Bump-Included Wafer Thinning via Carrier Adhesive Segmentation
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Solution Overview
Problem
The handling of semiconductor device wafers with reduced thickness is challenging due to chipping and reduced rigidity, and the use of adhesives to attach these wafers to carrier wafers can result in adhesive deposition in minute pits, leading to device failure.
Innovation Solution
A processing method involving a carrier wafer with a recess for the device area and an annular projection for the peripheral marginal area, where the adhesive is applied only to the annular groove, preventing adhesive deposition on devices and bumps, and ensuring the peripheral marginal area is supported during thickness reduction.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Length of moving object
If the back side of the wafer is ground to reduce the thickness to 50 μm or less, then the thickness is reduced as required, but the handling becomes more difficult and chipping occurs on the outer circumference
Solution Approach 1:
The wafer processing is segmented into two distinct phases: first attaching the wafer to a carrier wafer for support, then performing thickness reduction, and finally separating the processed wafer from the carrier. This segmentation allows the wafer to gain structural support during the critical thinning operation without compromising the final product integrity.
Solution Approach 2:
A carrier wafer is introduced as an intermediary object to support the device wafer during thickness reduction. The carrier wafer provides the necessary mechanical strength and stability during grinding, preventing chipping and handling difficulties, while being removable after processing to leave the final product unaffected.
2Strength
If adhesive is applied to attach the device wafer to the carrier wafer, then the wafer can be held securely, but adhesive enters the minute pits produced due to bumps and cannot be completely removed
Solution Approach 1:
The carrier wafer surface is designed with non-uniform local qualities: a flat region for attaching the device wafer and a recessed region that accommodates the bumps. Adhesive is applied only to the flat region, creating a localized bonding area that excludes adhesive from entering the bump pits, thus maintaining both attachment strength and manufacturing precision.
Solution Approach 2:
The carrier wafer is pre-formed with a recessed region before the attachment process. This preliminary structural preparation ensures that when adhesive is applied, it naturally settles only in the flat region, preventing adhesive intrusion into the bump areas before the attachment even occurs.
3Ease of operation
If the device wafer is held on a holding table for grinding, then the back side can be accessed, but the peripheral marginal area floats from the holding table causing damage
Solution Approach 1:
The device wafer is merged with the carrier wafer through adhesive bonding, creating a combined structure. This merging allows the peripheral marginal area to be supported by the carrier wafer during grinding operations, preventing floating and damage while maintaining full accessibility to the back side for processing.
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 safe reduction of wafer thickness without damage and prevents device failure from residual adhesive, ensuring accurate handling and functionality of the semiconductor device wafers.
Implementation Method 1
attaching and fixing the front side of the device wafer through the adhesive to the front side of the carrier wafer
Implementation Method 2
grinding or polishing the back side of the device wafer to reduce the thickness of the device wafer
Implementation Method 3
grinding or polishing the back side of the device wafer to reduce the thickness of the device wafer
Data Source
AI summary
A processing method for a bump-included device wafer which includes an adhesive providing step of providing an adhesive in an annular groove of a carrier wafer so that the adhesive projects from the upper surface of an annular projection of the carrier wafer; a wafer attaching step of attaching and fixing the front side of the device wafer through the adhesive to the front side of the carrier wafer so as to accommodate bumps in a recess of the carrier wafer after performing the adhesive providing step; and a thickness reducing step of grinding or polishing the back side of the device wafer to reduce the thickness of the device wafer to a predetermined thickness after performing the wafer attaching step.