MOS Transistor Threshold Control via Selective TiAl Oxidation
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Current methods for controlling the threshold of MOS transistors are complex and costly, requiring multiple steps and being difficult to manage as devices miniaturize, especially when altering the thickness of the TiN film as a cap.
Innovation Solution
A method using a microwave plasma processing apparatus for oxidation or nitridation treatment to inactivate the work function adjusting metal in the MOS transistor, allowing for threshold control without increasing the number of steps, by selectively applying the treatment to specific regions.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If the composition ratio of work function metal (Al) is changed to control threshold, then threshold control is achieved, but the process becomes complicated requiring lamp annealing and diffusion steps
Solution Approach 1:
The invention extracts the threshold control function from the complex diffusion and annealing process, isolating it to a simple oxidation treatment of the TiAl film. By removing the unnecessary lamp annealing and diffusion steps, the process complexity is reduced while maintaining threshold control capability through selective oxidation of Al in the TiAl film.
Solution Approach 2:
Instead of adding Al and then diffusing it to control threshold, the invention inverts the approach by forming a TiAl film and then selectively oxidizing the Al component. This reversal simplifies the process by using oxidation (a simple treatment) rather than diffusion (a complex multi-step process) to achieve threshold control.
2Manufacturing precision
If separate film formation steps are performed for pMOS and nMOS gate electrode laminates to control threshold, then threshold control is achieved, but the number of steps increases
Solution Approach 1:
The invention merges the threshold control steps for both pMOS and nMOS transistors into a single oxidation treatment process. By forming a unified TiAl film layer that can be selectively oxidized in different regions, the need for separate film formation steps is eliminated, increasing manufacturing efficiency while maintaining precise threshold control through spatially selective oxidation.
Solution Approach 2:
The TiAl film serves multiple functions: it provides the gate electrode structure and simultaneously enables threshold control through selective oxidation. This multi-functional layer eliminates the need for separate threshold control steps for different transistor types, as the same TiAl film can be differentiated through selective oxidation treatment in pMOS and nMOS regions.
3Length of moving object
If the thickness of TiN film as cap is reduced for further miniaturization, then device scaling is achieved, but threshold control by changing TiN thickness becomes difficult
Solution Approach 1:
The invention changes the control parameter from TiN film thickness to Al oxidation degree in the TiAl film. This parameter substitution allows threshold control to remain effective even as TiN thickness is reduced for miniaturization, because the oxidation state of Al (controlled by oxidation treatment conditions) provides a reliable threshold control mechanism independent of TiN thickness.
Solution Approach 2:
The TiAl film acts as an intermediary layer that enables threshold control through oxidation treatment. Instead of directly controlling threshold via TiN thickness (which becomes difficult at small dimensions), the TiAl film provides an oxidation-responsive mechanism that mediates threshold control, allowing precise adjustment even when TiN is extremely thin.
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 enables precise threshold control of MOS transistors with reduced complexity and cost, maintaining control even as devices miniaturize, by selectively oxidizing or nitriding the work function metal, thus stabilizing the threshold voltage without altering the TiN film thickness.
Implementation Method 1
performing an oxidation treatment or nitridation treatment using a microwave plasma processing apparatus to inactivate the work function adjusting metal
Implementation Method 2
performing an oxidation treatment or nitridation treatment using a microwave plasma processing apparatus to inactivate the work function adjusting metal
Implementation Method 3
performing an oxidation treatment or nitridation treatment using a microwave plasma processing apparatus
Data Source
AI summary
In a method of controlling a threshold of a transistor, a gate insulating film is formed in a channel region of a metal-oxide-semiconductor (MOS) transistor on a main surface of a semiconductor substrate. A first electrode layer is formed on the gate insulating film and a second electrode layer containing a work function adjusting metal is formed on the first electrode layer. Thereafter, an oxidation treatment or nitridation treatment using a microwave plasma processing apparatus is performed to inactivate the work function adjusting metal, thereby executing a threshold control of the MOS transistor.