X-ray Metrology for CMP Endpoint Control
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Solution Overview
Problem
Chemical mechanical polishing (CMP) processes face challenges in determining the polishing endpoint due to variations in material removal rates caused by initial thickness, slurry composition, polishing pad condition, and load, making it difficult to accurately assess when a substrate layer is planarized to the desired flatness or thickness.
Innovation Solution
Implementing an x-ray monitoring system that takes measurements of metal amounts on a substrate before and after a second metal layer is deposited, allowing for comparison and adjustment of polishing parameters to ensure accurate endpoint control, using either in-situ or in-sequence monitoring configurations within a CMP apparatus.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If polishing time is used to determine endpoint, then process simplicity is maintained, but manufacturing precision deteriorates due to variations in material removal rate
Solution Approach 1:
The patent replaces mechanical/time-based endpoint determination with X-ray measurement-based endpoint determination. The X-ray measurement system directly measures the thickness of the filler layer and patterned layer, substituting the mechanical polishing time control method with a precise non-contact measurement method that is not affected by variations in material removal rate.
Solution Approach 2:
The patent implements a feedback control system where X-ray measurements are taken during polishing, the measured thickness is compared to target thickness, and polishing parameters are adjusted based on the deviation. This closed-loop feedback ensures precise endpoint control while maintaining process simplicity through automated control.
2Manufacturing precision
If X-ray monitoring system is implemented, then manufacturing precision is improved, but device complexity increases
Solution Approach 1:
The X-ray measurement system serves multiple functions: it measures the thickness of the filler layer, measures the thickness of the patterned layer, determines the polishing endpoint, and provides feedback for process control. This multi-functionality reduces the need for separate measurement systems and integrates monitoring capabilities into a single universal device.
Solution Approach 2:
The patent introduces an X-ray beam as an intermediary that penetrates the polishing pad and slurry to directly measure the thickness of underlying layers. This intermediary measurement approach allows non-contact, real-time thickness measurement without interfering with the polishing process, simplifying the overall system architecture.
3Manufacturing precision
If polishing parameters are adjusted based on measurements, then manufacturing precision is improved, but loss of time increases due to additional measurement and adjustment steps
Solution Approach 1:
The X-ray measurements are performed continuously or periodically during the polishing process itself, rather than as separate pre-polishing or post-polishing inspection steps. This continuous measurement approach allows real-time feedback and adjustment without interrupting the polishing operation, eliminating idle time and maintaining continuous productive action.
Solution Approach 2:
The system performs preliminary X-ray measurements of the filler layer thickness before polishing begins, allowing pre-calculation of the required polishing time and parameters. This preliminary action enables proactive process control, reducing the need for iterative adjustments and minimizing total process time while ensuring precision.
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 method enables precise control of polishing operations, reducing within-wafer and wafer-to-wafer non-uniformity of line resistance by accurately determining metal thickness and adjusting polishing parameters accordingly.
Implementation Method 1
receiving a first measurement of a first amount of metal on a substrate made by a first x-ray monitoring system
Data Source
AI summary
A method of controlling a polishing operation includes receiving a first measurement of a first amount of metal on a substrate made by a first x-ray monitoring system after a first metal layer is deposited on the substrate and before a second metal layer is deposited on the substrate, transferring the substrate to a carrier head of a chemical mechanical polishing apparatus the substrate after the second metal layer is deposited on the substrate, making a second measurement of a second amount of metal on the substrate with a second x-ray monitoring system in the chemical mechanical polishing apparatus, comparing the first measurement to the second measurement to determine a difference, and adjusting a polishing endpoint or a polishing parameter of the polishing apparatus based on the difference.