In-situ Optical Metrology for CMP Thickness Uniformity
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Current chemical mechanical polishing (CMP) techniques face challenges in achieving uniform surface topography and predictable material removal across substrates, particularly in sub-quarter micron multi-level metallization processes, where variations in thickness and polishing times can lead to inconsistent results.
Innovation Solution
The method involves in-situ optical monitoring to obtain and compare spectra from different zones of a substrate, adjusting polishing parameters such as pressure to ensure that all regions reach a target thickness simultaneously, using techniques like robust line fitting and gain factors to optimize polishing rates and pressures across multiple platens.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If conventional CMP techniques are used with fixed polishing parameters, then the polishing process is simple and fast, but the surface topography uniformity and material removal predictability deteriorate
Solution Approach 1:
The polishing parameters (pressure, speed) are made dynamic and adjustable during the polishing process based on real-time thickness measurements. The system continuously monitors film thickness and adjusts polishing parameters to maintain uniform material removal across the substrate surface, resolving the contradiction between precision and complexity by introducing controlled adaptability.
Solution Approach 2:
An optical monitoring system provides real-time feedback on film thickness during polishing. This feedback is used to adjust polishing parameters dynamically, ensuring uniform surface topography and predictable material removal. The feedback loop transforms the simple but imprecise conventional process into a precise controlled process.
2Manufacturing precision
If polishing parameters are adjusted to achieve uniform thickness across zones, then manufacturing precision improves, but measurement and control complexity increases
Solution Approach 1:
The patent replaces complex mechanical measurement systems with optical monitoring. Light is passed through the polishing pad to measure film thickness non-contactly and in-real-time. This optical approach simplifies the measurement process while providing the precision needed to control thickness uniformity across different zones.
Solution Approach 2:
The optical monitoring system enables self-regulation of the polishing process. By continuously measuring thickness and automatically adjusting parameters based on these measurements, the system achieves uniform thickness control without requiring complex external intervention or manual measurement procedures.
3Reliability
If in-situ optical monitoring is implemented with real-time adjustments, then polishing consistency improves, but device complexity and processing time increase
Solution Approach 1:
The optical monitoring system serves multiple functions: it measures film thickness, determines polishing endpoint, and provides feedback for parameter adjustment. This multi-functionality consolidates what would otherwise require separate systems into a single integrated solution, improving reliability without proportionally increasing complexity.
Solution Approach 2:
The optical monitoring and parameter adjustment operate continuously throughout the polishing process rather than in discrete steps. This continuous control ensures consistent polishing results by maintaining optimal parameters throughout, improving reliability while the automation reduces the need for complex manual intervention.
4Manufacturing precision
If different polishing parameters are used for different zones, then within-wafer uniformity improves, but process complexity and adjustment difficulty increase
Solution Approach 1:
The substrate surface is divided into multiple zones with different polishing characteristics. The system independently controls polishing parameters for each zone based on real-time thickness measurements from that zone. This segmentation allows precise control of within-wafer uniformity while the automation of parameter adjustment based on feedback simplifies the operational complexity.
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 enables more uniform polishing across substrates, improving both wafer-to-wafer and within-wafer consistency by dynamically adjusting polishing parameters based on real-time thickness measurements and endpoint determinations, enhancing the reliability of CMP processes.
Implementation Method 1
an optical monitoring system is used to determine a polishing endpoint by measuring light transmission through a polishing pad
Implementation Method 2
Chemical Mechanical Planarization, or Chemical Mechanical Polishing (CMP), is a common technique used to planarize substrates. CMP utilizes a chemical composition, such as slurries or other fluid medium, for selective removal of materials from substrates.
Data Source
AI summary
A method of controlling the polishing of a substrate includes polishing a substrate on a first platen using a first set of parameters, obtaining first and second sequences of measured spectra from first and second regions of the substrate with an in-situ optical monitoring system, generating first and second sequences of values from the first and second sequences of measured spectra, fitting first and second linear functions to the first and second sequences of values, determining a difference between the first linear function and the second linear function, adjusting at least one parameter of a second set of parameters based on the difference, and polishing the substrate on a second platen using the adjusted parameter.