Vt Tuning Dielectric Layer for Multiple Threshold Voltages
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Solution Overview
Problem
As IC technologies shrink, existing gate replacement processes struggle to effectively pattern work function metal layers across multiple fins due to increased complexity and reduced channel lengths, leading to challenges in achieving multiple threshold voltages without increasing material thickness.
Innovation Solution
A zero-thickness treatment method is introduced, where threshold voltages are modulated by driving positive charged atoms or dipole-forming materials into a Vt tuning dielectric layer, comprising an interfacial and high-k dielectric layer, to achieve different threshold voltages across multiple fins without varying the thickness of work function metal layers.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If work function metal layers are patterned across multiple fins using existing gate replacement processes, then different threshold voltages can be achieved, but the process complexity increases and patterning becomes difficult due to reduced channel lengths
Solution Approach 1:
A dielectric layer is introduced as an intermediary between the metal gate electrode and the fin structure. This dielectric layer contains dopant atoms that modulate the threshold voltage, replacing the need for complex patterning of work function metal layers. The dielectric layer serves as a mediator that achieves Vt tuning through a simpler, more scalable process compatible with reduced channel lengths.
Solution Approach 2:
The threshold voltage is modulated by changing the concentration of dopant atoms within the dielectric layer rather than by changing the thickness or composition of metal layers. This parameter change approach allows for continuous tuning of Vt across multiple fins using a uniform processing step, avoiding the complexity of precise thickness control required in conventional methods.
2Adaptability or versatility
If multiple threshold voltages are achieved by varying work function metal layer thickness, then different Vt values are obtained, but the overall material thickness increases
Solution Approach 1:
Instead of varying metal layer thickness to achieve different threshold voltages, the invention changes the dopant concentration parameter within a uniform dielectric layer. This allows multiple Vt values to be achieved while maintaining a constant overall material thickness, as the dopant distribution within the fixed-thickness dielectric layer determines the threshold voltage characteristics.
Solution Approach 2:
The dielectric layer acts as an intermediary that replaces the need for variable-thickness metal layers. By embedding dopant atoms within this dielectric layer, the invention achieves threshold voltage modulation without increasing the overall stack thickness, thereby maintaining device scalability.
3Productivity
If channel length is reduced to increase functional density, then production efficiency improves, but the ability to effectively pattern work function metal layers deteriorates
Solution Approach 1:
The dielectric layer serves as an intermediary that enables threshold voltage modulation through a process that does not rely on precise patterning of thin metal layers. This intermediary approach allows the use of reduced channel lengths for increased functional density while avoiding the patterning difficulties that would otherwise arise from scaling.
Solution Approach 2:
The invention replaces the mechanical patterning process (physical deposition and etching of work function metal layers with precise thickness control) with a chemical/diffusion-based process where dopant atoms are introduced into the dielectric layer. This substitution eliminates the need for complex mechanical patterning steps, making the process more suitable for scaled devices with reduced channel lengths.
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 allows for the realization of multiple threshold voltages in FinFET devices with reduced feature sizes, maintaining a uniform thickness of dielectric and metal layers, enhancing patterning capabilities and reducing material usage, thus improving fabrication efficiency and cost-effectiveness.
Implementation Method 1
Properties of the Vt tuning dielectric layer are adjusted during the forming to achieve a different Vt for each of the plurality of fins
Data Source
AI summary
A method of fabricating an integrated circuit (IC) structure, includes forming a gate trench that exposes a portion of each of a plurality of fins and forming a threshold voltage (Vt) tuning dielectric layer in the gate trench over the plurality of fins. Properties of the Vt tuning dielectric layer are adjusted during the forming to achieve a different Vt for each of the plurality of fins. The method also includes forming a glue metal layer over the Vt tuning dielectric layer; and forming a fill metal layer over the glue metal layer. The fill metal layer has a substantially uniform thickness over top surfaces of the plurality of fins.