Bonded Wafer Laser Crack Control for Chamfer Removal
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Solution Overview
Problem
Conventional methods for removing chamfered portions on bonded wafers are time-consuming and can damage the other wafer, leading to poor productivity and potential harm to workers.
Innovation Solution
A method involving laser beam branching to create modified layers within the wafer, followed by grinding, which stabilizes crack development to the bonding layer's outer circumference, allowing reliable removal of the chamfered portion without damaging the other wafer.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the chamfered portion is removed by directly positioning a cutting blade or grinding stones at the periphery of the wafer, then the sharp knife edge shape is suppressed, but the processing time becomes considerable and productivity deteriorates
Solution Approach 1:
The patent applies preliminary action by forming modified layers within the wafer before the actual chamfered portion removal. The laser irradiation creates predetermined modified layers at specific positions and depths, which then guide crack propagation during the removal process. This preliminary modification of the wafer structure enables faster and safer removal without requiring time-consuming direct cutting or grinding operations.
Solution Approach 2:
The patent replaces the mechanical system of direct cutting blades or grinding stones with a laser-based system. Instead of mechanically removing the chamfered portion, the invention uses laser irradiation to form modified layers that guide crack propagation. This substitution of mechanical removal with laser-induced crack control significantly reduces processing time while maintaining safety.
2Productivity
If the chamfered portion is removed by conventional methods, then processing time is reduced, but the other wafer may be damaged
Solution Approach 1:
The patent applies local quality by creating modified layers at specific local positions within the wafer rather than uniformly treating the entire wafer. The laser irradiation is focused on forming modified layers at predetermined positions and depths, which then guide crack propagation locally to the bonding layer interface. This localized modification enables precise control of the removal process, preventing damage to the bonded wafer while maintaining high processing speed.
Solution Approach 2:
The patent introduces modified layers as an intermediary structure between the laser irradiation and the final crack propagation. These modified layers act as a mediator that controls and directs the crack path to the bonding layer interface, preventing uncontrolled crack propagation that could damage the bonded wafer. This intermediary structure enables fast processing while protecting the bonded wafer from damage.
3Device complexity
If a single laser beam is used for irradiation, then the device structure is simple, but the precision of modified layer formation is insufficient
Solution Approach 1:
The patent applies segmentation by dividing a single laser beam into multiple separate laser beams. Each laser beam is directed to a specific position and depth within the wafer to form modified layers at predetermined locations. This segmentation of the laser beam enables precise control of modified layer formation at multiple positions simultaneously, achieving high manufacturing precision while maintaining relatively simple device structure.
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 significantly reduces processing time, improves productivity, and ensures safe removal of the chamfered portion without affecting the bonded wafer, addressing the inefficiencies and damage risks of conventional methods.
Implementation Method 1
a modified layer forming step of forming a plurality of modified layers in a ring shape within the first wafer by positioning the condensing points of the branched laser beams in an inner part of the first wafer, the inner part being radially inward of the chamfered portion, and irradiating the coordinates of the undersurface position of the first wafer
Implementation Method 2
irradiating the coordinates of the undersurface position of the first wafer, the coordinates being generated in the coordinate generating step, with the laser beams
Implementation Method 3
a coordinate generating step of generating coordinates of an undersurface position of the first wafer, the undersurface position being to be irradiated with the laser beams, such that an end position of a crack extending from the condensing points to the bonding layer side is located at an outer circumference of the bonding layer
Implementation Method 4
a grinding step of holding the second wafer side by a second chuck table and thinning the first wafer by grinding an undersurface of the first wafer after performing the modified layer forming step
Data Source
AI summary
A method of processing a bonded wafer formed by bonding a first wafer and a second wafer to each other via a bonding layer includes a coordinate generating step of generating coordinates of an undersurface position of the first wafer, the undersurface position being to be irradiated with laser beams, such that an end position of a crack extending from modified layers formed within the first wafer is located at an outer circumference of the bonding layer, and a modified layer forming step of forming a plurality of modified layers in a ring shape by irradiating the coordinates generated in the coordinate generating step with the laser beams of a wavelength transmissible through the first wafer.