In-situ Optical Monitoring for CMP Uniformity Control
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Chemical mechanical polishing (CMP) processes face challenges in determining the endpoint of polishing, leading to variations in material removal rates and resulting in within-wafer and wafer-to-wafer non-uniformity due to factors like slurry distribution, polishing pad conditions, and load variations, which existing optical monitoring techniques struggle to address effectively.
Innovation Solution
The method involves using in-situ monitoring systems to fit functions to sequences of values obtained during polishing, adjusting polishing parameters such as pressure to synchronize the endpoint times for different zones on a substrate, and applying these adjustments to subsequent substrates to ensure uniformity, employing both feed-back and feed-forward control mechanisms to refine polishing parameters based on real-time data.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If polishing endpoint is determined merely as a function of polishing time, then the control process is simple, but within-wafer non-uniformity and wafer-to-wafer non-uniformity occur due to variations in material removal rate
Solution Approach 1:
The patent implements in-situ optical monitoring during CMP that continuously measures film thickness and provides real-time feedback to adjust polishing parameters. The system monitors the substrate surface through the polishing pad using optical techniques, detects variations in material removal rate across different zones, and dynamically adjusts polishing pressure or speed to maintain uniform polishing, thereby resolving the contradiction between simple time-based control and precise uniformity control
Solution Approach 2:
The patent transitions from static time-based endpoint determination to dynamic control by continuously adjusting polishing parameters based on real-time optical monitoring data. The system adapts polishing pressure, speed, or slurry flow rate during the polishing process to compensate for variations in material removal rate, transforming the control system from static to dynamic to achieve uniform polishing results
2Manufacturing precision
If in-situ monitoring is used to adjust polishing parameters during the process, then polishing uniformity improves, but the system complexity and control difficulty increase
Solution Approach 1:
The patent employs in-situ optical monitoring systems that provide real-time feedback on film thickness and polishing progress. The monitoring data is fed back to the control system, which automatically adjusts polishing parameters to maintain uniformity, reducing the need for complex manual intervention while achieving precise control
Solution Approach 2:
The patent replaces complex mechanical measurement and adjustment systems with optical monitoring techniques. By using light to measure film thickness and detect polishing progress in real-time, the system avoids the complexity of mechanical probes or contact-based measurement methods, simplifying the overall system while maintaining high precision
3Measurement precision
If optical monitoring techniques are used to monitor substrate during polishing, then real-time thickness measurement is achieved, but existing techniques cannot satisfy increasing demands for uniformity control
Solution Approach 1:
The patent divides the substrate surface into multiple zones and performs independent optical monitoring and control for each zone. By segmenting the polishing process into radially distinct regions, the system can detect and correct local variations in material removal rate, achieving superior uniformity control that satisfies increasing semiconductor manufacturing demands
Solution Approach 2:
The patent applies different polishing parameters to different zones of the substrate based on local measurements. The optical monitoring system detects thickness variations in specific regions, and the control system adjusts polishing pressure or speed locally for each zone, ensuring that each region reaches the target thickness simultaneously, thereby achieving the required uniformity control
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 reduces within-wafer and wafer-to-wafer non-uniformity by ensuring that different regions of a substrate reach the target thickness simultaneously, requiring fewer and more predictable pressure adjustments, thereby improving polishing uniformity and reducing defects.
Implementation Method 1
a first sequence of values for a first zone of the first substrate is obtained with an in-situ monitoring system
Data Source
AI summary
During polishing of a substrate at a first platen and prior to a first time, a first sequence of values is obtained for a first zone of the first substrate and a second sequence of values is obtained for a different second zone of the substrate with an in-situ monitoring system. A first function is fit to a portion of the first sequence of values obtained prior to the first time, and a second function is fit to a portion of the second sequence of values obtained prior to the second time. At least one polishing parameter is adjusted based on the first fitted function and the second fitted function so as to reduce an expected difference between the zones. A second substrate is polished on the first platen using an adjusted polishing parameter calculated based on the first fitted function and the second fitted function.