Trench Isolation Diffusion Preventive Film for Threshold Voltage Stability
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
The trench type element isolation method in semiconductor devices faces issues such as divot formation and stress induction due to repeated wet etching and thermal oxidation, leading to variations in threshold voltage and operation speed of field effect transistors, especially when forming gate insulation films with different thicknesses.
Innovation Solution
A semiconductor device structure featuring a trench type element isolation film with a diffusion preventive film and an overlying silicon oxide film, preventing divot formation and oxidation reactions, and including a gate insulation film with a High-k material and a metal gate electrode to maintain desired operation characteristics.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If repeated wet etching is used to form gate insulation films with different thicknesses, then the gate insulation films can be formed with desired thickness variations, but divots occur in the trench type element isolation film leading to threshold voltage reduction
Solution Approach 1:
A protective film is formed over the trench type element isolation film before the repeated wet etching process. This protective film prevents etching solution from attacking the isolation film, thereby preventing divot formation while allowing the gate insulation films to be formed with different thicknesses through repeated wet etching
Solution Approach 2:
The protective film acts as an intermediary layer between the wet etching process and the trench type element isolation film. It selectively protects the isolation film from etching damage while permitting the gate insulation films to be etched with varying thicknesses
2Adaptability or versatility
If repeated thermal oxidation is used to form gate insulation films with different thicknesses, then the gate insulation films can be formed with desired thickness variations, but oxidized species diffuse into the trench type element isolation film causing stress and mobility changes
Solution Approach 1:
The protective film is formed over the trench type element isolation film before repeated thermal oxidation processes. This protective film serves as a diffusion barrier that prevents oxidized species from penetrating into the isolation film, thereby preventing stress-induced mobility changes while allowing gate insulation films of different thicknesses to be formed
Solution Approach 2:
The protective film acts as an intermediary barrier that selectively blocks the diffusion of oxidized species into the trench type element isolation film during thermal oxidation, while still permitting the formation of gate insulation films with varying thicknesses
3Productivity
If trench type element isolation method is used to achieve higher integration, then the isolation capability is improved, but divot formation and stress induction occur leading to threshold voltage and operation speed variations
Solution Approach 1:
The protective film is formed over the trench type element isolation film at an early stage, before subsequent processing steps that could cause divot formation or stress induction. This allows the trench isolation structure to maintain its integrity and provide consistent transistor characteristics while supporting high integration
Solution Approach 2:
The protective film serves as an intermediary protective layer that shields the trench type element isolation film from harmful effects during manufacturing processes, thereby maintaining the isolation capability needed for high integration while preventing defects that would cause transistor characteristic variations
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 ensures desirable operation characteristics and prevents stress-induced changes in electron mobility and threshold voltage variations, enhancing the performance and reliability of field effect transistors.
Implementation Method 1
a diffusion preventive film with a thickness of 10 to 20 nm is formed over the top surface of the trench type element isolation film
Implementation Method 2
an overlying silicon oxide film with a thickness of 0.5 to 2 nm is formed over the top surface of the diffusion preventive film
Data Source
AI summary
There is provided a technology capable of providing desirable operation characteristics in a field effect transistor formed in an active region surrounded by a trench type element isolation part. An element isolation part includes trench type element isolation films, diffusion preventive films each including a silicon film or a silicon oxide film, and having a thickness of 10 to 20 nm formed over the top surfaces of the trench type element isolation films, and silicon oxide films each with a thickness of 0.5 to 2 nm formed over the top surfaces of the diffusion preventive films. The composition of the diffusion preventive film is SiOx (0≦x<2). Each composition of the trench type element isolation films and the silicon oxide films is set to be SiO2.