Tantalum Oxynitride Etching Stop Layer for Threshold Voltage Control
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Solution Overview
Problem
In semiconductor manufacturing, existing etching processes face challenges in controlling the intactness of structures during wet etching, leading to variations in the target threshold voltage (Vt) of semiconductor structures due to inadequate etching stop layers.
Innovation Solution
A tantalum oxynitride layer is formed on a tantalum nitride layer, providing a higher resistance to wet etching processes, allowing for precise control of the etching stop layer's partial removal and minimizing etching damage, thereby improving the control over the target threshold voltage (Vt) of semiconductor structures.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a standard etching stop layer is used in wet etching processes, then the etching process can be controlled, but the etching stop layer itself suffers from partial removal and damage, leading to variation in threshold voltage
Solution Approach 1:
The patent applies composite materials by creating a multi-layer etching stop structure consisting of a tantalum nitride layer and a tantalum oxynitride layer. The tantalum nitride layer provides primary etching stop functionality with high chemical resistance, while the tantalum oxynitride layer (formed by dry oxidation of the tantalum nitride) provides enhanced protection and reduced etching damage. This composite structure resolves the contradiction by combining materials with complementary properties to simultaneously improve reliability and manufacturing precision.
Solution Approach 2:
The patent applies preliminary action by performing a dry oxidation process on the tantalum nitride layer before the wet etching process to form the tantalum oxynitride layer. This preliminary oxidation creates a protective surface layer that reduces etching damage during subsequent wet etching operations. By preparing the etching stop layer in advance through oxidation, the patent minimizes partial removal and damage during the actual etching process, thereby improving both reliability and threshold voltage control.
2Object-affected harmful factors
If the etching stop layer is made more resistant to wet etching, then less etching damage occurs, but the etching process becomes less effective at removing sacrificial layers
Solution Approach 1:
The patent applies local quality by creating a gradient structure within the etching stop layer. The tantalum oxynitride layer formed on the surface has different chemical composition and etching resistance properties compared to the underlying tantalum nitride layer. This local variation in material properties allows the surface layer to provide high resistance to etching damage while the underlying layer maintains compatibility with the etching process for removing sacrificial layers, thus resolving the contradiction between damage resistance and etching effectiveness.
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
The use of a tantalum oxynitride layer as an etching stop layer in semiconductor manufacturing effectively minimizes etching loss and damage, enhancing the precision and stability of the semiconductor structure's threshold voltage.
Implementation Method 1
performing a dry oxidation process on the tantalum nitride layer for forming a tantalum oxynitride layer on the tantalum nitride layer
Data Source
AI summary
A semiconductor structure and a manufacturing method thereof are provided. The semiconductor structure includes an isolation layer, a gate dielectric layer, a tantalum nitride layer, a tantalum oxynitride layer, an n type work function metal layer and a filling metal. The isolation layer is formed on a substrate, and the isolation layer has a first gate trench. The gate dielectric layer is formed in the first gate trench, the tantalum nitride layer is formed on the gate dielectric layer, and the tantalum oxynitride layer is formed on the tantalum nitride layer. The n type work function metal layer is formed on the tantalum oxynitride layer in the first gate trench, and the filling metal is formed on the n type work function metal layer in the first gate trench.