Selective Gate Air Spacer Formation Without Gate Collapse
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Conventional methods of forming air spacers in semiconductor devices face issues such as gate structure collapse, damage to other components, and unwanted etching byproducts, particularly in high aspect ratio trenches, and fail to differentiate between IC devices that benefit from air spacers and those that do not.
Innovation Solution
The selective formation of air spacers using lithography to pattern hard masks defines regions where air spacers are formed, avoiding gate structure wiggling and damage to STI structures, while minimizing etching byproducts.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If conventional methods are used to form air spacers, then low dielectric constant gate spacers are achieved, but gate structure collapse and damage to other components occur
Solution Approach 1:
A mandrel structure is introduced as an intermediary element to enable air spacer formation. The mandrel serves as a temporary support structure that allows the air spacer to be formed without directly collapsing the gate structure. The mandrel is removed after air spacer formation, leaving the air spacer in place while maintaining gate structure integrity throughout the process.
Solution Approach 2:
The mandrel structure is formed in advance before the air spacer formation process. This preliminary action provides structural support during the subsequent air spacer etching process, preventing gate structure collapse. The mandrel is strategically positioned and formed with appropriate dimensions to provide necessary support during the critical air spacer formation step.
2Quantity of substance
If conventional air spacer formation is performed, then low-k dielectric spacers are created, but unwanted etching byproducts and damage to STI structures occur
Solution Approach 1:
The mandrel structure acts as a protective intermediary that confines the etching process to the desired region. By providing a physical barrier and defined etch boundaries, the mandrel prevents etchant from reaching STI structures and minimizes the generation of unwanted etching byproducts. The mandrel's material composition is selected to provide etch selectivity, allowing clean separation between the mandrel removal and air spacer formation steps.
3Reliability
If air spacers are formed in all regions, then capacitance reduction is achieved, but devices that do not benefit are also modified
Solution Approach 1:
The mandrel structure is selectively formed only in regions where air spacers are desired, allowing different device regions to have different structures. This local differentiation enables capacitance reduction in specific devices while leaving other devices unchanged. The mandrel formation process uses selective patterning techniques to place mandrels only where needed, creating local quality variations across the wafer surface.
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 improves device fabrication by reducing gate structure instability and etching damage, optimizing performance for IC devices that require air spacers without compromising those that do not.
Implementation Method 1
The selective formation of air spacers using lithography to pattern hard masks defines regions where air spacers are formed
Implementation Method 2
an etching process is performed through the opening to form an air spacer by removing a portion of the gate structure
Data Source
AI summary
A semiconductor device includes a substrate. A gate structure is disposed over the substrate in a vertical direction. The gate structure extends in a first horizontal direction. An air spacer is disposed adjacent to a first portion of the gate structure in a second horizontal direction that is different from the first horizontal direction. The air spacer has a vertical boundary in a cross-sectional side view defined by the vertical direction and the first horizontal direction.