Nanosheet Patterning With One Mask for Overlay and Capacitance Control
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Solution Overview
Problem
Current semiconductor technologies face challenges in miniaturizing structural features to achieve increased performance at lower power levels and costs, particularly in forming nanosheet field-effect transistors, where multiple mask solutions lead to overlay degradation and parasitic capacitance issues.
Innovation Solution
The method involves forming a nanosheet stack with alternating layers of sacrificial and channel materials over a substrate, using a single lithographic mask for both direct printing and self-aligned double patterning to create nanosheets of varying widths, reducing overlay degradation and enabling precise control over fin widths and spacings.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If multiple masks are used for direct printing and self-aligned double patterning, then nanosheet widths and spacings can be controlled, but overlay degradation occurs
Solution Approach 1:
The patent combines direct printing and self-aligned double patterning into a single lithographic mask, eliminating the need for multiple masks and their associated overlay alignment issues. The single mask defines both the direct print regions and the SADP mandrel regions in one patterning step.
Solution Approach 2:
The single lithographic mask performs multiple functions: it defines regions for direct printing of nanosheets, defines regions for SADP mandrels that will subsequently form additional nanosheets, and establishes the spacing between all nanosheets. This multi-functional approach replaces what previously required multiple specialized masks.
2Adaptability or versatility
If multiple masks are used for patterning, then different fin widths can be achieved, but parasitic capacitance increases
Solution Approach 1:
The patent merges the patterning of different fin widths into a single lithographic step using one mask, rather than requiring multiple sequential mask steps. This reduces the number of process interfaces and associated parasitic capacitances while still achieving the desired variety in fin widths through different regions of the same mask.
3Reliability
If a single mask is used for both direct printing and SADP, then overlay degradation is reduced, but process complexity increases
Solution Approach 1:
The single lithographic mask is segmented into different functional regions: regions that define direct print nanosheets, regions that define SADP mandrels, and regions that will become spacers after mandrel removal. This segmentation allows one mask to perform multiple patterning functions that previously required multiple masks, reducing overlay issues while managing process complexity through clear regional differentiation.
Data Source
AI summary
A method of forming a semiconductor structure includes forming a nanosheet stack including alternating layers of a sacrificial material and a channel material over a substrate, the layers of channel material providing nanosheet channels for one or more nanosheet field-effect transistors. The method also includes forming a hard mask stack over the nanosheet stack, and forming a patterning layer over the hard mask stack. The method further includes patterning a lithographic mask over the patterning layer, the lithographic mask defining (i) one or more first regions for direct printing of one or more fins of a first width in the nanosheet stack and the substrate and (ii) one or more second regions for setting the spacing between two or more fins of a second width in the nanosheet stack and the substrate using self-aligned double patterning. The second width is less than the first width.