Trapezoidal Dummy Gate Formation in Gate Last Process
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Solution Overview
Problem
In the gate last technology, the small size and high aspect ratio of gate trenches pose challenges for effective and uniform filling with high-k and metal gate materials after the removal of polycrystalline silicon dummy gates, particularly at technology nodes below 45 nm.
Innovation Solution
A method is introduced to form top-wide-bottom-narrow trapezoidal dummy gates using a hard mask pattern with a first and second mask layer, where the second mask layer has an overhang portion, allowing for controlled angle of inclination and facilitating the subsequent filling of gate trenches with high-k or metal gate materials by forming a top-wide-bottom-narrow hard mask pattern through dry and wet etching processes.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If conventional vertical dummy gates are used in gate last process, then the manufacturing process is simple, but the gate trench filling is ineffective and non-uniform due to small size and high aspect ratio
Solution Approach 1:
The patent applies asymmetry by changing the dummy gate cross-sectional shape from conventional vertical (rectangular) to trapezoidal with top-wide-bottom-narrow configuration. This asymmetric shape creates a corresponding trapezoidal gate trench after removal, which significantly improves material filling uniformity and effectiveness by reducing the aspect ratio effect, directly resolving the technical contradiction between filling quality and structural simplicity.
Solution Approach 2:
The patent employs curvature principles by forming rounded corners and smooth transitions in the trapezoidal dummy gate structure. The etching process creates curved profiles rather than sharp angles, which facilitates uniform material deposition and flow in the gate trench, addressing the filling uniformity issue while maintaining manufacturability.
2Reliability
If top-wide-bottom-narrow trapezoidal dummy gates are formed, then the gate trench filling is effective and uniform, but the manufacturing process complexity increases
Solution Approach 1:
The patent applies segmentation by dividing the mask structure into multiple layers (first mask layer and second mask layer) with different etching rates. This layered approach enables precise control over the trapezoidal profile formation through selective etching, achieving the desired geometry while maintaining process control and reliability.
Solution Approach 2:
The patent utilizes parameter changes by controlling the etching rates of different mask layers through material selection and process optimization. By adjusting etching parameters and mask layer properties, the process achieves the specific top-wide-bottom-narrow profile needed for reliable device manufacturing, balancing complexity with manufacturability.
3Length of moving object
If rectangular gate trenches with high aspect ratio are used, then the device size can be scaled down, but the material filling coverage and density are insufficient
Solution Approach 1:
The patent resolves this contradiction by creating asymmetric trapezoidal gate trenches instead of rectangular ones. The top-wide-bottom-narrow configuration reduces the effective aspect ratio that materials must traverse, enabling complete and dense filling even at scaled-down device dimensions, thus achieving both miniaturization and filling quality.
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 method improves the reliability of device manufacturing by enabling effective and uniform filling of gate trenches, enhancing the window for high-k or metal gate material filling and thus improving device performance.
Implementation Method 1
dry etching the dummy gate material layer using the hard mask to form a top-wide-bottom-narrow dummy gate
Implementation Method 2
etching the hard mask material layer to form a top-wide-bottom-narrow hard mask pattern
Data Source
AI summary
The present invention provides a method of manufacturing a dummy gate in a gate last process, which comprises the steps of forming a dummy gate material layer and a hard mask material layer sequentially on a substrate; etching the hard mask material layer to form a top-wide-bottom-narrow hard mask pattern; dry etching the dummy gate material layer using the hard mask pattern as a mask to form a top-wide-bottom-narrow dummy gate. According to the dummy gate manufacturing method of the present invention, instead of vertical dummy gates used conventionally, top-wide-bottom-narrow trapezoidal dummy gates are formed, and after removing the dummy gates, trapezoidal trenches can be formed. It facilitates the subsequent filling of the high-k or metal gate material and enlarges the window for the filling process; as a result, the device reliability will be improved.