Replacement Gate Structure for Higher Channel Stress in Transistors
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Solution Overview
Problem
In semiconductor devices, a small stress is applied to the transistor channel due to the repulsive force from the gate electrodes, limiting the effectiveness of stress-induced mobility enhancement.
Innovation Solution
The stress applying film is formed before the trench is formed, allowing the stress to be applied directly to the semiconductor substrate where the dummy gate is removed, thereby increasing the stress on the transistor channel.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Stress or pressure
If a stress applying film is formed on the transistor device, then the stress on the channel is increased, but the gate electrodes generate a repulsive force that limits the effective stress applied to the channel
Solution Approach 1:
The stress applying film is formed on the dummy gate structure before the trench is formed and before the actual gate electrode is created. This preliminary placement allows the stress film to be positioned where it can effectively stress the channel region without being repelled by the final gate electrode structure, as the gate electrode is not yet present to generate the repulsive force.
Solution Approach 2:
The dummy gate structure serves as an intermediary placeholder that allows the stress applying film to be positioned correctly on the channel region. The dummy gate is removed later to form the trench, and the stress film remains in place to continue applying stress to the channel without interference from the final gate electrode.
2Reliability
If the stress applying film is formed after the trench is formed, then the gate electrode structure is complete, but the repulsive force from the gate electrode reduces the effective stress on the channel
Solution Approach 1:
The stress applying film is placed on the dummy gate structure before the trench formation and gate electrode creation. This preliminary action ensures that the stress film is already positioned to effectively stress the channel region before the gate electrode is formed, avoiding the repulsive force issue that would occur if the film were placed after gate electrode completion.
3Stress or pressure
If the stress applying film is formed before the trench is formed, then the stress is applied directly to the semiconductor substrate channel region, but the dummy gate structure must be removed to form the trench
Solution Approach 1:
The dummy gate structure is extracted or removed after the stress applying film has been formed on it. This extraction allows the trench to be formed while leaving the stress applying film in place to continue applying stress to the channel region. The dummy gate serves only as a temporary placeholder to enable correct positioning of the stress film.
Solution Approach 2:
The dummy gate structure is discarded after serving its purpose of holding the stress applying film in the correct position. The removal of the dummy gate creates the trench while preserving the stress applying film's beneficial effect on the channel, effectively discarding the unnecessary component while recovering the useful stress application function.
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 significantly increases the stress applied to the transistor channel, leading to enhanced mobility and improved response performance of the transistors.
Implementation Method 1
a method of raising the mobility of carriers by applying a proper stress on a semiconductor device, with a stressed thin film layered on the surface thereof
Data Source
AI summary
A semiconductor device including, in cross section, a semiconductor substrate; a gate insulating film on the semiconductor substrate; a gate electrode on the gate insulating film, the gate electrode including a metal, a side wall insulating film at opposite sides of the gate electrode, the side wall insulating film contacting the substrate; a stress applying film at the opposite sides of the gate electrode and over at least a portion of the semiconductor substrate, at least portion of the side wall insulating film being between the gate insulating film and the stress applying film and in contact with both of them; source/drain regions in the semiconductor substrate at the opposite sides of the gate electrode, and silicide regions at surfaces of the source/drain regions at the opposite sides of the gate electrode, the silicide regions being between the source/drain regions and the stress applying layer and in contact with the stress applying layer.