Wafer Chamfer Removal via Support Substrate and Cutting Blade
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Solution Overview
Problem
Existing wafer processing methods face challenges in reducing wafer thickness to a predetermined value without damaging the wafer, as they often result in unstable handling, quality reduction due to cut dust, increased costs, and frequent cutting blade wear, especially when dealing with chamfered portions.
Innovation Solution
A method involving a stacked wafer formation with a support substrate, followed by a chamfered portion removal using a cutting blade positioned with its rotation axis parallel to the wafer's stacking direction, cutting from the outer circumference toward the center, and subsequent grinding to achieve the desired thickness.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If the back side of the wafer is ground to reduce the thickness to about tens of micrometers, then the desired thickness is achieved, but the wafer becomes flexible and unstable due to low rigidity of the protective tape
Solution Approach 1:
A support substrate is attached to the front side of the wafer before the grinding process begins. This preliminary action provides mechanical support to the wafer throughout the thickness reduction process, preventing flexibility and instability that would otherwise occur when the wafer is ground to tens of micrometers thickness.
Solution Approach 2:
The support substrate acts as an intermediary element between the wafer and the handling system. It transfers and distributes mechanical loads, providing the necessary rigidity to handle the thin wafer without direct contact points that could cause deformation or instability during grinding.
2Manufacturing precision
If a cut groove is formed on the front side of the wafer along the boundary between the flat portion and the chamfered portion, then the knife edge problem is solved, but cut dust sticks to the front side of each device causing quality reduction
Solution Approach 1:
The chamfered portion is completely removed from the wafer periphery through cutting, extracting the source of the knife edge problem. By removing rather than grooving the chamfered portion, the solution eliminates the boundary between flat and chamfered surfaces where cut dust would accumulate, thereby preventing contamination of the device front side.
3Manufacturing precision
If the chamfered portion is removed from the back side of the wafer toward the front side, then the knife edge problem is solved, but much time is required to process the wafer
Solution Approach 1:
Instead of removing the chamfered portion from the back side toward the front side, the invention inverts the approach by cutting from the front side toward the back side. This reversal allows the cutting blade to access and remove the chamfered portion more efficiently, significantly reducing processing time while still eliminating the knife edge problem.
4Manufacturing precision
If a cutting blade having a thickness larger than the width of the chamfered portion is used, then the chamfered portion can be removed, but the cost for the cutting blade is increased and partial wear occurs frequently
Solution Approach 1:
The cutting blade is designed with localized cutting edges positioned at specific locations to match the width of the chamfered portion. Rather than using a uniformly thick blade that is overly robust, the blade has cutting capability concentrated where needed, allowing removal of the chamfered portion with a thinner, more cost-effective blade that experiences less wear.
5Ease of manufacture
If a cutting blade having a thickness smaller than the width of the chamfered portion is used, then the blade cost is reduced, but circular cutting must be performed plural times causing reduction in productivity
Solution Approach 1:
The cutting blade is positioned with its rotation axis parallel to the stacking direction of the stacked wafer, creating a three-dimensional cutting configuration. This dimensional arrangement allows a thinner blade to effectively remove the entire chamfered portion in a single circular cutting pass by utilizing the vertical depth of cut, eliminating the need for multiple passes and maintaining high productivity.
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 efficient reduction of wafer thickness without damage, reduces costs, and minimizes the need for frequent cutting blade replacements, while preventing quality issues and handling instability.
Implementation Method 1
making the cutting blade cut into the wafer from the outer circumference toward the center thereof to thereby partially remove the chamfered portion
Implementation Method 2
a grinding unit including a rotatable grinding wheel, which has a plurality of abrasive members for grinding the wafer held on the chuck table
Data Source
AI summary
A wafer processing method for reducing the thickness of a wafer to a predetermined thickness, the wafer having a chamfered portion along the outer circumference thereof. The wafer processing method includes a stacked wafer forming step of attaching a support substrate to the front side of the wafer to thereby form a stacked wafer, and a chamfered portion removing step of positioning a cutting blade having a rotation axis parallel to the stacking direction of the stacked wafer formed by the stacked wafer forming step so that the outer circumference of the cutting blade faces the chamfered portion of the wafer, and then making the cutting blade cut into the wafer from the outer circumference toward the center thereof to thereby partially remove the chamfered portion in the range corresponding to the predetermined thickness from the front side of the wafer.