FinFET Gate Structure with Selective Wet Etch Height Control
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Solution Overview
Problem
In the semiconductor industry, FinFET devices face challenges with metal gate leakage and precise control of gate height and critical dimension in advanced processing nodes, particularly due to the close pitch between metal gates, which can lead to reliability issues and damage to underlying structures during etching processes.
Innovation Solution
A method is developed involving selective wet etch processes to reshape the metal fill instead of removing it, allowing for precise control of gate height and preserving the critical dimension of metal gates, while reducing metal gate leakage by modifying the etching selectivity of the wet etching solution to preferentially etch the glue layer over the fill metal.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional etching processes are used to remove metal fill, then metal gate leakage is reduced, but gate height control precision and critical dimension preservation deteriorate due to unintentional overetching
Solution Approach 1:
A glue layer is introduced as an intermediary material between the gate dielectric layer and the metal fill. This glue layer serves as a sacrificial layer that is selectively etched away, allowing the metal fill to be removed without directly contacting and damaging the gate dielectric layer. The selective etching of the glue layer prevents unintentional overetching and preserves the critical dimensions of the metal gates while still achieving metal gate leakage reduction.
Solution Approach 2:
The etching selectivity parameters are optimized to etch the glue layer at a significantly faster rate than the metal fill and gate dielectric layer. By controlling the etching solution composition and process parameters, the glue layer can be removed selectively, preserving the metal fill's critical dimensions and the gate dielectric layer integrity while enabling metal gate leakage reduction.
2Reliability
If aggressive etching is applied to remove metal fill, then metal gate leakage is reduced, but damage to gate dielectric layer and underlying structures increases
Solution Approach 1:
The glue layer acts as a protective intermediary that absorbs the etching action, preventing the etching solution from directly attacking the gate dielectric layer. This sacrificial layer can be aggressively etched without harming the underlying gate dielectric, thus reducing metal gate leakage while preventing damage to critical structures.
Solution Approach 2:
The glue layer is deposited beforehand as a cushioning protective layer between the metal fill and the gate dielectric layer. This pre-positioned protective layer anticipates and prevents potential damage to the gate dielectric during the metal fill removal process, allowing for more aggressive and effective etching of the metal fill.
3Ease of manufacture
If metal fill is completely removed, then manufacturing simplicity is improved, but gate height control and critical dimension preservation worsen due to loss of structural support
Solution Approach 1:
The glue layer serves as a temporary structural intermediary that maintains the metal fill's position and shape during processing. By selectively removing only the glue layer and preserving the metal fill, the process achieves manufacturing simplicity while the remaining metal fill continues to provide structural support for gate height control and critical dimension preservation.
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 the risk of unintentional overetching, increases the reliability of the device, and prevents damage to the gate dielectric layer, ensuring precise control of gate heights and maintaining the critical dimension of the metal gates.
Implementation Method 1
simultaneously etching the glue layer and the fill metal with a wet etching solution, the wet etching solution etching the glue layer at a faster rate than the fill metal and reshaping the fill metal
Data Source
AI summary
A semiconductor device includes a gate electrode over a channel region of a semiconductor fin, first spacers over the semiconductor fin, and second spacers over the semiconductor fin. A lower portion of the gate electrode is between the first spacers. An upper portion of the gate electrode is above the first spacers. The second spacers are adjacent the first spacers opposite the gate electrode. The upper portion of the gate electrode is between the second spacers.