Tilted Window for Interferometric Endpoint Detection
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Solution Overview
Problem
Conventional endpoint detection systems in semiconductor processing face significant internal reflections and reduced sensitivity due to the use of flat interferometry windows, which limits their effectiveness over a broad range of wavelengths without the need for anti-reflective coatings.
Innovation Solution
A tilted window is introduced in the endpoint detection system, oriented at specific acute angles to reduce internal reflections, allowing incident and reflected light to pass through without interference, thereby improving sensitivity and dynamic range.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If a flat transparent window is used in the endpoint detection system, then the structure is simple and easy to manufacture, but internal reflections occur significantly and sensitivity is reduced
Solution Approach 1:
The patent applies asymmetry by tilting the window at a specific angle (e.g., 45 degrees) relative to the substrate normal, breaking the symmetric flat window design. This asymmetric orientation causes incident light to reflect away from the detection path at non-perpendicular angles, eliminating internal reflections that would otherwise interfere with endpoint detection sensitivity.
Solution Approach 2:
The patent transitions from a two-dimensional flat window (parallel to substrate) to a three-dimensional tilted window configuration. By introducing angular orientation as an additional spatial dimension, the system directs reflected light away from the detection path while maintaining optical access through the window, thereby resolving the contradiction between structural simplicity and measurement precision.
2Object-affected harmful factors
If anti-reflective coatings are applied to the window surfaces, then internal reflections are reduced, but the solution is limited to a narrow wavelength range
Solution Approach 1:
The patent changes the geometric parameter of the window (its angular orientation) instead of modifying the optical parameter (anti-reflective coatings). This parameter change affects the reflection angle rather than the reflectivity magnitude, providing a broadband solution that works across all wavelengths without being constrained by coating material limitations.
Solution Approach 2:
Instead of trying to reduce reflection by modifying the window surface properties (coatings), the patent inverts the approach by orienting the window so that reflections are directed away from the detection path geometrically. This inverted strategy addresses internal reflections through spatial configuration rather than surface treatment, achieving broadband versatility.
3Measurement precision
If the window is tilted at an acute angle, then internal reflections are eliminated across a broad wavelength range, but the window orientation becomes more complex
Solution Approach 1:
The patent employs asymmetric tilting of the window at a specific acute angle (e.g., 45 degrees) to eliminate internal reflections. This asymmetric orientation creates a geometric configuration where reflected light follows a predictable path away from the detection system, achieving high measurement precision while maintaining a relatively simple tilted window structure.
Solution Approach 2:
The tilted window configuration serves multiple functions simultaneously: it maintains optical access to the substrate, eliminates internal reflections across broad wavelengths, and provides a stable mounting structure. This multi-functionality reduces the need for additional components, thereby managing device complexity while achieving superior endpoint detection sensitivity.
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 tilted window effectively reduces internal reflections across a wide range of wavelengths, enhancing etch depth and thickness control accuracy and extending the service life of the detection system, while maintaining compatibility with existing chamber designs.
Implementation Method 1
The transparent panel transmits the incident light beam to the substrate within the processing chamber at an angle perpendicular to the substrate and the substrate support
Implementation Method 2
The tilted window effectively reduces internal reflections across a wide range of wavelengths
Data Source
AI summary
A method is disclosed for operating an endpoint detection system of a processing chamber having a ceiling formed therein, a substrate support located internal to the processing chamber, and a substrate resting on the substrate support. A transparent panel is located in the ceiling of the processing chamber, the panel oriented at a first acute angle relative to the substrate and the substrate support. The transparent panel receives an incident light beam from the endpoint detection system at a second acute angle relative to the panel. The transparent panel transmits the incident light beam to the substrate within the processing chamber at an angle perpendicular to the substrate and the substrate support.