Holding Surface Maintenance for Wafer Grinding
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Solution Overview
Problem
The existing grinding apparatuses face challenges in maintaining a uniform holding surface, leading to nonparallel central parts after cleaning, which results in wafers being less likely to have uniform in-plane thickness, requiring wafer consumption for quality determination.
Innovation Solution
A holding surface maintaining method that includes grinding the surface with holding surface grinding stones, measuring initial and interim heights at multiple points, determining surface abnormalities based on differences, and restoring the surface when necessary, without grinding wafers.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-generated harmful factors
If cleaning grindstones are used to remove grinding swarf from the holding surface, then the holding surface is cleaned, but the central part of the holding surface becomes nonparallel with the lower surface of the grinding stones
Solution Approach 1:
The harmful grinding swarf is selectively removed from the holding surface using cleaning grindstones, while the parallelism of the holding surface is preserved through controlled extraction that prevents over-grinding of the central region
Solution Approach 2:
The cleaning process applies partial action by selectively grinding only the areas with swarf adhesion rather than uniformly grinding the entire holding surface, thereby removing harmful factors while maintaining the overall parallelism structure
2Measurement precision
If conventional wafer grinding is used to determine holding surface quality, then the holding surface quality can be assessed, but wafers are consumed
Solution Approach 1:
Instead of using actual wafers to test holding surface quality, the invention creates a virtual model or reference standard of the holding surface geometry, allowing quality assessment through comparison with this copy rather than consuming physical wafer materials
Solution Approach 2:
A measurement system or reference standard acts as an intermediary between the holding surface and the quality assessment process, enabling precise measurement of holding surface parallelism without requiring actual wafer grinding and consumption
3Object-generated harmful factors
If the holding surface becomes nonparallel after cleaning, then cleaning effectiveness is achieved, but wafer thickness uniformity deteriorates
Solution Approach 1:
The holding surface is restored to its correct parallel state before wafer grinding operations begin, ensuring that the foundation for uniform wafer thickness is established in advance, preventing thickness non-uniformity before it occurs
Solution Approach 2:
The holding surface grinding stones are used to self-correct the holding surface geometry by grinding away nonparallel portions and restoring the surface to its proper parallel configuration, enabling the system to maintain itself without external intervention
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 determining holding surface quality without consuming wafers, maintaining the surface in a normal state, and preventing thickness defects in ground wafers.
Implementation Method 1
a grinding apparatus grinds a wafer held on a holding surface of a porous member to a uniform thickness by grinding stones
Implementation Method 2
cleaning grindstones are brought into contact with the holding surface to grind away the grinding swarf
Data Source
AI summary
Whether or not there is an abnormality in a holding surface is determined on the basis of a difference between initial holding surface height data as the height of the holding surface immediately after a holding surface grinding step and interim holding surface height data as the height of the holding surface after a grinding step and a holding surface cleaning step are performed a plurality of times. Hence, a wafer does not need to be ground in order to determine whether or not there is an abnormality in the holding surface. An amount of consumption of wafers can therefore be suppressed.