Wafer Grinding Method for Orientation Flat Thickness Uniformity
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Solution Overview
Problem
The grinding of wafers with an orientation flat often results in variations in thickness due to reduced contact area and load on abrasive members near the orientation flat, leading to dimensional errors and processing challenges in subsequent steps.
Innovation Solution
A wafer grinding method involving a chuck table with suction holding and frame portions featuring cutout portions corresponding to the orientation flat, allowing for modified holding surface grinding to reduce local grinding near the orientation flat, thereby minimizing thickness variations.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If the wafer is ground using a conventional grinding apparatus, then the wafer thickness is reduced, but thickness variations occur near the orientation flat due to reduced contact area and load on abrasive members
Solution Approach 1:
The chuck table is designed with a recessed portion at the position corresponding to the orientation flat, creating a localized structural feature. This recessed portion increases the contact area between the chuck table and the wafer near the orientation flat, thereby distributing the grinding load more evenly and preventing excessive material removal in that specific region, which resolves the thickness variation problem.
Solution Approach 2:
The chuck table is pre-formed with a recessed portion at the orientation flat position before the grinding process begins. This preliminary structural preparation ensures that when the wafer is placed on the chuck table, the contact area and load distribution are already optimized, preventing the formation of thickness variations during the subsequent grinding operation.
2Productivity
If the contact area near the orientation flat is reduced, then grinding proceeds more easily in that area, but this causes thickness variations and dimensional errors in the final product
Solution Approach 1:
The recessed portion in the chuck table creates a localized structural feature that specifically addresses the orientation flat area. By increasing the contact area at this specific location, the grinding load is redistributed, preventing the excessive material removal that would otherwise occur due to the naturally reduced contact area, thus maintaining both efficiency and precision.
Solution Approach 2:
The recessed portion is designed to counteract the harmful effect of reduced contact area near the orientation flat. By pre-forming this recessed structure, the system anticipates and compensates for the uneven load distribution that would occur during grinding, applying a counterbalancing geometric feature that prevents thickness variations before they can develop during the grinding 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
The method effectively reduces thickness variations in wafers by ensuring consistent contact and load distribution, improving the precision and accuracy of wafer thinning and subsequent device chip processing.
Implementation Method 1
a suction holding portion for holding the wafer under suction
Implementation Method 2
a grinding wheel having a plurality of abrasive members for grinding the wafer
Data Source
AI summary
There is provided a wafer grinding method of grinding a wafer having an orientation flat for indicating a crystal orientation in the condition where the wafer is held on a holding surface of a chuck table. The chuck table includes a suction holding portion for holding the wafer under suction and a frame portion surrounding the suction holding portion. The suction holding portion has a first cutout portion corresponding to the orientation flat, and the frame portion has a second cutout portion formed along the first cutout portion. The wafer grinding method includes a holding surface grinding step of grinding the holding surface by using abrasive members of a grinding wheel, and a wafer grinding step of grinding the wafer by using the abrasive members in the condition where the wafer is held on the holding surface ground by the abrasive members.