Substrate Position Detection Using Polarizing Plate to Block Window Reflection
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Solution Overview
Problem
Existing substrate position detecting apparatuses face challenges in maintaining high contrast image pickup within a chamber, especially when a colored film forms on the window of a deposition apparatus, leading to deteriorated visibility of the susceptor mark due to reflection issues.
Innovation Solution
The apparatus includes an illumination reflecting plate with a reflection restricting part to prevent light from illuminating the image pickup target, forming a shadow and maintaining high contrast, and uses a cutout susceptor mark for improved visibility even when a reflective film is deposited on the window.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a window is provided on the chamber for observation, then substrate position detection is enabled, but deposition on the window forms a reflective film that deteriorates image contrast
Solution Approach 1:
A polarizing plate is introduced as an intermediary component between the window and the image pickup device. This polarizing plate selectively transmits or blocks polarized light reflected from the window, thereby eliminating the harmful reflection effect while preserving the transmitted light from the substrate for accurate position detection.
Solution Approach 2:
The optical properties of the window system are modified by adding a polarizing plate that changes the polarization state of light. This parameter change in light polarization allows differentiation between reflected light (which becomes polarized) and transmitted light from the substrate, enabling the system to maintain detection accuracy despite the presence of the window.
2Illumination intensity
If illumination is provided to make the wafer appear white for clear recognition, then substrate visibility is improved, but light reflects off the window film and deteriorates image contrast
Solution Approach 1:
The polarizing plate serves as a mediator that allows the illumination to effectively light up the wafer while simultaneously filtering out the reflected light from the window. It transmits the illumination light that passes through the window and the light reflected from the wafer, but blocks the light reflected from the window surface.
Solution Approach 2:
The polarizing plate creates local quality differentiation in the light paths: it selectively transmits light with specific polarization orientations while blocking others. This allows the system to maintain high illumination intensity for wafer visibility in the desired direction while locally suppressing reflections from the window surface.
3Loss of time
If the window is used for continuous observation during deposition, then real-time position monitoring is achieved, but the reflective film formation progressively worsens image quality
Solution Approach 1:
The polarizing plate provides continuous protection against reflection throughout the deposition process, enabling real-time observation without degradation. As the reflective film builds up on the window during deposition, the polarizing plate continuously filters the reflected light, maintaining consistent image contrast and measurement precision throughout the entire process.
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 configuration allows for accurate detection of the substrate position with high contrast images, even when a reflective film is present on the window, ensuring reliable substrate positioning during deposition processes.
Implementation Method 1
an illumination reflecting plate provided above the illumination device and including a reflecting surface configured to reflect the light from the illumination device towards the window
Implementation Method 2
a reflection restricting part provided on the reflecting surface of the illumination reflecting plate and configured to form a shadow in a predetermined region that includes the target inside the chamber
Data Source
AI summary
A substrate position detecting apparatus detects a position of a substrate inside a chamber from an image of a target inside the chamber. The apparatus includes an image pickup device to pick up the image of the target inside the chamber through a window, an illumination device to irradiate light upwards, an illumination reflecting plate provided above the illumination device and including a reflecting surface to reflect the light from the illumination device towards the window, and a reflection restricting part provided on the reflecting surface to form a shadow in a predetermined region that includes the target inside the chamber.