FinFET Gate Replacement via Dummy Gate Segmentation
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Solution Overview
Problem
In the fabrication of FinFETs with short channels, the high etching of the oxide layer leads to leakage and extrusion paths for the metal gate, which complicates the gate replacement process and affects the yield and reliability of the semiconductor device.
Innovation Solution
A method is developed that involves forming dummy gate strips with different lengths and widths, followed by the removal of these strips and the subsequent thinning of the dielectric layer between spacers, allowing for the formation of gates that cover the thinned portions, thereby preventing leakage and extrusion paths and enhancing the gate replacement process.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If high etching amount of oxide layer is performed for gate replacement in short channel FinFET, then the oxide layer is sufficiently removed to allow metal gate formation, but leakage paths and extrusion paths are created compromising device reliability
Solution Approach 1:
The gate replacement process is segmented into distinct stages: forming a first dummy gate strip for short channel fins with different dimensions than a second dummy gate strip for long channel fins, forming spacers on both, selectively removing the first dummy gate strip and thinning the dielectric layer, then forming the metal gate. This segmentation allows tailored etching and gate formation for different fin types, preventing leakage paths while enabling successful gate replacement.
2Adaptability or versatility
If dummy gate strips with different dimensions are formed for short and long channel fins, then selective gate replacement is enabled, but device structure and fabrication complexity increase
Solution Approach 1:
Dummy gate strips serve as intermediary structures that facilitate the gate replacement process. The first dummy gate strip (for short channel fins) and second dummy gate strip (for long channel fins) are temporary structures formed on the dielectric layer, enabling selective metal gate formation. These intermediaries are later removed (the first dummy gate strip is removed and thinned, the second is removed) allowing the actual metal gate to be formed in their place, thus mediating between the original oxide layer and the final metal gate structure.
Data Source
AI summary
A substrate is patterned to form trenches and a semiconductor fin between the trenches. Insulators are formed in the trenches and a dielectric layer is formed to cover the semiconductor fin and the insulators. A dummy gate strip is formed on the dielectric layer. Spacers are formed on sidewalls of the dummy gate strip. The dummy gate strip and the dielectric layer underneath are removed until sidewalls of the spacers, a portion of the semiconductor fin and portions of the insulators are exposed. A second dielectric layer is selectively formed to cover the exposed portion of the semiconductor fin, wherein a thickness of the dielectric layer is smaller than a thickness of the second dielectric layer. A gate is formed between the spacers to cover the second dielectric layer, the sidewalls of the spacers and the exposed portions of the insulators.