Anisotropic Gate Spacer for Transistor Capacitive Coupling
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Solution Overview
Problem
Field effect transistors face challenges in achieving optimal capacitive coupling between the gate electrode and source/drain extension regions while minimizing coupling with source/drain contact via structures due to the isotropic nature of traditional gate spacer dielectric materials.
Innovation Solution
The use of an anisotropic dielectric material for the gate spacer, aligned vertically within the spacer cavity, providing a higher dielectric constant along the vertical direction and a lower dielectric constant along the horizontal direction to enhance coupling with source/drain extension regions while reducing coupling with source/drain contact via structures.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a high dielectric constant material is used for the gate spacer, then capacitive coupling between the gate electrode and source/drain extension regions is enhanced, but capacitive coupling between the gate electrode and source/drain contact via structures increases (increasing parasitic capacitance)
Solution Approach 1:
The patent applies local quality by using different dielectric constant values in different spatial directions within the same gate spacer material. The anisotropic dielectric material provides a first dielectric constant (higher) in the vertical direction to enhance coupling with source/drain extension regions, and a second dielectric constant (lower) in the lateral direction to reduce parasitic capacitance with contact via structures. This directional differentiation of material properties resolves the contradiction between enhancing useful coupling and minimizing harmful parasitic effects.
Solution Approach 2:
The patent changes the dielectric parameter from an isotropic single value to an anisotropic multi-value system. By utilizing an anisotropic dielectric material with different dielectric constants along different axes, the invention transforms the uniform dielectric property into a directionally-dependent property, allowing optimization of capacitive coupling in the vertical direction while simultaneously minimizing parasitic capacitance in the lateral direction.
2Adaptability or versatility
If a single dielectric material with optimized dielectric constant is used for the gate spacer, then overall performance is balanced, but the ability to independently optimize coupling with source/drain extension regions and contact via structures is limited
Solution Approach 1:
The patent implements local quality by making the dielectric constant spatially direction-dependent within the gate spacer. Instead of using a single isotropic material with uniform properties, the invention employs an anisotropic dielectric material that provides different dielectric constant values along different directions, enabling independent optimization of electrical characteristics in vertical and lateral directions while maintaining a single continuous material structure.
Solution Approach 2:
The patent utilizes composite material principles by employing an anisotropic dielectric material that combines multiple dielectric constant characteristics within a single material system. This anisotropic material effectively acts as a composite with directionally-dependent properties, allowing the gate spacer to exhibit different electrical behaviors in different directions without requiring multiple separate material layers or structures.
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 effectively maximizes electrical channel length and minimizes parasitic outer fringe capacitance, improving the electrostatic integrity of the transistor by optimizing capacitive coupling.
Implementation Method 1
The anisotropic dielectric material is aligned with an electrical field such that lengthwise directions of the molecules of the anisotropic dielectric material are aligned vertically within the spacer cavity
Data Source
AI summary
Capacitive coupling between a gate electrode and underlying portions of the source and drain regions can be enhanced while suppressing capacitive coupling between the gate electrode and laterally spaced elements such as contact via structures for the source and drain regions. A transistor including a gate electrode and source and drain regions is formed employing a disposable gate spacer. The disposable gate spacer is removed to form a spacer cavity, which is filled with an anisotropic dielectric material to form an anisotropic gate spacer. The anisotropic dielectric material is aligned with an electrical field such that lengthwise directions of the molecules of the anisotropic dielectric material are aligned vertically within the spacer cavity. The anisotropic gate spacer provides a higher dielectric constant along the vertical direction and a lower dielectric constant along the horizontal direction.