Anisotropic Wet Etching for Multi-Gate Metal Patterning Control
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Solution Overview
Problem
As semiconductor devices continue to shrink in size, the challenge of reducing unwanted lateral etching during wet etching operations, particularly in the formation of multi-gate transistors, leads to issues such as metal loss and threshold voltage imbalances, affecting device performance and yield.
Innovation Solution
Employing anisotropic wet etching techniques that selectively target specific materials in the epitaxial layers, minimizing lateral etching and preserving the integrity of gate structures in multi-gate devices.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If conventional wet etching is used to remove metal layers in multi-gate transistor fabrication, then the etching process is simple and fast, but unwanted lateral etching occurs causing metal loss and threshold voltage imbalances
Solution Approach 1:
The patent modifies the chemical composition and physical parameters of the etchant solution to achieve anisotropic wet etching. By adjusting parameters such as pH, temperature, and chemical concentration, the etching process becomes directionally selective, removing metal vertically while minimizing lateral etching, thus resolving the contradiction between etching speed and lateral etching control.
Solution Approach 2:
The invention employs a composite etchant system that combines multiple chemical agents with specific properties. This composite approach creates a synergistic effect where the combined chemicals provide both high etching rate and directional selectivity, enabling fast vertical etching while suppressing lateral etching through the coordinated action of different chemical components.
2Loss of time
If isotropic wet etching is used to remove metal layers, then the process is simple and rapid, but metal loss occurs leading to threshold voltage imbalances and reduced device yield
Solution Approach 1:
The patent transforms the etching process from isotropic to anisotropic by changing key parameters of the wet etchant, including chemical composition, temperature, and pH. This parameter modification enables the etching to proceed primarily in the vertical direction, significantly reducing lateral metal loss while maintaining rapid processing speeds, thereby improving device yield without sacrificing productivity.
Solution Approach 2:
The invention replaces the conventional mechanical/isotropic removal approach with a chemically-driven anisotropic etching mechanism. By substituting the etching mechanism itself through chemical composition adjustments, the process achieves directional selectivity that prevents metal loss and threshold voltage imbalances while maintaining process efficiency.
3Ease of manufacture
If standard photolithographic patterning is used, then the process is well-established and simple, but unwanted lateral etching penetrates the photolithographic layer causing metal boundary loss
Solution Approach 1:
The patent modifies the etching parameters, particularly the chemical composition and anisotropy characteristics of the wet etchant, to change the etching directionality. This allows the etching to proceed vertically without penetrating laterally into the photolithographic layer, maintaining metal boundary precision while preserving the simplicity of the established photolithographic patterning process.
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 reduces unwanted lateral etching effects, maintains the integrity of gate materials, and enhances the reliability and yield of semiconductor devices by preventing metal loss and threshold voltage imbalances.
Implementation Method 1
removing the metal layer from the second semiconductor structure via wet etch operations using a chemical etchant that is tuned to resist penetration into the photolithographic layer
Implementation Method 2
Employing anisotropic wet etching techniques that selectively target specific materials in the epitaxial layers, minimizing lateral etching and preserving the integrity of gate structures
Data Source
AI summary
Disclosed is a method comprising: providing at least two structures with a metal layer over each; forming a patterned photolithographic layer over the metal layer over the first structure; removing the metal layer from the second structure via wet etch operations using a chemical etchant that is resistant to penetration into the photolithographic layer; and achieving, after wet etch operations, a remaining metal ratio of a distance X over a distance Y that is less than 179 and greater than 1, wherein X is the distance from a first line extending from an edge of the metal layer over the first structure to a second line extending from an edge of a channel region in the second structure, and Y is a second distance from the first line to a third line extending from an edge of the metal layer formed over the channel region in the first structure.