Source/Drain Contact Opening Shrinkage via Multi-Layer Etching
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Solution Overview
Problem
Current methods for forming source/drain contact plugs in integrated circuits face limitations in reducing the width of contact openings beyond the capabilities of lithography processes, leading to potential process difficulties and yield loss.
Innovation Solution
A method is developed to shrink the dimensions of source/drain contact openings by adjusting the etching masks and etching processes across multiple layers, achieving significant reduction in opening widths through controlled etching and polymer-forming gas ratios, ensuring the widths of the contact openings are smaller than the lithography limit without excessive shrinkage in any single layer.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If lithography processes are used to form contact openings, then the process is simple and straightforward, but the minimum width of contact openings is limited by lithography capabilities
Solution Approach 1:
The etching mask is divided into multiple layers (first etching mask layer, second etching mask layer, third etching mask layer) with each layer contributing to the overall pattern formation. This segmentation allows the contact opening width to be reduced beyond single-layer lithography limits by combining the patterning effects of multiple layers through selective etching processes.
Solution Approach 2:
The solution transitions from two-dimensional planar patterning to three-dimensional multi-layer stack patterning. By adding the vertical dimension with multiple etching mask layers, the system achieves lateral resolution beyond the diffraction limit of single-layer lithography, effectively using the z-dimension to overcome x-y plane resolution constraints.
2Manufacturing precision
If the width of contact openings is reduced significantly, then smaller contact plugs can be formed, but process difficulties increase and yield loss occurs
Solution Approach 1:
The total width reduction is segmented across multiple etching mask layers, with each layer responsible for a portion of the dimensionality control. This distributes the precision requirement across layers rather than demanding extreme precision from a single layer, reducing process sensitivity and improving yield.
Solution Approach 2:
Each etching mask layer is optimized with specific properties (material composition, thickness, patterning characteristics) tailored to its role in the overall process. This local optimization allows each layer to contribute maximally to width control while maintaining robustness against process variations.
3Manufacturing precision
If excessive shrinkage is applied in a single layer, then contact opening width can be reduced, but the process becomes difficult to control
Solution Approach 1:
The dimensionality control is segmented across multiple etching mask layers, distributing the shrinkage function. This prevents any single layer from requiring excessive shrinkage that would be difficult to control, instead achieving cumulative width reduction through coordinated etching of multiple layers with moderate individual contributions.
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 allows for the formation of contact plugs with reduced widths, minimizing process problems and yield loss, while maintaining control over the shrinking process by distributing the width reduction across multiple layers.
Implementation Method 1
etching the middle layer using the patterned upper layer as an etching mask to extend an opening in the patterned upper layer into the middle layer
Implementation Method 2
controlling a ratio of a polymer-forming gas to an etching gas
Data Source
AI summary
A method includes forming a first hard mask layer and a second hard mask layer over the first hard mask layer, and forming a tri-layer including a bottom layer, a middle layer, and a patterned upper layer. The method further includes etching the middle layer to extend an opening in the patterned upper layer into the middle layer, wherein the opening has a first portion in the middle layer, and the first portion has a first top width and a first bottom width smaller than the first top width; etching the bottom layer to extend the opening into the bottom layer; and etching the second hard mask layer to extend the opening into the second hard mask layer. The opening has a second portion in the second hard mask layer, and the second portion has a second top width and a second bottom width smaller than the second top width.