Fin Density Control via Sidewall Image Transfer
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Solution Overview
Problem
Current sidewall image transfer methods for multigate devices require complex patterning stacks and are costly, making it challenging to control fin density effectively.
Innovation Solution
The method involves forming mandrels with sidewalls of different materials that are selectively etchable, allowing for a simplified patterning process and a single fin cut to achieve quadrupled fin density using a relaxed overlay margin lithography mask, leveraging the selectivities of the sidewalls to control the sidewall image transfer pattern.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If a complex patterning stack with at least ten different layers is used for sidewall image transfer, then fin density control can be achieved, but the fabrication cost and process complexity increase significantly
Solution Approach 1:
The mandrel sidewalls are segmented into different materials (first material and second material) with different etching selectivities. This segmentation allows selective removal of specific sidewalls to create the desired fin pattern, achieving precise fin density control without requiring a complex multi-layer patterning stack
Solution Approach 2:
Different materials are applied to different locations (sidewalls) of the mandrel structure based on their etching selectivity requirements. The first sidewall uses a material with different etching characteristics than the second sidewall, enabling localized control over the sidewall image transfer process and simplifying the overall patterning approach
2Manufacturing precision
If multiple sidewall image transfer etching steps are performed to quadruple fin density, then fin density control is achieved, but the process time and manufacturing complexity increase
Solution Approach 1:
The mandrels are pre-formed with sidewalls of different materials before the sidewall image transfer process. This preliminary differentiation of sidewall materials enables the subsequent etching process to selectively remove specific sidewalls in a single operation, achieving fin density quadrupling without requiring multiple sequential etching steps
Solution Approach 2:
The etching process parameters are optimized to exploit the selectivity difference between the first and second sidewall materials. By controlling the etching conditions to selectively remove the first material while preserving the second material, the process achieves complex fin patterns in fewer steps, reducing overall process time
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 simplifies the fin formation process, reduces costs, and enables precise control of fin density by using a single fin cut and a simple patterning stack, achieving quadrupled fin density with improved process efficiency.
Implementation Method 1
a plurality of sidewalls are formed in a plurality of mandrels over a semiconductor substrate by performing an angular ion implantation process
Implementation Method 2
a plurality of sidewalls are formed on a plurality of mandrels over a semiconductor substrate by performing an angular deposition process
Implementation Method 3
each of the mandrels includes a first sidewall composed of a first material and a second sidewall composed of a second material that is different from the first material... The first sidewall of a first mandrel of the plurality of mandrels is selectively removed
Data Source
AI summary
Methods and structures for fabricating fins for multigate devices are disclosed. In accordance with one method, a plurality of sidewalls are formed in or on a plurality of mandrels over a semiconductor substrate such that each of the mandrels includes a first sidewall composed of a first material and a second sidewall composed of a second material that is different from the first material. The first sidewall of a first mandrel of the plurality of mandrels is selectively removed. In addition, a pattern composed of remaining sidewalls of the plurality of sidewalls is transferred onto an underlying layer to form a hard mask in the underlying layer. Further, the fins are formed by employing the hard mask and etching semiconducting material in the substrate.