Wafer Back Grinding Using Cut Resin Film
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Solution Overview
Problem
Existing methods for grinding the back-side surface of semiconductor wafers result in uneven thickness due to thickness unevenness in protective members, making it difficult to achieve high precision in wafer thinning, especially at small thicknesses like 30 μm.
Innovation Solution
A method involving a resin film covering the face-side surface of the wafer, with the surface being cut to be parallel to the wafer's face-side surface, and then using this flat resin film as a reference for precise back-side grinding to ensure uniform thickness without direct contact between the wafer's face-side surface and the grinding apparatus.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-affected harmful factors
If a protective tape is adhered to the face-side surface of the wafer, then the face-side surface is protected from direct contact with the chuck table, but thickness unevenness of the protective tape is transferred to the wafer, resulting in non-uniform wafer thickness
Solution Approach 1:
The patent changes the physical state of the protective material from a pre-formed tape with fixed thickness to a liquid resin that can be coated and cured. This allows the protective layer to be applied in a controlled manner and then solidified to maintain uniform thickness during the grinding process, eliminating the thickness variation problem inherent in pre-formed protective tapes.
2Length of moving object
If the wafer is thinned to a very small thickness of 50 μm or 30 μm, then the wafer thinning requirement is met, but the thickness unevenness of the protective tape becomes as large as 10% of the wafer thickness, making it difficult to achieve high precision
Solution Approach 1:
The patent applies the protective resin to the face-side surface before the back-side grinding process begins. The resin is coated, cured, and then ground together with the wafer back-side in an integrated process. This preliminary application ensures that the protective layer is present from the start and maintains uniform thickness throughout the thinning process, rather than being a separate post-application component.
3Object-affected harmful factors
If a protective film is formed by spin coating or printing process, then the face-side surface is protected, but the protective film still has unevenness of thickness and is not superior to protective tape
Solution Approach 1:
The patent merges the protective layer application with the wafer thinning process by using the same grinding apparatus for both operations. The protective resin is applied to the face-side surface, and then both the protective layer and the wafer back-side are ground together in one integrated process. This eliminates the need for separate protective film application and grinding operations, ensuring thickness uniformity throughout the entire process.
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 effectively suppresses thickness unevenness, allowing for high-precision uniformity of the wafer thickness, even at extremely small thicknesses, by using a resin film as a protective and reference surface during the back grinding process.
Implementation Method 1
a protective film formed by applying a fluid resist to the back-side surface of a wafer by a spin coating process
Implementation Method 2
the wafer is suction held onto a vacuum chuck type chuck table
Data Source
AI summary
A back grinding method for a wafer includes covering a face-side surface of the wafer with a resin film, and cutting the surface of the resin film to form a flat surface parallel to the face-side surface of the wafer. The wafer is held with the surface of the resin film in contact with a suction surface of a chuck table in a grinding apparatus, and the exposed back-side surface of the wafer is ground. Unevenness in thickness of the resin film is suppressed, whereby the thickness of the wafer subjected to back grinding is made to be uniform.