Replacement Metal Gate Transistor Sidewall Material Removal
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Solution Overview
Problem
The manufacturing of replacement metal gate (RMG) transistors faces challenges due to material build-up on sidewalls, which increases parasitic capacitance, reduces trench opening, and leads to non-uniform deposition, limiting the minimum gate width and number of layers that can be deposited effectively, especially as device sizes scale down.
Innovation Solution
The solution involves depositing layers onto the bottom and sidewalls of a trench and then removing a portion of these layers from the sidewalls using angled ion beams to reduce the aspect ratio, improve deposition uniformity, and allow for smaller gate widths, thereby enhancing transistor performance by reducing electrical resistance and capacitance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If material layers are deposited into the trench to form the replacement metal gate, then the transistor structure is formed with proper gate layers, but material build-up on the sidewalls increases parasitic capacitance and reduces transistor performance
Solution Approach 1:
The patent extracts and removes the harmful material build-up from the sidewalls of the trench after deposition. This is achieved through selective etching processes that remove the deposited material from the sidewalls while preserving the material on the bottom of the trench, thereby eliminating the source of parasitic capacitance and improving transistor performance.
Solution Approach 2:
The patent applies different treatments to different regions of the trench: the bottom of the trench retains the full deposited material thickness for proper gate formation, while the sidewalls have the material selectively removed. This local differentiation allows the structure to maintain necessary electrical properties at the bottom while eliminating harmful parasitic effects at the sidewalls.
2Device complexity
If multiple layers of material are deposited into the trench, then the replacement metal gate structure is completed, but the trench opening decreases due to sidewall material build-up
Solution Approach 1:
The patent removes the sidewall material build-up after each deposition step, effectively extracting the space-consuming material that would otherwise reduce the trench opening. This allows subsequent layers to be deposited without the cumulative narrowing effect, maintaining adequate trench opening throughout the multi-layer formation process.
Solution Approach 2:
The patent performs sidewall material removal as a preliminary action before depositing subsequent layers. By clearing the sidewalls after each deposition, the process prepares the trench for the next layer deposition with adequate opening, preventing the cumulative narrowing that would occur if material were allowed to accumulate on the sidewalls.
3Length of stationary object
If the trench aspect ratio increases due to material deposition, then the gate structure is built up, but deposition uniformity deteriorates with non-uniform material distribution
Solution Approach 1:
The patent removes material from the sidewalls where non-uniform deposition tends to accumulate, particularly from the upper portions of the trench. This selective removal compensates for the non-uniform deposition that occurs at high aspect ratios, restoring uniformity to the final gate structure despite the increased trench height.
Solution Approach 2:
The patent changes the physical state or distribution parameters of the deposited material by selectively removing it from certain regions. By altering the material distribution through selective sidewall removal, the process compensates for the non-uniform deposition that occurs when the trench aspect ratio increases, achieving the desired uniformity in the final gate structure.
4Length of moving object
If the trench width decreases to achieve smaller gate widths, then device scaling is achieved, but the minimum thickness requirements for deposited layers become harder to meet
Solution Approach 1:
The patent removes sidewall material that would otherwise consume a significant portion of the already-narrow trench width. By extracting this excess material from the sidewalls, more of the deposited material can be allocated to achieving the minimum required thickness on the bottom of the trench, enabling proper layer formation even in narrower trenches required for device scaling.
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 and quality of RMG transistors by reducing parasitic capacitance, increasing the trench opening, and enabling the deposition of thinner layers, thus facilitating the manufacturing of devices with smaller gate widths and improving the overall electrical characteristics of integrated circuits.
Implementation Method 1
a first layer is deposited onto a bottom of the trench and onto sidewalls of the trench and a second layer is deposited into the trench
Implementation Method 2
various layers of material are deposited to form the RMG
Implementation Method 3
removing a portion of the material deposited on the sidewalls of the trench
Implementation Method 4
removing a portion of these layers from the sidewalls using angled ion beams
Data Source
AI summary
A replacement metal gate transistor is described. Various examples provide a replacement metal gate transistor including a trench, a first sidewall and a second sidewall. A layer is disposed in the trench where the layer has a bottom section disposed on a bottom of the trench and sidewall sections disposed on the first and second sidewalls, wherein the sidewall sections of the layer are at least 50% thinner than the bottom section of the layer.