Multi-Layer Gate Work Function Structure With Oxygen Treatment
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Solution Overview
Problem
The semiconductor industry faces challenges in achieving optimal work function structures for gate electrodes, which affect the performance and speed of semiconductor devices.
Innovation Solution
A method involving the deposition of a work function layer, exposure to an oxygen-containing environment, and repeating this process to achieve a sufficient thickness, is used to form an improved work function structure over a gate dielectric layer.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a work function layer is deposited to increase effective work function and improve device performance, then device speed and performance are enhanced, but the process complexity and manufacturing steps increase
Solution Approach 1:
The gate electrode is divided into multiple functional layers including a work function layer and a barrier layer, with each layer serving a specific purpose. The work function layer (e.g., TiN) is segmented into multiple sub-layers with different oxygen concentrations to independently control electrical properties while simplifying the overall process by separating deposition and oxygenation steps
Solution Approach 2:
Oxygen is pre-introduced into the work function layer during deposition or through preliminary annealing steps before final gate formation. This preliminary oxygenation establishes the desired work function characteristics early in the process, reducing the need for complex post-processing adjustments and simplifying subsequent manufacturing steps
2Reliability
If multiple work function layers with different oxygen concentrations are deposited, then effective work function and flat band voltage are increased, but the number of deposition cycles and process time increase
Solution Approach 1:
The deposition process uses periodic cycles of material deposition followed by controlled oxygen exposure or annealing steps. Each cycle creates a layer with a specific oxygen concentration profile, and by optimizing the number and duration of these periodic cycles, the process achieves the desired flat band voltage while minimizing total process time through efficient cycle management
Solution Approach 2:
The oxygen concentration in the work function layer is controlled by changing deposition parameters such as oxygen partial pressure during deposition, deposition temperature, or post-deposition annealing conditions. By adjusting these parameters across different deposition cycles, multiple layers with gradient oxygen concentrations are created, optimizing flat band voltage without requiring an excessive number of cycles
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 the effective work function, flat band voltage, and reduces the threshold voltage of semiconductor devices, thereby enhancing device speed and performance.
Implementation Method 1
exposing the work function layer to an oxygen-containing environment, and repeating this process until a sufficient thickness is achieved
Implementation Method 2
depositing a work function layer, exposing the work function layer to an oxygen-containing environment, and repeating this process until a sufficient thickness is achieved
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.