Internal Laser Focusing for Semiconductor Wafer Singulation
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Solution Overview
Problem
Conventional laser singulation processes for semiconductor wafers result in surface contamination due to debris redeposition, which complicates the production process and reduces yield, as they focus the laser beam on the surface exceeding the material ablation threshold.
Innovation Solution
A laser processing method and apparatus that focuses the laser beam internally within the semiconductor wafer to create a crack propagating to the surface, minimizing surface debris and allowing precise separation without external contamination, using a laser-emitting device and a positioning system to control the relative motion and energy density of the laser beam.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If the laser beam is focused on the surface of the semiconductor wafer with irradiance at or above the material ablation threshold, then laser singulation can be achieved, but debris is removed and redeposited onto the surface causing contamination
Solution Approach 1:
Instead of focusing the laser beam on the surface of the semiconductor wafer as in conventional processes, this invention inverts the approach by focusing the laser beam at a point inside the semiconductor wafer below the surface. The laser energy creates internal damage that propagates cracks to the surface, achieving singulation without surface debris contamination.
Solution Approach 2:
The invention transitions from two-dimensional surface processing to three-dimensional volumetric processing by focusing the laser beam at a specific depth inside the wafer. This dimensional shift allows crack propagation from the internal focal point to the surface, eliminating the harmful surface debris generation inherent in surface-focused processing.
2Object-affected harmful factors
If surface coating and washing are performed before and after laser processing to avoid debris contamination, then surface contamination is reduced, but the process complexity and cost increase
Solution Approach 1:
The invention performs preliminary action by focusing the laser beam inside the wafer before surface processing occurs, preventing debris generation at the source. This proactive approach eliminates the need for subsequent surface coating and washing steps, simplifying the overall process.
Solution Approach 2:
The invention converts the potentially harmful laser-material interaction that normally creates surface debris into a beneficial internal crack propagation mechanism. By focusing energy inside the wafer, the harmful surface ablation is transformed into useful internal damage that drives clean crack formation and propagation to the surface.
3Object-affected harmful factors
If the laser beam is focused internally within the workpiece to form internal damage and propagate cracks, then surface contamination is minimized, but the laser processing complexity increases
Solution Approach 1:
The invention changes critical processing parameters by focusing the laser beam at a specific depth inside the workpiece rather than on the surface, and by controlling the irradiance to achieve internal damage formation. These parameter changes enable crack propagation from the internal focal point while minimizing surface contamination.
Solution Approach 2:
The invention replaces conventional mechanical surface processing methods with laser-induced internal crack propagation. Instead of mechanically removing or coating surfaces, the laser energy directly creates and propagates cracks from within the material, eliminating the need for mechanical intervention and reducing overall process complexity.
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 effectively reduces surface contamination and allows for precise singulation of semiconductor wafers, improving production yield and reducing post-processing complexities by forming internal cracks that propagate to the surface, serving as a reference for dicing without generating significant debris.
Implementation Method 1
focusing the laser beam within the workpiece until an internal damage forms within the workpiece and a crack propagates from the internal damage to at least one surface of the workpiece
Implementation Method 2
a crack propagates from the internal damage to at least one surface of the workpiece to form a surface crack on the workpiece
Data Source
AI summary
A laser processing method is disclosed, comprising the steps of: directing a laser beam to a workpiece; and effecting a relative motion between the laser beam and the workpiece. In particular, the step of directing the laser beam to the workpiece comprises focusing the laser beam within the workpiece until an internal damage forms within the workpiece and a crack propagates from the internal damage to at least one surface of the workpiece to form a surface crack on the workpiece. Further, the step of effecting the relative motion between the laser beam and the workpiece is such that the surface crack on the workpiece propagates along a line of separation on the workpiece. A laser processing apparatus is also disclosed.