FinFET Spacer Structure for Source/Drain Width Control
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Solution Overview
Problem
The semiconductor industry faces challenges in forming reliable semiconductor devices at increasingly smaller sizes due to the complexity and difficulty of fabrication processes as feature sizes decrease, affecting production efficiency and costs.
Innovation Solution
The formation of semiconductor device structures using FinFETs, where fins are patterned using photolithography and self-aligned processes like double-patterning or multi-patterning, and nanostructure transistors, with spacers formed alongside sacrificial layers to create smaller pitches and pattern GAA structures, allowing for more precise control over device dimensions.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If feature sizes are decreased to increase functional density, then production efficiency is improved and costs are lowered, but fabrication process complexity increases and reliability decreases
Solution Approach 1:
The fabrication process is divided into multiple sequential steps including forming first spacers over gate stacks, selectively removing dielectric material, forming second spacers over fin structures, and selective removal. This segmentation allows each step to be optimized independently, managing the overall process complexity while achieving reduced feature sizes and improved functional density.
Solution Approach 2:
Spacers are formed in advance before source/drain structures are created. The first spacers are formed over gate stacks and second spacers are formed over fin structures prior to source/drain formation. This preliminary action defines precise boundaries that prevent merging and ensure proper dimensional control in subsequent processing steps.
2Productivity
If feature sizes are decreased to increase functional density, then production efficiency is improved and costs are lowered, but manufacturing precision becomes more difficult to achieve
Solution Approach 1:
The spacer structures serve as self-aligned boundaries that automatically define the precise edges of source/drain regions. The spacers are formed conformally on existing structures (gate stacks and fins), ensuring that source/drain structures formed between them inherit the precise dimensional control of the spacer widths, thereby maintaining manufacturing precision at reduced feature sizes.
Solution Approach 2:
Different materials are used for spacers (e.g., nitride, oxide) with distinct etch selectivities compared to surrounding dielectric and semiconductor materials. This parameter change in material properties enables precise selective removal of dielectric material while preserving spacer and fin structures, achieving the required manufacturing precision for small feature sizes.
3Reliability
If spacers are formed over sidewalls to constrain source/drain structures, then yield is improved by preventing merging, but device structure complexity increases
Solution Approach 1:
Spacer structures serve as intermediary elements between gate stacks/fin structures and source/drain structures. These spacers mediate the spatial relationship by providing physical boundaries that prevent direct contact between adjacent source/drain regions, thereby improving yield while adding a controlled level of structural complexity that is necessary for reliable device operation.
Solution Approach 2:
The fabrication process forms first spacers over gate stacks and second spacers over fin structures at different stages with different material compositions. This asymmetric approach allows each spacer type to be optimized for its specific function and removed selectively when no longer needed, managing structural complexity while maintaining the yield benefits of spacer-based source/drain confinement.
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 improves the yield and constrains the size of source/drain structures, preventing them from merging, thereby enhancing the reliability and efficiency of semiconductor device fabrication at smaller scales.
Implementation Method 1
using etch-selective materials and processes such as anisotropic and isotropic etching
Data Source
AI summary
A method for forming a semiconductor device structure is provided. The method includes forming a dielectric layer over a substrate. The substrate has a base and a fin structure over the base, and the dielectric layer is over the base and surrounds the fin structure. The method includes forming a gate stack over the fin structure and the dielectric layer. The method includes removing portions of the dielectric layer, which are not covered by the gate stack. The method includes forming first spacers over first sidewalls of the gate stack. The method includes forming second spacers over second sidewalls of the fin structure. The method includes partially removing the fin structure, which is not covered by the gate stack and the first spacers. The method includes forming a source/drain structure over the fin structure, which is not covered by the gate stack and the first spacers.