Backside Wafer Dicing via Infrared Scribe Line Detection
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Solution Overview
Problem
In semiconductor packaging, cutting a wafer from its backside is challenging when the backside is sealed by molding materials or covered with non-transparent materials, as it complicates the alignment and detection of scribe lines necessary for precise dicing.
Innovation Solution
The method involves forming a support structure on the front surface of the wafer, grinding the backside to a uniform thickness, depositing a metal layer on the backside, and using an infrared camera to detect scribe lines through the metal layer, allowing for accurate alignment and cutting along the detected lines to separate individual chips from the backside.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the backside of the wafer is sealed by molding materials or covered with non-transparent materials, then the wafer is protected and structurally intact, but sawing the wafer from its backside along the scribe line becomes challenging due to inability to detect alignment marks
Solution Approach 1:
An infrared-transparent window is introduced as an intermediary layer that allows infrared detection of scribe lines while maintaining the protective sealing function. This window is formed by removing molding material at specific locations to create openings that permit infrared transmission, thus mediating between the need for protection and the need for detection.
Solution Approach 2:
The detection method is replaced from optical/visual inspection to infrared detection. By using infrared imaging technology, the system can detect scribe lines through the infrared-transparent window without requiring direct visual access, thus substituting the detection mechanism while maintaining protection.
2Manufacturing precision
If the wafer is ground at its backside to expose the groove for dicing, then dicing alignment is improved, but the wafer thickness must be precisely controlled and the process becomes more complex
Solution Approach 1:
The infrared-transparent window is formed in advance before the dicing process. By pre-preparing the detection pathway through the window, the actual dicing operation can proceed with high alignment precision without requiring additional wafer thinning or complex real-time adjustment mechanisms.
Solution Approach 2:
The wafer backside is segmented into different regions: areas with molding material for protection and areas with infrared-transparent windows for detection. This segmentation allows simultaneous achievement of protection and detection capabilities without requiring complete wafer thinning.
3Ease of manufacture
If the groove depth is controlled to expose the groove at the backside, then dicing can be performed, but the wafer must be thinned to a certain thickness which increases process complexity
Solution Approach 1:
The infrared-transparent window serves as an intermediary that enables detection without requiring the groove to be exposed. The window provides a direct detection pathway through the molding material, eliminating the need for precise groove depth control and wafer thinning.
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 enables precise and efficient wafer dicing from the backside, even when the backside is covered, by ensuring accurate alignment and minimizing the risk of wafer damage or misalignment, thus facilitating the separation of individual chips with high precision.
Implementation Method 1
depositing a metal layer on the backside, and using an infrared camera to detect scribe lines through the metal layer
Data Source
AI summary
A packaging method with backside wafer dicing includes the steps of forming a support structure at the front surface of the wafer then depositing a metal layer on a center area of the backside of the wafer after grinding the wafer backside to reduce the wafer thickness; detecting from the backside of the wafer sections of scribe lines formed in the front surface in the region between the edge of the metal layer and the edge of the wafer and cutting the wafer and the metal layer from the wafer backside along a straight line formed by extending a scribe line section detected from the wafer backside.