables successful filling of high aspect ratio contact openings without requiring proportional reduction of ILD thickness, thus maintaining mechanical strength while enabling down-scaling
Solution Approach 2:
The introduction of the mandrel structure changes the effective parameters of the contact formation process. By providing a bottom foundation, the mandrel modifies the filling dynamics and allows for successful deposition even with high aspect ratios, effectively decoupling the scaling of contact plug dimensions from ILD thickness requirements
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 method ensures the formation of contact plugs without voids, enhancing their quality and electrical performance by maintaining the contact area and preventing the etch stop layer and metal lines from falling into seam holes, thus widening the process window for integrated circuit down-scaling.
Implementation Method 1
using Atomic Layer Deposition (ALD) for gap-filling
Data Source
AI summary
A method includes forming a metallic layer over a Metal-Oxide-Semiconductor (MOS) device, forming reverse memory posts over the metallic layer, and etching the metallic layer using the reverse memory posts as an etching mask. The remaining portions of the metallic layer include a gate contact plug and a source/drain contact plug. The reverse memory posts are then removed. After the gate contact plug and the source/drain contact plug are formed, an Inter-Level Dielectric (ILD) is formed to surround the gate contact plug and the source/drain contact plug.