FinFET Gate Stack Oxygen Scavenging 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 affects device performance and reliability.
Innovation Solution
Incorporating oxygen-absorbing layers between work function metal layers and gate dielectric layers in the gate stack structure to prevent oxidation and maintain the integrity of the gate stack, thereby stabilizing the threshold voltage and device performance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If gate stack structure is formed without oxygen-absorbing layers, then manufacturing process is simpler, but oxidation occurs 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 the gate electrode layer. This intermediate layer actively absorbs oxygen and moisture that would otherwise penetrate into the gate dielectric and cause oxidation, thereby preventing threshold voltage shifts and performance deterioration without fundamentally changing the manufacturing process flow
Solution Approach 2:
The gate stack structure is transformed from a simple three-layer configuration into a composite multi-layer structure by incorporating oxygen-absorbing materials (such as nitride or oxide layers) between the gate dielectric and gate electrode. This composite structure provides both the electrical functionality of the original gate stack and the protective oxygen-absorbing capability
2Reliability
If oxygen-absorbing layers are incorporated in the gate stack, then oxidation is prevented and device performance is stabilized, but manufacturing process becomes more complex
Solution Approach 1:
The oxygen-absorbing layer is formed in advance during the gate stack fabrication process, specifically between the deposition of the gate dielectric layer and the gate electrode layer. This preliminary incorporation ensures that oxygen absorption capability is built into the structure before any oxidation can occur, eliminating the need for additional post-processing steps
3Area of stationary object
If gate dielectric and interfacial layers are allowed to grow and thicken during processing, then coverage is improved, but device performance deteriorates due to oxidation and moisture penetration
Solution Approach 1:
The oxygen-absorbing layer serves as a protective intermediary positioned between the gate dielectric layer and the gate electrode layer. It actively captures oxygen and moisture that would otherwise penetrate through the gate dielectric and cause oxidation, allowing the gate dielectric to maintain its coverage area without suffering from oxidation-induced performance deterioration
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 oxygen-absorbing layers effectively inhibits the growth and thickening of gate dielectric and interfacial layers, preventing oxidation of work function metals and maintaining excellent device performance characteristics, such as flat band voltage, and ensuring consistent device operation.
Implementation Method 1
Incorporating oxygen-absorbing layers between work function metal layers and gate dielectric layers in the gate stack structure to prevent oxidation
Implementation Method 2
The use of oxygen-absorbing layers effectively inhibits the growth and thickening of gate dielectric and interfacial layers, preventing oxidation of work function metals
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.