Wafer Level Packaging Alignment for Reduced-Height Infrared Detectors
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Solution Overview
Problem
The challenge in manufacturing reduced thickness infrared detectors is aligning dicing equipment with thinned semiconductor wafers, as the thinning process removes the surface alignment marks typically used for alignment, making it difficult to perform wafer level packaging operations efficiently.
Innovation Solution
The solution involves forming alignment marks on or within both wafers, allowing them to be viewed through a transparent lid wafer, enabling the use of an infrared camera to align dicing equipment for precise processing, even after wafer thinning, thus maintaining alignment for further processing steps.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Length of moving object
If the wafer is thinned to reduce package thickness, then the overall device size is reduced, but the alignment marks are removed making alignment difficult
Solution Approach 1:
Alignment marks are formed on the wafer before the thinning process. This preliminary action ensures that the marks are embedded within the wafer structure, allowing them to survive the subsequent thinning operation and remain available for alignment purposes.
Solution Approach 2:
The alignment marks are positioned in a location that can be viewed through the transparent lid wafer. This dimensional approach allows the alignment system to access marks that are embedded within the wafer structure by viewing from the opposite side, bypassing the problem of marks being removed during thinning.
2Manufacturing precision
If alignment marks are formed on the wafer surface, then alignment is enabled, but the marks are removed during thinning process
Solution Approach 1:
Alignment marks are formed on the wafer before the thinning process. This preliminary action ensures that the marks are embedded within the wafer structure, allowing them to survive the subsequent thinning operation and remain available for alignment purposes.
Solution Approach 2:
The alignment marks are created as permanent features within the wafer structure itself, essentially creating a copy of the alignment reference that cannot be removed. This embedded copying ensures alignment capability is preserved through all subsequent processing steps.
3Ease of operation
If the lid wafer is made transparent to enable viewing of alignment marks, then alignment is facilitated, but visibility of other features may be affected
Solution Approach 1:
The lid wafer is made transparent specifically in the regions where alignment marks need to be viewed, while maintaining appropriate opacity or characteristics in other regions. This localized transparency allows alignment operations without compromising the overall functionality or visibility requirements of the device.
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 method allows for the reliable and efficient production of reduced height infrared detectors, facilitating volume production by ensuring accurate alignment and processing of thinned wafers, reducing the thickness of infrared detector packages while maintaining mechanical integrity.
Implementation Method 1
The first wafer may, for example, represent a lid or cap wafer... The first wafer may be substantially transparent in some or all of the infrared (IR) portion of the electromagnetic spectrum. For example, the first wafer may be substantially transparent to short wave infrared (SWIR) light.
Data Source
AI summary
Systems and methods may be provided for generating reduced-height circuit packages such as infrared detector packages. An alignment and dicing system may include an infrared camera that captures images of alignment marks of a wafer assembly through a lid wafer of the wafer assembly, a light source that illuminates the alignment marks through the lid wafer, and dicing equipment that dices the wafer assembly based on infrared images captured using the infrared camera. The light source may illuminate the alignment marks through the lid wafer by providing light such as infrared light to the wafer assembly through optics of the infrared camera. The infrared camera may capture images of alignment marks formed on a detector wafer of the wafer assembly or on an interior or lower surface of the lid wafer through the lid wafer. The dicing equipment may be aligned with the wafer assembly based on the captured images.