Through-Hole Optical Inspection Using Inclined Projection and Interference
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Solution Overview
Problem
Conventional inspection methods for semiconductor through holes are time-consuming and incapable of analyzing taper angles, which are crucial for modern metal plating processes due to smaller critical dimensions.
Innovation Solution
An optical inspection apparatus utilizing a projection optical system and a digital microscope system to obtain inclined projection and 2D interference images, combined with a calculating unit for analyzing parameters and stereoscopic data, enabling contactless and nondestructive inspection of multiple through holes simultaneously.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If conventional inspection methods (laser confocal microscopy, color confocal microscopy, white light scan) are used, then inspection can be performed, but inspection time is long (30 minutes for SEM scan) and multiple through holes cannot be inspected simultaneously
Solution Approach 1:
The patent combines projection optical system imaging with digital microscope interference imaging to create a hybrid inspection method. The projection optical system captures inclined projection images of multiple through holes simultaneously, while the digital microscope system captures 2D interference images. This merging of two imaging approaches enables parallel inspection of multiple through holes, reducing inspection time from 30 minutes to a few seconds while maintaining measurement capability.
Solution Approach 2:
The patent introduces inclined projection imaging from a different optical dimension to complement the traditional digital microscope imaging. By using a projection optical system that projects light through the substrate at an angle, the system captures three-dimensional information about through hole structures in a single image, enabling simultaneous inspection of multiple through holes without sequential scanning.
2Measurement precision
If conventional inspection methods are used, then through holes can be inspected, but taper angles of corners cannot be analyzed which is crucial for metal plating process
Solution Approach 1:
The patent segments the inspection task into two complementary imaging systems: the projection optical system captures the geometric structure and taper angles of through hole corners, while the digital microscope system captures interference patterns for dimensional measurement. This segmentation allows each system to specialize in specific measurement aspects, with the projection system providing the taper angle data crucial for metal plating process control.
3Productivity
If projection optical system is used to obtain inclined projection image, then multiple through holes can be inspected simultaneously, but additional equipment and processing algorithms are required
Solution Approach 1:
The patent makes the projection optical system serve multiple functions: it acts as both an imaging device for capturing through hole structures and a measurement device for obtaining geometric parameters like taper angles. The same inclined projection images are used for both structural visualization and dimensional measurement, reducing the need for separate specialized equipment and simplifying the overall system architecture.
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
Reduces inspection time to seconds, allows real-time feedback, and enables inspection of taper angles, facilitating the formation of through hole vias with smaller critical dimensions for metal plating.
Implementation Method 1
a light source configured to illuminate a back side of the substrate
Implementation Method 2
a projection lens located at a front side of the substrate
Implementation Method 3
a laser light source configured to emit an incident light
Implementation Method 4
a digital microscope system configured to obtain a 2D interference image
Data Source
AI summary
An optical inspection apparatus includes a projection optical system, a digital microscope system, and a calculating unit electrically connected to the projection optical system and the digital microscope system. The projection optical system is configured to obtain an inclined projection image of multiple through hole structures in a substrate. The digital microscope system is configured to obtain a 2D interference image. The calculating unit is electrically connected to the projection optical system and the digital microscope system. The calculating unit is configured to analyze the 2D interference image to obtain a stereoscope image data and to analyze the inclined projection image to obtain multiple parameters of the through hole structures. The optical inspection apparatus can be used to get a feedback in real-time. Multiple through hole structures can be inspected at the same time such that the time required to scan the substrate is reduced.