Semiconductor Mandrel Structure for Uniform Fin Patterning
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Solution Overview
Problem
Existing methods for forming mandrels of different widths for semiconductor fabrication, such as for field-effect transistors, face challenges in achieving sufficient selectivity during etching, leading to non-uniform widths of resulting mandrels and three-dimensional active regions, which affects the precision of the fabricated structures.
Innovation Solution
A method involving the formation of a mandrel structure with first and second mandrels of different materials, where the second mandrels are formed on the sidewalls of the first mandrels, and a protective layer is used to maintain desired dimensions during etching, employing phosphoric acid for selective removal of the second mandrels to achieve uniform widths of the resulting mandrels.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If conventional etching methods are used to form mandrels of different widths, then the fabrication process can be completed, but the selectivity during etching is insufficient leading to non-uniform widths of mandrels and three-dimensional active regions
Solution Approach 1:
The mandrel structure is segmented into multiple material layers (first mandrel material layer and second mandrel material layer) with different etching characteristics. This segmentation allows selective removal of the second mandrel material layer while preserving the first mandrel material layer, achieving uniform mandrel width and improved etching selectivity.
Solution Approach 2:
Different regions of the mandrel structure are assigned different material compositions (first mandrel material vs. second mandrel material) to create local quality variations. The second mandrel material layer is specifically engineered to be more susceptible to the etching solution, enabling precise control over etching depth and maintaining uniform mandrel width throughout the structure.
2Productivity
If mandrels of various widths are formed for scaling down, then functional density increases, but the complexity of patterning and manufacturing increases
Solution Approach 1:
The mandrel structure is divided into multiple material layers that can be selectively processed. This segmentation enables the formation of mandrels with different widths and configurations from a single patterned layer, reducing the number of patterning steps required and simplifying the manufacturing process while maintaining high functional density.
Solution Approach 2:
Instead of forming different width mandrels through multiple patterning steps, the invention inverts the approach by creating a single patterned mandrel structure with varying material compositions. The selective etching of the second mandrel material layer automatically generates the desired width variations, simplifying the patterning process while achieving the required functional density.
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 ensures the mandrels maintain uniform width along their height, improving the critical dimension of subsequently formed fins and reducing height loss, thereby enhancing the precision and uniformity of semiconductor structures like nanosheet FETs and FinFETs.
Implementation Method 1
removing the second mandrels from the sidewalls of the first mandrels in a wet etching process
Implementation Method 2
a protective layer is used to maintain desired dimensions during etching
Data Source
AI summary
A method includes forming a semiconductor substrate, forming hard mask layers (HMs) over the semiconductor substrate, forming first mandrels over the HMs, forming second mandrels along sidewalls of the first mandrels, forming a protective layer over the first mandrels and the second mandrels, removing a portion of the protective layer to expose portions of the first and the second mandrels, removing the exposed portions of the second mandrels with respect to the exposed portions of the first mandrels, removing remaining portions of the protective layer to expose remaining portions of the first and second mandrels, where the exposed portions of the first mandrels and the remaining portions of the first and second mandrels form a mandrel structure, patterning the HMs using the mandrel structure as an etching mask, and patterning the semiconductor substrate to form a fin structure using the patterned HMs as an etching mask.