Wafer Back Surface Grinding Method for Expanded Device Region
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Solution Overview
Problem
Conventional TAIKO grinding methods face challenges in expanding the device region on semiconductor wafers while maintaining processing efficiency, as the finish grinding abrasive's deformation leads to a reduction in the device region due to increased processing time when grinding curved surfaces.
Innovation Solution
A wafer processing method involving a first grinding step to form a circular recess and a second grinding step where a finer abrasive is moved obliquely from the center toward the periphery to grind the inner circumferential wall and bottom surface, allowing for expanded device regions without significantly extending processing time.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If the finish grinding abrasive is moved down at finish grinding speed when passing through the curved surface part, then the curved surface part is ground more effectively, but the processing time becomes very long
Solution Approach 1:
The grinding process is divided into two distinct stages: rough grinding to remove the curved surface part and create a flat surface, and finish grinding to achieve the final precision. This segmentation allows each stage to be optimized independently - rough grinding removes material quickly without speed constraints, while finish grinding operates at high speed only on the already-flattened surface, avoiding the time penalty of high-speed curved surface grinding.
Solution Approach 2:
The rough grinding abrasive performs preliminary action by removing the curved surface part and creating a flat bottom surface before the finish grinding abrasive operates. This preliminary flattening action eliminates the need for the finish grinding abrasive to grind curved surfaces, thereby preventing time loss while maintaining the ability to achieve high precision in the final stage.
2Area of stationary object
If the finish grinding abrasive is brought closer to the outer circumference to expand the device region, then a larger area of the curved surface part needs to be ground, but the deformation attributed to wear is promoted and the device region becomes smaller
Solution Approach 1:
The grinding function is segmented between two abrasives with different roles: the rough grinding abrasive positioned at the outer circumference removes the curved surface part and defines the device region boundary, while the finish grinding abrasive positioned inward achieves final precision without excessive wear deformation. This segmentation allows the outer circumference abrasive to create the expanded device region without suffering from the wear deformation problems that would limit precision.
Solution Approach 2:
Different regions of the wafer back surface are processed by different abrasives with appropriate properties: the outer circumference region (curved surface part) is processed by the rough grinding abrasive designed for aggressive material removal, while the inner region (future device region) is processed by the finish grinding abrasive designed for high precision with minimal deformation. This local quality differentiation resolves the contradiction between expanding device region and maintaining boundary precision.
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 expands the device region on the wafer's back surface while suppressing the extension of processing time by reducing abrasive wear and deformation, resulting in a larger flat region for device fabrication.
Implementation Method 1
a region in a back surface corresponding to the device region is ground by a grinding abrasive to set the thickness of the device region to a predetermined finished thickness
Data Source
AI summary
A wafer processing method includes a first grinding step and a second grinding step. In the first grinding step, first grinding abrasives are moved in a processing feed direction that is a direction orthogonal to a holding surface of a chuck table of grinding apparatus and a wafer is ground to form a first circular recess in the back surface of the wafer. In the second grinding step, second grinding abrasives formed of finer abrasive grains than the first grinding abrasives are moved down in an oblique direction from the center side of the wafer toward the periphery of the wafer and the first circular recess is ground.