Two-Step STI CMP Process for Uniform Planarization
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Solution Overview
Problem
Conventional chemical mechanical polishing (CMP) processes for shallow trench isolation (STI) in semiconductor devices face challenges with non-uniform planarization due to high dependency on pattern density, leading to over-polishing and potential device failure from residual oxide and nitride residue.
Innovation Solution
A two-step STI CMP process is employed, using a silicon dioxide slurry in the first step and cerium dioxide slurry in the second, with advanced processing control to determine the time limit for the second step based on the oxide thickness after the first step to achieve a tighter polishing window and reduce within-wafer non-uniformity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If conventional single-step CMP process is used, then the process is simple and fast, but the planarization is non-uniform due to high dependency on pattern density
Solution Approach 1:
The CMP process is divided into two distinct steps: a first CMP step using a first slurry to perform initial planarization, and a second CMP step using a second slurry to perform final planarization and remove residual nitride. This segmentation allows each step to be optimized for its specific function, improving overall planarization uniformity across different pattern densities.
2Reliability
If conventional CMP process is used, then the process time is short, but over-polishing occurs leading to device failure
Solution Approach 1:
The first CMP step performs preliminary planarization to remove the majority of the oxide layer and prepare the surface, reducing the burden on the second step. This preliminary action allows the second step to focus on achieving the final planarity and removing residual nitride with minimal polishing time, thereby preventing over-polishing while ensuring device reliability.
3Manufacturing precision
If conventional CMP process is used, then the oxide removal is fast, but residual oxide and nitride residue remain affecting device performance
Solution Approach 1:
The second CMP step uses a second slurry with different properties (e.g., different particle size, chemistry) specifically optimized for removing residual oxide and nitride layers. This local quality approach ensures that the final polishing step targets the specific requirement of complete residue removal without compromising overall polishing efficiency, as the first step has already removed the bulk material.
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
The two-step process effectively reduces within-wafer non-uniformity and minimizes the risk of device failure by maintaining a tight polishing window and ensuring a residue-free nitride layer, thereby improving the overall polishing efficiency and accuracy.
Implementation Method 1
the surface may be softened by the chemical action of the slurry, and then removed by the action of the particles
Implementation Method 2
CMP combines both chemical action and mechanical forces and is commonly used to remove metal and dielectric overlayers
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.