Spacer Profile Modification for Accurate Pattern Transfer
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
In semiconductor fabrication, spacer-based patterning faces challenges due to asymmetric profiles between spacer and mandrel sides, leading to issues like line edge roughness and pattern transfer inaccuracies.
Innovation Solution
A method involving plasma-based etch processing steps to reform asymmetric spacers into symmetric profiles by depositing a filler material, executing anisotropic and isotropic etch steps to equalize spacer heights, and using highly selective plasma etch chemistry to achieve flat surfaces.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If spacer-based patterning is used to create narrow pitch features, then pattern density is doubled, but asymmetric profiles between spacer and mandrel sides cause line edge roughness and pattern transfer inaccuracies
Solution Approach 1:
The method performs preliminary actions by depositing filler material between spacers before the final pattern transfer, then using selective etching to remove the filler and reshape the spacer profiles. This preliminary restructuring eliminates asymmetric profiles and undercuts before critical pattern transfer operations, thereby improving line edge roughness while maintaining the high pattern density achieved through spacer-based patterning
Solution Approach 2:
The filler material serves as an intermediary substance that temporarily occupies the space between spacers during processing. This intermediary material enables profile reshaping through selective etching, allowing the spacer profiles to be corrected for asymmetry without affecting the underlying mandrel structure or the final pattern transfer accuracy
2Ease of manufacture
If asymmetric spacers are formed through conformal deposition, then spacer pattern formation is achieved, but the asymmetric profiles create undercuts and reduce pattern transfer accuracy
Solution Approach 1:
The method performs preliminary profile correction by depositing filler material and executing selective etching steps before the critical pattern transfer operation. This preliminary action reshapes asymmetric spacers into symmetric profiles with squared corners, eliminating undercuts that would otherwise compromise pattern transfer accuracy
Solution Approach 2:
The method changes the physical parameters of the spacer profiles through controlled etching processes. By using plasma etch chemistry with high selectivity ratios, the spacer profile parameters (height, width, corner radius) are modified to achieve symmetric, squared profiles that ensure accurate pattern transfer while maintaining ease of manufacture
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 line edge roughness and line width roughness, ensuring accurate pattern transfer by squaring spacer profiles and eliminating undercuts, thereby enhancing microfabrication precision.
Implementation Method 1
The second etch step uses a plasma etch chemistry that etches the spacers at an etch rate that is greater than at least five times an etch rate of the filler material
Implementation Method 2
A second etch step is executed that isotropically etches the substrate until the top of the first side wall and the top of the second sidewall are approximately equal in height
Implementation Method 3
The filler material can planarize the substrate such that the spacers are buried
Data Source
AI summary
Techniques herein provide a process to reform or flatten asymmetric spacers to form a square profile which creates symmetric spacers for accurate pattern transfer. Initial spacer formation typically results in spacer profiles with a curved or sloped top surfaces. This asymmetric top surface is isolated while protecting a remaining lower portion of the spacer. The top surface is removed using a plasma processing step resulting in spacers having a squared profile that enables further patterning and/or accurate pattern transfer.