Stress-Compensating Pick-Up Tool for PIC Chip Curvature Alignment
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Solution Overview
Problem
Existing stress compensation methods for photonic integrated circuits (PICs) are limited by passive tools that cannot finely correct curvature in singulated dies, leading to alignment challenges and complexity in assembly processes, especially when adhesive curing introduces additional curvature.
Innovation Solution
A stress compensating pick-up tool with a tool tip and actuator that rotates opposite tip portions to optically align companion chips with host chips, using vacuum tubes for holding and piezoelectric actuation for active alignment based on optical feedback, allowing for precise curvature adjustment and adhesive curing.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Shape
If passive stress compensation layers are applied to the backside of the wafer, then the wafer can be straightened to a planar surface, but the singulated die cannot be finely corrected or adapted for during later assembly
Solution Approach 1:
The pick-up tool incorporates an actuator that can dynamically adjust the curvature of the companion chip during assembly. The actuator applies controlled stress to the companion chip, enabling real-time curvature adjustment to compensate for bowing and achieve precise optical alignment with the host chip, transforming the static curvature compensation approach into a dynamic one.
Solution Approach 2:
The pick-up tool serves as an intermediary device between the companion chip and host chip during assembly. It holds the companion chip and uses the actuator to apply controlled stress, mediating the alignment process by actively compensating for curvature issues rather than relying solely on passive pre-compensation layers.
2Manufacturing precision
If the wafer thickness is adjusted using backside grinding, then the stress compensation layer can be removed or added, but it removes the stress compensation layer or adds complexity to the wafer process flow
Solution Approach 1:
The invention replaces mechanical wafer processing methods (grinding, backside modification) with a mechanical actuation system applied during assembly. Instead of physically modifying the wafer structure through grinding, the actuator applies controlled mechanical stress to adjust curvature, simplifying the wafer fabrication process while maintaining alignment precision.
3Manufacturing precision
If some dicing methods (such as stealth dicing and other laser dicing techniques) are used, then precise cutting can be achieved, but they require a specific wafer backside surface finish and are often not compatible with the stress compensation layer
Solution Approach 1:
The invention performs curvature compensation as a preliminary action during the assembly process, before final bonding. By using the actuator to pre-adjust the companion chip curvature to match the host chip, the process becomes compatible with various dicing methods regardless of their specific surface finish requirements, as the curvature adjustment is applied after dicing.
4Ease of manufacture
If the singulated die is left as-is once singulated, then the process is simple, but if the adhesive curing process or host chip cavity require fine tuning of the curvature of the die to optically align them, it may not be possible with some passive pick-up tools
Solution Approach 1:
The system incorporates feedback mechanisms to monitor alignment status during the assembly process. The actuator adjusts the companion chip curvature based on alignment feedback, enabling precise optical alignment between waveguides on the companion chip and host chip while maintaining an otherwise simple assembly process.
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
Enables precise optical alignment and compensation for curvature in PICs, improving assembly efficiency by actively adjusting the companion chip's shape during adhesive curing, thereby reducing alignment complexities and ensuring accurate waveguide alignment.
Implementation Method 1
A stress compensating pick-up tool with a tool tip and actuator that rotates opposite tip portions to optically align companion chips with host chips, using vacuum tubes for holding and piezoelectric actuation for active alignment based on optical feedback
Implementation Method 2
The stress compensating pick-up tool further comprises two vacuum tubes extending through the tool tip, wherein a vacuum connection is created via the vacuum tubes to hold the companion chip by the tool tip
Data Source
AI summary
A stress compensating pick-up tool for aligning a companion chip with a host chip includes a tool tip and an actuator. The tool tip holds the companion chip, and includes a first tip portion and a second tip portion. The actuator applies a force to the tool tip, wherein the force causes the first tip portion and the second tip portion to rotate in opposite directions with respect to one another to optically align a portion of the companion chip with a corresponding portion of the host chip.