Laser Beam Shaping for Wafer Processing With Reduced Leaked Light Damage
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Solution Overview
Problem
Laser processing techniques face challenges in minimizing damage caused by leaked light during the formation of modified regions in wafers, as leaked light can damage devices on the opposite surface, leading to potential device failure.
Innovation Solution
A laser processing apparatus and method that utilizes a spatial light modulator to control the beam shape of the laser light, creating an inclined converging spot in the YZ-plane, allowing for uneven distribution of damage by directing it away from vulnerable regions, and adjusting the beam shape to a non-inclined form when farther from the surface to extend fractures appropriately.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If laser light is used to form modified regions inside the wafer, then processing efficiency is improved, but leaked light may cause damage to devices on the opposite surface
Solution Approach 1:
The patent applies local quality by making the beam shape asymmetric specifically on the first surface side of the wafer. The beam is designed to be concentrated toward the second surface (opposite to the incident surface) while having reduced intensity toward the first surface, creating localized intensity distribution that protects vulnerable devices on the first surface while maintaining effective processing on the second surface.
Solution Approach 2:
The patent implements asymmetry by creating an inclined beam shape in the YZ-plane that is not symmetric with respect to the wafer thickness direction. The beam intensity distribution is deliberately made asymmetric, with the inclination angle designed to direct leaked light away from vulnerable regions on the first surface while maintaining processing effectiveness on the second surface.
2Reliability
If the beam shape is made inclined to direct leaked light away from vulnerable regions, then device protection is improved, but fracture extension control becomes more difficult
Solution Approach 1:
The patent applies dynamics by making the beam shape adjustable rather than fixed. The inclination angle and intensity distribution of the beam can be dynamically modified based on the specific processing requirements and wafer characteristics, allowing optimization of both device protection and fracture control for different scenarios.
Solution Approach 2:
The patent implements parameter changes by modifying the beam shape parameters (inclination angle, intensity distribution) to achieve the desired effect. By carefully controlling these parameters, the patent balances the competing requirements of directing leaked light away from vulnerable regions while maintaining adequate fracture extension control.
3Object-affected harmful factors
If the converging spot is positioned closer to the second surface, then leaked light damage is reduced, but fracture extension from the modified region becomes insufficient
Solution Approach 1:
The patent applies another dimension by introducing the inclination angle as an additional degree of freedom in beam shaping. Instead of only adjusting the position of the converging spot along the Z-axis, the patent tilts the beam in the YZ-plane, creating a two-dimensional control space that independently addresses both damage reduction and fracture extension requirements.
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
Effectively reduces the influence of leaked light damage by strategically directing it to less vulnerable areas, thereby protecting sensitive structures and ensuring precise control over the modified regions and fractures formed during the laser processing.
Implementation Method 1
a spatial light modulator configured to modulate the laser light output from the light source in correspondence with a modulation pattern and output the modulated laser light
Implementation Method 2
a converging lens configured to converge the laser light output from the spatial light modulator toward the object, and form a converging spot of the laser light in the object
Implementation Method 3
forming a modified region inside the wafer by irradiating the wafer with laser light
Data Source
AI summary
Provided is a laser processing apparatus including: a support unit that supports an object; a light source that outputs laser light; a spatial light modulator that modulates the laser light output from the light source in correspondence with a modulation pattern and outputs the modulated laser light; a converging lens that converges the laser light output from the spatial light modulator toward the object, and forms a converging spot of the laser light in the object; a movement unit that relatively moves the converging spot with respect to the object; and a control unit that controls at least the light source, the spatial light modulator, and the movement unit. The modulation pattern is controlled so that a beam shape of the converging spot becomes an inclined shape on at least the first surface side in relation to the center of the converging spot.