Semiconductor Work Function Layer Thickness Control via Etch Stop
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
The existing semiconductor manufacturing technologies face challenges in accurately controlling the thickness of work function layers in high-K metal gate structures, which affects the threshold voltage and performance of transistors due to difficulties in etching rates between titanium nitride and tantalum nitride, leading to process control issues.
Innovation Solution
The introduction of an etch stop layer formed on the first material layer, which allows for the removal of the second material layer with improved process control, thereby protecting the gate dielectric layer and facilitating the adjustment of threshold voltages by enlarging the process window for etching.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If a work function layer is introduced into the high-K metal gate structure to adjust threshold voltage, then the threshold voltage control is improved, but the process control difficulty increases due to etching rate matching problems between titanium nitride and tantalum nitride
Solution Approach 1:
The patent introduces an etch stop layer as an intermediary between the first material layer (titanium nitride) and the second material layer (tantalum nitride). This etch stop layer serves as a mediator that enables selective etching processes, allowing the second material layer to be removed while protecting the first material layer. The etch stop layer resolves the etching rate matching problem by providing a distinct etching interface that simplifies the removal process and improves thickness control precision.
Solution Approach 2:
The work function layer structure is segmented into multiple distinct layers: a first material layer (titanium nitride), an etch stop layer, and a second material layer (tantalum nitride). This segmentation allows each layer to perform its specific function independently - the first material layer provides work function adjustment, the etch stop layer enables selective etching, and the second material layer can be selectively removed to expose the first material layer. This segmentation resolves the process control difficulty by creating distinct etching stages.
2Adaptability or versatility
If multiple material layers are formed to create work function layers for different transistors, then the threshold voltage adjustment capability is improved, but the device structure complexity increases
Solution Approach 1:
The etch stop layer serves multiple functions simultaneously: it acts as a protective barrier during etching of the second material layer, provides a distinct etching interface for process control, and enables the selective exposure of the first material layer. This multi-functionality reduces the need for additional process steps and simplifies the overall fabrication process despite the multi-layer structure.
Solution Approach 2:
The patent applies different materials and thicknesses at different locations to create work function layers with specific properties for different transistor types. The first material layer and second material layer can have different thicknesses in different regions, allowing independent threshold voltage adjustment for n-type and p-type transistors. This local quality approach enables versatile threshold voltage control while maintaining a systematic fabrication process.
Data Source
AI summary
Semiconductor structures are provided. The semiconductor structure includes a base including first, second, third, and fourth regions, used for first, second, third, and fourth transistors, respectively. A gate dielectric layer is on the first, second, third and fourth regions of the base. A first material layer is on the gate dielectric layer. A second material layer is on the first material layer above the fourth region. A third material layer is on the first material layer above the third region and on the second material layer above the fourth region. A fourth material layer is on the third material layer above the third and fourth regions and on the first material layer on the second region. The first material layer above the first region is used as a first work function layer for the first transistor.