Wafer Edge Separation Using Laser Ring Scribing Before Grinding
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Solution Overview
Problem
Existing wafer processing methods face issues such as debris smear during edge trimming and damage to grinding stones due to break-off of the outer peripheral surplus region during grinding.
Innovation Solution
A wafer processing method that involves bonding a first wafer with a device region and an outer peripheral surplus region to a second wafer, segmenting the first wafer using a laser beam to create an annular modified region, and then using an expandable tape to break off the outer peripheral annular portion, thereby preventing damage to grinding stones.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-affected harmful factors
If the outer peripheral surplus region is removed by edge trimming before grinding, then edge chipping is prevented, but devices are smeared with debris that cannot be fully removed by rinsing
Solution Approach 1:
The outer peripheral annular portion is extracted and removed from the wafer before the grinding process. This is achieved by forming a bonded wafer, creating an annular modified region through laser irradiation, and then removing the outer peripheral portion. By extracting this surplus region beforehand, the source of debris that would contaminate devices during grinding is eliminated, preventing both edge chipping and debris smear problems
Solution Approach 2:
The removal of the outer peripheral surplus region is performed as a preliminary action before the grinding step. The process sequence is specifically designed to: (1) form a bonded wafer, (2) create an annular modified region by laser irradiation, (3) remove the outer peripheral annular portion, and (4) then perform grinding on the remaining central region. This preliminary removal prevents the surplus region from generating debris during subsequent grinding operations
2Device complexity
If the outer peripheral surplus region is left intact during grinding, then no additional processing steps are needed, but the surplus region breaks off and damages grinding stones
Solution Approach 1:
The outer peripheral annular portion is extracted and removed from the wafer before grinding. This extraction eliminates the harmful factor of surplus region break-off that would damage grinding stones. The removed portion is separated cleanly through laser-induced modification and subsequent removal processes, preventing fragments from scratching or damaging the grinding stones during the thinning operation
Solution Approach 2:
The process applies preliminary anti-action by removing the outer peripheral surplus region before grinding to prevent the harmful effect of break-off during grinding. The annular modified region is created through laser irradiation, and the outer peripheral portion is removed in advance, thereby preventing the potential damage to grinding stones before the grinding operation begins
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 effectively reduces the deleterious effects of break-off during grinding, preventing damage to grinding stones and reducing the frequency of cleaning, while ensuring precise thinning of the wafer.
Implementation Method 1
a segmenting step of irradiating a laser beam of a wavelength that has transmissivity for the first wafer along a position on a side inner by a predetermined distance from the outer peripheral edge of the first wafer and forming an annular modified region
Implementation Method 2
an expand tape bonding step of, before or after performing the segmenting step, bonding an expand tape which has expandability, to the other surface of the first wafer, an outer peripheral annular portion break-off step of, after performing the bonded wafer forming step, the segmenting step, and the expand tape bonding step, expanding the expand tape, thereby splitting the first wafer into the outer peripheral annular portion and the central region from the annular modified region as a starting point
Data Source
AI summary
A wafer processing method includes the steps of forming a bonded wafer by bonding one surface of a first wafer which is chambered at an outer peripheral edge and includes a device region and an outer peripheral surplus region, to a second wafer, irradiating a laser beam along the outer peripheral edge of the first wafer and forming an annular modified region, thereby segmenting the first wafer into an outer peripheral annular portion and a central region, bonding an expand tape to the other surface of the first wafer, expanding the expand tape, thereby splitting the first wafer into the outer peripheral annular portion and the central region from the annular modified region as a starting point and breaking off the outer peripheral annular portion from the bonded wafer, and grinding the first wafer from the other surface to a finish thickness.