Circular Wafer Grinding with Two-Step Damaged-Layer Removal
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Existing grinding methods for circular plate-shaped workpieces, such as wafers, result in reduced rigidity and formation of damaged layers with scratches and distortions, limiting the usable area for products and requiring excessive grinding time.
Innovation Solution
A two-step grinding process using first and second grinding wheels with different abrasive grain sizes, where the second wheel grinds the thick plate portion at a distance from its inner edge, ensuring even wear and minimizing the damaged layer, thus preserving a larger effective area for products without prolonged processing time.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If a grinding wheel with large abrasive grains is used to coarsely ground the wafer, then grinding time is reduced, but a damaged layer with scratches and distortions is formed on the ground surface
Solution Approach 1:
The grinding process is divided into two distinct stages: coarse grinding using a first grinding wheel with large abrasive grains to remove material efficiently, and fine grinding using a second grinding wheel with small abrasive grains to eliminate the damaged layer and achieve high surface quality. This segmentation allows each stage to optimize for its specific function without compromise
Solution Approach 2:
The patent implements continuous grinding action by maintaining contact between the grinding wheel and wafer throughout both coarse and fine grinding stages. The wafer is fed continuously through the grinding zone, ensuring uninterrupted material removal and consistent surface treatment across the entire wafer surface
2Manufacturing precision
If only the central area of the wafer is ground to avoid contact with the thick plate portion, then the damaged layer is removed from the thin plate portion, but the effective area for products is reduced
Solution Approach 1:
The patent applies different grinding characteristics to different regions of the wafer through the annular arrangement of grindstones. The grindstones are positioned to contact primarily the thin plate portion while the spacing and arrangement ensure the thick plate portion remains substantially unground, creating localized quality differences that maximize usable area
3Manufacturing precision
If the grinding wheel contacts the thick plate portion during fine grinding, then the damaged layer is removed from the outer edge area, but the thick plate portion is chipped
Solution Approach 1:
The annular arrangement of grindstones with specific spacing creates a grinding zone that selectively treats the thin plate portion while preserving the thick plate portion. The grindstones contact the wafer in a pattern that removes damaged layers from the thin region without applying sufficient force or duration to cause chipping in the thicker supporting region
Solution Approach 2:
The patent applies partial grinding action by using an annular pattern that covers only the necessary areas. The grindstones are spaced to provide coverage over the thin plate portion and boundary areas where damaged layers exist, while intentionally leaving the central thick plate portion substantially unground to maintain its structural integrity
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
The method effectively forms a thin plate portion with no damaged layer, maximizing the usable area while reducing grinding time compared to conventional methods, ensuring high mechanical strength and efficient production.
Implementation Method 1
a grinding wheel to which grindstones including abrasive grains are fixed and the chuck table are mutually rotated. Then, the grindstones are pressed against a reverse side of the wafer while liquid such as pure water is supplied, so that the wafer is ground and thinned
Data Source
AI summary
There is provided a grinding method that is applied when a workpiece having a first surface and a second surface is to be ground from the second surface. The grinding method includes a first grinding step of causing first grindstones to come into contact with the workpiece to grind the workpiece and thereby form on the workpiece a circular plate-shaped first thin plate portion and an annular first thick plate portion surrounding the first thin plate portion, and a second grinding step of causing second grindstones to come into contact with the first thick plate portion and the first thin plate portion to grind the workpiece and thereby form on the workpiece a thin circular plate-shaped second thin plate portion that has a larger diameter than the first thin plate portion and an annular second thick plate portion surrounding the second thin plate portion.