CMP Optical Probe Layout for Precise End-Point Detection
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Solution Overview
Problem
Existing CMP end-point detection methods lack precision and reliability, particularly for dielectric layers with similar properties, and require complex setups that are not universally applicable.
Innovation Solution
An online monitoring device for CMP utilizing beam propagation in free space and through an optical fiber, with a detection probe comprising a quartz light tube and single-core optical fiber, to achieve high-precision detection by collecting spectral information from the wafer surface.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If mechanical end-point detection method is used to monitor motor torque change, then detection can be implemented, but the application range is narrow and requires two dielectric layers with drastically different friction coefficients
Solution Approach 1:
The patent replaces mechanical end-point detection methods that monitor motor torque changes with an optical detection system using light sources, optical fibers, and detectors. This substitution eliminates the requirement for two dielectric layers with different friction coefficients and expands applicability to various materials including metals, dielectrics, and transparent materials.
Solution Approach 2:
The optical detection system is designed to be universally applicable to different material types (metals, dielectrics, transparent materials) by using light interaction principles that work across material categories, rather than being limited to specific friction coefficient differences required by mechanical methods.
2Adaptability or versatility
If electromagnetic end-point detection method is used to monitor eddy current, then metal film thickness can be detected, but it cannot be applied to insulating materials
Solution Approach 1:
The patent replaces electromagnetic eddy current detection with optical detection methods. By using light sources and optical fibers to interact with the wafer surface, the system can detect both metallic and insulating materials, as light interaction (reflection, absorption, transmission) occurs with all material types, not just conductive materials.
3Measurement precision
If optical end-point detection method with monochromatic laser is used, then reflectivity change can be monitored, but film thickness information cannot be obtained for transparent dielectric layers
Solution Approach 1:
The patent changes the optical parameter from monochromatic laser to broadband light source. This enables the detection system to capture spectral information across multiple wavelengths, allowing differentiation between reflectivity changes and film thickness information even for transparent dielectric layers, as different wavelengths interact differently with varying film thicknesses.
4Loss of information
If spectral end-point detection method with polychromatic light is used, then film thickness can be detected, but the system complexity increases
Solution Approach 1:
The patent uses optical fiber as an intermediary to transmit broadband light to the wafer surface and carry the reflected spectral information back to the detector. This intermediary approach simplifies the overall system architecture by consolidating light delivery and collection into a single flexible component, reducing the complexity associated with handling polychromatic light while maintaining spectral information acquisition capability.
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 device provides high-precision, accurate positioning, and low-noise detection, enabling reliable determination of the polishing end-point, suitable for various materials, and extending the life of the light source by optimizing light utilization and stability.
Implementation Method 1
an optical lens set, configured to receive a light beam emitted by the light source and generate a collimated beam
Implementation Method 2
the single-core optical fiber being configured to receive an emergent beam reflected by a surface of the wafer
Data Source
AI summary
An online monitoring device for CMP is arranged in a polishing disc, rotates with the polishing disc, and comprises: a light source; an optical lens set, configured to receive a light beam emitted by the light source and generate a collimated beam; a reflecting unit, configured to receive the collimated beam and reflect the collimated beam to form an incident beam; a detection probe, arranged below a light window of a polishing pad and at least comprising a quartz light tube and a single-core optical fiber, the quartz light tube being configured to receive the incident beam and emit the incident beam from an end, close to a wafer, of the detection probe, and the single-core optical fiber being configured to receive an emergent beam reflected by a surface of the wafer; and a detector, connected to the single-core optical fiber.