Metal Gate Electrode Tiger-Tooth Profile for Threshold Voltage Control
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Solution Overview
Problem
Existing technologies face challenges in accurately controlling the threshold voltage of transistor devices with metal gate structures, as it is difficult to tune the threshold voltage by adjusting individual work function metals after depositing multiple work function metals.
Innovation Solution
A method is introduced where selective etching is performed on one of the work function metals in the metal gate structure, allowing the height of the metal gate to be maintained and enabling precise tuning of the threshold voltage, resulting in a 'tiger tooth' profile for the gate electrode.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If multiple work function metals are deposited to form a metal gate structure, then the threshold voltage tuning capability is improved, but the difficulty of controlling threshold voltage by adjusting individual work function metals increases
Solution Approach 1:
The metal gate structure is segmented into multiple work function metal layers with different etch selectivities. By selectively etching specific layers, the patent enables independent adjustment of threshold voltage while maintaining overall gate structure integrity. This segmentation allows precise control of individual work function contributions to the threshold voltage.
Solution Approach 2:
Different regions of the metal gate structure have different local properties through selective etching of specific work function metal layers. The patent applies local quality by preserving certain work function metal layers in specific areas while removing others, creating spatially varying work function characteristics that enable precise threshold voltage control.
2Manufacturing precision
If selective etching is performed on work function metals to tune threshold voltage, then the threshold voltage control precision is improved, but the manufacturing process complexity increases
Solution Approach 1:
The patent performs preliminary action by depositing multiple work function metal layers with different etch selectivities before the final gate formation. This preliminary structuring enables subsequent selective etching to precisely adjust threshold voltage without requiring complex in-situ tuning processes during manufacturing.
Solution Approach 2:
The patent utilizes parameter changes in the form of different etch selectivities among work function metal layers. By selecting materials with distinct etch responses, the patent enables precise control of threshold voltage through selective removal of specific layers, transforming a complex tuning problem into a controlled material selection and etching process.
3Reliability
If the height of the metal gate is maintained during selective etching, then the effective resistance of the metal gate structure is reduced, but the process control difficulty increases
Solution Approach 1:
The patent introduces intermediary sacrificial layers or spacer structures that mediate the selective etching process. These intermediaries protect the gate height while allowing selective removal of specific work function metal layers, thus maintaining low effective resistance without compromising gate structure integrity or requiring extreme process control.
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 allows for accurate control of the threshold voltage and reduces the effective resistance of the metal gate structure, enhancing the performance of transistor devices.
Implementation Method 1
at least one selective etching process can be performed to etch one of the work function metals
Data Source
AI summary
A semiconductor device is disclosed. The semiconductor device includes a semiconductor fin. The semiconductor device includes first spacers over the semiconductor fin. The semiconductor device includes a metal gate structure, over the semiconductor fin, that is sandwiched at least by the first spacers. The semiconductor device includes a gate electrode contacting the metal gate structure. An interface between the metal gate structure and the gate electrode has its side portions extending toward the semiconductor fin with a first distance and a central portion extending toward the semiconductor fin with a second distance, the first distance being substantially less than the second distance.