CMP Wafer Rotation Control for Thickness Asymmetry Correction
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Solution Overview
Problem
Chemical mechanical polishing (CMP) processes struggle to correct thickness asymmetry in substrates, leading to inconsistent integrated circuit performance due to symmetric material removal, resulting in varying RC time constants and device quality issues.
Innovation Solution
Implementing a method that varies the rotational speeds of the carrier head and polishing pad during CMP to create an asymmetric removal profile, aligning with the substrate's thickness profile, ensuring the thickest areas are polished at higher rates than thinner areas, thus reducing asymmetry.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If the substrate is polished using conventional CMP with constant rotational speeds, then the material removal is symmetric and the process is simple, but the thickness asymmetry in the substrate cannot be corrected
Solution Approach 1:
The patent applies dynamics by varying the rotational speeds of the carrier head and/or polishing pad during the CMP process. Instead of maintaining constant rotational speeds, the system dynamically adjusts the rotation velocities to create different relative velocities at different angular positions, enabling asymmetric material removal that corrects substrate thickness asymmetry while maintaining process controllability
Solution Approach 2:
The patent directly applies asymmetry by intentionally creating an asymmetric material removal profile through variable rotational speeds. The asymmetric removal rate is designed to match the asymmetric thickness profile of the substrate, with higher removal rates at thicker regions and lower rates at thinner regions, thereby correcting the thickness uniformity issue
2Manufacturing precision
If the rotational speeds are varied to create asymmetric removal profile, then the thickness asymmetry can be corrected, but the process control becomes more complex
Solution Approach 1:
The patent applies parameter changes by modifying the rotational speed parameters of the carrier head and polishing pad during the CMP process. The system changes these operational parameters dynamically based on the substrate's thickness profile, enabling precise control over the material removal rate at different locations while maintaining ease of operation through programmable speed variations
3Ease of operation
If constant rotational speeds are used, then the process is easy to operate, but the material removal is symmetric which fails to correct thickness asymmetry
Solution Approach 1:
The patent transitions from static constant-speed operation to dynamic variable-speed operation. The system maintains ease of operation by using programmable speed profiles that automatically adjust rotational velocities based on pre-characterized substrate thickness profiles, eliminating the need for manual intervention while achieving the desired asymmetric material removal for thickness uniformity correction
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 effectively corrects the thickness asymmetry, resulting in a more uniform substrate thickness profile, enhancing the consistency and quality of integrated circuits by ensuring uniform material removal across the substrate.
Implementation Method 1
The polishing pad and the carrier head each rotate at a constant rotational speed and the abrasive slurry removes material from one or more of the layers
Implementation Method 2
A polishing slurry with abrasive particles is typically supplied to the surface of the polishing pad and spreads in between the substrate and the polishing pad. The polishing pad and the carrier head each rotate at a constant rotational speed and the abrasive slurry removes material
Data Source
AI summary
Certain aspects of the present disclosure provide techniques for a method of removing material on a substrate. An exemplary method includes rotating a substrate about a first axis in a first direction and urging a surface of the substrate against a polishing surface of a polishing pad while rotating the substrate, wherein rotating the substrate about the first axis includes rotating the substrate a first angle at a first rotation rate, and then rotating the substrate a second angle at a second rotation rate, and the first rotation rate is different from the second rotation rate.