Wafer Backside Groove Laser Processing
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Solution Overview
Problem
The existing wafer processing methods face challenges such as reduced productivity, blade deviation, thermal strain, and increased device width due to the need for multiple laser grooves and the application of laser beams from the front side, which can cause damage and reduce die strength.
Innovation Solution
A method involving a protective member on the front side, height recording, and cut groove formation on the back side to position the cutting blade, followed by laser processing along the bottom of the cut groove to divide the wafer without forming laser grooves in the functional layer, thereby improving productivity and reducing thermal strain.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If two laser processed grooves are formed along each division line to divide the functional layer, then the functional layer can be divided, but the productivity is reduced
Solution Approach 1:
The method forms grooves in the substrate before applying the functional layer, rather than forming grooves in the functional layer itself. This preliminary action on the substrate eliminates the need for multiple laser passes through the functional layer, thereby improving productivity while still achieving proper device separation.
2Manufacturing precision
If laser beam is applied from the front side of the wafer to form laser processed grooves, then the functional layer can be divided, but debris scatters and sticks to the front side of the wafer
Solution Approach 1:
Instead of applying the laser beam from the front side of the wafer, the method applies the laser beam from the back side of the substrate. This inversion of the laser application direction prevents debris from scattering onto the front side of the wafer where the functional layer and devices are located, thereby eliminating contamination while still achieving effective groove formation.
3Manufacturing precision
If the spacing between two laser processed grooves is larger than the width of the cutting blade, then the functional layer can be divided, but the width of each division line must be increased
Solution Approach 1:
The grooves are formed in the substrate before the functional layer is applied, allowing for precise groove positioning and spacing. This preliminary groove formation enables the use of narrower division lines since the groove spacing is determined by the substrate processing rather than being constrained by the functional layer thickness and laser processing parameters.
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 eliminates the need for multiple laser grooves, prevents blade deviation, reduces thermal strain, and allows for a higher device density by applying the laser beam along the cut groove, enhancing the strength and yield of the divided devices.
Implementation Method 1
applying a laser beam to the wafer from the back side thereof along the bottom of the cut groove
Implementation Method 2
applying a laser beam... to thereby divide the wafer along each division line
Data Source
AI summary
A wafer has a substrate, a functional layer and division lines. The wafer is held on a chuck table with a protective member attached to the front side of the functional layer in contact with the chuck table. The height of the back side of the wafer is detected in a Z direction along each division line while moving the chuck table in an X direction. An X coordinate is recorded for each division line, as well as a corresponding Z coordinate. A cutting blade is positioned on the back side of the wafer and moved in the Z direction according to the recorded X and Z coordinates while moving the chuck table in the X direction to thereby form a cut groove having a depth not reaching the functional layer, with a part of the substrate left between the bottom of the cut groove and the functional layer.