Optical Edge Thickness Measurement During Polishing
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Solution Overview
Problem
During electronic device manufacturing, there is a need to measure substrate edge thickness accurately during polishing to determine the endpoint of the polishing process, as undesirable materials like dielectrics and metals build up on the substrate edges, and existing methods lack effective solutions for in-situ thickness measurement.
Innovation Solution
A system comprising a light source and detectors is used to transmit and reflect light from the substrate edge, with a controller analyzing the reflected light spectrum to determine the polishing endpoint by comparing it to a reference spectrum, and a jacket assembly provides a uniform fluid medium to minimize interference.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If conventional polishing methods are used without in-situ measurement, then the polishing process can be completed, but the endpoint cannot be accurately determined and substrate edge thickness cannot be measured
Solution Approach 1:
The patent replaces mechanical thickness measurement methods with optical measurement. A light source emits light through a fluid medium to the substrate edge, and detectors measure the transmitted or reflected light. The controller analyzes the light signal to determine thickness, substituting mechanical contact measurement with non-contact optical measurement to achieve precise in-situ thickness measurement during polishing.
Solution Approach 2:
The patent introduces a fluid medium as an intermediary between the light source and the substrate edge. The fluid medium (typically water or water-based slurry used in polishing) serves as the transmission medium for light, allowing optical measurement through the polishing interface without interfering with the polishing process. This intermediary enables the optical measurement system to function effectively in the polishing environment.
2Reliability
If in-situ measurement system is implemented, then real-time endpoint determination is achieved, but the system complexity and cost increase
Solution Approach 1:
The patent makes the polishing slurry serve multiple functions: it acts as both the polishing agent for material removal and as the optical transmission medium for thickness measurement. This multi-functionality eliminates the need for separate fluid delivery systems for measurement, reducing overall system complexity while maintaining reliable in-situ measurement capability.
Solution Approach 2:
The measurement system utilizes the existing polishing infrastructure (slurry delivery system, polishing pad, etc.) to serve the measurement function. The same fluid that enables polishing also enables optical measurement, and the system leverages the existing mechanical components for both polishing and measurement operations, reducing the need for additional dedicated components.
3Measurement precision
If light transmission through fluid medium is used for measurement, then non-contact measurement is achieved, but fluid interference with light signal may occur
Solution Approach 1:
The patent optimizes the optical parameters of the measurement system, including selecting light wavelengths that transmit effectively through the polishing slurry and adjusting the optical geometry to minimize scattering and absorption effects. By carefully selecting the wavelength range and optimizing the optical path, the system achieves accurate measurements despite the presence of the fluid medium.
Solution Approach 2:
The patent replaces direct mechanical contact measurement with optical measurement through the fluid medium. Instead of using physical probes that would be affected by the fluid and require complex sealing and positioning, the system uses light transmission that naturally passes through the fluid, converting a mechanically problematic measurement into an optically-based solution.
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
Enables real-time determination of the polishing endpoint, allowing for adjustments during the process and improving throughput by accurately measuring film thickness and ensuring a desired film profile is achieved.
Implementation Method 1
one or more detectors adapted to detect an arrangement of light reflected from the substrate edge
Data Source
AI summary
Systems, methods and apparatus are provided for determining a substrate polishing endpoint. The invention includes a light source adapted to transmit light to an edge of a substrate; one or more detectors adapted to detect an arrangement of light reflected from the substrate edge; and a controller adapted to determine a polishing endpoint for the substrate edge based on the arrangement of reflected light. Numerous other aspects are provided.