Protective Tape Alignment Using Red-Light Wafer Edge Detection
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Solution Overview
Problem
There is a lack of high-accuracy alignment methods for applying protective tapes to bump wafers, and existing methods struggle with accurately aligning protective tapes with wafers that have transparency, such as glass or lithium niobate, due to issues with light penetration.
Innovation Solution
An alignment device and method using red light to detect the center of a semiconductor wafer through its outer peripheral edge, and an image pickup system to determine the center position of a protective tape with a protective layer, allowing for precise alignment and application of the protective tape.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If infrared light is used for alignment of transparent wafers, then alignment can be performed without breaking wafer elements, but alignment accuracy deteriorates because infrared light passes through transparent wafers
Solution Approach 1:
The patent changes the wavelength parameter of the light from infrared to red light. Red light has shorter wavelength and lower energy than infrared light, which prevents damage to wafer elements while also providing sufficient contrast for accurate alignment detection on transparent wafers.
Solution Approach 2:
The patent replaces the infrared light-based alignment system with a red light-based alignment system. This substitution maintains the non-contact optical alignment approach while resolving the contradiction by using light properties that work for both transparent and non-transparent wafers.
2Reliability
If a protective layer with smaller diameter than protective tape is used to cover bump wafer irregularities, then protection effectiveness is improved, but alignment accuracy deteriorates due to lack of high-accuracy alignment methods
Solution Approach 1:
The patent introduces an optical filter as an intermediary component in the alignment system. The filter enables precise detection of the protective layer's outer peripheral edge by enhancing the contrast between the protective layer and the bump wafer surface, thereby achieving high alignment accuracy despite the protective layer's smaller diameter.
Solution Approach 2:
The patent utilizes red light illumination which creates optimal contrast for detecting the protective layer boundaries. The specific wavelength of red light enhances the visibility of the protective layer's outer peripheral edge, enabling accurate alignment even when the protective layer is smaller than the protective tape.
3Ease of operation
If visible light optical sensors are used to detect wafer notches for alignment, then alignment can be performed, but detection fails when notches are covered with protective tape
Solution Approach 1:
The patent extracts the alignment detection from the traditional notch-based method to the outer peripheral edge-based method. By detecting the outer peripheral edge of the protective layer instead of notches on the wafer, the system maintains alignment capability while avoiding the problem of notch coverage by protective tape.
Solution Approach 2:
The patent inverts the detection approach: instead of detecting features on the wafer (notches) that may be covered, it detects features on the protective layer (outer peripheral edge) that are always visible. This inversion ensures reliable detection regardless of protective tape application.
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 solution enables high-accuracy alignment of protective tapes with both standard and transparent wafers, ensuring that the protective layer effectively covers the wafer's irregularities without positional displacement, thus providing adequate protection for bump wafers.
Implementation Method 1
illumination means for illuminating the semiconductor wafer with red light from one surface side of the semiconductor wafer; and image pickup means for imaging the semiconductor wafer on another surface side of the semiconductor wafer, in which the alignment device is configured to determine a center position of the semiconductor wafer through detection of an outer peripheral edge portion of the semiconductor wafer based on a reception state of the red light by the image pickup means
Data Source
AI summary
To perform alignment of a protective tape having a protective layer with high accuracy, provided is an alignment device (5) to be used for applying a protective tape (PT) to a semiconductor wafer (W), including: a tape holding body (30) configured to hold the protective tape (PT) laminated with a protective layer (PL) having an outer diameter smaller than an outer diameter of the protective tape (PT), and one image pickup means (50) for imaging a plurality of parts of an outer peripheral edge portion of the protective layer (PL), wherein the alignment device is configured to determine a center position of the protective layer (PL) based on positional information on each of the plurality of parts of the outer peripheral edge portion of the protective layer (PL) through determination of the positional information on the each of the plurality of parts based on image data acquired by imaging of the image pickup means (50).