FinFET Fin Width Uniformity via Substrate Recess and SiGe Material
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Solution Overview
Problem
The challenge in fabricating fin field effect transistors (FinFETs) is to form nFETs and pFETs with different materials while maintaining comparable fin widths, as existing methods result in disparities due to different material responses to processing conditions, leading to variations in electrical properties and increased complexity and cost.
Innovation Solution
A method is developed to form vertical fins on a substrate with different material compositions simultaneously by creating a recess in the substrate, depositing a fin layer with a different material, and using a filler layer to achieve comparable fin widths, allowing for the adjustment of germanium concentration in SiGe fins to match Si fins, thereby reducing processing differences and eliminating the need for additional masking and stripping steps.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If different fin channel materials are used for nFETs and pFETs, then electrical properties can be optimized for each transistor type, but fin width disparities occur due to different material responses to processing conditions
Solution Approach 1:
A recess is formed in the substrate before depositing the fin layer. The recess depth is specifically designed to compensate for the expected width disparity that will occur during subsequent processing. This preliminary structural preparation ensures that after standard processing, both Si fins and SiGe fins achieve comparable final widths, resolving the fin width uniformity issue while maintaining material optimization.
Solution Approach 2:
The substrate topography is modified by creating a recess, changing the starting parameter (substrate surface level) to compensate for material-specific processing responses. This parameter change in substrate structure allows different fin materials to converge to the same final fin width, addressing both electrical property optimization and width uniformity requirements.
2Ease of manufacture
If separate masking and stripping steps are performed for different fin materials, then material-specific processing can be achieved, but processing complexity and cost increase
Solution Approach 1:
The patent merges the processing paths for different fin materials by using a common recess structure and unified fin layer deposition process. Instead of separate masking and stripping steps for Si and SiGe fins, the invention combines these operations into a single integrated process flow, reducing processing complexity while maintaining the ability to form different fin materials from the same substrate region.
Solution Approach 2:
The recess structure serves multiple functions: it compensates for width disparities, enables different fin materials to be formed simultaneously, and eliminates the need for material-specific masking steps. This multi-functional design simplifies the overall manufacturing process while maintaining material-specific processing capabilities.
3Productivity
If device dimensions are scaled down, then higher integration density is achieved, but forming individual components and electrical contacts becomes more difficult
Solution Approach 1:
The recess is formed in advance at the scaled-down device dimensions, providing a pre-prepared structure that facilitates subsequent fin formation. This preliminary action at the target scale eliminates the need for additional size-adjustment steps, making component formation easier despite the reduced dimensions and higher integration density requirements.
Data Source
AI summary
A method of forming vertical fins on a substrate at the same time, the method including, forming a mask segment on a first region of the substrate while exposing the surface of a second region of the substrate, removing a portion of the substrate in the second region to form a recess, forming a fin layer in the recess, where the fin layer has a different material composition than the substrate, and forming at least one vertical fin on the first region of the substrate and at least one vertical fin on the second region of the substrate, where the vertical fin on the second region of the substrate includes a fin layer pillar formed from the fin layer and a substrate pillar.