Wafer Back-Grinding Tape Contraction to Prevent Peeling Defects
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Solution Overview
Problem
During the grinding of semiconductor wafers, the protrusion of protective tapes beyond the wafer's edge causes defects when trying to peel them off, especially when using dicing tapes with die attach films, as the tapes stick to the dicing tape or are forcibly peeled off, leading to potential damage.
Innovation Solution
A wafer processing method and grinding apparatus that involves attaching a protective tape with a diameter matching the wafer, grinding the wafer to reduce its thickness, and using a heating unit to contract and remove the protruding tape portion, preventing it from sticking to the dicing tape during peeling.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the protective tape diameter is made larger than the wafer diameter to ensure complete coverage, then the protective tape can fully cover the wafer surface, but the protective tape protrudes from the wafer edge causing sticking to dicing tape and peeling defects
Solution Approach 1:
The patent changes the physical state of the protective tape by heating it above its glass transition temperature, causing thermal contraction that reduces the tape diameter. This parameter change (temperature-induced dimensional change) allows the tape to shrink from a protruding state to a retracted state, eliminating the sticking problem while maintaining coverage during grinding
Solution Approach 2:
The protective tape is attached with a diameter larger than the wafer before grinding to ensure complete coverage and prevent wafer damage during the grinding process. This preliminary oversized attachment ensures reliability during the critical grinding operation, and the tape is subsequently contracted after grinding is complete
2Object-affected harmful factors
If the protective tape diameter is reduced to match the wafer diameter exactly to prevent protrusion, then the tape edge aligns with the wafer edge, but the tape may not fully cover the wafer surface especially at the periphery
Solution Approach 1:
The patent utilizes thermal parameter changes to dynamically adjust the tape diameter. Initially, the tape is attached at a larger diameter for complete coverage, then heated to contract to the appropriate size, combining the benefits of both oversized and precisely-sized attachment
3Manufacturing precision
If the wafer is ground to reduce thickness below half the original thickness, then the wafer achieves the required thin specification, but the protective tape protrudes more significantly from the reduced diameter wafer
Solution Approach 1:
The patent applies thermal parameter changes (heating above glass transition temperature) to cause the protective tape to contract and shrink. This compensates for the increased protrusion that occurs when the wafer is ground down to thin specifications, as the heated tape shrinks to reduce its diameter and eliminate the protruding portion
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 effectively removes the protruding protective tape portion, ensuring smooth peeling without defects, as the tape does not stick to the dicing tape or die attach film, thus preventing damage and ensuring proper wafer handling.
Implementation Method 1
a heating unit that heats and contracts a protruding portion where the protective tape protrudes from the wafer
Data Source
AI summary
A wafer processing method for processing a wafer having a chamfered portion formed at a periphery thereof includes a tape attaching step of attaching a protective tape to a front surface of the wafer and making a diameter of the protective tape coincide with a diameter of the wafer; a grinding step of grinding a back surface of the wafer held by a holding table with use of grinding stones so as to thin the wafer to a thickness thinner than half of an original thickness, to reduce the diameter of the wafer, and to form a protruding portion where the protective tape protrudes from the wafer; and a contracting step of heating and contracting the protruding portion of the protective tape after the grinding step is carried out.