FinFET Trench Depth Control via Decoupled Etch and Fill
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Solution Overview
Problem
Current fabrication processes for FinFET and forksheet devices lack control over critical dimensions such as the height of the fin structure and dielectric isolation, leading to limitations in design and performance.
Innovation Solution
A method involving separate and decoupled process steps for forming trenches and recessing substrates allows independent control of trench depth and fin height, reducing micro-loading effects and achieving straighter wall profiles and better critical dimension control through filling the trench before forming the fin structure.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If the trench and fin structure are formed simultaneously in a single process step, then the process is simpler and faster, but the trench depth becomes dependent on the fin height and local variations in etch rate occur
Solution Approach 1:
The patent divides the trench formation and fin structure formation into two separate and independent process steps. First, the trench is formed and filled with dielectric material. Second, the fin structure is formed by recessing the substrate. This segmentation allows independent control of trench depth and fin height, eliminating the coupling effect that would occur in simultaneous formation.
Solution Approach 2:
The trench is formed and filled with dielectric material before the fin structure is formed. This preliminary action protects the trench walls during subsequent fin formation processes and establishes the trench depth independently, so that the final fin height does not affect the trench depth.
2Device complexity
If the trench and fin structure are formed simultaneously, then fewer process steps are required, but micro-loading effects and intra-cell fin loading cause local variations in etch rate
Solution Approach 1:
The patent segments the formation process into distinct steps: trench formation and filling, followed by fin structure formation. This separation eliminates micro-loading effects that occur when trench and fin etching are performed simultaneously, as each structure is formed under controlled, independent conditions without competing for etch resources.
3Manufacturing precision
If the trench depth and fin height are controlled independently through separate process steps, then critical dimension control is improved, but the fabrication process becomes more complex
Solution Approach 1:
The dielectric filling material in the trench serves a dual function: it defines the trench depth and simultaneously protects the trench walls during fin formation. This self-service approach eliminates the need for additional protective layers or complex process coordination, making the independent control mechanism relatively simple to implement.
4Reliability
If the trench is filled before forming the fin structure, then the inner walls of the trench are protected, but an additional process step is required
Solution Approach 1:
The dielectric filling material performs multiple functions: it defines the trench depth, protects the trench walls during fin formation, and serves as a barrier during doping processes. This multi-functionality justifies the additional filling step, as it eliminates the need for separate protective measures and simplifies subsequent processing.
Data Source
AI summary
A method for processing a forksheet device includes providing a substrate and forming a trench in the substrate, extending along a first direction, in the substrate. The formation of the trench includes forming a grating structure on the substrate that includes a pair of maskings, arranged at a distance from each other, and etching the trench into the substrate in a region between the pair of maskings. The method also includes filling the trench with a filling material and partially recessing the substrate to form a fin structure. This fin structure includes the filled trench, a first section of the substrate at a first side of the filled trench and a second section of the substrate at a second side of the filled trench, and forming a gate structure on and around the fin structure. The method additionally includes forming a gate structure on and around the fin structure.