Oblique Incidence Detection for Multi-Layer Substrate Height
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Solution Overview
Problem
Existing detection apparatuses face challenges in accurately measuring the height of substrates with multiple layers due to noise components from light reflected by the top surface, leading to detection errors, especially when trying to isolate p-polarized light at the Brewster's angle.
Innovation Solution
The apparatus optimizes the angle of incidence between 40° to 55° to minimize the noise component ratio by adjusting the polarizing state, ensuring that the intensity difference between interface-reflected and surface-reflected light is maximized, allowing for precise height detection by configuring the exposure apparatus to use slit-shaped light and interferometric position detection units.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If p-polarized light is incident on the substrate at the Brewster's angle to eliminate surface-reflected light, then the detection precision of substrate height is improved, but it becomes extremely difficult to extract only p-polarized light by removing s-polarized light completely from light
Solution Approach 1:
The patent changes the angle of incidence parameter from the Brewster's angle to a range of 40° to 55°. This parameter change reduces the intensity ratio of surface-reflected light to interface-reflected light to 1/5 or less, achieving effective noise suppression without requiring complete s-polarized light removal, thus resolving the contradiction between detection precision and device complexity
Solution Approach 2:
The patent uses a polarizer to generate p-polarized light from unpolarized or mixed polarized light. Instead of attempting to completely remove s-polarized light through complex polarization extraction systems, the patent employs a polarizer to create the desired polarization state, simplifying the device while maintaining detection precision
2Measurement precision
If light is incident on the substrate to detect the interface-reflected light for height measurement, then the substrate height can be detected, but the light reflected by the surface of the top layer becomes a noise component and generates detection error
Solution Approach 1:
The patent optimizes the angle of incidence to be in the range of 40° to 55°, which is specifically chosen to minimize the noise component ratio. At this angle range, the intensity ratio of surface-reflected light to interface-reflected light is reduced to 1/5 or less, effectively suppressing the harmful noise while maintaining the ability to detect interface-reflected light for accurate height measurement
Solution Approach 2:
The patent converts the potentially harmful surface-reflected light into a beneficial signal by optimizing the angle of incidence. The same angle range (40° to 55°) that reduces surface reflection noise also enhances the intensity of interface-reflected light, turning what could be a noise problem into a signal enhancement opportunity
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 approach reduces detection errors by minimizing the intensity ratio of surface-reflected light to interface-reflected light, enabling accurate measurement of substrate height with improved precision and reduced noise components.
Implementation Method 1
light reflected by the substrate
Implementation Method 2
causing p-polarized light to be incident on a substrate at the Brewster's angle
Implementation Method 3
controlling the polarizing state of a polarizing element so as to reduce reflected light components
Data Source
Figure 1
Figure 2
Figure 3~4
AI summary
The present invention provides a detection apparatus which causes light to be incident obliquely on a substrate (3) including a plurality of layers whose refractive indices are different from each other and detects a height of the substrate using light reflected from the substrate, the apparatus comprising an optical system (41a) including a polarizer (41a1) for reducing s-polarized light and configured to cause light, in which s-polarized light has been reduced by the polarizer, to be incident on the substrate at an angle of incidence within a range of 40° to 55°.