Self-aligned double patterning fincut process
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Solution Overview
Problem
Existing methods for cutting fins in semiconductor devices, such as EUV direct print, result in variations in fin length due to optical proximity correction, lithographic, etch, and mask variations, leading to device width variances outside tolerances.
Innovation Solution
A self-aligned double patterning process involving a material stack with multiple mask layers, mandrels, spacers, and cutting masks is used to form multiple fin lengths, allowing for precise cutting of short and long fins by selectively removing mandrels and patterning the material stack to define fin widths.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If EUV direct print is used to cut fins, then fin cutting can be performed, but fin length variations occur due to optical proximity correction, lithographic, etch, and mask variations
Solution Approach 1:
The fin cutting process is segmented into multiple discrete steps: forming mandrels at a first pitch, depositing spacers to define fin lengths, selectively removing mandrels, and performing a second lithographic patterning. This segmentation allows each step to be optimized independently, reducing cumulative variations from a single lithographic step.
Solution Approach 2:
The invention transitions from a two-dimensional lithographic pattern to a three-dimensional self-aligned structure by depositing spacers vertically on mandrels. This dimensional transition creates physical constraints that automatically define fin lengths, reducing dependence on lithographic resolution and optical proximity correction accuracy.
2Productivity
If lithographic process is used to define fin lengths, then fins can be formed, but device width variance falls outside tolerances due to process variations
Solution Approach 1:
The spacer structures serve themselves by automatically defining the fin lengths through their physical dimensions. The spacer width, controlled by deposition thickness rather than lithographic patterning, directly determines the fin length, making the process self-aligning and reducing sensitivity to lithographic variations.
Solution Approach 2:
The invention changes the controlling parameter for fin length from lithographic line width (subject to OPC and LER) to spacer deposition thickness (controlled by atomic layer deposition or chemical vapor deposition). This parameter change shifts the critical dimension control to a more precise and repeatable process.
3Manufacturing precision
If self-aligned double patterning process is used to form multiple fin lengths, then fin length variations are reduced, but process complexity increases
Solution Approach 1:
Mandrels are formed in advance at a relaxed pitch that is easier to pattern lithographically. These preliminary mandrels serve as templates for subsequent spacer deposition, allowing the critical fin lengths to be defined by the spacer width rather than direct lithographic patterning.
Solution Approach 2:
The spacer structures act as intermediaries between the mandrels and the final fin structures. The spacers transfer the dimensional information from the mandrel pitch to the fin lengths, providing a buffer that reduces the direct impact of lithographic variations on the final fin dimensions.
Data Source
AI summary
Methods and devices for forming multiple fin lengths includes forming a material stack on vertical fins. A plurality of mandrels are formed on the material stack. Spacers are formed along the plurality of mandrels with the spacers width being a length of short fins. One or more of the plurality of mandrels are removed. The material stack is patterned to form the short fins beneath the spacers and long fins. The vertical fins are cut with the pattern of the material stack to form the short fins and the long fins.