Gate Stack Oxygen-Absorbing Layer for Threshold Voltage Stability
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Solution Overview
Problem
In semiconductor devices, particularly FinFETs, the oxidation of work function metal, gate dielectric, and interfacial layers during processing leads to unwanted threshold voltage changes and performance deterioration due to moisture and oxygen penetration, which is not effectively addressed by existing technologies.
Innovation Solution
Incorporating oxygen-absorbing layers between work function metal layers and a gate dielectric layer in the gate stack structure to prevent oxidation and maintain the integrity of the gate dielectric and interfacial layers, thereby stabilizing the threshold voltage and device performance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If gate dielectric and interfacial layers are formed without oxygen-absorbing layers, then device manufacturing is simpler, but oxidation occurs during processing leading to threshold voltage changes and performance deterioration
Solution Approach 1:
An oxygen-absorbing layer is introduced as an intermediary between the gate dielectric layer and work function metal layers. This layer acts as a mediator that captures oxygen and moisture during processing, preventing oxidation of the gate dielectric and interfacial layers. The oxygen-absorbing layer sacrificially reacts with oxygen, protecting the critical gate stack components and maintaining device performance stability.
Solution Approach 2:
The oxygen-absorbing layer is formed in advance before the gate electrode layers are deposited. This preliminary action ensures that oxygen and moisture are captured before they can penetrate and oxidize the gate dielectric and interfacial layers during subsequent processing steps. The protective function is established beforehand, preventing threshold voltage shifts and performance deterioration.
2Manufacturing precision
If oxygen-absorbing layers are incorporated in the gate stack, then oxidation is prevented and threshold voltage is stabilized, but manufacturing process becomes more complex
Solution Approach 1:
The oxygen-absorbing layer serves as a protective intermediary that precisely controls the chemical environment during manufacturing. By positioning this layer between the gate dielectric and metal layers, it selectively absorbs oxygen and moisture, preventing oxidation reactions and ensuring precise threshold voltage control throughout the fabrication process.
Solution Approach 2:
The introduction of the oxygen-absorbing layer changes the chemical composition and oxygen partial pressure parameters within the gate stack during processing. This parameter change creates a controlled atmosphere that prevents oxidation, allowing for precise control of threshold voltage and device characteristics even as manufacturing complexity increases.
3Adaptability or versatility
If multiple work function metal layers are used to adjust threshold voltage, then device performance is optimized, but oxidation of metals and dielectric occurs leading to performance deterioration
Solution Approach 1:
The oxygen-absorbing layer is positioned between the gate dielectric and multiple work function metal layers, serving as a protective intermediary. This allows the use of multiple metal layers with different work functions for threshold voltage optimization while preventing oxidation of both the dielectric and metal layers, maintaining device performance stability.
Solution Approach 2:
The gate stack employs a composite structure combining gate dielectric, oxygen-absorbing layer, and multiple work function metal layers. This composite material approach enables threshold voltage adjustment through metal layer selection while the oxygen-absorbing component protects the entire structure from oxidation, ensuring long-term reliability.
4Ease of manufacture
If gate dielectric and interfacial layers are exposed to moisture and oxygen during processing, then manufacturing is simpler, but unwanted threshold voltage changes occur
Solution Approach 1:
The oxygen-absorbing layer acts as a protective intermediary that shields the gate dielectric and interfacial layers from moisture and oxygen exposure during processing. This maintains manufacturing simplicity while preventing unwanted threshold voltage changes, as the oxygen-absorbing layer sacrificially reacts with contaminants before they can reach the critical components.
Solution Approach 2:
The oxygen-absorbing layer creates an inert chemical environment within the gate stack during processing. By capturing oxygen and moisture, it establishes a protected atmosphere that prevents oxidation reactions and threshold voltage drift, allowing for simpler processing without compromising manufacturing precision.
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 solution effectively inhibits the growth and thickening of gate dielectric and interfacial layers, preventing performance deterioration and maintaining excellent device characteristics such as flat band voltage by capturing and neutralizing oxygen, thus ensuring consistent and improved transistor performance.
Implementation Method 1
the oxidation of work function metal, gate dielectric, and interfacial layers during processing leads to unwanted threshold voltage changes
Implementation Method 2
oxygen-absorbing layers between work function metal layers and a gate dielectric layer in the gate stack structure to prevent oxidation
Data Source
AI summary
A method of manufacturing a semiconductor device includes forming a plurality of work function metal layers and an oxygen absorbing layer over a channel region of the semiconductor device, including forming a first work function metal layer over the channel region, forming an oxygen absorbing layer over the first work function metal layer, forming a second work function metal layer over the oxygen absorbing layer. A gate electrode metal layer is formed over the plurality of work function metal layers. The work function metal layers, oxygen absorbing layer, and gate electrode metal layer are made of different materials.