Wafer Grinding Chuck Table Holding Surface Correction
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Solution Overview
Problem
The existing wafer grinding methods often result in minute thickness differences in the circumferential direction of ground wafers due to self-grinding of the chuck table, which cannot be effectively adjusted by inclination adjustments alone.
Innovation Solution
A method where the chuck table is made to communicate with a suction source during wafer grinding, involving a holding surface forming step, test grinding, distribution measuring, and holding surface correction processing to ensure a flat and parallel surface, using either atmospheric-pressure plasma etching or small-diameter grindstones for correction.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If self-grinding is used to form the holding surface without suction communication, then the chuck table can be ground efficiently, but deformation occurs causing partial thickness difference in the ground wafer
Solution Approach 1:
The patent applies preliminary action by performing a test grinding step before actual wafer grinding to detect potential thickness variations. The test wafer is ground first to reveal holding surface irregularities, which are then corrected before proceeding to product wafer grinding, preventing deformation-induced thickness differences
Solution Approach 2:
The patent implements feedback by measuring the thickness distribution of the test wafer after grinding and using this information to guide correction processing of the holding surface. The measured thickness data provides feedback on holding surface accuracy, directing subsequent correction actions to achieve uniform wafer thickness
2Manufacturing precision
If inclination adjustment of the chuck table is performed, then radial thickness difference can be prevented, but circumferential thickness difference caused by self-grinding deformation remains
Solution Approach 1:
The patent applies local quality by performing localized correction processing on specific areas of the holding surface rather than uniform adjustment. The correction target is determined based on measured thickness distribution, allowing precise correction of localized deformations in the circumferential direction while maintaining overall holding surface functionality
Solution Approach 2:
The patent changes the approach from mechanical inclination adjustment to holding surface shape correction through localized material removal or addition. This parameter change enables correction of circumferential thickness variations that cannot be addressed by simple inclination adjustment alone
3Reliability
If the chuck table communicates with suction source during self-grinding, then wafer holding is achieved, but the holding surface cannot be properly formed due to deformation
Solution Approach 1:
The patent separates the holding surface formation process from the wafer holding process by performing self-grinding without suction communication first, then establishing suction communication for subsequent test grinding and product grinding. This preliminary action allows proper holding surface formation before applying suction forces that cause deformation
Solution Approach 2:
The patent segments the grinding process into distinct phases: holding surface formation without suction, test grinding with suction to detect variations, and correction processing. This segmentation allows each phase to optimize for its specific function without interference from suction-induced deformation
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 prevents partial thickness differences in the ground wafers, allowing for uniform thickness grinding by ensuring the holding surface is flat and parallel to the wafer grinding grindstones.
Implementation Method 1
a wafer held under suction by a holding surface of the chuck table is ground by a wafer grinding grindstone
Implementation Method 2
partially plasmatized etching gas is jetted from an etching gas jet nozzle to the holding surface to subject the holding surface to correction processing by atmospheric-pressure plasma etching
Data Source
AI summary
In a holding surface correction processing step, a shape of a holding surface is corrected by an etching mechanism in such a manner as to have a surface shape similar to that of an upper surface of a test grinding wafer having been ground in a test grinding step. As a result, at a time of a grinding step, when a holding section of a chuck table communicates with a suction source and a product wafer is held under suction on the holding surface, the holding surface becomes a substantially flat surface, and a radius part of the holding surface becomes parallel to a lower surface of a wafer grinding grindstone. Hence, it is possible to prevent partial thickness differences from being generated in the product wafer having been ground by the wafer grinding grindstone.