Elevated Source-Drain Structure for Easier Gate Trench Filling
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Solution Overview
Problem
The challenge is to reduce the manufacturing difficulty of a gate structure in transistors with smaller active regions and improve the electrical performance, as the reduced size leads to increased resistance and filling limitations due to narrower trenches with higher depth-to-width ratios.
Innovation Solution
A method involving the formation of elevated source and drain regions using a selective epitaxial process, which increases the top width of these regions while maintaining or reducing the bottom width, allowing for wider trenches with lower depth-to-width ratios, facilitating easier gate material filling and reducing resistance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Length of moving object
If the transistor size is reduced continuously, then the gate structure size is reduced, but the manufacturing difficulty increases and electrical performance deteriorates
Solution Approach 1:
The patent introduces elevated source and drain regions that protrude from the substrate surface, creating a three-dimensional structure. This vertical dimension allows the gate trench to be shallower while maintaining effective gate control, as the gate can wrap around or contact the elevated regions from the side, effectively adding a lateral control dimension to the gate's influence.
Solution Approach 2:
The elevated source and drain regions are formed before gate trench filling. This preliminary formation of elevated regions with controlled topologies (such as inclined or curved surfaces) prepares the structure in advance to facilitate easier material deposition and reduce manufacturing complexity in subsequent gate formation steps.
2Length of moving object
If the transistor size is reduced continuously, then the gate structure size is reduced, but the resistance of the gate structure increases
Solution Approach 1:
By elevating the source and drain regions, the gate structure can extend laterally along the elevated surfaces, increasing the effective gate area and contact perimeter without increasing the vertical depth. This dimensional change allows for reduced resistance through increased conductive path area while maintaining compact vertical footprint.
3Length of moving object
If the trench width is reduced, then the transistor size is reduced, but the depth-to-width ratio increases making material filling difficult
Solution Approach 1:
The elevated source and drain regions create a stepped or terraced structure where the gate trench becomes shallower in the vertical dimension. Material can be deposited more easily from the top down onto the elevated regions, and the reduced vertical depth-to-width ratio facilitates complete filling without voids or incomplete coverage.
Solution Approach 2:
Forming the elevated regions with specific surface topologies (inclined planes, curved surfaces) before gate deposition creates favorable surfaces that guide material flow and deposition, ensuring complete and uniform filling of the gate trench while reducing the need for complex multi-step deposition processes.
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 reduces manufacturing difficulty, improves electrical performance by ensuring effective electrical connection, and decreases the resistance of the gate structure, while maintaining accurate position and size control of the elevated regions.
Implementation Method 1
An elevated source region and an elevated drain region is formed on the source region and the drain region, respectively. In one of the embodiments, the elevated source region and the elevated drain region is formed by a selective epitaxial process.
Data Source
AI summary
A semiconductor structure and a method for forming the same are provided. The method includes: forming an active region on a substrate; forming at least one trench in the active region, the trench at least dividing the active region into a source region on one side of the trench and a drain region on the other side of the trench; and forming an elevated source region and an elevated drain region on the source region and the drain region respectively.