SRAM Fin Epitaxial Structure to Prevent Bridging Short Circuits
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Solution Overview
Problem
As semiconductor process nodes shrink, the performance of pull-down transistors in static random access memory (SRAM) fails to meet increasing requirements, and the bridging of epitaxial layers between adjacent fins can lead to short circuits, affecting the performance of the semiconductor structure.
Innovation Solution
The method involves forming epitaxial layers in multiple fins on a semiconductor substrate, controlling the growth rate and size of these layers to prevent bridging, and strategically removing portions of the epitaxial layer to avoid interference with subsequent processes, thereby enhancing the performance of the semiconductor structure.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Area of moving object
If the process node is reduced to shrink transistor sizes, then the integration density is improved, but the performance of pull-down transistors deteriorates
Solution Approach 1:
The patent applies local quality by forming different epitaxial layer structures in different regions of the fin. Specifically, a first epitaxial layer is formed in a first region of the fin, and a second epitaxial layer is formed in a second region of the fin. This allows different material compositions or doping profiles in different locations to optimize both the drive current (performance) and the scaling behavior (size) of the transistor, resolving the contradiction between shrinking size and maintaining performance.
2Productivity
If epitaxial layers are formed in adjacent fins, then the manufacturing efficiency is improved, but the risk of bridging between fins increases
Solution Approach 1:
The patent applies preliminary action by performing a first etch process to form a first opening in the epitaxial layer before forming the second epitaxial layer. This preliminary removal of material creates separation or control features that prevent bridging between adjacent fins during subsequent epitaxial growth. The preliminary action ensures that even when processing multiple fins simultaneously, the epitaxial layers will not bridge, thus maintaining reliability while preserving manufacturing efficiency.
3Reliability
If the size of epitaxial layers is increased to improve transistor performance, then the drive current is improved, but the bridging between adjacent fins occurs
Solution Approach 1:
The patent applies segmentation by dividing the fin structure into multiple regions (first region and second region) and forming separate epitaxial layers in each region. This segmentation allows each epitaxial layer to be optimized for performance without excessive size, while the physical separation through different regions and the preliminary etching process prevents bridging between adjacent fins. Thus, the harmful effect of bridging is eliminated while maintaining the performance benefits of adequately sized epitaxial layers.
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 performance of SRAM by reducing short circuits and optimizing the size and growth of epitaxial layers, ensuring better transistor performance and structural integrity.
Implementation Method 1
forming a first epitaxial layer in the first opening and the second opening; forming a third opening in the at least one third fin; removing at least a portion of the first epitaxial layer in the at least one second fin to form a fourth opening; and forming a second epitaxial layer in the third opening and the fourth opening
Data Source
AI summary
Semiconductor structures is provided. The semiconductor structure includes a semiconductor substrate having at least one first region, a plurality of second regions and a plurality of third regions; at least one second fin formed on one second region of the plurality of second region; at least one third fin formed on one third region of the plurality of third regions; a first epitaxial layer formed in the at least one first fin; and a second epitaxial layer formed in the at least one second fin and the at least one third fin.