Laser Dicing of Optical Devices With Slanted Sidewalls
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Solution Overview
Problem
Conventional methods for dicing optical devices from substrates, such as laser ablation cutting or filamentation, struggle to accurately form angled sidewalls, which are critical for maintaining the quality and performance of optical devices like those used in VR and AR applications, especially when dealing with brittle high bandgap materials like glass and silicon carbide.
Innovation Solution
A method involving a laser machining system that forms a series of trenches around the optical devices with varying depths and radial positions, allowing for the creation of slanted outer surfaces and adjustable draft angles by controlling the number, length, and power of radiation pulses, enabling the formation of smooth, low-roughness surfaces with desired angles.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If conventional laser ablation cutting or filamentation methods are used to dice optical devices from substrates, then the dicing process can be performed, but the ability to form angled sidewalls is poor and device quality deteriorates
Solution Approach 1:
The dicing process is divided into multiple sequential laser passes, each creating trenches at different depths and angles. The first pass creates a initial trench, subsequent passes create additional trenches at progressively greater depths with adjusted angles, collectively forming the desired angled sidewall profile without requiring single-pass high-precision positioning
Solution Approach 2:
The laser applies periodic pulsed energy to the substrate in multiple cycles. Each cycle consists of laser pulses that ablate material to form a trench, followed by pauses for cooling and repositioning. This periodic action allows controlled material removal at different stages to achieve the target angled geometry while managing thermal effects on the brittle optical material
2Manufacturing precision
If multiple laser passes are used to form angled sidewalls, then sidewall angle precision improves, but processing time increases
Solution Approach 1:
The first laser pass creates a preliminary trench structure that establishes the initial geometry and removes a significant portion of material. Subsequent passes then refine this pre-formed structure to achieve the final precise angled sidewall, reducing the total material removal burden in later stages and optimizing overall processing time
Solution Approach 2:
The laser processing parameters are dynamically adjusted between passes: pulse duration, power, frequency, and scanning speed are optimized for each specific pass based on the current trench depth and desired angle. This dynamic parameter adaptation allows each pass to be as efficient as possible, minimizing total processing time while achieving the target geometry
3Manufacturing precision
If laser parameters are optimized for angled sidewall formation, then sidewall quality improves, but chipping defects increase
Solution Approach 1:
Different laser parameters are applied to different regions and depths of the trench formation process. Shallow trenches use parameters optimized for smooth surface formation, while deeper trenches use parameters that prioritize complete material removal. The laser focus position, pulse energy, and scanning speed are locally adapted to each depth zone to balance sidewall smoothness with defect prevention
Solution Approach 2:
Coolant or process gases are introduced as intermediary substances during laser processing to manage heat accumulation and reduce thermal stress on the brittle optical material. This intermediary cooling action allows higher laser powers to be used for efficient material removal while preventing thermal shock that would cause chipping, thus enabling smooth sidewalls without excessive defect generation
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 allows for the precise dicing of optical devices with slanted sidewalls, improving device performance by reducing chipping defects and maintaining die strength, while enabling smoother sidewalls and adjustable draft angles.
Implementation Method 1
forming a first trench by exposing the substrate to one or more first radiation pulses around a circumference of the optical device, forming a second trench by exposing the substrate to one or more second radiation pulses around the circumference of the optical device
Data Source
AI summary
A method and apparatus for dicing optical devices from a substrate are described herein. The method includes the formation of a plurality of trenches using radiation pulses delivered to the substrate. The radiation pulses are delivered in a pattern to form trenches with varying depth as the trenches extend outward from a top surface of the optical device. The varying depth of the trenches provides edges of each of the optical devices which are slanted. The radiation pulses are UV radiation pulses and are delivered in bursts around the silhouette of the optical devices.