Wafer Laser Processing Ring Reinforcement
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Solution Overview
Problem
The existing methods for processing wafers with a ring-shaped reinforcing portion result in the formation of modified layers or debris at the outer circumference, which can damage the wafer and limit the setting of the device region, leading to poor productivity.
Innovation Solution
A wafer processing method involving a modified layer forming step using a laser beam to create a ring-shaped modified layer that does not reach the finished thickness, a protective member disposing step, a reinforcing portion forming step to create a cleavage plane, and an undersurface processing step to form a ring-shaped reinforcing portion, allowing for the removal of the modified layer and debris along this plane, thereby enabling the wafer to be divided without damage and improving productivity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the annular reinforcing portion is formed on the undersurface corresponding to the peripheral surplus region by grinding the undersurface corresponding to the device region, then the wafer is supported stably and handled excellently during processing, but the reinforcing portion needs to be removed by a cutting blade which may damage devices located in the vicinity of the reinforcing portion
Solution Approach 1:
The patent replaces the mechanical cutting blade removal method with laser processing to remove the reinforcing portion. The laser beam processes the reinforcing portion without physical contact, eliminating the risk of mechanical damage to nearby devices while maintaining stable wafer handling during processing.
Solution Approach 2:
The patent introduces a cleavage plane as an intermediary structure between the reinforcing portion and the final wafer surface. This cleavage plane allows the reinforcing portion to be removed cleanly along a predetermined path, preventing direct contact between removal tools and the wafer surface, thus avoiding device damage.
2Reliability
If the outer edge of the device region is set so as to be separated sufficiently inward from the region in which the reinforcing portion is formed, then device damage is avoided, but a region in which the device region is set is limited, resulting in poor productivity
Solution Approach 1:
By using laser processing instead of mechanical cutting for removing the reinforcing portion, the patent eliminates the need for large safety margins between the device region and reinforcing portion. The laser's precision and non-contact nature allow the device region to be positioned closer to the wafer edge, maximizing usable area and improving productivity.
3Productivity
If the annular reinforcing portion formed at the outer circumference of the wafer is removed by laser processing, then a modified layer or debris remains at the outer circumference of the wafer, but the wafer is damaged from a position at which the modified layer or the debris remains
Solution Approach 1:
The patent performs preliminary formation of a cleavage plane before removing the reinforcing portion. This cleavage plane serves as a pre-established separation path that guides the subsequent laser processing, ensuring that any modified layer or debris is generated only along the cleavage plane and not on the functional wafer surface, thus preventing wafer damage.
Solution Approach 2:
The cleavage plane acts as an intermediary layer that confines laser-induced modifications and debris generation to a specific removal path. By processing along this pre-formed cleavage plane, the patent ensures that harmful modified layers and debris are isolated to the area being removed, protecting the rest of the wafer from damage.
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 allows for the wafer to be divided along the cleavage plane, preventing modified layer and debris from remaining on the wafer, thus avoiding damage and enabling the device region to be set closer to the edge of the reinforcing portion, thereby enhancing productivity.
Implementation Method 1
forms, in a ring shape, a modified layer not reaching a finished thickness of the wafer by irradiating the wafer with a laser beam of a wavelength transmissible through the wafer from an undersurface of the wafer
Implementation Method 2
thins a region corresponding to a device region of the wafer to the finished thickness, and forms a ring-shaped reinforcing portion in a region corresponding to the peripheral surplus region of the wafer by holding the protective member side by a chuck table and grinding the undersurface of the wafer
Data Source
AI summary
A wafer processing method includes a modified layer forming step, a protective member disposing step, a reinforcing portion forming step, and an undersurface processing step. The modified layer forming step forms, in a ring shape, a modified layer not reaching a finished thickness of a wafer by irradiating the wafer with a laser beam such that a condensing point of the laser beam is positioned in an inner part of the wafer, the inner part corresponding to a peripheral surplus region. The reinforcing portion forming step makes a cleavage plane reach the top surface from the modified layer formed in a ring shape, removes the modified layer, thins a region corresponding to a device region of the wafer to the finished thickness, and forms a ring-shaped reinforcing portion in a region corresponding to the peripheral surplus region of the wafer by grinding the undersurface of the wafer.