Wafer Edge Imaging for Alignment of Epoxy-Molded Substrates
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Solution Overview
Problem
Existing semiconductor substrate alignment methods, such as rotary aligners and backlight imaging, are ineffective for molded substrates where the notch is obscured by epoxy, making it difficult to detect the substrate's orientation during back end processing.
Innovation Solution
An in-situ aligner system with a machine vision system that provides controlled high-contrast images of the substrate, allowing for the identification of notches and other features regardless of epoxy obstruction, using a combination of image sensors and controlled contrast surfaces to determine misalignment angles and registration shifts during on-the-fly substrate transport.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If rotary aligners or backlight imaging methods are used for substrate alignment, then alignment can be achieved for standard substrates, but the notch outline becomes undetectable when the substrate is molded with epoxy
Solution Approach 1:
The patent introduces an intermediary illumination system with specifically positioned light sources that illuminate the substrate from angles optimized to create visible contrast of the notch outline through the epoxy molding compound. This intermediary lighting mechanism enables detection that would otherwise be impossible with standard backlighting alone.
Solution Approach 2:
The patent changes the illumination parameters by using multiple light sources at specific angles rather than uniform backlighting. By adjusting the illumination angle and intensity distribution, the system creates optimal contrast conditions for detecting the notch outline through the epoxy material.
2Reliability
If epoxy molding is applied to cover the substrate frontside, then substrate protection and packaging are improved, but the notch outline becomes obscured and difficult to detect
Solution Approach 1:
The patent applies local quality by creating non-uniform illumination with specific light sources positioned to illuminate particular regions of the substrate at optimized angles. This localized illumination strategy enhances the visibility of the notch outline through the epoxy while leaving other regions unaffected.
Solution Approach 2:
The patent utilizes optical contrast changes by strategically positioning light sources to create varying illumination patterns that highlight the notch outline. The controlled illumination creates optical effects that make the notch visible through the epoxy molding compound.
3Productivity
If traditional alignment methods are used for molded substrates, then processing can proceed, but alignment accuracy deteriorates due to inability to detect notch position
Solution Approach 1:
The patent performs preliminary alignment by detecting the notch outline position before the substrate enters the main processing sequence. The specialized illumination system enables this preliminary detection action to occur, establishing accurate positioning that carries through subsequent processing steps.
Solution Approach 2:
The patent implements feedback by using the detected notch outline position to adjust and refine substrate alignment. The imaging system provides feedback information about the actual notch position, which is then used to correct alignment deviations and achieve precise positioning.
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 accurate substrate alignment and registration even with epoxy-covered notches, improving processing efficiency and reducing transfer times within the substrate processing system.
Implementation Method 1
An illumination source is provided and the image sensor is disposed with respect to the illumination source so that the surface directs reflected surface illumination, from the illumination source, at the image sensor
Data Source
AI summary
A semiconductor wafer transport apparatus having a transport arm and at least one end effector. An optical edge detection sensor is coupled to the transport arm and is configured so as to register and effect edge detection of a wafer supported by the end effector. An illumination source illuminates a surface of the wafer and is disposed with respect to the optical edge detection sensor so that the surface directs reflected surface illumination, from the illumination source, toward the optical edge detection sensor, and optically blanks, at the peripheral edge of the wafer, background reflection light of a background, viewed by the optical edge detection sensor coincident with linear traverse of the wafer supported by the at least one end effector. The peripheral edge of the wafer is defined in relief in image contrast to effect edge detection coincident with traverse of the wafer supported by the end effector.