Two-Step CMP Process for Residual Silicon Nitride Removal
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
The shallow trench isolation process in semiconductor fabrication faces challenges with residual silicon nitride formation during chemical mechanical polishing, particularly in diffusion areas, due to the wide variations in trench size, spacing, and density, leading to incomplete removal of dielectric layers and resulting in non-planar surfaces.
Innovation Solution
A two-step chemical mechanical polishing process using ceria-based compositions, where the first polishing step is followed by a rinse and a slurry purge, and then a second polishing step with ceria, effectively removing residual silicon nitride from diffusion areas, ensuring a planar surface without the need for reworking the wafer.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If standard silica slurries are used for polishing silicon dioxide, then the oxide layer can be removed, but residual silicon nitride forms in the diffusion area
Solution Approach 1:
The polishing process is divided into two distinct steps: first polishing with silica slurry to remove oxide, then switching to ceria slurry to remove residual nitride. This segmentation allows each polishing step to target specific materials with optimized selectivity, preventing residual nitride formation while maintaining surface planarity.
Solution Approach 2:
The invention changes the polishing slurry composition from silica-based to ceria-based for the second polishing step. This parameter change in slurry chemistry alters the polishing selectivity, enabling effective removal of residual silicon nitride that remained after the first silica-based polishing step.
2Manufacturing precision
If continued polishing is performed to remove residual oxide, then more oxide is removed, but residual silicon nitride formation is not reduced
Solution Approach 1:
Instead of continuing with the same silica-based polishing parameters, the invention changes the slurry composition parameter to ceria-based slurry. This chemical parameter change fundamentally alters the polishing mechanism and selectivity, enabling removal of residual nitride without requiring excessive oxide removal that would not solve the nitride residue problem.
3Device complexity
If a single polishing step is used, then the process is simple, but residual silicon nitride remains in the diffusion area
Solution Approach 1:
The polishing process is segmented into two sequential steps with different slurry compositions: first step uses silica slurry for oxide removal, second step uses ceria slurry for nitride residue removal. This segmentation increases process steps but enables complete removal of residual nitride that cannot be achieved in a single polishing step.
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 significantly reduces residual silicon nitride in diffusion areas, achieving a planar surface and improving the efficiency and throughput of the polishing process, eliminating the need for reworking the wafer and reducing operational costs.
Implementation Method 1
CMP combines both chemical action and mechanical forces and is commonly used to remove metal and dielectric overlayers
Implementation Method 2
rinsing the first polished surface with a rinse composition to provide a rinsed surface
Data Source
AI summary
A chemical mechanical polishing method is disclosed. The method includes forming a film on a wafer having at least one trench structure thereon; polishing the surface of the film by providing a polishing composition to provide a first polished surface; rinsing the first polished surface with a rinse composition to provide a rinsed surface; and polishing the rinsed surface by providing a second polishing composition to provide a second polished surface.