CMP Film Thickness Measurement Using Relative Reflectance Correction
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Solution Overview
Problem
The variation in the spectrum of reflected light from a workpiece during chemical mechanical polishing (CMP) leads to unstable film thickness measurement, affecting accurate monitoring of film thickness in semiconductor manufacturing.
Innovation Solution
A polishing apparatus and method that uses a first and second spectrometer to measure light intensity, coupled with a processing system to calculate relative reflectance data, correcting for variations in light source intensity and optical path changes through optical fiber cables, enabling accurate film thickness determination.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If a light source is used to measure film thickness during polishing, then real-time monitoring capability is improved, but measurement stability deteriorates due to light intensity variation
Solution Approach 1:
The patent implements a feedback mechanism where the actual light intensity measured during polishing is used to correct the film thickness measurement. The system measures the light intensity from the light source, compares it with the reference intensity, and applies a correction factor to the film thickness calculation based on the intensity ratio, thereby compensating for light source variation in real-time
Solution Approach 2:
The patent changes the measurement approach from absolute reflectance to relative reflectance. Instead of measuring absolute light intensity which varies with light source instability, the system measures the ratio of actual light intensity to reference light intensity, and uses this ratio to correct the film thickness measurement, making the measurement stable despite parameter changes in light intensity
2Productivity
If dynamic measurement during wafer rotation is performed, then polishing process monitoring is improved, but measurement accuracy deteriorates due to inability to average multiple measurements
Solution Approach 1:
The system uses feedback from the measured light intensity variations to dynamically correct the film thickness measurement. By continuously monitoring the light intensity and comparing it with reference values, the system adjusts the measurement in real-time to compensate for the dynamic conditions during wafer rotation
Solution Approach 2:
The patent performs preliminary measurement of reference light intensity before the actual film thickness measurement during polishing. This reference measurement is stored and used to correct the subsequent measurements, allowing the system to account for light source characteristics before dynamic measurement begins
3Adaptability or versatility
If optical fiber cable is used to transmit light, then system flexibility is improved, but measurement stability deteriorates due to optical path variation
Solution Approach 1:
The system implements feedback by measuring the actual light intensity received through the optical fiber cable during operation and comparing it with the reference intensity. The ratio of these measurements provides correction information that compensates for optical path variations in the fiber cable
Solution Approach 2:
The patent transitions from assuming constant optical path transmission to measuring and correcting for variable transmission. By changing from absolute intensity measurement to relative intensity ratio measurement, the system accounts for parameter changes in the optical fiber cable's light transmission characteristics
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
The solution stabilizes film thickness measurement by removing variations in light quantity and optical path, allowing for precise film thickness determination during polishing.
Implementation Method 1
a light-emitting optical fiber cable coupled to the light source and configured to direct the light to the workpiece
Implementation Method 2
a light-receiving optical fiber cable configured to receive reflected light from the workpiece
Implementation Method 3
a first spectrometer coupled to the light-receiving optical fiber cable... configured to determine a film thickness of the workpiece based on relative reflectance data
Implementation Method 4
a polishing table configured to support a polishing pad... a polishing head configured to press the workpiece against the polishing pad to polish the workpiece
Data Source
AI summary
A polishing apparatus and a polishing method capable of accurately measuring a film thickness of a workpiece, such as wafer, substrate, or panel, used in manufacturing of semiconductor devices during polishing of the workpiece are disclosed. The processing system is configured to determine a film thickness of the workpiece based on relative reflectance data calculated by a calculation formula expressed as: the relative reflectance data=MD1/[BD1·k], where MD1 represents first intensity measurement data indicating intensity of the reflected light from the workpiece measured by the first spectrometer, BD1 represents the first base intensity data, and k represents a rate of change in second intensity measurement data with respect to the second base intensity data. The second intensity measurement data is indicative of intensity of the light of the light source measured by the second spectrometer during polishing of the workpiece.