Sacrificial Fill for Gate Opening Corner Rounding
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Solution Overview
Problem
In the fabrication of advanced integrated circuits, the replacement of silicon dioxide with high-k dielectric materials for gate insulation layers and the use of non-polysilicon materials for gate electrodes lead to challenges in maintaining capacitive coupling and adjusting the work function, resulting in variability and increased leakage current, especially in aggressively scaled transistors.
Innovation Solution
The use of a sacrificial fill material to modify the cross-sectional shape of gate openings, allowing for improved filling of conductive electrode materials and work function adjusting species, thereby reducing irregularities and variability in transistor performance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Use of energy by moving object
If high-k dielectric materials are used to replace silicon dioxide for gate insulation, then capacitive coupling is improved, but leakage current increases and manufacturing precision deteriorates
Solution Approach 1:
The gate electrode structure is segmented into multiple functional layers: a work function adjusting species layer deposited on the high-k dielectric, and a conductive electrode material layer filled in the opening. This segmentation allows the work function to be independently adjusted while maintaining the high capacitive coupling of the high-k dielectric, and the filling process is optimized to prevent leakage paths.
2Reliability
If non-polysilicon materials are used for gate electrodes, then device performance is improved, but work function adjustment becomes complex and manufacturing precision deteriorates
Solution Approach 1:
A work function adjusting species layer is deposited on the high-k dielectric material before filling the conductive electrode material. This preliminary action establishes the desired work function characteristics in advance, simplifying the subsequent filling process and improving manufacturing precision by decoupling the work function adjustment from the electrode material selection.
3Productivity
If gate openings are aggressively scaled to improve transistor density, then productivity is improved, but filling completeness deteriorates and non-functional gate electrodes increase
Solution Approach 1:
The approach transitions from attempting to fill extremely narrow vertical openings to creating a layered structure where the work function adjusting species is deposited as a thin film on the high-k dielectric surface, and the conductive electrode material is deposited as another layer. This dimensional approach to filling ensures complete coverage even in aggressively scaled openings, preventing non-functional gate electrodes while maintaining high transistor density.
Data Source
AI summary
In a replacement gate approach, a top area of a gate opening has a superior cross-sectional shape which is accomplished on the basis of a plasma assisted etch process or an ion sputter process. During the process, a sacrificial fill material protects sensitive materials, such as a high-k dielectric material and a corresponding cap material. Consequently, the subsequent deposition of a work function adjusting material layer may not result in a surface topography which may result in a non-reliable filling-in of the electrode metal. In some illustrative embodiments, the sacrificial fill material may also be used as a deposition mask for avoiding the deposition of the work function adjusting metal in certain gate openings in which a different type of work function adjusting species is required.