Metal Gate Fill via Dummy Gate Removal
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Solution Overview
Problem
The integration of high-k/metal gate features in CMOS processes is challenging due to narrow gate trenches, which can lead to bridging and voids during metal gate fill, especially in replacement polysilicon gate (RPG) devices with trench widths less than 10 nm for N-MOS and less than 2 nm for P-MOS, complicating the processing and manufacturing of advanced semiconductor devices.
Innovation Solution
A method involving the formation of a semiconductor device with a gate structure that includes spacers and a dummy gate, where portions of the dummy gate and spacers are removed to create widened trenches, allowing for the deposition of a high-k film and metal gate, thereby addressing the bridging and void issues by enlarging the trench space for better metal fill.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If narrow gate trenches are used to achieve higher functional density, then device scaling is improved, but bridging and voids occur during metal gate fill
Solution Approach 1:
The gate structure is segmented into multiple components: spacers, dummy gates, and real metal gates. The dummy gates are temporarily formed to define trench regions, then removed to create openings for metal gate fill. This segmentation allows the trench width to be effectively increased during the fill process while maintaining the original narrow device geometry.
Solution Approach 2:
Dummy gates serve as intermediary structures that facilitate the metal gate fill process. These temporary structures are formed between the spacers, then selectively removed to create widened trench openings. The dummy gates mediate between the narrow device dimensions and the requirements for adequate metal gate fill, enabling both high functional density and reliable metal deposition.
2Length of stationary object
If gate trench width is reduced for scaling, then geometry size decreases, but voids and bridging increase during metal fill
Solution Approach 1:
Dummy gates are formed in advance between the spacers to establish the trench geometry before metal gate deposition. This preliminary action creates a template that ensures proper trench width and alignment. The dummy gates are then removed, leaving behind precisely defined openings that facilitate uniform metal gate fill, thereby improving manufacturing precision.
Solution Approach 2:
The solution introduces an additional temporal dimension to the trench width problem. The trench width is effectively dynamic: narrow during device operation (defined by spacer spacing) but widened during metal gate fill (after dummy gate removal). This dimensionality change allows the same structure to satisfy both scaling requirements and fill uniformity requirements at different process stages.
3Reliability
If dummy gate and spacer removal is performed to widen trenches, then metal gate fill quality improves, but process complexity increases
Solution Approach 1:
The dummy gates serve multiple functions: they define trench regions, act as placeholders for metal gate deposition, and can be selectively removed to create openings. The spacers simultaneously define device boundaries and protect regions that should not be etched. This multi-functionality reduces the need for additional dedicated structures, thereby limiting the increase in process complexity.
Solution Approach 2:
The dummy gates are temporary structures that are discarded after serving their purpose of defining trench regions. Their removal is a deliberate step to create openings for metal gate fill. The spacers are retained as permanent structures that define the final device geometry. This selective discarding and recovery strategy optimizes the balance between process complexity and fill quality.
Data Source
AI summary
The present disclosure provides various methods of fabricating a semiconductor device. A method of fabricating a semiconductor device includes providing a semiconductor substrate and forming a gate structure over the substrate. The gate structure includes a first spacer and a second spacer formed apart from the first spacer. The gate structure also includes a dummy gate formed between the first and second spacers. The method also includes removing a portion of the dummy gate from the gate structure thereby forming a partial trench. Additionally, the method includes removing a portion of the first spacer and a portion of the second spacer adjacent the partial trench thereby forming a widened portion of the partial trench. In addition, the method includes removing a remaining portion of the dummy gate from the gate structure thereby forming a full trench. A high k film and a metal gate are formed in the full trench.