EUV Trench CD Control via Trim Layer Isotropic Etching
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Solution Overview
Problem
Current photolithography techniques, including extreme ultraviolet (EUV) lithography, face challenges in achieving precise control over critical dimensions (CD) for structures with pitches of 36 nm or less, leading to defects such as single line opens, particularly in back-end-of-line (BEOL) trench formation processes.
Innovation Solution
A method involving a substrate with a patterned layer and a trim layer, where the trim layer is etched and then isotropically trimmed to reduce its critical dimension, allowing for nanometer-level control of EUV lithography processes. This process involves using the trim layer as a mask to replicate smaller linewidths in underlying layers, enabling precise control of trench dimensions.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If EUV lithography is used for 36 nm and lower pitch structures, then lithography capability is improved, but single line open defects increase
Solution Approach 1:
The patent segments the lithography process into multiple steps: initial EUV patterning to form first patterned structures, followed by a separate trim process using isotropic gaseous etching to adjust critical dimensions. This segmentation allows the patterning and dimension control functions to be performed independently, achieving both high precision and low defect rates.
Solution Approach 2:
The patent applies preliminary action by first forming the patterned structures with EUV lithography, then performing a preliminary trim on the trim layer before final pattern transfer. This preliminary trimming adjusts the critical dimensions to account for process variations, ensuring accurate final dimensions while maintaining defect-free structures.
2Manufacturing precision
If trim layer structures are formed with smaller linewidths than patterned layer, then CD control is improved, but process complexity increases
Solution Approach 1:
The patent introduces a trim layer as an intermediary between the patterned layer and the underlying layers. This trim layer serves as a mediator that absorbs the complexity of dimension control, allowing the final pattern transfer to proceed with simplified process steps while maintaining nanometer-level CD control through the trim layer's pre-adjusted dimensions.
Solution Approach 2:
The patent utilizes parameter changes by employing isotropic gaseous etching to precisely control the trim layer's critical dimensions. By adjusting etching parameters such as gas composition, pressure, and power, the process achieves nanometer-level dimension control, improving CD precision without requiring complex lithography tool modifications.
3Measurement precision
If isotropic gaseous process is used to trim structures, then linewidth precision is improved, but material removal increases
Solution Approach 1:
The patent applies local quality by making the trim layer compositionally or structurally distinct from surrounding layers, enabling selective isotropic gaseous etching. The trim layer is designed with specific properties (such as oxide material with controlled thickness) that allow it to be preferentially removed with high precision while minimizing material removal from other critical structures.
Solution Approach 2:
The patent implements partial action by trimming only the trim layer to the required precision rather than trimming all layers. The isotropic gaseous process is applied selectively to the trim layer with controlled duration and intensity, achieving the necessary linewidth precision for CD control while removing only the minimal amount of material needed for the trim layer, thus reducing overall material loss.
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
The method provides accurate control of critical dimensions with nanometer-level precision, reducing linewidths by 0.2-5 nm, thereby avoiding single line opens and enhancing the process window for EUV lithography at pitches of 36 nm or less, allowing for increased trench dimensions and improved defect control.
Implementation Method 1
utilizing an isotropic gaseous process to trim the structures of the trim layer
Data Source
AI summary
A substrate is provided with a patterned layer over a stack of one or more processing layers. The processing layers include at least one trim layer and at least one masking layer under the trim layer. The trim layer may have structures that have smaller linewidths than the structures of the patterned layer by utilizing an isotropic gaseous process to trim the structures of the trim layer. The structures of the trim layer, after trimming, may then be replicated in the mask layer to provide a linewidth in the mask layer that is smaller than the linewidth in the patterned layer. The technique may allow nanometer control of an EUV lithography process at pitches of 36 nm or less. In one embodiment, the technique may be utilized to provide an EUV lithography process for increasing the trench dimensions in a BEOL trench formation process step.