Inverting Lithographic Patterns for High Aspect Ratio Structures
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Solution Overview
Problem
Existing photolithographic techniques face challenges in producing high aspect ratio structures with minimum feature sizes below 50 nm, as they often result in unacceptable feature variation due to mechanical instability of thin photoresist regions, making it difficult to meet desired tolerances in semiconductor device manufacturing.
Innovation Solution
A method involving a workpiece with multiple etching chemistry layers, where hole precursors are formed in a first hard mask material, transferred to a substrate, and high aspect ratio structures are created by selectively removing etch stop and substrate layers, using different etching chemistries to maintain stability and precision, allowing for the formation of features with widths ranging from 2 to 50 nm.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Length of moving object
If photolithographic techniques are used to produce features with minimum feature size below 50 nm, then feature size reduction is achieved, but feature variation becomes unacceptably high
Solution Approach 1:
The patent inverts the conventional photolithographic approach by forming high aspect ratio structures first, then using them as masks to define the final features. Instead of directly patterning features with photoresist, the process creates sacrificial structures that are subsequently removed to leave the desired features, thereby avoiding the mechanical instability issues of thin photoresist regions
Solution Approach 2:
The patent introduces high aspect ratio structures as intermediary elements in the fabrication process. These structures serve as temporary masks that enable precise feature definition without requiring thin photoresist layers. The intermediaries are formed using thicker, more stable materials and are later removed to reveal the final features with controlled dimensions
2Shape
If photolithographic techniques are used to form high aspect ratio structures, then structure formation is achieved, but mechanical instability of thin photoresist regions occurs
Solution Approach 1:
Instead of using thin photoresist to directly form high aspect ratio structures, the patent inverts the approach by first forming the high aspect ratio structures using thicker, more stable materials, then using them as masks for the final patterning step
Solution Approach 2:
The patent changes the physical parameters of the masking material by using thicker layers (e.g., 50-200 nm) compared to conventional photoresist thicknesses. This parameter change improves mechanical stability while maintaining the ability to define sub-50 nm features through the inverted process sequence
3Ease of manufacture
If conventional photolithography is used, then manufacturing simplicity is maintained, but tolerance requirements cannot be met
Solution Approach 1:
The patent segments the fabrication process into distinct stages: forming high aspect ratio structures, depositing additional hardmask material, performing planarization, and selective removal. This segmentation allows each step to be optimized independently, achieving both precision and reasonable manufacturing complexity
Solution Approach 2:
The patent transitions from two-dimensional photoresist patterning to three-dimensional structure formation using high aspect ratio features. This dimensional change enables precise lateral feature definition through vertical structure masks, achieving sub-50 nm tolerances that are difficult to obtain with conventional planar photolithography
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 enables the production of high aspect ratio structures with minimal feature size variation, achieving desired tolerances and precision, suitable for applications in semiconductor devices such as via plugs and non-planar transistors.
Implementation Method 1
selectively removing etch stop and substrate layers, using different etching chemistries to maintain stability and precision
Data Source
AI summary
Technologies for inverting lithographic patterns are described. In some embodiments the technologies include a method for inverting a lithographic pattern of hole precursors, so as to form one or more high aspect ratio structures on or in a surface of a substrate.