Wafer Processing Method for Two-Layer Structure
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Solution Overview
Problem
During the grinding of wafers with a two-layer structure, sharp chamfered parts can form, leading to chipping and cracks that damage device regions, and removing these chamfers before grinding results in loss of crystal orientation notches, hindering subsequent treatments.
Innovation Solution
A wafer processing method involving stepped part formation, laser beam application to create modified layers, and protective tape use to prevent knife edge formation and preserve crystal orientation notches, allowing for safe grinding and accurate device separation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If chamfered parts are removed by cutting before grinding, then chipping and cracks are prevented, but crystal orientation notches are lost
Solution Approach 1:
The chamfered parts are removed by cutting before the grinding process to prevent knife edge formation, chipping, and cracks. This preliminary removal of potentially harmful structures ensures the reliability of the wafer during subsequent thinning operations.
Solution Approach 2:
A adhesive layer is introduced as an intermediary between the first wafer and second wafer. This adhesive layer acts as a mediator that allows the chamfered parts to be removed while preserving the crystal orientation information through the notches formed in the adhesive layer, which can be used to identify crystal orientation in subsequent steps.
2Manufacturing precision
If back surfaces are ground to thin the wafers, then wafer thickness is reduced to specification, but knife edges form at periphery causing chipping
Solution Approach 1:
The chamfered parts at the peripheral ends of the wafers are removed by cutting before the grinding process begins. This preliminary removal eliminates the formation of sharp knife edges that would otherwise occur during grinding, preventing chipping and cracks while allowing the grinding process to achieve the required wafer thickness with 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
Prevents chipping and damage to device regions while maintaining crystal orientation information, enabling effective processing and division of wafers into individual device chips without reducing the wafer's outside diameter.
Implementation Method 1
applying a laser beam of such a wavelength as to be transmitted through the first wafer while positioning a focal point of the laser beam inside a base of the stepped part formed in the peripheral surplus region of the first wafer to form an annular modified layer
Implementation Method 2
grinding an exposed surface of the second wafer to make the second wafer have a predetermined thickness
Data Source
AI summary
A wafer processing method for processing a wafer of a two-layer structure having a second wafer laminated on a front surface of a first wafer includes a stepped part forming step of cutting from the second wafer side to a peripheral surplus region of the first wafer to a depth corresponding to a finished thickness of the first wafer, thereby removing a chamfered part formed at a peripheral end of the second wafer and forming an annular stepped part in the peripheral surplus region of the first wafer, and a second wafer griding step of, after the stepped part forming step is carried out, grinding an exposed surface of the second wafer to make the second wafer to have a predetermined thickness.