Laser Die Integration in Wafer Cavities for Shorter Thermal Paths
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Solution Overview
Problem
The integration of lasers in photonics integrated circuits (PICs) poses challenges related to thermal performance, manufacturing cost, and yield, primarily due to suboptimal placement and fabrication processes, which affect the performance and reliability of the devices.
Innovation Solution
The described method involves integrating a laser within a cavity of a wafer, with the n-layer proximate to a heat sink for enhanced thermal contact, using conductive and insulating layers to route signals, and employing optical fill materials and conductive posts for improved thermal management and electrical connectivity, while also considering edge sealing and annealing processes to optimize device performance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Temperature
If the laser is integrated using conventional placement methods, then the fabrication process is simpler, but the thermal performance deteriorates due to longer thermal paths and reduced heat sinking efficiency
Solution Approach 1:
The laser is merged with the wafer substrate by directly bonding the laser die to the wafer, integrating the light source into the wafer structure. This merging eliminates the need for separate mounting structures and creates direct thermal coupling between the laser and wafer heat sink, improving thermal performance while maintaining manufacturing simplicity
Solution Approach 2:
The laser is positioned within a cavity formed in the wafer, utilizing the vertical dimension to achieve optimal thermal contact. The cavity structure allows the laser to be embedded at a specific depth, creating a shorter thermal path from the laser active region to the wafer heat sink, thereby improving thermal management
2Temperature
If the n-layer is positioned farther from the heat sink, then the electrical connection is easier, but the thermal contact is reduced leading to performance degradation
Solution Approach 1:
The laser die is oriented with the n-layer (heat-generating layer) positioned adjacent to the cavity bottom for optimal thermal contact with the heat sink. This local optimization of layer positioning ensures that the region requiring best thermal contact has superior heat sinking, while electrical connections are established through conductive paths that accommodate this orientation
3Temperature
If more material is removed to reduce thermal path, then thermal performance improves, but manufacturing complexity and time increase
Solution Approach 1:
The cavity is formed in the wafer before the laser die is bonded to the wafer. This preliminary cavity formation allows the laser to be positioned with optimal thermal contact from the beginning of the assembly process, eliminating the need for subsequent material removal steps to achieve the desired thermal path length
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 enhances thermal contact and reduces thermally-induced performance degradation, improving the reliability and efficiency of the integrated photonics device by creating a shorter thermal path and facilitating better heat spreading, thus addressing the limitations of existing integration methods.
Implementation Method 1
A heat sink can be located on the other side of the bottom of the cavity such that the n-layer of the light source is located proximate to the heat sink. The proximity of the n-layer of the light source to the heat sink can create a shorter thermal path, which can enhance thermal contact and heating spreading.
Data Source
AI summary
Described herein are one or more methods for integrating an optical component into an integrated photonics device. The die including a light source, an outcoupler, or both, may be bonded to a wafer having a cavity. The die can be encapsulated using an insulating material, such as an overmold, that surrounds its edges. Another (or the same) insulating material can surround conductive posts. Portions of the die, the overmold, and optionally, the conductive posts can be removed using a grinding and polishing process to create a planar top surface. The planar top surface enables flip-chip bonding and an improved connection to a heat sink. The process can continue with forming one or more additional conductive layers and/or insulating layers and electrically connecting the p-side and n-side contacts of the laser to a source.