P-Type Work Function Layer Oxygen Staging for Nano-FET Gates
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Solution Overview
Problem
Current semiconductor devices face challenges in achieving optimal work function structures for improved device speed and performance, particularly in nano-FETs, due to limitations in integrating high oxygen concentrations at the interface between gate dielectric and work function layers.
Innovation Solution
A method involving the iterative deposition of work function layers followed by exposure to an oxygen-containing environment to increase oxygen concentration within the work function structure and at the interface with the gate dielectric, enhancing the effective work function and reducing threshold voltage.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If conventional single-layer work function structures are used, then manufacturing process is simple, but device speed and performance are insufficient
Solution Approach 1:
The work function structure is divided into multiple layers (first work function layer, second work function layer, third work function layer) with different materials and oxygen concentrations. Each layer serves a specific function: the first layer provides base work function, the second layer enhances oxygen concentration at the interface, and the third layer provides additional work function adjustment. This segmentation allows optimization of device speed and performance while maintaining manageable manufacturing complexity through systematic layer-by-layer deposition.
Solution Approach 2:
Different regions of the work function structure have different oxygen concentrations and material compositions. The second work function layer is specifically designed with higher oxygen concentration at the gate dielectric interface region, while other layers have different compositions optimized for their specific positions. This local quality variation enables precise control of the electric field distribution and work function characteristics at critical interfaces, improving device performance without requiring uniform complexity throughout the entire structure.
2Reliability
If high oxygen concentration is integrated at the gate dielectric interface, then effective work function increases, but manufacturing precision requirements increase
Solution Approach 1:
The second work function layer is deposited and exposed to oxygen-containing environment before the third work function layer is added. This preliminary oxygen treatment ensures that the interface region between the gate dielectric and the work function structure has the desired high oxygen concentration established early in the manufacturing process. Subsequent layers are then deposited on top of this pre-oxygenated interface, maintaining the oxygen concentration profile without requiring precise control during later manufacturing steps.
Solution Approach 2:
The manufacturing process employs periodic cycles of layer deposition followed by oxygen exposure treatments. Each cycle deposits a work function layer and then exposes it to an oxygen-containing environment for a specific duration, creating a periodic pattern of oxygen incorporation. This periodic action allows controlled buildup of oxygen concentration at the interface through multiple stages, reducing the precision requirements for any single exposure step while achieving the cumulative effect of high interfacial oxygen concentration.
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 increases device speed and performance by increasing the flat band voltage and reducing threshold voltage, thereby improving the overall performance of semiconductor devices like nano-FETs.
Implementation Method 1
exposing the first work function layer to an oxygen-containing environment increases a concentration of oxygen within the first work function layer and at an interface between the gate dielectric layer and the first work function layer
Data Source
AI summary
A method of forming semiconductor devices having improved work function layers and semiconductor devices formed by the same are disclosed. In an embodiment, a method includes depositing a gate dielectric layer on a channel region over a semiconductor substrate; depositing a first p-type work function metal on the gate dielectric layer; performing an oxygen treatment on the first p-type work function metal; and after performing the oxygen treatment, depositing a second p-type work function metal on the first p-type work function metal.