Infrared Metrology for CMP Endpoint Detection
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Solution Overview
Problem
Traditional metrology methods for determining the structural phase and thickness of GST layers in phase-change memory devices are time-consuming and costly, limiting their application in CMP processes.
Innovation Solution
A fast and economic metrology method using non-polarized light beams to measure the infra-red component of reflected light during polishing, allowing for in-line or standalone monitoring of GST layer thickness and structural phase, enabling real-time control of polishing parameters.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If traditional metrology methods (ellipsometry or X-ray reflectometry) are used to measure GST layer thickness and structural phase, then accurate and reliable measurements can be obtained, but the process becomes time-consuming and costly
Solution Approach 1:
The patent replaces traditional mechanical/optical metrology systems (ellipsometry, X-ray reflectometry) with an infrared absorption-based measurement system. This substitution uses infrared light transmission through the GST layer to determine thickness and structural phase, enabling faster measurements that can be performed in-line during CMP processing without requiring complex traditional metrology equipment
Solution Approach 2:
The patent creates a simplified measurement model using infrared absorption characteristics that replicates the measurement capability of complex traditional metrology systems. By measuring infrared transmission at specific wavelengths and using lookup tables or algorithms to correlate absorption characteristics with thickness and phase, the system produces equivalent measurement results much more quickly
2Measurement precision
If traditional metrology methods are used, then accurate GST layer characterization is achieved, but equipment cost and complexity increase
Solution Approach 1:
The patent replaces complex traditional metrology equipment (ellipsometers, X-ray reflectometers) with a simpler infrared transmission measurement system. The system uses an infrared light source, transmission measurement device, and lookup table or algorithm to determine GST layer properties, eliminating the need for expensive and complex traditional instrumentation while maintaining measurement accuracy
Solution Approach 2:
The patent employs a cost-effective measurement approach using infrared absorption characteristics that can be implemented with relatively simple and inexpensive equipment compared to traditional metrology systems. The method uses readily available infrared light sources and measurement devices, making the system more economically viable for production environments
3Extent of automation
If in-line metrology is implemented during polishing, then real-time polishing control is enabled, but the system complexity and cost increase
Solution Approach 1:
The patent replaces complex real-time metrology systems with an infrared transmission measurement system that can be easily integrated into the polishing process. By measuring infrared transmission during polishing and using pre-established lookup tables or algorithms to determine endpoint, the system achieves real-time control without requiring complex additional instrumentation
Solution Approach 2:
The patent implements feedback control by continuously monitoring infrared transmission during polishing and adjusting polishing parameters based on measured GST layer thickness and structural phase. The system uses the measured absorption characteristics to determine when the underlying layer is exposed and adjusts polishing load or speed to maintain optimal polishing conditions
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 provides accurate and efficient determination of GST layer thickness and structural phase, improving polishing uniformity and endpoint detection, and can be implemented in-line or standalone, reducing the need for costly equipment and increasing production efficiency.
Implementation Method 1
directing a non-polarized light beam onto the layer of GST, the non-polarized light beam reflecting from the first substrate to generate a reflected light beam having an infra-red component
Implementation Method 2
generating a sequence of measurements of intensity of the infra-red component of the reflected light beam
Data Source
AI summary
During polishing of a first substrate at a first polishing station, a sequence of measurements by a first in-situ monitoring system is monitored to determining a first time at which the first sequence exhibits a first predefined feature indicating a predetermined thickness of an overlying layer, and during polishing of the first substrate at a second polishing station, a sequence of measurements by a second in-situ monitoring system is monitored to determine a second time indicating clearance of the overlying layer and exposure of the underlying layer. The first time is used to calculate a first adjusted polishing pressure for a second substrate at the first polishing station, and the second time is used to calculate a second adjusted polishing pressure for the second substrate at the second polishing station.